Printer Friendly

Multicomponent phytotherapeutic approach gaining momentum: is the "one drug to fit all" model breaking down?


Article history:

Received 6 May 2013

Received in revised form 22 June 2013

Accepted 26 July 2013



Blockbuster drugs

Combination therapy


Drug development


Natural product based drugs constitute a substantial proportion of the pharmaceutical market particularly in the therapeutic areas of infectious diseases and oncology. The primary focus of any drug development program so far has been to design selective ligands (drugs) that act on single selective disease targets to obtain highly efficacious and safe drugs with minimal side effects. Although this approach has been successful for many diseases, yet there is a significant decline in the number of new drug candidates being introduced into clinical practice over the past few decades. This serious innovation deficit that the pharmaceutical industries are facing is due primarily to the post-marketing failures of blockbuster drugs. Many analysts believe that the current capital-intensive model-"the one drug to fit all" approach will be unsustainable in future and that a new "less investment, more drugs" model is necessary for further scientific growth. It is now well established that many diseases are multi-factorial in nature and that cellular pathways operate more like webs than highways. There are often multiple ways or alternate routes that may be switched on in response to the inhibition of a specific target. This gives rise to the resistant cells or resistant organisms under the specific pressure of a targeted agent, resulting in drug resistance and clinical failure of the drug. Drugs designed to act against individual molecular targets cannot usually combat multifactorial diseases like cancer, or diseases that affect multiple tissues or cell types such as diabetes and immunoinflammatory diseases. Combination drugs that affect multiple targets simultaneously are better at controlling complex disease systems and are less prone to drug resistance. This multicomponent therapy forms the basis of phytotherapy or phytomedicine where the holistic therapeutic effect arises as a result of complex positive (synergistic) or negative (antagonistic) interactions between different components of a cocktail. In this approach, multicomponent therapy is considered to be advantageous for multifactorial diseases, instead of a "magic bullet" the metaphor of a "herbal shotgun" might better explain the state of affairs. The different interactions between various components might involve the protection of an active substance from decomposition by enzymes, modification of transport across membranes of cells or organelles, evasion of multidrug resistance mechanisms among others.

[c] 2013 Elsevier GmbH. All rights reserved.

Is the drug combination strategy the future of drug discovery?

Switching over from single drug to multi-drug therapy

Traditional medicine unceasingly continues to provide frontline medicinal products for millions of people all across the globe. Although their usage is often considered with skepticism by the western pharmaceutical establishments, but these medicinal extracts which have been used in ancient system of medicine like Ayurveda in the Indian subcontinent and traditional Chinese medicine (TCM) are a very rich bioresource of therapeutic leads for pharmaceutical companies. In these systems of medicine, parent extracts have been "clinically" tested in their traditional background, in some cases over millennia. The transformation of traditional medicines into modern western drugs has its origins in the examples of the antimalarial quinine and the anti-pyretic analgesic aspirin. The success of these two early "blockbuster" drugs set the stage for ongoing drug discovery efforts from traditional medicines. Compounds obtained from medicinal extracts are more advantageous and appealing than synthetics for several reasons. Firstly, they are often stereochemically very complicated, multi-or macrocyclic molecules with limited likelihood of prior chemical synthesis and secondly they are embellished with interesting biological properties (Schmidt et al., 2007). Despite these advantages, the route from traditional medicine to western pharmaceutical is full of hurdles and challenges such as discovering the traditional medicine, isolation and synthesis of the bioactive compound, establishing the molecular mechanism of action and finally development as a pharmaceutical agent (Fig. 1). This has resulted in the introduction of fewer New Chemical Entities (NCE's) into the drug discovery process. Many analysts believe that the current model--"the one drug to fit all", approach will be unsustainable in future and that a new model is necessary for further scientific growth. It is believed that the blockbuster model is dying away.

A new chemical entity (NCE) travels a path from laboratories to clinics, involving target identification, lead identification, lead optimization, preclinical studies, and then four phases of the clinical trials: a 12-14 years odyssey is usual! The extremely complex and capital-intensive process makes companies 'target rich' but 'lead poor'. The pharmaceutical industries are facing a serious innovation deficit. Although we have become high throughput in technology, yet we have remained low throughput in thinking.

The pharmaceutical industry has historically seen incredible growth due primarily to the industry's strategy of focusing efforts toward development of "blockbuster" drugs with the potential to generate over $1 billion in sales. However, recent trends indicate that this model may no longer ensure high growth rates (Frantz, 2005). The average cost of discovering, developing and launching a new drug in June 2008 was inordinately high and represented a dramatic increase over the average cost from 1995. R&D expenses have risen from $2 billion in 1980 to over $40 billion in 2007. Surprisingly, these increases have not led to a corresponding increase in the number and efficacy of new drugs. From 1995 to 2000 (as compared to the previous five years), the number of New Molecular Entities (NMEs) approved dropped by nearly 50%, to about 40, and the number of New Chemical Entities (NCEs) produced per company declined by 41%. Moreover, the number of approvals for New Molecular Entities (NMEs) has steadily declined reaching a low of 17 in 2002 and even lower to less than 10 in 2007 and 2008 (Frantz, 2007; Thayer, 2004).

Post marketing failures of bestseller drugs have become major cause of concern for pharma-industries, leading to a paradigm shift in favor of single to multi targeted drugs and affording greater respect to traditional knowledge. Multi-target approaches are coming into the main stream (Zimmermann et al., 2007). Drugs designed to act against individual molecular targets cannot usually combat multigenic diseases such as cancer, or diseases that affect multiple tissues or cell types such as diabetes and immunoinflammatory disorders. Combination drugs that impact multiple targets simultaneously are better at controlling complex disease systems, are less prone to drug resistance and are the standard of care in many important therapeutic areas. The combination drugs currently employed are primarily of rational design, but the increased efficacy they provide justifies in vitro discovery efforts for identifying novel multi-target mechanisms. Alternative and Complementary approaches in therapeutics which are becoming popular options are based on the principle of multi-component drugs acting synergistically in a holistic fashion. Typical reductionist approach of modern science is being revisited over the background of systems biology and holistic approaches of traditional practices. Scientifically validated and technologically standardized botanical products may be explored on a fast track using innovative approaches like reverse pharmacology and systems biology, which are based on traditional medicine knowledge. Traditional medicine constitutes an evolutionary process as communities and individuals continue to discover practices transforming techniques. Many modern drugs have origin in ethnopharmacology and traditional medicine. Traditional system of medicine is based on the principle of multi-component therapy which involves synergistic interactions giving rise to a therapeutic effect. Synergism plays a key role in the traditional system of medicine like Ayurveda, traditional Chinese medicine, etc. (Corson and Crews, 2007; Patwardhan et al., 2008; Zimmermann et al., 2007).

Existing multi-target therapeutics

Increasingly, drug combinations are the standard of care for the treatment of diseases including cancer, type 2 diabetes mellitus (T2DM), viral and bacterial infection, and asthma. Often, these combinations are applied as co-therapy regimens, but in many cases the individual components of the combination are co-formulated as a single pill or injection. A new generation of multi-target drugs is currently emerging from clinical development: single chemical entities that act simultaneously at multiple molecular targets. There are several categories of multi-target therapeutics that can be defined on the basis of target relationship. In the first class, the therapeutic effect occurs at separate molecular targets that can reside within individual signaling pathways, between pathways within a cell or at separate tissues in the body. In the second category, modulation of one target facilitates action at a second target, for example by altering compound metabolism, inhibiting efflux pumps or blocking other resistance mechanisms (Table 1). Third, a coordinated action at multiple sites on a single target or macromolecular complex (e.g. prokaryotic ribosome) yields the therapeutic effect.

Note that the set of targets in each of these three cases can be modulated either by a mixture of separate chemical entities or by a single compound designed to have multiple actions. Although multi-target action can be achieved in several ways, it is the coordinated effect at the set of targets that results in the biological and, hopefully, therapeutic effect (Kubinyi, 2003). Table l lists some examples of multi-target therapeutics from various indications.

The benefits of multi-target action are well established in cancer. Traditional chemotherapeutic agents have been routinely applied as co-therapies. For example, adjunctive agents can sensitize cancer cells to DNA-damaging drugs, and newer co-therapy protocols including 5-FU, leucovorin and oxaliplatin (i.e. FOLFOX) are now applied in colorectal cancer. Currently, the molecularly targeted agents such as Herceptinl (trastuzumab) and Erbituxl (cetuximab) are being developed in combination protocols with traditional antineoplastics, estrogen blockade and other targeted agents (Dancey and Chen, 2006; Johnston, 2005). For example, Herceptinl, which targets ErbB2 (HER-2/neu), is being applied in combination with the anti-VEGF (vascular endothelial growth factor) antibody Avasti n1 to treat breast cancer, and Erbi tux1 (which targets ErbB1) is applied in combination with irinotecan for the treatment of colorectal cancer. A novel class of receptor tyrosine kinase (RTK) inhibitors that possess multi-target action in a single chemical entity are currently in clinical development. Lapatinib and canertinib are examples of a new class of pan-ErbB inhibitors. These new agents with multi-target action will almost certainly be applied in combination with other molecularly targeted or traditional chemotherapeutic agents once they reach the market (Britten, 2004; Hynes and Lane, 2005).

Table 1

Some of the examples of drug-combination products.

Trade name  Indication       Compound 1      Compound 2

Vytorin     Hyperlipidemia   Ezetimibe       Simvastatin

Caduet      Coronary heart   Amlodipine      Atorvastatin

Lotrel      Hypertension     Amlodipine      Benezapril

Glucovance  Type 2 diabetes  Metformin       Clyburide

Avandamet   Type 2 diabetes  Metformin       Rosiglitasone

Truvada     Anti-HlV         Emtricitabine   Tenofovir

Kaletra     Anti-HIV         Lopinavir       Ritonavir

Rebetron    Anti-Hepatitis   PEC-interferon  Ribavirin

Bactrim     Antibacterial    Trimethoprim    Sulfamethoxazole

Trade name  Target or        Target or
            mechanism of     mechanism of
            action 1         action 2

Vytorin     Dietary          HMC-CoA
            cholesterol      reductase

Caduet      Calcium-channel  HMC-CoA
            antagonist       reductase

Lotrel      Calcium-channel  ACE inhibitor

Glucovance  Gluconeogenesis  Insulin

Avandamet   Cluconeogenesis  PPAR-y agonist

Truvada     RT inhibitor     RT inhibitor

Kaletra     Protease         Protease
            inhibitor        inhibitor

Rebetron    Interferons B    Antimetabolite

Bactrim     Dihydrofolate    Dihydropteroate
            reductase        synthase

What synergy means in phytomedicine?

It is very difficult at the first instance to provide an unequivocal universal definition for the term synergism or synergy effect, because synergy has a precise mathematical definition according to the method used to prove it. The term synergy comes from the Greek word "Synergos" meaning "working together". Synergy means working together of two or more substances to produce an effect greater than the sum of their individual effects. In nature, synergy phenomena are ubiquitous ranging from physical science (e.g. the different combinations of quarks to form protons or neutrons) to chemistry (hydrogen and oxygen combine to produce water) to the cooperative combination among the genes to produce genomes (Wikipedia). The concept of synergy is based on the view that a cohesive group is more than the sum of its parts; synergy is the ability of a group to outperform even its best individual member. However, synergy is not always positive, in various cases synergy produces negative results.

Conventional medicine follows a reductionist approach. Specific compounds are assigned for defined biological functions or target molecules. Chemotherapy of infectious diseases represents a successful example for this "one target-one drug" concept. This is what Paul Ehrlich had in mind with his idea of "magic bullets" to specifically target diseases. This approach explains the reluctance of western medicine toward multi-component therapies with broad spectrum activities such as phytotherapy. Observable treatment successes by phytopoharmaceuticals are frequently neglected or classified as placebo effects. On the other side, the majority of diseases are multi-factorial and targeting a single cause of a disease by a single drug may not deliver satisfactory treatment results. Traditional medicinal systems including European phytotherapy, traditional Chinese medicine (TCM) or Ayurveda have a holistic approach. Instead of mono-substances, mixtures of medicinal plants with complex interactions of dozens to hundreds of compounds are used. Here, multicomponent recipes are considered as advantageous for pleiotropic diseases compared to single compounds. Instead of a "magic bullet", the metaphor of an "herbal shotgun" might better describe this situation (Wagner and Ulrich-Merzenich, 2009; Williamson, 2001).

As for as drug discovery is concerned, the therapeutic value of synergistic interactions among the different components has been known since early time and many traditional healing systems still rely on this principle of synergy. Aromatherapy is fundamentally based on the principle of combination of highly complex mixtures of essential oils to produce a therapeutic effect. The use of polyherbals has been carried down the ages and today allopathic medicine is based on the principle of synergy in which various compounds are mixed in single or isolated dosage forms which are then administered concomitantly. The combination therapy has recently got tremendous response and is now widely accepted particularly in the treatment of infectious diseases (Efferth and Koch, 2011). The world Health Organization (WHO) has advised pharmaceutical companies to use artemisinin combination therapy not only because of its 95% cure rate against Plasmodium falciparum - the causative malarial parasite, but this combination therapy may also decrease the incidence of resistance. The WHO has also urged to stop artemisinin derivatives monotherapy which not only has a lower cure rate than combination therapy but it has also higher chances of developing resistance (Douglas et al., 2010). In the fight against the multidrug resistant microbes, the combination therapy is becoming more and more of utmost importance. The current treatment regimen for tuberculosis constitutes a cocktail of five drugs viz., pyrazinamide, rifampicin isoniazid, streptomycin and ethambutol (PRISE). Another renowned antimicrobial agent having a synergistic effect in combination is amoxicillin (a 13-lactam antibiotic) and clavulanic acid. Clavulanic acid binds to 13-lactamase producing microorganisms, which protects amoxicillin from 13-lactamase attack, which in turn results in an extended spectrum of activity for amoxicillin (Chan and lseman, 2002; KaIan and Wright, 2011; Matsuura et al., 1980). Multi-drug therapy is also being practiced worldwide in the treatment of AIDS and other infectious diseases, hypertension numerous types of cancer and rheumatic diseases. The multi-drug concept in current cancer therapy has been designated as biomodulatory-metronomic chemotherapy. The idea is to fight the tumor via a process of concerted and concomitant action not through direct destruction of the tumor but rather by suppression or activation of different processes which are essential for the tumor's survival (e.g. by angiogenesis, induction of apoptosis, activation of the immune system, etc.). Multi-target therapy is more effective and less vulnerable to adaptive resistance because the biological systems are less able to compensate the action of two or more substances simultaneously. As a result, mono-target drugs are incapable of effectively combating complex pathological conditions like cancer and infectious diseases (Berenbaum, 1989).

Definition and proof of synergy

If two drugs A and B are combined, and if drug A has an effect and drug B has no effect and if in combination they have an effect that is greater than that of drug A, then it is enhancement or potentiation. We can describe the effect simply as percent enhancement or - fold of potentiation. If A and B alone each has an effect, then in combination they may produce a synergistic, an additive, or an antagonistic effect. By definition, synergism is an effect that is more than additive, whereas the definition for antagonism is an effect that is less than additive. Synergism occurs when two or more herbal ingredients mutually enhance each other's effect more significantly than the simple sum of these ingredients. Synergy represents a form of interaction as opposed to a simple addition response. Among all the methods proposed for the proof of synergy effects, the "isobole method" of Berenbaum (1989) appears to be one of the most experimentally practicable and also the most demonstrative method. An isobole is an "iso-effect" curve, in which a combination of constituents (da, db) is represented on a graph, the axes of which are the dose-axes of the individual agents (Da and Db). If the agents do not interact, the isobole (the line joining the points representing the combination to those on the dose axes representing the individual doses with the same effect as the combination) will be a straight line. If synergy is occurring, i.e. the effect of the combination is greater than expected from their individual dose-response curves, the dose of the combination needed to produce the same effect will be less than for the sum of the individual components and the curve is said to be 'concave..The opposite applies for antagonism, in which the dose of the combination is greater than expected, and produces a 'convex' isobole (Figs. 2 and 3). It is quite possible to have synergy at one dose combination and antagonism at another, with the same substances and this would give a complicated isobole with a wave-like or even elliptical appearance. To demonstrate synergy effect, in vitro or animal models are utilized for the demonstration of the isoboles of a mixture of two substances (Berenbaum, 1989: Chou, 2006, 2010).

Combination index ((CI)

A combination index (Cl) method was put forth by Chou and Talalay (1983) for quantifying the synergism or antagonism of two drugs and assesses the nature of the interaction (synergy, additivity, or antagonism) (Chou, 2006). The combination index is calculated on the basis of their concentration and biological activity (like cell growth inhibition, [IC.sub.50]). Cl analysis provides quantitative data and the numerical value is calculated as:

CI = [C.sub.A, X]/[IC.sub.X, A] + [C.sub.B, X]/[IC.sub.X, B]

where [C.sub.A, X] and [C.sub.B, X] are the concentrations of the drug A and drug B used in combination to produce a mean effect X ([IC.sub.50]). [IC.sub.X, A] and [IC.sub.X, B] are the median effect values ([IC.sub.50]) for single drug A and B. Combination index (CI) is used to quantitatively depict synergism (CI < I ), additive effect (CI = 1) and antagonism (CI > 1) (Table 2). The combination index or the interaction index is a quantitative measure of the degree of synergism or sub-additivity that occurs when two drugs are mixed together. Doses of drugs that give the same effect are called isoboles and the method of analysis is called isobolar method. An isobologram is a cartesian plot of doses that in combination yield a specified level of effect. It is a convenient and currently popular way of graphically exhibiting results of drug-combination studies, because paired values of experimental points that lie below or above the line joining the axial points ([IC.sub.50] or [ED.sub.50] values) represent supra- and sub-additive combinations, respectively.

Table 2 Symbols and description of synergism or antagonism in
drug combination models analyzed with the combination index (Cl)
method. This method is based on those described by Chou and
Talalay (1984). CI < 1, CI = 1, and CI > 1 indicate synergism,
additive effect and antagonism, respectively.

Range of combination  Description             Graded symbols
index (Cl)
<0.1                  Very strong synergism   +++++
0.1-0.3               Strong synergism        ++++
0.3-0.7               Synergism               +++
0.7-0.85              Moderate synergism      ++
0.85-0.90             Slight synergism        +
0.90-1.10             Nearly additive         [+ or -]
1.10-1.20             Slight antagonism       -
1.20-1.45             Moderate antagonism     --
1.45-3.3              Antagonism              ---
3.3-10                Strong antagonism       ----
>10                   Very strong antagonism  -----

Experimental evidence in favor of synergism

It is a routine practice for phytochemists to examine and prepare extracts from medicinal plants keeping in view isolating the single chemical entity responsible for the therapeutic effect. But this approach may lead to inconclusive findings. If a mixture of substances is required for the effect, then the bioassay-led isolation, which narrows activity down initially to a fraction and finally to a compound, is doomed to failure and this has led to the result that the plants are in fact lacking the desired therapeutic effect. An excellent example is that of Kigelia pinnata, in which the previously reported cytotoxic activity was destroyed after fractionation. These and other related misconceptions regarding synergy can be dispelled by clinical trials. Most of the time when activity is thought to be lost during purification, synergy should be suspected. If synergism is known or suspected to be present, the mixture is necessary for the therapeutic effect. Sometimes the presence of whole plant material, which may contain for instance antioxidants, may protect the active secondary metabolites from decomposition and degradation. Sometimes the active compound may be a minor unidentified compound.

The following examples investigated through in vitro and in vivo experiments are forwarded in support of synergism:

Example 1. Marihuana (Cannabis sativa)

The well-known cannabis and tetra hydrocannabinol (THC = 6,9--THC) possess antispastic action, hallucinogenic, antiemetic, anxiolytic and analgesic effects. Baker et al. (2000) have proved it in an immunogenic animal model of multiple sclerosis. Because there were some indications that showed a stronger muscle-antispastic effect of the extract than of pure THC, a comparative i.v. test of 1 mg/THC and 5 mg/kg Cannabis extract, the latter standardized on a concentration of 20% of THC, was carried out. It was shown that the whole cannabis extract with equimolar THC concentration was much more effective antispastic agent than THC alone (Baker et al., 2000). Since in a preliminary investigation, THC free extract did not exhibit strong antispastic effect, concomitant chemical constituents of the Cannabis extract, most probably cannabidiol, may be responsible for the synergy effects. It has been reported that cannabidiol which is also a constituent of the extract promotes an increase in the transport of ananclamide through the brain membrane not evident with THC. This could explain the stronger antispastic effect of the Cannabis extract (Wilkinson et al., 2003; Williamson and Evans, 2000; Zuardi et al., 1982).

Example 2. St. John's Wort (Hypericum perforatum)

Standardized Hypericum extracts have been shown by more than 40 placebo-controlled clinical studies to be effective for the treatment of mild, moderate and even severe depression. The pharmacological effects of several of these extracts are comparable with the synthetic psychopharmacological drugs like amitriptyline, imipramin and flumazenil. Evidence for the synergistic pharmacokinetic interactions has been obtained for St. John's Wort extracts (Woelk, 2000). During a bio-assay guided fractionation of a methanolic extract, hypericin and pseudohypericin were identified as components that showed pharmacological effect in the forced swimming test while the purified compounds were found to be inactive after treatment at doses comparable to the total extracts. When a fraction containing procyanidins, which itself was inactive in the test model, was combined with hypericin or pseudohypericin, activity was detected at relatively low oral doses. According to various investigations performed so far on the pharmacological effects of Hypericum, several chemical constituents are believed to be involved in its effectiveness particularly hyper-Ion i n, the hypercines, amentoflavon, rutin, hyperosid, xanthones and proanthocyanidines (Fig. 3). This idea has been hypothesized by various in vitro neurochemical studies with various CNS receptors making the use of radioligand-binding techniques to prove that the antidepressant activity of standardized Hypericum extract might be a result of the cooperative action of several chemical constituents of H. perforatum. As shown in the figure, various targets are believed to be involved like presynaptic and postsynaptic neurons, the pituitary gland and hypothalamus are all involved as possible targets and all the main chemical constituents of St. John's Wort show affinities to any of the above targets (Schulz, 2001, 2003; Simmen et al., 2001).

Example 3. Iberogast[R] (a phytopreperation of nine plant extracts)

This is an example for the multi-target principle which comprises of nine plant extracts and is considered in Germany and other European countries as a leading phytopreperation for the treatment of functional dyspepsia and motility-related intestinal disorders (Fig. 4). Twelve clinical studies, among them two in comparison with the synthetic drugs cisapride and metoclopramide, showed a complete therapeutic equivalence with the two synthetic drugs, with the additional benefit that the phytopreperation showed fewer or no side effects in comparison to the two synthetics. lberogast exhibits a multi-target effect by balancing the disturbed gastrointestinal motility function, by alleviating gastro-intestinal hypersensitivity, by inhibiting the inflammation, suppression of gastric juice secretion and effects on gastro-intestinal autonomic afferent function. On the contrary to this multiphytopreperation, the synthetic monodrugs cisapride and metoclopramide as classical proton pump inhibitors target only one symptom of functional dyspepsia. Each plant extract of the preparation was investigated separately in all relevant pharmacological in vitro and in vivo models with the result that all extracts, some of them multifunctionally or synergistically, are involved in the overall pharmacological effect (Allescher, 2006; Sailer et al., 2002; Wagner, 2006).

Example 4. Kava Kava (Piper methysticum)

Kava Kava (Piper methysticum) is a plant native to the South Pacific islands with anxiolytic and sedative activities. Controlled human clinical trials show it to be superior to placebo for the treatment of anxiety, an equivalent in efficacy to the benzodiazepine oxazepam (Serax[R]) (Pittler and Ernst, 2000). The bioactive chemical constituents from Kava are the kava lactones, particularly kavain, dihyd rokava in, yangonin, dimethoxyyangonin, methysticin and dihydromethysticin (Fig. 5). The kava lactones yangonin and dimethoxyyangonin act in an anticonvulsant manner. Their efficacy is much more in combination with other kava constituents rather than when they are applied separately. One constituent namely di hydromethysticin, seems to be particularly important for the synergy. In some experiments, in mice and dogs it was observed that the oral bioavailability of kavain was greater if it was administered in an extract when compared to an equivalent quantity of the pure constituent. Kava lactones pass the blood--brain barrier and behavioral effects occur at micromolar concentrations. Kava lactones enhance binding to the GABAA receptor in the low micromolar range, through a non-benzodiazepine mechanism. These lactones also block voltage-gated [Na.sup.+] and [Ca.sup.2+] channels in micromolar concentrations (Friese and Gleitz, 1998; Jussofie et al., 1994; Keledjian et al., 1988; Lindenberg and Pitule-Schodel, 1990).

Example 5. Antimicrobial action of berberine potentiated by 5'-methoxyhydnocarpin (5'-MHC)

In a study published in Proceedings of National Academy of Sciences (PNAS) USA, Stermitz et al., 2000 have convincingly demonstrated the occurrence of synergy in some Berberis medicinal plants (Stermitz et al., 2000). Berberine alkaloids are the cationic antimicrobials synthesized by a variety of plants particularly of the family Berberidaceae. These cationic alkaloids are readily extruded by multidrug resistant pumps

(MDRs) present in various bacterial strains. These MDRs protect the microbial cells from both synthetic and natural antimicrobials. Several Berberis medicinal plants producing berberine are also found to synthesize an inhibitor of the Nor A MDR pump of a human pathogen Staphylococcus aureus, namely 5'-methoxyhydnocarpin (5'-MHC), previously known as a minor constituent of Chaulmoogra oil, a traditional therapy for leprosy (Fig. 7). 5'-MHC itself alone does not possess the antimicrobial activity but strongly potentiates the action of berberine and other Nor A substrates against S. aureus (Fig. 6). It has been reported that MDR-dependent efflux of ethidium bromide and berberine from S. aureus cells is completely inhibited by 5'-MHC. The degree of accumulation of berberine in the bacterial cells is increased considerably in the presence of 5'-MHC, proving that this plant compound effectively disabled the bacterial resistance mechanism against the berberine antimicrobial.

The chloroform extracts of the leaves from Berberis repens, Berberis aquifolia, Berberis fremonti had no antimicrobial activity at >500 [micro]g/m1 concentration, but inhibited S. aureus growth completely in the presence of 30[micro]g/m1 berberine, a concentration which is 1/8th the MIC for this compound. This extract that inhibited the cell growth in the presence of berberine but had no activity when added alone is likely to contain an MDR inhibitor namely 5'-MHC.

Objectives of synergistic combinations

The main objectives of the use of synergistic and potentiative drug combinations are the following:

a. The combination therapy is expected to exhibit greater efficacy than the monotherapy.

b. The combination of drugs is expected to reduce the dosage at equal or increased level of efficacy.

c. The combination of drugs may reduce or delay the development of drug resistance due to the inhibition of multiple pathways.

d. The combination therapy is expected to reduce the unwanted side effects but at the same time exhibit enhanced therapeutic action.

Synergistic/antagonistic interactions of natural products with clinically used anticancer and antimicrobial drugs

Cancer with more than 11 million death cases every year is the second leading cause of mortality. It is estimated that there will be 16 million new cases of death due to cancer each year by 2020. Death rate from this dreadful disease in the world is projected to rise, with an estimated 9 million people dying from cancer in 2015 and 11.4 million dying in 2030 (jemal et al., 2005). Given the fact that cancer is a multi-factorial disorder resulting in unlimited division of cells, remedial strategies that target tumor cells while causing fewer side effects on normal cells are desired. In such cases, chemical, biological and clinical informatics methods can be used to discover or design novel treatment strategies for specific tumor cell targeting, overcoming drug resistance and increasing protection of normal cells against antitumor drugs (Krishna and Mayer, 2000). Over 90% of the cancer death cases attributable to failure in chemotherapy are generally related to multidrug resistance (MDR). MDR refers to a series of events characterized by the property of drug resistant tumors exhibiting simultaneous resistance to a number of structurally and functionally unrelated chemotherapeutic agents. Occurrence of multidrug resistance (MDR) mechanisms in cancer has presented serious barrier for successful cancer treatment. Two mechanisms which play a key role in MDR are the amplified activity of efflux pumps, as the multidrug resistance proteins (MRPs) and the detoxification by phase II conjugating evizymes, such as glutathione 5-transferases and UDP-glucuronosyltransferases. A synergistic interaction between these two mechanisms, MRPs and phase II enzymes, in the field of MDR has been reported. Presenting solution to overcome MDR in tumor cells is the main consideration in chemotherapy of cancer, which mainly is focused on combinational strategy (Meijerman et al., 2008; Tsuruo, 2003).

Combinational drug therapy has a long history and roots in traditional Chinese medicines. Today, parallel to new advances in cancer chemotherapy, cancer combinational drug therapy has been well developed and wide ranges of scientific efforts are focused on that. More and more medicinal chemists are turning their attention to natural medicines in order to overcome 'more investment, less drugs' challenge in drug discovery. Natural medicines are thought to be a hidden treasure of unexplored new-entity drugs. Although, some promising drug candidates have been derived from natural medicines, but because of the fact that the efficacy of most natural medicines lies in the synergy of diverse components rather than a single component, it is a great challenge to find single-component new entity drugs from the natural medicine. Even if the drug molecule is isolated from the source, either it is not as active as expected or it can be toxic. In many other cases, even if the drug candidate is developed, but with the passage of time it develops resistance and becomes therapeutically inefficient. Therefore, understanding the synergistic mechanisms of natural medicines is of great significance to drug discovery (Gertsch, 2011; Junio et al., 2011; Li and Vederas, 2009).

The fact that synergy does exist in natural medicines can be detected, at least, at two levels. First, the various components present in a single medicinal agent might work synergistically. For example, the high antimicrobial potential of some medicinal plants (e.g. Berberis sp.) results from the synergy of antimicrobial agents (e.g. berberine) and multidrug resistance (MDR) inhibitors (e.g. 5'-methoxyhydnocarpin). Some mostly used anticancer natural medicines, such as Rhizoma Polygoni Cuspidati, Fructus Schisandrae Chinensis and Rhizoma Zingiberis Recens, also comprise anticancer agents (e.g. apigenin and limonene) and MDR inhibitors for cancer cells (e.g. quercetin and [beta]-elemene). Of course most of the MDR inhibitors have no biological activities (such as microbicidal or anticancer activities) on their own, they effectively potentiate the antimicrobial or anticancer effects of bioactive agents by avoiding them from being pumped out of the cells by the MDR pumps. Secondly, synergism can also be observed by combining various individual natural agents in a formula to enhance the therapeutic efficacy and/or reduce toxicity. Traditional Chinese Medicine (TCM), which has collected more than 100 000 formulae in the past 1500-2000 years best reveals the above fact. The synergistic mechanisms of some TCM formulae have been understood on at least preliminary level. For instance, the combination of Realgar (tetraarsenic tetrasulfide), Indigo Naturalis, Radix Salviae Miltiorrhizae and Radix Pseudostellariae has been proved to be effective in the treatment of human acute promyelocytic leukemia (APL). Through pinpointing the roles of active ingredients derived from Realgar, Indigo Naturalis and Radix Salviae Miltior-rhizae, the synergy of this formula basically has been elucidated. That is, tetraarsenic tetrasulfide (Fig. 7) directly attacks promyelocytic leukemia retinoic acid receptor a (PML-RARa) oncoprotein and promotes APL cell differentiation. The principal components of Indigo Naturalis and Radix Salviae Miltiorrhizae, which is indirubin and tanshinone 11A (Fig. 7), potentiate tetraarsenictetrasulfide-induced ubiquitination and degradation of PML-RARa. In addition, indirubin and tanshinone IIA enhance the expression of aquaglyc-eroporin 9, which helps transport tetraarsenic tetrasulfide into APL cells and, thus, augments its efficacy (Qiu, 2007; Wang et al., 2008).

Although the rational design of targeted drugs has made lot of progress

due to advances in genomics and cell biology, but the effects of these targeted drugs are not durable when they are used alone. This problem arises partially because agents directed at an individual target often exhibit limited efficacies, poor safety and resistance profiles. It is now well established that cellular pathways operate more like webs than highways. There are often multiple ways or alternate routes that may be switched on in response to the inhibition of a specific target. This facilitates the emergence of resistant cells or resistant organisms under the specific pressure of a targeted agent, resulting in drug resistance and clinical failure of the drug. To overcome this limitation of monotherapy, combination therapies involving more than one agents, are often required to effectively cure many malignant tumors and infectious diseases. This combinatorial approach to drug design has been supported by clinical successes with combination therapies and multi-target agents and attempts have been made in the direction of the discovery of new multicomponent therapies. Understanding the molecular mechanism of action of drug combinations involving synergistic and antagonistic interactions could pave the way for the discovery of novel effective combination therapies.

Natural products have always played a significant role in the drug discovery process. In particular, natural product combinations have been extensively investigated, clinically tested, and widely used in traditional, folk and alternative medicines. The novel multi-target mechanisms of natural product combinations may be valuable sources of information for developing the multi-target therapeutics. Various natural product combinations produce significantly better effects than equivalent doses of their components. Synergism effect could not only occur among natural compounds, but also between natural compounds and marketed chemotherapeutic agents. A list of recently used natural products in cancer combination therapy is given in Table 3. List of patents pertaining to use of natural products in cancer combination therapy is given in Table 4.

Anticancer enhancing effects of isoprenoid natural products from essential oils

The toxic effects of anticancer drugs during the treatment is a growing concern. The use of non-toxic potentiating agent or synergistic compound in combination with anticancer drugs may considerably potentiate their effectiveness while minimizing their toxicity. Most of the currently used cancer treatments employ a cocktail of various anticancer drugs acting in synergism. For example, MVAC protocol comprises of four drugs including methotrexate, vinblastine, cloxorubicin and cis-platin. But, each component of these types of cocktails is toxic as well as their combination (Blick et al., 2012). If a compound which itself is non-toxic but potentiates the efficacy of other anticancer drugs is identified, it can solve many problems of the clinical cancer treatment.

Such kinds of molecules are terpenes. Terpenes are a class of natural products having wide distribution in nature, mostly found in plants. [beta]-Caryophyllene, a well-known sesquiterpene present as a major component in various essential oils has been reported to enhance the efficacy of paclitaxel synergistically against MCF-7 cell lines (Legault and Pichette, 2007). Cancer cells have been reported to be sensitized to radiation therapy by using one or more monoterpenes or sesquiterpenes particularly perillyl alcohol. The cancer cell that was exposed to the terpenes has been reported to be more sensitive to the irradiation than a control cell that has not been exposed to the above treatment. Geranium oil in combination with paclitaxel slowed down the growth of human breast and lung cancer cells up to 87% (Rajesh et al., 2003). Geraniol, which is an acyclic dietary oxygenated monoterpene found in many essential oils has been reported to exert anti-tumor activity against various cancer cells both in vitro and in vivo. Geraniol inhibited Caco-2 cell growth by reducing DNA synthesis leading to a blockage of the cells in the S-phase of the cell cycle. Geraniol also increased the cytotoxicity of 5-FU and increased its uptake in human colon cancer cell lines. Geraniol caused a 2-fold reduction of thymidylate synthase and thymidine kinase expression in cancer cells (Carnesecchi et al., 2002). In another study, perillyl alcohol, which is a constituent of many essential oils, inhibited the growth of human breast cancer cells (MDA-MB-231, MDA-MB-435, and MCF-7) and induced apoptosis. The novel discovery in the study was that perillyl alcohol (IC20), methyl jasmonate ([IC.sub.20]), and cis-platin (1 [micro]M) in combination exhibited synergistic effects in growth inhibition in MDA-MB-435 and MDA-MB-231 cells. The [IC.sub.50] for cis-platin is 600 [micro]M and in combination with perillyl alcohol and methyl jasmonate, it decreases to 1 [micro]M, which is a 600-fold increase in sensitivity to cis-platin. In case of MDA-MB-231 cells in the presence of perillyl alcohol and methyl jasmonate, a 1200-fold increase in sensitivity to cis-platin was observed. Mechanistic study revealed that the combination treatment increased the TNFR1 expression and decreased mitochondrial membrane potential in MDA-MB-435 and MDA-MB-231 cells (Yeruva et al., 2010). Peril-lyl alcohol has also been reported to inhibit growth of cancer cells and induce apoptosis. Another report indicated that perillyl alcohol sensitized human myeloid U937 cells to pentoxifylline. Combination treatment of perillyl alcohol with pentoxifylline increased Bc1 and Bax expression as well as induced apoptosis. Perillyl alcohol has also been reported to sensitize prostate and malignant glioma cells to cisplatin/radiation via Fas mediated death receptor pathway (Rajesh and Howard, 2003; Rajesh et al., 2003). Malignant glioma cells preincubation with POH exhibited a concentration dependent sensitivity to cisplatin and doxorubicin. Essential oils have also been reported to exhibit synergistic effects with various chemotherapeutic anticancer drugs. For instance geranium oil has been reported to exhibit synergistic effects with some chemotherapeutic anticancer agents used in different cancers including breast, lung, ovary, colon, prostate, liver, kidney, neuroblastoma, leukemia, lymphoma, and other cancers.

Table 3 Natural products and medicinal extracts exhibiting
synergism with anticancer agents.

Source             Natural product                  Cell line/in vivo

Cotton seeds       (--)-Cossypol                    BxPC-3cell line

Ferula             Conferone                        MDCK-MDR1 cells

Cimcifuga          Cycloartane-type triterpenoids   Human breast cancer
racemosa                                            cell line MCF-7

Solatium           Coramsine                        Murine model of
linnaeanum                                          malignant

Glycine max        Genistein                        PC-3 human prostate
                                                    cancer cell line

Ailanthus          1 -Methoxy-canthin-6-one         Human leukemia
altissima                                           (Jurkat), thyroid

Swingle                                             carcinoma (ARO
                                                    and N PA) and
                                                    carcinoma (HuH7)

Rhizome of Alisma  Alisol B 23-acetate(ABA)         MDR cell lines
orientate                                           HepG2-DR and

Glycine max        Genistein                        Pancreatic cancer
                                                    cell lines BxPC-3

Glycine max        Genistein                        Human prostate
                                                    cancer cells PC-3

Glycine max        Genistein                        HeLa (cervical
                                                    cancer), OAW-42
                                                    (ovarian cancer)
                                                    and L929 (normal

Glycine max        Genistein                        MCF-7 human B RCA

Rosa sp.           Geraniol                         Colonic cancer cell
oil/Cymbopogon                                      lines Caco-2 and
martinii                                            SW620 cells
oi 1/Cymb op ogon
nardus L oil

Euphorbia          Latilagascenes B                 Human MDR I gene
lagascae                                            transacted mouse
                                                    lymphoma cells

Azadiraclua        Neem leaf preparation (NLP)      Swiss mice
indica                                              diminishes
                                                    leucopenia And
                                                    peripheral blood
                                                    mononuclear cells

Panax notoginseng  Notoginseng flower extract       HCT-116 human
                   (NGF)                            colorectal cancer

Epilohium          Oenothein B (OeB)                Prostate cancer
angustifolium                                       cells PC-3

Olea sp. Oil       Oleic acid                       Breast cancer cells
                                                    with HER-2/neu

Tanacetum          Parthenolide                     Hs605T. MCF-7
partlienium (L.)

Plant products     Perillyl alcohol (POH)           NSCLC, A549 and
                                                    H520 cells

Viris vinifera     Proanthocyanidin                 K562. A549. CNE
seeds                                               cells, experimental
                                                    Sarcoma 180 (SI80)
                                                    and Hepatoma 22
                                                    (H22) in vivo

Torilb japonica    Torilin                          Multidrug-resistant
                                                    KB-V1 and
                                                    MCF7/ADR cells

Tripterygiurn      Triptolide (TPL)                 Ovarian cancer and
wilfordii                                           Nude mice

Scutellaria        Wogonin                          Jurkat and HL-60
baicalensis                                         cells

Celastnis          Dihydro [beta]-agarofuran            Human
vulcanicola        sesquiterpenes                   MDR1-transfected

A plant alkaloid   NSC77037                         MDR ovarian cancer

Camellia sinensis  (--)-Epigallocatechin-3-gallate  MCF-7Tam cells

Source             Anticancer agent      Refs.

Cotton seeds       Genistein             Mohammad et
                                         al. (2005)

Ferula             Vinblastine           Barthomeuf et
schtschurowskiana                        al.(2006)

Cimcifuga          Tamoxifen             Gaube et
racemosa                                 al,(2007)

Solatium           CpG-containing        Van der Most
linnaeanum         oligodeoxy            et al.(2006)

Glycine max        SB715992              Davis et al.

Ailanthus          Human recombinant     Ammirante
altissima                                etal. (2006)

Swingle            tumor necrosis
                   related apoptosis
                   ligand (TRAIL)

Rhizome of Alisma  Vinblastine.          Wang et
orientate          Puromycin.            al.(2004)

Glycine max        Erlotinib             El-Rayes et

Glycine max        Docetaxel             Li etal.

Glycine max        Camptothecins         Papazisiset
                                         al. [2006)

Glycine max        Tamoxi fen            Mai et

Rosa sp.           5-Fluorouracil(5-FU)  Carnesecchi et
oil/Cymbopogon                           al. (2002)
nardus L oil

Euphorbia          Doxorubicin           Duarte et al.
lagascae                                 (2007)

Azadiraclua        Cyclophosphamide      Ghosh et al.
indica                                   (2006)

Panax notoginseng  5-Fluorouracil        Wang et al.

Epilohium          Arabinosylcytosine    Kiss et al.
angustifolium                            (2006)

Olea sp. Oil       Trasmzumab            Menendez et
                   (Herceptine)          al. (2005)

Tanacetum          Parthenolide          Wu et al.
partlienium (L.)                          (2006)

Plant products     Cisplatin             Yeruva et al.

Viris vinifera     Doxorubicin           Zhang et
seeds                                    al.(2005)

Torilb japonica    Adriamycin.           Kim et
                   Vinblastine,          al.(1998)
                   Taxol and Colchicine

Tripterygiurn      Carboplatin           Westfall et
wilfordii                                al. (2008)

Scutellaria        Etoposide             Lee et al.
baicalensis                              (2007)

Celastnis          Verapamil             Torres-Romero
vulcanicola                              et al. (2009)

A plant alkaloid   Paclitaxel            Susa et al.

Camellia sinensis  Tamoxifen             Farabegoll et
Table 4 List of recent patents pertaining to use
of natural products in cancer combination therapy.

Research area/      A brief synopsis of  Year/patent     Refs.
title                 the patent           number

Preparation and     This invention       2003/           Wang et al.
composition of      describes the        US6617335       (2003)
bis-benzyl-         preparation of
isoquinoline class  various
derivatives         bis-isoquinoline
alkaloids           possessing multi-
                    resistance (MDR)
                    reversal activities
                    and are used as
                    sensitizing agents
                    (potentiators) in

Synergistic         This invention       2003/           Lee (2003)
compositions and    reports a            US6537988
methods for         pharmaceutical
cancer treatment    preparation
                    for the synergistic
                    treatment of cancer
                    consisting one
                    agent from
                    cytotoxic class and
                    other from
                    cytostatic class

Methods and use of  This invention       2003 /          Horwitzetal.
combination         relates to the       US65415Q9       (2003)
chemotherapy for    synergistic effects
the treatment of    of Taxol
cancer              in combination with
                    discodermolide in
                    treatment of

Therapy for B cell  This                 2005 /          Chan et al.
disorders using     invention describes  US20050095243   (2005)
combination         a combination
therapy approach    therapy of
                    antibody with a
                    BLyS antagonist for
                    treatment of cell
                    based malignancies
                    and B-cell

Combination         This invention       2007/           Sliwkowski and
therapy of HER      relates to the use   US20070020261   Kelsey
expressing          of HER2-                             (2007)
cancers             dimerization
                    inhibitors (HDIs)
                    and EGER inhibitors
                    for tumors
                    expressing HER2 and

Compounds for       This invention       2007/           Ekstrom et al.
potentiating and    describes methods    US20070264241   (2007)
augmenting          for using
Cancer Therapy      nucleoside
                    analog prodrugs for
                    augmenting cancer

Composition and     This invention is    2008/           Kim et al.
methods for         related to a         US20080268072   (2008)
enhancing the       composition
antiproliferative   enriched
effect of           with 3-0-
Pulsatillas radix   [O-[alpha]-L-
                    hederagenin which
                    shows strong
                    antitumor by enzyme
                    -reacting and
                    Pulsatiliac radix

Development of      This invention       2008/           Scott (2008)
methods to          relates to methods   US20080026400
identify most       which uses a
potent bioactive    specific
agents and          type of assay
synergistic         system, the
combinations        Multi-Pathway High
                    Throughput Assay,
                    in combination with
                    a novel
                    strategy, in which
                    repetitive cycles
                    experiments result
                    in the
                    identification of
                    the most
                    combinations of
                    potential active
                    agents from a
                    library of

Method of using     This invention       2008/           Adimooiam et
histone             demonstrates         US20080153877   al.
deacetylase         advantageous                         (2008)
inhibitors          effects of a
and monitoring      combinational
biomarkers in       therapy including a
combination         histone
therapy             deacetylase
                    inhibitor and
                    another therapeutic
                    agent as well
                    forecasting the
                    between them.

Hixed drug          This invention       2008/           Louie et
proportions for     describes a          US20080I99515   al.(2008)
treatment of        pharmaceutical
hematopoietic       composition
tumors and cancer   comprising a fixed,
disorders           non-antagonistic
                    molar ratio of
                    cytarabine and an
                    anthracycline for
                    hematologic cancers
                    or proliferative

Methods and         The invention        2008/           Borisyetal.
screening system    describes a method   L1S20D80194421  (2008)
for identifying     for screening and
Drug-drug           identifying drug-
interactions        drug interactions

Combination cancer  This invention       2008/           Xu et al.
treatment with a    demonstrates the     US20080159980   (2008)
GST-activated       synergistic effects
antiproliferative   of
molecule and        effective dose a
another anticancer  GST-activated
therapy             anticancer
                    and a
                    effective dose of
                    anticancer therapy

Combination Cancer  This invention       2008/           Arnold
therapy             relates to the       US200802G7957   et al.(2008)
                    evaluation of
                    therapy using an
                    anti-cancer agent
                    an IGF1R inhibitor

Phyto-              This invention       2008/           Rangel and
nutraceurical       demonstrates that a  US20080260771   Angel
synergistic         specific                             (2008)
composition         combination of
for Prostate        extracts of plants
disorder(s)         and nutraceuticals
                    possess synergistic
                    effects, with
                    minimal side
                    for treatment of
                    prostate disorders

Compositions and    This invention is    2008/           Majeed (2008)
methods to          related to a         U520080226571
provide             composition
enhanced            containing
photoprotection     Labdane-
against UV A and    diterpenoids that
UV  induced        provides better
insult of human     photo
skin                protection against
                    both UV A and UV A
                    radiations in
                    the HaCaT human
                    keratinocyte cell

Pharmaceutical      This invention       2008/           Chu
composition and     relates to the       US20O80113042   et al.(2008)
method for          Synergistic effects
cancer therapy      geranium essential
based on            oil or its chemical
combinational use   constituents and
of conventional     a chemotherapeuric
anticancer agents   agent or plant
and                 extract in
geranium essential  treatment of
oil or compounds    different cancers

Combination         This invention       2008/           Moodleyand
products            relates to a         US20080020018   Coulter
                    pharmaceutical                       (2008)
                    methyxanthine as
                    one active agent,
                    and at
                    least containing a
                    corticosteriod as
                    another active

Combination         This invention       2009/           Johnstone et
formulations of     demonstrates useful  U52G090074848   al. (2009)
platinum agents     effects of a
and cytidine        cytidine
analogs             analog and a
                    platinum agent in
                    therapeutic effects
                    when are used in

Method for          This invention       2009/           Lanzara
determining drug-   describes how to     US200900127I7   (2009)
molecular           combine
combinations that   pharmaceutical or
modulate and        biological
increase            molecules or drugs
the therapeutic     in
safety and          order to prepare
effectiveness of    specific ratio
pharmaceutical      combinations that
drugs               are
                    adjusted to
                    increase the
                    overall safety and
                    efficacy of the
                    molecules or drugs
                    while minimizing
                    side effects and
                    more economical.

Fixed ratio drug    This invention       2009/           Andrew et al.
combination         relates to the       US20090023680   (2009)
therapy for solid   methods for
tumors              treating
                    cancer by
                    administering a
                    containing a fixed,
                    molar ratio of
                    irinotecan and

Potentiator of      The invention        2009/           Pichette and
anticancer agents   relates to using     US20090286865   Legault
in cancer           essential oil                        (2009)
treatment           terpene or
                    derivative thereof
                    as a potentiator
                    for increasing
                    therapeutic effect
                    of an anticancer
                    agent (paclitaxel)

Combinatorial anti  This invention is    2009/           Buck et
- cancer therapy    related to           US20090274698   al.(2009)
                    combination therapy
                    comprising an anti
                    -cancer agent that
                    increase pAkt
                    levels in tumor
                    cells and an mTOR
                    inhibitor that
                    binds to and
                    directly inhibits
                    both mTORCI and
                    mTORC2 kinases

Anticancer,         This invention       2009/           Ricciardiello
chemopreventive.    relates to using     US20090048187   et al.
and                 compositions                         (2009)
Anti-               extracted
inflammatory        from pinoresinol-
effects of          rich Oka europaea
pinoresinol-        Caiazzana olives
rich                in treating cancer
olives              and its synergic
                    effects with a
                    isolated from Oka
                    europaea Caiazzana

Cucurbitacin 8 and  This invention       2009/           Xie et al.
its uses            demonstrates         US20090247495   (2009)
                    methods for
                    preventing or
                    treating various
                    disorders by
                    cucurbitacin A

Flavopereirine and  This invention       2009/           Hail and
alstonine           presents a method    US20090215853   Beljanski
cocktails in the    for administration                   (2009)
treatment and       an effective dose
prevention of       of a cocktail of
prostate cancer     flavopereirine and
                    alstonine for
                    preventing prostate
                    cancer and/or
                    decreasing PSA

Cancer therapy      This invention       2009/           Shuangand Ci
                    relates to           US2D09008240G   (2009)
                    presenting a method
                    of regulating the
                    cell cycle and
                    treating cancer
                    with a peroxisome
                    activated receptor
                    agonist and a
                    mevalonate pathway

Role of synergism in the antimicrobial properties of essential oils (E0s)

The antimicrobial properties of E0s have been reported in several studies. In many cases the activity results from the complex interactions between the different classes of compounds such as phenols, aldehydes, ketones, alcohols, esters, ethers or hydrocarbons found in E0s. Though in some cases, the bioactivities of E0s are closely related with the activity of the main components of the oils. Several studies have found that a number of these compounds exhibited significant antimicrobial properties when tested separately. It has been reported that E0s containing aldehydes or phenols, such as cinnamaldehyde, citral, carvacrol, eugenol or thymol as major components showed the highest antibacterial activity, followed by E0s containing terpene alcohols (Bakkali et al., 2008: Burt, 2004). Other E0s, containing ketones or esters, such as [beta]-myrcene, [alpha]-thujone or geranyl acetate had much weaker activity. While volatile oils containing terpene hydrocarbons were usually inactive. Different terpenoid components of E0s can interact to either reduce or increase antimicrobial efficacy. The interaction between EO compounds can produce four possible types of effects: indifferent, additive, antagonistic, or synergistic effects. Interestingly, phenolic monoterpenes and phenylprcpanoids (typically showing strong antimicrobial activities) in combination with other components were found to increase the bioactivities of these mixtures. Most of the studies have focused on the interaction of phenolic monoterpenes (thymol, carvacrol) and phenylpropanoids (eugenol) with other groups of components, particularly with other phenols, phenylpropanoids and monoterpene alcohols, while monoterpenes and sesquiterpenes hydrocarbons were used to a lesser extent (Table 5). The combination of phenolics with monoterpene alcohols produced synergistic effects on several microorganisms, in particular, the combination of phenolics (thymol with carvacrol, and both components with eugenol) were synergistically active against E. coli strains. Though other reports have observed additive and antagonism effects (Ben Arfa et al., 2006; Cox et al., 2001; Hammer et al., 1999; Juliani et al., 2002; Lambert et al., 2001) (Table 5).

Table 5 Combination of essential oils and components and
their antimicrobial interactions against several

Pair combinations          Organism                 Methods

Thymol/carvacrol           Staphylococcus aureus    Half

                           Pseudomonas aeruginosa

                           Escherichia coli         Checkerboard

                           S. aureus. Bacillus      Checkerboard

                           E coli

                           S. aureus, P.            Mixture

                           E. coli                  Checkerboard

Thymol/eugenol             E. coli                  Checkerboard

Carvacrol/eugenol          E. coli                  Checkerboard

                           S. aureus. B. cereus, E  Checkerboard

Carvacroi/cymene           B. cereus                Mixture

Carvacrol/linalool         Listeria monocytogenes.  Checkerboard
Eugenol/linalool           Enterobacter

Eugenol/menthol            aerogenes. E. coli. P.

Cinnamaldehyde/eugenol     Staphylococcus sp.,       Mixture
                           Micrococcus sp.,

                           Bacillus sp., and
                           Enterobacter sp.

1.8-Cineole/aromadendrene  Methieillin-resisranr   Checkerboard
                           S. aureus (MRSA)


                           (VRE) Enterococcus

[alpha]-Pinene/limonene    Saccliaromyces           Checkerboard

[alpha]-Pinene/linalaol    L monocytogenes.         Mixture
Linalool/terpinen-4-ol 0.  Yersinia
vulgare/Rosmarinus         enterocolitica.
officinalis 0.             Aeromonas hydrophilla.
vulgare/T. vulgaris        P. fluorescens

Lippia multiflora/Mentha   E. coli. E. aerogenes,   Checkerboard
piperita L                 Enterococcus
imiltifiora/O. basiiicum   faecalis, L.
M.                         monocytogenes. P.
piperita/0, basilicum       aeruginosa,
                           Salmonella enterica, S.
                           Shigella, dysenteriae,
                           S. aureus E. coli. E.
                           aerogenes, E. faecalis.
                           L monocytogenes

Pair combinations          Interaction  References

Thymol/carvacrol           Additive     Lambert etal.

                           Synergism    Pei etal.


                           Additive     Lambert et
                                        al. (2001)

                           Additive     Rivas etal.

Thymol/eugenol             Synergism    Pei
                                        et al.(2009)

Carvacrol/eugenol          Synergism    Pei et al.


Carvacroi/cymene           Synergism    Ultee et

Carvacrol/linalool         Synergism    Bassole etal.
Eugenol/linalool                        (2010)


Cinnamaldehyde/eugenol     Additive     Moleyarand

1.8-Cineole/aromadendrene  Additive     Mulyaningsih
                                        et al.(2010)

[alpha]-Pinene/limonene     Synergism,   Tserennadmid
                           additive     et al.

[alpha]-Pinene/linalaol     Synergism

Linalool/terpinen-4-ol 0.
officinalis 0.
vulgare/T. vulgaris

Lippia multiflora/Mentha   Synergism,   Bassole etal.
piperita L                 additive     (2010)

imiltifiora/O. basilicum
piperita/0, basiiicum


Allescher, H.D., 2006. Functional dyspepsia-a multicausal disease and its therapy. Phytomedicine 13 (Suppl. 5). 2-11.

Adimoolam, S., Buggy, J.J., Magda, D., Miller, R., 2008. Method of using histone deacetylase inhibitors and monitoring biomarkers in combination therapy, US20080153877.

Ammirante, M., Di Giacomo, R., De Martino, L, Rosati, A., Festa, M., Gentilella, A., Pascale, M.C., Belisario, M.A., Leone, A., Turco, M.C., De Feo, V., 2006. 1-Methoxy-canthin-6-one induces c-Jun NH2-terminal kinase-dependent apoptosis and synergizes with tumor necrosis factor-related apoptosis-inducing ligancl activity in human neoplastic cells of hematopoietic or endodermal origin. Cancer Research 66, 4385-4393.

Andrew, J., Lawrence, M., John, R., Gerald, B., Christine, S., Karen, G., 2009. Fixed ratio drug combination treatments for solid tumors, 1JS20090023680.

Arnold, L.D., JI, Q.S.. Buck, E., Haley, J.D., Mulvihill, M.J., 2008. Combination cancer therapy. US20080267957.

Baker, D., Pryce, G., Croxford, J.L., Brown, P., Pertwee, R.G., Huffman, J.W., Layward, L., 2000. Cannabinoids control spasticity and tremor in a multiple sclerosis model. Nature 404, 84-87.

Bakkali. F., Averbeck, S., Averbeck, D., ldaomar, M., 2008. Biological effects of essential oils - a review. Food and Chemical Toxicology 46, 446-475.

Barthomeuf, C., Demeule, M., Grassi, J., Saidkhocljaev, A., Beliveau. R., 2006. Con-ferone from Ferula schtschurowskiana enhances vinblastine cytotoxicity in MDCK-MDR1 cells by competitively inhibiting P-glycoprotein transport. Planta Medicine 72, 634-639.

Bassole, I.H., Lamien-Meda, A., Bayala, B., Tirogo, S., Franz, C.. Novak, J., Nebie, R.C., Dicko, M.H., 2010. Composition and antimicrobial activities of Lippia multiflora Molclenke, Mentha x piperita L and Ocimttm basilicum L. essential oils and their major monoterpene alcohols alone and in combination. Molecules 15, 7825-7839.

Ben Arfa, A., Combes, S., Preziosi-Belloy, L, Gontard, N., Chalier, P., 2006. Antimicrobial activity of carvacrol related to its chemical structure. Letters in Applied Microbiology 43, 149-154.

Berenbaum, M.C., 1989. What is synergy? Pharmacological Reviews 41, 93-141.

Blick, C., Hall. P., Pwint, T., Al-Terkait, F., Crew, J., Powles, T.. Macaulay. V., Munro, N.. Douglas, D., Kilbey, N., Protheroe, A.. Chester, J.D., 2012. Accelerated methotrexate, vinblastine, doxorubicin, and cisplatin (AMVAC) as neoadjuvant chemotherapy for patients with muscle-invasive transitional cell carcinoma of the bladder. Cancer 118, 3920-3927.

Borisy, A., Grail, D.. Stockwell, B.R., Keith, C., 2008. Screening system for identifying drug-drug interactions and methods of use thereof, US20080194421.

Britten, C.D., 2004. Targeting ErbB receptor signaling: a pan-ErbB approach to cancer. Molecular Cancer Therapeutics 3, 1335-1342.

Buck, A.E., Eyzaguirre, A., Bhagwat. S., Barr, S., Russo, S., 2009. Combination anticancer therapy, US20090274698.

Burt, S., 2004. Essential oils: their antibacterial properties and potential applications in foods-a review. International Journal of Food Microbiology 94,223-253.

Carnesecchi, S., Langley, K., Exinger. F., Gosse, F., Raul, F., 2002. Geraniol, a component of plant essential oils, sensitizes human colonic cancer cells to 5-fluorouracil treatment. Journal of Pharmacology and Experimental Therapeutics 301,625-630.

Chan, A., Gong, Q., Martin, F., 2005. Combination therapy for B cell disorders, US20050095243.

Chan, E.D., lseman, M.D., 2002. Current medical treatment for tuberculosis. British Medical Journal 325, 1282-1286.

Chou, T.C., 2006. Theoretical basis, experimental design, and computerized simulation of synergism and antagonism in drug combination studies. Pharmacological Reviews 58, 621-681.

Chou, T.C., 2010. Drug combination studies and their synergy quantification using the Chou-Talalay method. Cancer Research 70, 440-446.

Chou, T.C., Talalay, P., 1983. Analysis of combined drug effects: a new look at a very old problem. Trends in Pharmacolgical Science 4, 450-454.

Chou, T.C., Talalay, P., 1984. Quantitative analysis of dose-effect relationships: the combined effects of multiple drugs or enzyme inhibitors. Advances in Enzyme Regulation 22, 27-55.

Chu, K., Xie, W., Ho, C.. 2008. Pharmaceutical composition and method for cancer treatment based on combinational use of conventional anticancer agents and geranium oil or compounds thereof, US20080113042.

Corson, T.W., Crews, C.M., 2007, Molecular understanding and modern application of traditional medicines: triumphs and trials. Cell 130, 769-774.

Cox, S.D., Mann, C.M., Markham, J.L.. 2001. Interactions between components of the essential oil of Melaleuca alternifolia. Journal of Applied Microbiology 91, 492-497.

Dancey, J.E., Chen, H.X., 2006. Strategies for optimizing combinations of molecularly targeted anticancer agents. Nature Reviews Drug Discovery 5. 649-659.

Davis, D.A., Sarkar. S.H., Hussain, M., Li, V., Sarkar, F.H., 2006. Increased therapeutic potential of an experimental anti-mitotic inhibitor SB715992 by genistein in PC-3 human prostate cancer cell line. BMC Cancer 6, 22.

Douglas, N.M., Anstey, N.M., Angus, B.J., Nosten, F., Price, R.N., 2010. Artemisinin combination therapy for vivax malaria. The Lancet Infectious Diseases 10, 405-416.

Duarte, N., Varga, A., Cherepnev, G., Radics, R., Molnar, J., Ferreira, M.J., 2007. Apoptosis induction and modulation of P-glycoprotein mediated multidrug resistance by new macrocyclic lathyrane-type diterpenoids. Bioorganic and Medicinal Chemistry 15, 546-554.

Efferth, T., Koch, E.. 2011. Complex interactions between phytochemicals: the multi-target therapeutic concept of phytotherapy. Current Drug Targets 12, 122-132. Ekstrom, T.J.. Almqvist, P.M., Asklund, T.H., 2007, Compounds for enhanced cancer therapy, US20070264241.

El-Rayes, B.F., All, S., Mi, I.F., Philip. P.A.. Abbruzzese, J., Sarkar, F.H..2006. Potentiation of the effect of erlotinib by genistein in pancreatic cancer: the role of Ala and nuclear factor-kappaB. Cancer Research 66, 10553-10559.

Farabegoli, F., Papi, A., Bartolini, G., Ostan, R., Orland i, M., 2010. (-)-Epigallocatechi n3-gal late downregulates Pg-P and BCRP in a tamoxifen resistant MCF-7 cell line. Phytomedicine 17, 356-362.

Frantz, S., 2005. 2004 approvals: the demise of the blockbuster? Nature Reviews Drug Discovery 4, 93-94.

Frantz, S., 2007. Pharma faces major challenges after a year of failures and heated battles. Nature Reviews Drug Discovery 6, 5-7.

Friese, J., Gleitz, J., 1998. Kavain, dihydrokavain, and dihydromethysticin non-competitively inhibit the specific binding of [31-11-batrachotoxinin-A 20-alpha-benzoate to receptor site 2 of voltage-gated Na channels. Planta Medicine 64,458-459.

Gaube, F., Wolfl. S., Pusch, L., Kroll, T.C.. Hamburger, M.. 2007. Gene expression profiling reveals effects of Chnicifuga racernosa (L.) NUTT. (black cohosh) on the estrogen receptor positive human breast cancer cell line MCF-7. BMC Pharmacology 7, 11.

Gertsch, J., 2011. Botanical drugs, synergy, and network pharmacology: forth and back to intelligent mixtures. Planta Medicine 77, 1086-1098.

Ghosh, D., Bose, A., Hague, E., Baral, R.. 2006. Pretreatment with neem (Azadirachta indica) leaf preparation in Swiss mice diminishes leukopenia and enhances the antitumor activity of cyclophosphamide. Phytotherapy Research 20.814-818.

Hall, J., Beljanski, S.. 2009. Flavopereirine and alstonine combinations in the treatment and prevention of prostate cancer, US20090215853.

Hammer, K.A., Carson, C.F., Riley, T.V., 1999. Antimicrobial activity of essential oils and other plant extracts. Journal of Applied Microbiology 86, 985-990. Horwitz, S.B., McDaid, H.M., Martello, LA., 2003. Method for treating neoplasia using combination chemotherapy, US6541509.

Hynes, N.E., Lane, N.A., 2005. ERBB receptors and cancer: the complexity of targeted inhibitors. Nature Reviews Cancer 5, 341-354.

Jemal, A., Murray, T., Ward, E., Samuels, A., Tiwari, R.C., Ghafoor, A., Feuer, E.J., Thun, M.J., 2005. Cancer statistics. 2005. CA: A Cancer Journal for Clinicians 55, 10-30.

Johnston, S.R., 2005. Combinations of endocrine and biological agents: present status of therapeutic and presurgical investigations. Clinical Cancer Research 11, 889s-899s.

Johnstone, S., Harvie, P., Tardi, P., Harasym, T., Mayer, L. 2009. Combination formulations of cytidine analogs and platinum agents, US20090074848.

Juliani Jr., FIR., Biurrun, F., Koroch, A.R., Oliva. M.M., Demo, M.S., Trippi. V.S., Zygadlo, J.A., 2002. Chemical constituents and antimicrobial activity of the essential oil of Lantana xenica. Planta Medicine 68, 762-764.

Sy-Cordero, A.A., Ettefagh, K.A., Burns, J.T., Micko, K.T., Graf, T.N., Richter, S.J., Cannon, R.E., Oberlies, N.H., Cech, N.B., 2011. Synergy-directed fractionation of botanical medicines: a case study with goldenseal (Hydrastis canadensis). Journal of Natural Products 74. 1621-1629.

Jussofie, A., Schmiz, A., Hiemke, C., 1994. Kavapyrone enriched extract from Piper methysticum as modulator of the GABA binding site in different regions of rat brain. Psychopharmacology (Berlin) 116.469-474.

Kalan, L., Wright, G.D., 2011. Antibiotic adjuvants: multicomponent anti-infective strategies. Expert Reviews in Molecular Medicine 13, e5.

Keledjian. J., Duffield, P.H., Jamieson, D.D., Lidgard, R.O., Duffield, A.M., 1988. Uptake into mouse brain of four compounds present in the psychoactive beverage kava. Journal of Pharmaceutical Sciences 77, 1003-1006.

Kim, S.E., Kim, Y.H., Kim, Y.C., Lee, JJ., 1998. Torilin, a sesquiterpene from Torilisjapon-ica, reverses multidrug-resistance in cancer cells. Planta Medicine 64. 332-334.

Kim, S.-B., An, BJ., Kim, FLY., Kim, J.S., Kim, J.U., Bang, S.C., Lee, J.F1., 2008. Method of improving anticancer effect of pulsatillae radix and a composition prepared by the method, US20080268072.

Kiss, A., Kowalski, J., Melzig, M.F., 2006. Induction of neutral enclopeptidase activity in PC-3 cells by an aqueous extract of Epilobitrm angustifolium L. and oenothein B. Phytomedicine 13, 284-289.

Krishna, R., Mayer, LD., 2000. Multidrug resistance (MDR) in cancer: mechanisms, reversal using modulators of MDR and the role of MDR modulators in influencing the pharmacokinetics of anticancer drugs. European Journal of Pharmaceutical Sciences 11, 265-283.

Kubinyi, H., 2003. Drug research: myths, hype and reality. Nature Reviews Drug Discovery 2, 665-668.

Lambert, R.J., Skandamis, P.N., Coote, P.J., Nychas, G.J., 2001. A study of the minimum inhibitory concentration and mode of action of oregano essential oil, thymol and carvacrol. Journal of Applied Microbiology 91, 453-462.

Lanzara, R.G., 2009. Method for determining drug-molecular combinations that modulate and enhance the therapeutic safety and efficacy of biological or pharmaceutical drugs, US20090012717.

Lee, E., Enomoto, R., Suzuki, C., Ohno, M., Ohashi, T., Miyauchi, A., Tanimoto, E., Maeda, K., Hirano, H., Yokoi, T., Sugahara, C.. 2007. Wogonin, a plant flavone. potentiates etoposide-induced apoptosis in cancer cells. Annals of the New York Academy of Sciences 1095, 521-526.

Lee, F.Y., 2003. Synergistic methods and compositions for treating cancer, US6537988.

Legault,J., Pichette, A.. 2007. Potentiating effect of beta-caryophyllene on anticancer activity of alpha-humulene, isocaryophyllene and paclitaxel. Journal of Pharmacy and Pharmacology 59, 1643-1647.

Li, J.W., Vederas, J.C., 2009. Drug discovery and natural products: end of an era or an endless frontier? Science 325, 161-165.

Li, Y., Kucuk, 0., Hussain, M., Abrams, J., Cher, M.L., Sarkar, F.H., 2006. Antitumor and antimetastatic activities of docetaxel are enhanced by genistein through regulation of osteoprotegerinfreceptor activator of nuclear factor-kappaB (RANK)/RANK ligand/MMP-9 signaling in prostate cancer. Cancer Research 66.4816-4825.

Lindenberg, D., Pitule-Schodel, H., 1990. D, L-Kavain in comparison with oxazepam in anxiety disorders. A double-blind study of clinical effectiveness. Fortschritte der Meclizin 108. 49-50, 53-44.

Louie, A., Swenson, C., Mayer. L, Janoff, A., 2008. Fixed drug ratios for treatment of hematopoietic cancers and proliferative disorders, US20080199515.

Mai, Z., Blackburn, G.L, Zhou, J.R., 2007. Soy phytochemicals synergistically enhance the preventive effect of tamoxifen on the growth of estrogen-dependent human breast carcinoma in mice. Carcinogenesis 28, 1217-1223.

Majeed, M., 2008. Compositions and methods to effect enhanced photoprotection against UV A and UV B induced damage of human skin, US20080226571.

Matsuura, M., Nakazawa, H., Hashimoto. T., Mitsuhashi, S., 1980. Combined antibacterial activity of amoxicillin with clavulanic acid against ampicillin-resistant strains. Antimicrobial Agents and Chemotherapy 17, 908-911.

Meijerman, I., Beijnen, Schellens, J.H., 2008. Combined action and regulation of phase II enzymes and multidrug resistance proteins in multidrug resistance in cancer. Cancer Treatment Reviews 34,505-520.

Menendez, J.A., Vellon, L., Colomer, R., Lupu, R., 2005. Oleic acid, the main monounsaturated fatty acid of olive oil, suppresses Her-2/neu (erbB-2) expression and synergistically enhances the growth inhibitory effects of trastuzumab (Herceptin) in breast cancer cells with Her-2/neu oncogene amplification. Annals of Oncology 16, 359-371.

Mohammad, R.M., Wang, S., Banerjee, S., Wu, X., Chen, J., Sarkar, F.H., 2005. Non-peptidic small-molecule inhibitor of BcI-2 and Bcl-XL, (-)-Gossypol, enhances biological effect of genistein against BxPC-3 human pancreatic cancer cell line. Pancreas 31, 317-324.

Moleyar, V., Narasi m ham, P., 1992. Antibacterial activity of essential oil components. International Journal of Food Microbiology 16, 337-342.

Moodley, J., Coulter, I., 2008. Combination products, US20080020018.

Mulyaningsih, S., Sporer, F., Zimmermann, S., Reichling, J., Wink, M., 2010. Synergistic properties of the terpenoids aromadendrene and 1,8-cineole from the essential oil of Eucalyptus globulus against antibiotic-susceptible and antibiotic-resistant pathogens. Phytomedicine 17, 1061-1066.

Papazisis, K.T., Kalemi, T.G., Zambouli, D., Geromichalos, G.D., Lambropoulos. A.F., Kotsis, A., Boutis, LL, Kortsaris, A.H., 2006. Synergistic effects of protein tyrosine kinase inhibitor genistein with camptothecins against three cell lines in vitro. Cancer Letters 233, 255-264.

Patwardhan, B., Vaidya, A.D., Chorghade, M.. Joshi. S.P., 2008. Reverse pharmacology and systems approaches for drug discovery and development. Current Bioactive Compounds 4, 201-212.

Pei, R.S., Zhou, F., Ji, B.P., Xu, J., 2009. Evaluation of combined antibacterial effects of eugenol. cinnamaldehyde. thymol, and carvacrol against E. coli with an improved method. Journal of Food Science 74, M379-M383.

Pichette, A., Legault, J., 2009. Potentiator of antitumoral agents in the treatment of cancer, US20090286865.

Pittler, M.H., Ernst, E., 2000. Efficacy of kava extract for treating anxiety: systematic review and meta-analysis. Journal of Clinical Psychopharmacology 20,84-89. Qiu, J.. 2007. Traditional medicine: a culture in the balance. Nature 448. 126-128. Rajesh, D., Howard, S.P., 2003. Perillyl alcohol mediated radiosensitization via augmentation of the Fas pathway in prostate cancer cells. Prostate 57, 14-23. Rajesh, D., Stenzel, R.A., Howard, S.P., 2003. Perillyl alcohol as a radio- icheinosensitizer in malignant glioma. The Journal of Biological Chemistry 278, 35968-35978.

Rangel. 0., Angel, J., 2008. Prostate disorder(s) phyto-nutraceutical synergistic composition, US20080260771.

Ricciardiello, L. Boland, R.C., Roman, M., Fogliano, V., 2009. Chemopreventive. anticancer and anti-inflammatory effects of pinoresinol-rich olives, US20090048187.

Rivas, L. McDonnell, Mj., Burgess. C.M., O'Brien, M., Navarro-Villa, A., Fanning, S., Duffy, G., 2010. Inhibition of verocytotoxigenic Escherichia coli in model broth and rumen systems by caivacrol and thymol. International Journal of Food Microbiology 139, 70-78.

Sailer, R., Pfister-Hotz, G., [ten, F., Melzer, J., Reichling, J., 2002. lberogast: a modern phytotherapeutic combined herbal drug for the treatment of functional disorders of the gastrointestinal tract (dyspepsia, irritable bowel syndrome) - from phytomedicine to "evidence based phytotherapy."

A systematic review. Forsch Komplementarmed Klass Naturheilkd 9 (Suppl. 1), 1-20.

Schmidt, B.M., Ribnicky, D.M.* Lipsky, P.E., Raskin, 1., 2007. Revisiting the ancient concept of botanical therapeutics. Nature Chemical Biology 3, 360-366. Schulz, V., 2001. Incidence and clinical relevance of the interactions and side effects of Hypericurn preparations. Phytomedicine 8. 152-160.

Schulz, V., 2003. New therapeutic studies and meta-analysis. St. John's wort extract vs. synthetics. Pharm Unserer Zeit 32, 228-234, discussion 234-225.

Scott, I.R., 2008. Methods to identify biologically active agents and synergistic combinations, US20080026400.

Shuang, C.J., Ci, M., 2009. Cancer therapy, US20090082406.

Simmen, U., Higelin, J., Berger-Buter, K., Schaffner, W., Lundstrom, K., 2001. Neurochemical studies with St. Joh 11'S wort in vitro. Pharmacopsychiatry 34 (Suppl. 1), S137-S142.

SI iwkows ki, M.X.. Kelsey, S.M., 2007. Combination therapy of her expressing tumors, US20070020261.

Stermitz, FR., Lorenz, P., Tawara, J.N., Zenewicz, LA., Lewis, K.. 2000. Synergy in a medicinal plant: antimicrobial action of berberine potentiated by 5'-methoxyhydnocarpin, a multidrug pump inhibitor. Proceedings of the National Academy Sciences of the United States of America 97,1433-1437.

Susa, M., Choy, E., Yang. C.. Schwab, J., Mankin, H., Hornicek, F., Duan, Z., 2010. Multidrug resistance reversal agent. NSC77037, identified with a cell-based screening assay. Journal of Biomolecular Screening 15, 287-296.

Thayer, A.M., 2004. Blockbuster model breaking down. Modern Drug Discovery 7. 23-24.

Torres-Romero, D., Munoz-Martinez, F., Jimenez, I.A., Castanys, S., Gamarro, F., Bazzocchi, I.L., 2009. Novel dihydro-beta-agarofuran sesquiterpenes as potent modulators of human P-glycoprotein dependent multidrug resistance. Organic and Biomolecular Chemistry 7,5166-5172.

Tserennadmid, R., Tako, M., Galgoczy, L, Papp, T., Pesti, M., Vagvolgyi, C., Almassy, K., Krisch, J., 2011. Anti yeast activities of some essential oils in growth medium, fruit juices and milk. International Journal of Food Microbiology 144.480-486.

Tsuruo, T., 2003. Molecular cancer therapeutics: recent progress and targets in drug resistance. Internal Medicine 42, 237-243.

Ultee, A., Slump, R.A.. Steging, G., Smicl, E.J., 2000. Antimicrobial activity of carvacrol toward Bacillus cereus on rice. Journal of Food Protection 63, 620-624. van der Most, R.G., Himbeck, R., Aarons, S., Carter, S.J., Lartna, I., Robinson, C.. Currie, A., Lake, R.A., 2006. Antitumor efficacy of the novel chemotherapeutic agent coramsine is potentiated by cotreatment with CpG-containing oligodeoxynu-cleotides. Journal of Immunotherapy 29, 134-142.

Wagner. H., 2006. Multitarget therapy-the future of treatment for more than just functional dyspepsia. Phytomedicine 13 (Suppl. 5), 122-129.

Wagner, H., Ulrich-Merzenich, G., 2009. Synergy research: approaching a new generation of phytopharmaceuticals. Phytomedicine 16, 97-110.

Wang, C.Z., Luo, X., Zhang, B., Song, W.X., Ni, M., Mehendale, S., Xie, J.T., Aung, H.H., He, T.C., Yuan, C.S., 2007. Notoginseng enhances anti-cancer effect of 5-fluorouracil on human colorectal cancer cells. Cancer Chemotherapy and Pharmacology 60, 69-79.

Wang, F.. Wang, L., Yang, J., Chen, D., Jian, X., 2003. Preparation and drug composition of bis-benzylsoquinoline class alkaloids, US6617335.

Wang, C., Zhang, J.X.. Shen, X.L. Wan, C.K., Tse, A.K., Fong, W.F., 2004. Reversal of P-glycoprotein-mediated multidrug resistance by Aliso! B 23-acetate. Biochemical Pharmacology 68, 843-855.

Wang, L., Zhou, G.B., Liu, P., Song, J.H., Liang, Y., Van. Xu, F., Wang, B.S., Mao, J.H., Shen, Z.X., Chen, S.J., Chen, Z., 2008. Dissection of mechanisms of Chinese medicinal formula Realgar-Indigo naturalis as an effective treatment for promyelocytic leukemia. Proceedings of the National Academy of Sciences of the United States of America 105,4826-4831.

Westfall, S.D.. Nilsson, E.E., Skinner, M.K., 2008. Role of triptolicle as an adjunct chemotherapy for ovarian cancer. Chemotherapy 54,67-76.

Wilkinson, J.D., Whalley, B.J., Baker, D., Pryce. G., Constanti, A., Gibbons. S., Williamson, E.M., 2003. Medicinal cannabis: is delta9-tetrahydrocannabinol necessary for all its effects? Journal of Pharmacy and Pharmacology 55, 1687-1694.

Williamson, E.M., 2001. Synergy and other interactions in phytomedicines. Phy-tomedicine 8, 401-409.

Williamson, E.M., Evans, F.J., 2000. Cannabinoids in clinical practice. Drugs 60, 1303-1314.

Woelk, H., 2000. Comparison of St John's wort and imipramine for treating depression: randomised controlled trial. British Medical Journal 321,536-539.

Wu, C., Chen, F.. Rushing, .J.W., Wang, X., Kim, H.J., Huang, G., Haley-Zitlin, V., He, G., 2006. Antiproliferative activities of parthenolide and golden feverfew extract against three human cancer cell lines. Journal of Medicinal Food 9, 55-61.

Xie, W., Li, K., Liu, E., Chu, K., 2009. Cucurbitacin B and uses thereof, US20090247495. Xu, H., Brown, G.L., Schow, S.R., Keck, J.G., 2008, Combination cancer therapy with a GST-activated anticancer compound and another anticancer therapy. US20080159980.

Yeruva, L., Hall, C., Elegbede, J.A., Carper, S.W., 2010. Perillyl alcohol and methyl jasmonate sensitize cancer cells to cisplatin. Anticancer Drugs 21, 1-9.

Yeruva, L., Pierre, K.J., Elegbede, A., Wang, R.C., Carper, S.W., 2007. Perillyl alcohol and perillic acid induced cell cycle arrest and apoptosis in non small cell lung cancer cells. Cancer Letters 257, 216-226.

Zhang, X.Y., Bai, D.C., Wu, Y.J., Li, W.G., Liu, N.F., 2005. Proanthocyanidin from grape seeds enhances anti-tumor effect of doxorubicin both in vitro and in vivo. Phar-mazie 60, 533-538.

Zimmermann, G.R., Lehar, J., Keith, C.T., 2007. Multi-target therapeutics: when the whole is greater than the sum of the parts. Drug Discov Today 12, 34-42.

Zuardi, A.W., Shirakawa, I., Finkel farb, E., Karniol, I.G., 1982. Action of cannabidiol on the anxiety and other effects produced by delta 9-THC in normal subjects. Psychopharmacology (Berlin) 76, 245-250.

0944-7113/$--see front matter [c] 2013 Elsevier GmbH. All rights reserved.

Manzoor A. Rathera(a), *, Bilal A. Bhata (a), ** Mushtaq A. Qurishi (b)

(a) Medicinal Chemistry Division, Indian Institute of Integrative Medicine, Sanat Nagar, Srinagar, India

(b) Department of Chemistry, University of Kashmir, Srinagar, India

* Corresponding author. Tel.: +91 9622452835.

* Corresponding author.

E-mail addresses:, (M.A. Rather). (B.A. Bhat).


Is the drug combination strategy the future of drug discovery?    2
      Switching over from single drug to multi-drug therapy       2
      Existing multi-target therapeutics                          2
What synergy means in phytomedicine?                              3
Definition and proof of synergy                                   4
      Combination index (CI)                                      4
      Experimental evidence in favor of synergism                 5
            Example 1. Marihuana (Cannabis sativa)                5
            Example 2. St. John's Wort (Hypericum perforatum)     6
            Example 3. Iberogast[R] (a phytopreperation of        6
            nine plant extracts)
            Example 4. Kava Kava (Piper methysticum)              6
            Example 5. Antimicrobial action of berberine          6
            potentiated by 5'-methoxyhydnocarpin (5'-MHC)
Objectives of synergistic combinations                            6
Synergistic/antagonistic interactions of natural products         8
with clinically used anticancer and antimicrobial drugs
     Anticancer enhancing effects of isoprenoid natural           9
     products from essential oils
     Role of synergism in the antimicrobial properties of        10
     essential oils (E0s)
 References                                                      13
COPYRIGHT 2013 Urban & Fischer Verlag
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2013 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Rather, Manzoor A.; Bhat, Bilal A.; Qurishi, Mushtaq A.
Publication:Phytomedicine: International Journal of Phytotherapy & Phytopharmacology
Article Type:Report
Date:Dec 15, 2013
Previous Article:Saikosaponin a of bupleurum chinense (Chaihu) elevates bone morphogenetic protein 4 (BMP-4) during hepatic stellate cell activation.
Next Article:Antidyslipidemic and antioxidant activity of an unusual amino acid (2-amino-5-hydroxyhexanoic acid) isolated from the seeds of Crotalaria juncea.

Terms of use | Privacy policy | Copyright © 2020 Farlex, Inc. | Feedback | For webmasters