Ethnomedical and veterinary uses of Tephrosia vogelii Hook F (Fabaceae): a review.
Medicinal plants are the most ancient source of drugs for curing human and animal diseases. Their recognised biological actions led to their cultivation, even in antiquity, in Egypt, Greece, along the Mediterranean and in China. Almost one quarter of all medicines are derived from the 250,000 flowering plants on the earth's surface. Some of the secondary metabolites therein may be toxic to lower beings or man, or indeed both. Their use in the crude or refined form is of utmost interest in the efforts aimed at integrating herbal with orthodox medicine. With the understanding that only one in eight of the potential drugs has been found, it is estimated that more than 300 drugs are yet to be discovered in the rainforests worldwide (Balick 1996, Ekpendu 1998a, Satoh 2001).
The efficacy of plant extracts is due to the presence of one or more biologically active principle. Pharmacological assays have shown that the activity is not always due to the main components, but the minor ones, or even to the synergism of all the active principles (Galeffi 1980). With modern advances in the techniques for isolation and structure determination of active principles, even minute amounts of them can be isolated and their structures determined (Salemink 1980).
The aim of the present review was to highlight the ethnomedical and veterinary uses of the most common Tephrosia species and especially the great potential of pharmacologically active principles contained in T. vogelii in the therapy and prophylaxis of human and livestock diseases with special reference to the tropics.
Ethnomedical and veterinary use of Tephrosia spp.
The plant genus Tephrosia is a legume with about 300 species found in the tropical and subtropical regions of the world, some of which have been used for many beneficial purposes (Barnes 1967, Gaskins 1972). Tephrosia bracteolata Guill. & Perr is widespread in tropical Africa and provides grazing for horses and other livestock (Dalziel 1937). It is cultivated on the Ivory Coast as a fish poison. In Tanzania the pounded root is taken twice daily as a therapeutic agent by pregnant Sukuma women who are infected with syphilis (Burkill 1995). The leaf and root are used for charms in Northern Nigeria against injury by hunters and warriors (Dalziel 1937). Tephrosia candida (Roxb) DC has been used as fish poison in Bangladesh, Burma and Sierra Leone (Chadha 1976).
Tephrosia densiflora Hook. F. is very closely related to T. vogelii, and some authorities have taken it to be a variety. It is grown specifically for use as fish poison in West Africa. The leaves and sometimes the fruit pods are crushed and thrown into streams for fishing (Kerharo 1950). The plant has abortifacient properties and it is used against parasitic skin diseases (Oliver 1960).
The leaf of Tephrosia elegans Schum is occasionally cultivated for use as a fish poison. Where it is not cultivated the leaf is collected from wild plants, but is not a fish-poison of importance as foliage is generally sparse (Kerharo 1950). In South Africa an arrow poison is obtained from the root (Watt 1962). Tephrosia flexuosa G Don provides some grazing to cattle and other livestock. It is a fish poison, but not a particularly good one (Dalziel 1937). Tephrosia linearis (Willd.) Pers is grazed by all livestock in Senegal, pulped up leaves are used by the Fulanis to add to milk, millet or guinea corn pap as a seasoning. In North western Nigeria the plant is given as a postnatal medicine, although the purpose is not disclosed (Dalziel 1937). Tephrosia lupinifolia DC provides some grazing in Senegal for livestock. In Barotseland, West Zambia, a decoction obtained from the root is drunk as an abortifacient, acting to kill the fetus which is expelled in about 10 hours. The root is also used by women in suicide, the root being pounded into a bolus which is inserted into the vagina. This results into considerable local and abdominal swelling in about one hour and death ensues in 12-24 hours (Watt 1962).
Tephrosia nana Kotschy ex Schweinf is grazed by livestock in Eastern Cameroon. It serves as a fish poison on the Ivory Coast and Democratic Republic of Congo and is deemed to be as good as T. vogelii, with which it is sometimes mixed (Kerharo 1950). In the Congo (Brazzaville) the seed is used as bait in snares to catch rodents called nsibilikis, and in Nigeria Igbo people grind up the parched leaf for treating the sores of yaws (Burkill 1995). Tephrosia noctiflora Bak is cultivated in East and West Africa as a source of fish poison, but there is no report on its toxicity (Gillett 1971). Tephrosia nubica (Boiss) Bak provides grazing for livestock, and birds take the flowers and seeds in Turkana Kenya. The whole plant is infused to produce a drink taken by women after childbirth (Burkill 1995). Tephrosia pedicellata Bak is grown on the Ivory Coast to produce fish poison. In Sudan the Dinkas chew the root for throat and lung complaints (Burkill 1985). Tephrosia platycarpa Guill & Perr furnishes grazing for cattle, sheep and horses. The seed is oil bearing, yielding a cooking oil used in the Kordofan of Sudan (Burkill 1995).
The dried herb of Tephrosia purpurea (Linn.) Pers is used in medicine in India for its tonic, laxative, diuretic and deobostruant properties, for bronchitis and bilious febrile attacks, the treatment of boils, pimples and bleeding piles, and for cough and kidney disorders. The seed is said to be edible. The seed pod is used by extraction and administered for pain and inflammation, to stop vomiting and as a vermifuge. The seed oil is applied to scabies, itch, eczema and other eruptions of the skin (Chadha 1976, Rastogi 1990). In Tanzania the root slightly burnt is chewed for stomach pains. The root and leaf are recognised as purgative and emetic (Burkill 1995). It is used as a fish poison in Senegal and Gambia but its insecticidal action is low (Watt 1962). The plant has many medicinal uses in Senegal: for treating diarrhoea and whooping cough in children; vaginal douches; diarrhoea in adults, spasmodic coughing, fevers, sterility, rickets and syphilis (Kerharo 1964). In Nigeria the plant is used as a diuretic, blood purifier, a gargle and internally for coughs, colds etc. (Ainslie 1937).
Tephrosia subtriflora Hochst is often confused with T. uniflora and the latter's usages may apply (Gillett 1958). Tephrosia uniflora Pers provides grazing for cattle and elephants; stems are used as tooth brushes in Ethiopia. Stems and roots of the plant have been shown to be toxic to Bulinus globulus, a fresh water snail vector of schistosomosis (Adewunmi 1980). Some other Tephrosia species of less ethnomedical importance include Tephrosia deflexa Bak, T. gracilipes Guill & Perr, T. humilis Guill & Perr, T. mossiensis A Chev and T. radicans Welw Ex Bak.
The plant species Tephrosia vogelii is normally eaten in the wild by mammals, especially rabbits, with impunity, and is also grazed by domestic animals. It is used in traditional medicine as purgative and emetic, and for many other ethnomedical purposes. It is also widely distributed and readily available locally. The species is reviewed in detail below.
Morphology and taxonomy of Tephrosia vogelii Hook. F.
Tephrosia vogelii is a leguminous plant. It is a much branched shrub reaching up to 4 m high. It is always under cultivation, and ubiquitous in tropical Africa and India (Burkill 1995). The plant was first identified and named by the German botanist JT Vogel in Fernando Po and in Niger (Kerharo 1950). There are two morphologically alike forms differing only in flower colour, red or bluish purple commonly in West Africa, and white in East Africa (Dalziel 1937, Tattersfield 1960). The plant is easy to propagate by seed, seeding at 6-7 months, but taking about 3 years to reach maturity (Chadha 1976, Burkill 1995).
Tephrosia vogelii is a shrub, 1.83-3.05 m high, clothed with dense yellowish or rusty tomentum. The stems are more or less erect and the leaflets are five or more pairs. The flowers of the plant are 2 cm or more long and are densely crowded, conspicuous, red or red purple and in dense racemes. Fruits of Tephrosia vogelii are large and 2-12 cm long, very densely villous or tomentose (Hutchinson 1958). The shrub may grow as rapidly as 2-3 m in 7 months.
According to Gaskins et al (1972), the flower of T. vogelii is typically papilionaceous, about 2.5 cm across and purple with white markings or white. The flowers are borne on compact racemes that bloom over a 3 to 6 week period. There may be 20 to 30 flowers per raceme with up to 200 flowers per plant. Pods usually contain 8 to 16 seeds. The flowers have a faint but definite pleasant aroma, and bees visit them freely for both nectar and pollen. Flowering occurs on decreasing day lengths.
Taxonomy of Tephrosia vogelii
The plant belongs to the class Magnoliopsida (dicotyledons), subclass Rosidae order Fabales, family Fabaceae, genus Tephrosia Pers. and species vogelii Hook. F.--Vogel's tephrosia. Origin and geographical distribution of
Tephrosia vogelii is native to West Africa, including Nigeria, and other regions of tropical Africa in general, but is now found in India, Asia and other tropical regions (Dalziel 1937, Lambert 1993). According to Burkill (1995) the exact origin of the plant is uncertain. However an origin in Angola has been postulated (Kerharo 1950). It is cultivated throughout tropical Africa, particularly in West Africa and chiefly in the forest regions, but also in the Savannah zones (Lambert 1993). Tephrosia vogelii is cultivated around many villages, either casually or by riverine people in fields for use in stupefying fish (Dalziel 1937, Lambert 1993, Bajaj 1998). The principal use from which the very wide dispersal of the plant has arisen is as a fish poison (Burkill 1995). Although Tephrosia vogelii is a tropical plant, it has yielded well when grown as an annual in south eastern United States of America (Barnes 1966, 1967). According to Martin and Cabanillas (1970), the plant requires a tropical home for seed production.
Common names for Tephrosia vogelii
Some common names for Tephrosia vogelii in different parts of the world, compiled for Natural Products Alert (NAPRALERT) by the Board of Trustees, University of Illinois include: amena, anoume, bantaculudje, bantamaro, fish bean, dawa al sammaki, defa daba, diabi--die, diabi, diefa diaba, fish benan, igongo, kioubi, lembe, mbaga, mene, ndawole, ngudu, nyawula, ombwe, panghe, tebi, utapa. A synonymous Latin binomials for Tephrosia vogelii is Tephrosia aequilata (Quinn-Beattie 2000).
Ethnomedical uses of fish bean, Tephrosia vogelii
Many ethnomedical uses have been advocated for this plant. Apart from its wide spread use as a fish poison, it is cultivated to a lesser extent as part of a medicament for bone setting (Ekpendu 1998a). Ground leaves and stem bark are mixed with vegetable oil and rubbed on the skin around the fractured limb; pieces of cut stem are used to hold the broken limb in position; roots are boiled in water and when warm, feet with localised fungal infections are immersed therein for some minutes (Ekpendu 1998b).
In East Africa the leaf is used as an abortifacient (Bally 1937, Kerharo 1950). The hot water extract of the bark, leaf and unripe fruit has been used in Gabon to induce abortion in pregnant women (Walker 1961). In Guinea-Bissau a decoction of the hot water extract of the bark is used internally as an abortifacient (Viera 1959). A decoction of the hot water extract of the leaf is used in Guinea Conakry as an abortifacient (Vasileva 1969). On the Ivory Coast the hot water extract of the plant (part not specified) is used as an abortifacient (Kerharo 1950). In Cameroon the hot water extract of the leaf is drunk to induce menses (Haaf 1971).
The leaf macerate is purgative and emetic (Walker 1961, Burkill 1995). The crude methanolic extract of T. vogelii leaves has been shown to induce contraction of isolated rabbit jejunum (Dzenda 2004a) and guinea pig ileum (Dzenda 2004b) in a concentration dependent manner, supporting its use as purgative. The sap is added to palm wine to treat diarrhea (Burkill 1995). Pulped leaves and leaf sap obtained from the plant are used in Tanzania for ear ache, and root scrapings are applied to aching teeth (Watt 1962, Vergiat 1970).
In Angola it is one of the medicinal plants used as a piscicide, anthelminthic, insecticide and for treating tuberculosis (Bossard 1993), and as a bactericide (Roark 1937). Its anthelminthic property is dose dependent (Bossard 1993). The roots are used by natives to treat typhoid fever (Dalziel 1937). It is used in China as a botanical insecticide and fly repellent (Chiu 1989a, 1989b). Tephrosia vogelii has been shown to have toxic and repellent effects against certain insect pests of stored grains (Pandey 1986, Sharma 1992, Smith 2000, Ogendo 2004, Koona 2005) supporting the widespread use of the plant by local farmers as a grain protectant. Tephrosia has been used as a rat poison by compounding with ground nut (Dalziel 1937, Aliu 1996, Nwude 1997).
Powders of Tephrosia vogelii are effectively used in the Congo against the stored ground nut pest Caryedon serratus (Delobel 1987). In Nigeria it is used as a seed dresser for cereals and legumes (Nwude 1997). It is also applied directly to treat head lice, fleas, scabies and other ectoparasites (Klaassen 1996, Nwude 1997). The leaf extract has been observed to be highly toxic to one, two and three host ticks; cattle sprayed with the extract had a residual protection period from reinfection by ticks of 10 days (Kaposhi 1992). Fresh water snails have been found to be susceptible to extracts of crushed, unboiled root, and this could have some bearing in combating schistosomosis (Dalziel 1937, Kerharo 1950, Weiss 1973, Burkill 1995).
Biological activities for extracts of Tephrosia vogelii
Extracts of the leaf, bark, root, seed and/or flower of Tephrosia vogelii possess numerous biological activities when tested in the laboratory.
The water extract of the dried flowers, stem and leaves showed molluscicidal activity against Physopsis globosa (Cowper 1948). The water extract of the dried leaf possessed molluscicidal activity against Bulinus globosus (Chiotha 1986). The flower and flower bud of Tephrosia vogelii have been reported to be toxic to Bulinus (Physopsis) globosus (Adewunmi 1980). The petroleum ether extract of the plant demonstrated molluscicidal activity against Biomphalaria glabrata (Marston 1984). Ethanol (80%) extract of the dried leaf showed weak molluscicidal activity against Biomphalaria pfeifferi and Bulinus truncatus (Abdel-Aziz 1990). Water extract of oven dried stem, leaf and seed showed weak molluscicidal activity against Biomphalaria pfeifferi (Kloos 1987).
Ethanol (80%) extract of the dried fruit showed weak antibacterial activity against Staphylococcus aureus on agar plate, weak antiviral activity against measles virus on cell culture, strong antifungal activity against Microsporum canis; and weak antifungal activity against Trichophyton mentagrophytes on agar plate (Vlietinck 1995).
The hot water extract of the leaf showed piscicidal activity against goldfish Carassius auratus (Gaudin 1938).
Acetone extract of the leaf showed feeding deterrent activity against the insect Pieris rapae (Shin 1989), and the acetone extract of the seed showed larvicidal activity against Aedes aegypti (Manson 1939).
The methanolic leaf extract showed anthelminthic activity against Nippostrongylus braziliensis (Edeki 1997).
In view of its great potential in the therapy and prophylaxis of diseases, efforts have been made to identify and isolate the active compounds contained in the plant.
Compounds isolated from Tephrosia vogelii
Compounds isolated from T. vogelii include flavonoids, glycosides, steroids, tannins and reducing sugars (Ekpendu 1998b) (Table 1). Rotenone is the compound of primary interest in T. vogelii (as far as its insecticidal property is concerned) but it is usually found in combination with several related rotenoids, the principal one being deguelin (Barnes 1967).
Analysis of the rotenoid content of leaf extracts of T. vogelii showed that rotenolone, tephrosin, rotenone and deguelin are the main rotenoids produced (Lambert 1993). Rotenolone and tephrosin are believed to be the oxidation products of rotenone and deguelin respectively. Although rotenone is considered the most active (insecticidal) ingredient in T. vogelii, the other extractives also possess appreciable activity (Matsumura 1975).
Chemical structures, properties and beneficial effects of some compounds isolated from Tephrosia vogelii
The chemical structures of rotenone and its derivatives (collectively called rotenoids) were independently determined by Butenandt and McCartney (1932), Laforge and Haller (1932), and Takei et al (1932). The rotenoids are composed of an isoflavone nucleus (C6-C3-C6) with an isoprene moiety attached to it. They are classified into the isoflavonoid family, the end product of the phenylpropanoid pathway (Hahlbrock 1975). Rotenoids are advanced isoflavonoids (Crombie 1998).
Rotenone is colourless and odourless, and has an empirical formula of C23H22O6 and a molecular weight of 394.41. Its melting point is 165-166[degrees]C (Watt 1962, Ware 1983). It is very soluble in many organic solvents, for example alcohol and acetone, but is almost completely insoluble in water (Tomlin 2000). Rotenone is generally unstable and decomposes quickly in water, sometimes as fast as two weeks after its application. However it may persist for up to six months depending on a variety of factors including light, temperature, depth, dose and presence of organic debris (Copping 1998). Rotenone readily breaks down in the presence of light into at least 20 products, only one of which, 6ab, 12ab-rotenolone, is toxic. None of the other degradation products is toxic meaning it is considered safe for use on land and in water (Newsome 1980). The decomposition process occurs at a faster rate as the temperature of the water increases. The depth and the presence of organic debris in the water affect the amount of light and therefore the rate of rotenone degradation. Lack of light decreases the rate of degradation (Marking 1988). The two main commercial uses of rotenone today are as a piscicide and as an insecticide. Rotenone has acaricidal (lice, tick, mite and spider killing) properties (Menichini 1982, Hollingworth 1995). Although rotenone is considered the most insecticidal ingredient in T. vogelii, the other rotenoids (deguelin, rotenolone and tephrosin) also possess appreciable insecticidal activity (Hagermann 1972, Matsumura 1975, Uddin 1979).
Deguelin is a dimethoxylactone [(7aS, BaS)--13, 13a-dihydro-9, 10-dimethoxy-3, 3-dimethyl-3H-bis  benzo-pyrano [3, 4-b: 6', 5'-e] pyran-7 (7aH)-one], pale green in colour and has a chemical formula of [C.sub.23][H.sub.22][O.sub.6]; its melting point is 171[degrees]C. Deguelin mediates antiproliferative properties in a variety of cell types. It exerts its growth inhibitory effects via the induction of apoptosis. It was found to suppress the growth of HT-29 colon cancer cells, with an IC (50) of 4.32 x 10 (-8) M, through the induction of apoptosis and cell cycle arrest (Murillo 2002).
Tephrosin is a nearly colourless crystalline substance with a chemical formula of [C.sub.23][H.sub.22][O.sub.7] and melting point of 198 oC, and is thought to be the oxidation product of deguelin (Watt 1962, Murillo 2002).
The chemical formula of quercetin is C15H10O7-3D. It is a member of a group of naturally occurring compounds, the flavonoids, which have a common flavone nucleus composed of two benzene rings, linked through a heterocyclic pyrone ring. Quercetin is a water soluble plant pigment (Young 1999). The synonyms for quercetin are: CI natural yellow 10; CI 75670; cyanidelonon 1522; flavin meletin; quercetine; quercitol; quertin; quertine; sophoretin; xanthaurine; 3,3',4',5,7-pentahydroxyflavone; 3,5,7,3',4'-pentahydroxyflavone; 2-(3,4- dihydroxyphenyl)-3,5,7-trihydroxy-4H-1-benzopyran-4-one. Quercetin is a natural compound found in T. vogelii and it helps to reduce painful swelling because of its potent anti-inflammatory capabilities (Shoskes 1999). It is a water soluble plant pigment that may help prevent heart disease. It also blocks sorbitol accumulation, which seems to bring about nervous conditions in diabetics. Quercetin is an antihistamine, anti-inflammatory and an antioxidant agent. It promotes proper circulation of blood in the body (Stoewsand 1984, Ishikawa 1985, Castillo 1989, Hertog 1994, Miodini 1999). It is effective in reducing allergic reactions and may be beneficial in treating canker sores, hives, asthma and other inflammatory conditions (Lieberman 2003). Other conditions for which quercetin may be helpful include diabetes, dysentery, gout, cataracts, and atopic dermatitis (Duthie 1997, Hollman 1997, Young 1999, Damianaki 2000, Feng 2001, Begum 2002). Quercetin has been shown to possess antiviral properties (Weisburger 2000, Feng 2001).
Rutin, which is a component of T. vogelii, has important medicinal application in blood circulation and capillary fragility (Oliver-Bever 1982).
Toxicity of compounds isolated from Tephrosia vogelii
Rotenone is classified by the World Health Organisation (WHO) as a moderately hazardous compound Class II (2001). Although rotenone is considered the most toxic ingredient isolated from T. vogelii, the other extractives (rotenoids) also possess appreciable toxicity (Matsumura 1975).
Rotenone is the most insecticidal rotenoid and can act either as a contact or a stomach poison (Ware 1983, DeWilde 1986). It is a selective, non-systemic insecticide with some acaricidal properties (Kumar 1984). The poisoning of insects by rotenone is usually a slow process and is manifested in inactivity, locomotive instability, refusal to eat, knockdown, paralysis and slow death. The heart and respiratory rates are depressed (Matsumura 1975). The use of rotenone is permitted as an insecticide under European Union Regulation 2092/91, amended by 1488/97, Annex II (B).
In response to recent studies linking rotenone to Parkinson's disease (Betarbet 2000, Gaisson 2000), the UK Soil Association put a temporary ban on its use, pending further investigations. Rotenone is also highly toxic to fish, acting through the gills (Matsumura 1975): most values for the 96 hour LC50 (lethal concentration required to kill half the test organisms) for different fish species and for daphnids (water fleas) lie in the range of 0.02 to 0.2 mg/litre. If used as a piscicide it may also cause a temporary decrease in numbers of other aquatic organisms (Blommaert 1950,, Bourgois 1989, Bossard 1993). Rotenone is used to clear ponds of unwanted organisms and trash fish which may predate on fish when the ponds are stocked. Toxicity tests using water extract of the leaves of Tephrosia vogelii which contain rotenone, conducted on rotifers (Brachionus species), Cyclops, mosquito larvae (Culex species) and fish (Aphyosemion gardneri nigerianum) revealed that the fish A. gardneri nigerianum was the most sensitive; the mosquito larvae were the least sensitive (Agbon 2004).
Rotenone is also a potent poison for mammals. The mammalian oral L[D.sub.50] (the amount of the chemical lethal to one half of experimental animals) is of the order of 10-30 mg/kg. The mammalian toxicity of rotenone, however, varies greatly with the animal species, method of administration and type of formulation. The acute oral L[D.sub.50] of crystalline rotenone to rats is 132 mg/kg, to rabbits-3000 mg/kg, and to guinea pigs-60 mg/kg (O'Brien 1970, Matsumura 1975). The L[D.sub.50] for rats is between 132 and 1,500 mg per kilogram. One factor in this wide variation may be the difference in the plant extracts used (IPCS 2002). The acute oral toxicity of rotenone is moderate for mammals, but there is a wide variation between species. It is less toxic to the mouse and hamster than for the rat; the pig seems to be especially sensitive (Marking 1988).
Recent studies have shown that in rats, rotenone is more toxic for females than males. It is highly irritating to the skin and eyes of rabbits (IPCS 2002).
In rats and dogs exposed to rotenone in dust form, the inhalation fatal dose was uniformly smaller than the oral fatal dose. On the basis of data obtained from rabbit studies, absorption through the intact skin is low (Moriya 1983). Studies on dogs at high doses produced adverse changes in blood chemistry. In dogs fed rotenone at 10 mg/ml per day for six months, weight loss and haematological effects were found. A no observed adverse effects level (NOAEL) of 0.4 mg/kg per day has been determined for rats (2-year study), and dogs (16-month study) (Gosalvez 1983).
Fetotoxicity and death of offspring are reported in guinea pigs at doses of 4.5 and 9.0 mg/kg/day, and pregnant rats fed 5 mg/kg/day produced a significant number of young ones with skeletal deformities (Moriya 1983). The optimal dose of rotenone (administered by continuous infusion into the jugular vein of rats) for producing Parkinson-like pathology was found to be 2 to 3 mg/kg/body weight per day, clearly above the intravenous L[D.sub.50] (Betarbet 2000).
In animals rotenone is very poorly absorbed by the gastrointestinal tract and is so irritating that it promptly induces vomiting. However in prolonged feeding tests in rodents, rotenone caused growth depression. Test animals fed dust formulations of rotenone developed muscle tremors, severe pulmonary and skin irritation from exposure to dust, severe hypoglycaemia, clonic convulsions, and respiratory depression, resulting in death (Marking 1988).
The symptoms of rotenone poisoning in mammals include buccal numbness, nausea, vomiting, gastric pain, muscle tremors, incoordination, clonic convulsions and stupor. The respiration is first stimulated, later depressed and the immediate cause of death is asphyxia from respiratory paralysis (Watt 1962). Respiratory depression is the most marked symptom of poisoning by rotenone. Kidney and liver damages occur from chronic poisoning. In severe poisoning, convulsions and coma may occur (Matsumura 1975). Local application of rotenone produces skin irritation, and inhalation of the dust results in severe pulmonary irritation. Severe hypoglycaemia has been reported to follow the administration of rotenone to laboratory animals (Watt 1962).
Rotenone is believed to be moderately toxic to humans with an oral lethal dose estimated from 300 to 500 mg/kg. A lowest lethal dose of 143 mg/kg has been cited in a child (DeWilde 1986). The estimated lethal dose for man is 100-200 g/kg orally (Matsumura 1975). Human poisoning by rotenone is rare (Klaassen 1996). Clinical experience seems to indicate that children in particular are rather sensitive to the acute effects of rotenone (Newsome 1980). Human fatalities are rare, perhaps because its irritating action causes prompt vomiting. If the dust particle size is very small and can enter deep regions of the lungs, rotenone's toxicity when inhaled may be increased. Acute local effects include conjunctivitis, dermatitis, sore throat, congestion and vomiting. Inhalation of high doses can cause increased respiration followed by depression and convulsions (Gosalvez 1983).
Rotenone represents a curious example of a toxicant which is a metabolic inhibitor as well as a nerve poison (Matsumura 1975). It is a slow acting nerve poison which acts by inhibiting respiratory metabolism in cells, essentially paralyzing affected insects. It exerts its toxic action by acting as a general inhibitor of cellular respiration. Specifically rotenone interferes with the mitochondrial electron transport system (Fukami 1970, 1976). More precisely rotenone owes its inhibitory potency to its ability to interfere with the electron transport process between reduced diphosphopyridine nucleotide or reduced nicotinamide adenine dinucleotide (NADH) and cytochrome b. Inhibition of respiratory metabolism is one of the major causes of nerve conduction block by rotenone (Fukami 1970, Matsumura 1975). Rotenone is selectively toxic to fish and insects but mammals are more resistant.
The problems evident for rotenone are insufficient usage data, inconclusive studies, concern about unknown synergistic activity with other substances, and potential health hazards (DeWilde 1986).
In conclusion, Tephrosia vogelii contains many active principles of toxicological importance and offers great potential for use in therapy and prophylactics of human and livestock diseases.
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* Corresponding author email: email@example.com
* T. Dzenda (1), JO Ayo (1), AB Adelaiye (2), AO Adaudi (1)
(1) Department of Veterinary Physiology and Pharmacology
(2) Department of Human Physiology, Ahmadu Bello University, Zaria, Nigeria
Table 1 Chemical Substances Isolated from Tephrosia vogelii Part of Compound Nature plant used Reference Beta-sitosterol Steroid Fruit coat Kamal 1978, Pradhan 1988 Cholesterol Steroid Not stated Kamal 1978 Deguelin Flavonoid Leaf, stem Sharma 1975, Marston and root 1984, Lambert 1993 Elliptone Flavonoid Leaf, stem Sharma and Khanna 1975 and root Isoquercetrin Flavonoid Leaf Marston 1984 Lanosterol Steroid Fruit coat Pradhan 1988 Quercetin-3- Flavonoid Leaf Marston 1984 arabinopyranoside Rotenolone Flavonoid Not stated Lambert 1993 Rotenone Flavonoid Leaf, stem, Barnes 1967, Sharma root and 1975, Pradhan 1988, fruit coat Lambert 1993 Rutin Flavonoid Leaf Marston 1984 Stigmasterol Steroid Fruit coat Kamal 1978, Pradhan 1988 Tephrosin Flavonoid Leaf, stem, Sharma 1975, Marston root and 1984, Pradhan 1988, fruit coat Lambert 1993 Vogeloside Glycoside Seed Sambamurthy 1962
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|Title Annotation:||Global dispensary; Tephrosia vogelii Hook F|
|Author:||Dzenda, T.; Ayo, J.O.; Adelaiye, A.B.; Adaudi, A.O.|
|Publication:||Australian Journal of Medical Herbalism|
|Date:||Jun 22, 2008|
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