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Antioxydant activities from the aerial parts of Pulicaria jaubertii.

Introduction

The genus Pulicaria which belongs to the Asteraceae family (Compositae, trible Inuleae, subtrible Inulinae), comprises more than 77 species widespread all around the world (Dubaie and El-Khulaidi, 1993; Anderberg 1991). Chemically, this genus is not homogenous. As pointed out previously some species contain monoterpenes, diterpenes, sesquiterpene lactones (Abdel-Mogib et al 1990; Dendougui et al 2000). and caryophyllane derivatives (Hafez et al., 1987). Also the literature reports that Pulicaria species afforded different flavonoid profiles (Rizk et al., 1993). The Pulicaria species proved various activities such as antiinflammatory, antilukemic (Al-Yahaya et al., 1984). potential cancer chemopreventive and cytotoxic agents (AlYahaya et al., 1988).The Pulicaria jaubertii indigenous to Yemen, locally known as Anssif, is traditionally used as diuretic, pyritic conditions in urogenetic organs, and to cure fever. The flowers of Pulicaria jaubertii was also used as spice and to make various delicious foods. Some investigation reported that this species reveal antimicrobial, antifungal, antimalaria and insecticides properties (Dubaie and El-Khulaidi., 2005).

Free radicals are generated by a process known as redox cycling and they are catalysed by transition metals, to cause DNA and RNA damage, thiol oxidation and lipid peroxidation (Halliwell and Guttridge., 1999; Halliwell 1994). The great potential of free radicals to react with various compounds by electron transfer, proton transfer, H-atom abstraction or addition reaction may involved in the pathological of various diseases (Halliwell., 1993; Havsteen., 1983). Many plant compounds can scavenge reactive oxygen species (ROS) and thereby directly reduce-oxidative stress (Walgren et al., 2000b). Among these, flavonoids seem to be potent candidates because they show broad pharmacological activities and widely distributed in many edible plants (Rice-Evans et al., 1996). The beneficial effect of flavonoids is mainly associated with the different various antioxidative mechanisms which act as enzyme inhibitor, reducing agents, trapping free radical and by acting as iron-chelating (Bravo., 1998; Hollman., 2001).

In this respect, since up to the present, there is no study on the chemical or the antioxidative activity of Pulicaria jaubertii, the aim of this study was to investigate the antioxidative activity of different extracts of the leaves of Pulicaria jaubertii: CH[Cl.sub.3], AcOEt and n-BuOH extracts as new potential source of natural antioxidants.

Materials and methods

Plant material

The leaves of Pulicaria jaubertii were collected from Aljar region (Hajja-Yemen) in October 2008. The plant was taxonomically identified by Pr. Abdellah Amine (Sana'a University). A voucher specimen of the plant material has been deposited at the department of biology (Sana'a University).

Preparation of the extracts

Dried and powdered leaves (400 g) of P. jaubertii were extracted with 70% MeOH solution three times during 24 hours. The aqueous MeOH extract was concentrated to dryness; the residue was dissolved in water (200 ml). The resulting solution was extracted successively with petroleum ether, CH[Cl.sub.3], AcOEt and n-BuOH. The organic layers were dried with [Na.sub.2]S[O.sub.4] to give after concentration the extracts CH[Cl.sub.3] (2 g), AcOEt (2.5 g) and n-BuOH (6 g) respectively.

Chemicals

1,1-Diphenyl-2-picrylhydrazyl ([DPPH.sup.o]), potassium ferricyanide, gallic acid, ethylenediamine tetra acetic acid (EDTA), ferrozine, Folin- Ciocalteus's phenol reagent, quercetin, ascorbic acid, ferric chloride and sodium carbonate were from sigma, sigma Aldrich. All the chemicals used including the solvents, were of analytical grade.

Determination of antioxidant activity

Determination of DPPH radical scavenging activity

The ability to scavenge the stable free radical 1,1-diphenyl-2-picrylhydrazyl ([DPPH.sup.o]) was determined based on the method of Ohinishi et al(Ohinishi et al., 1994).with minor modifications. A solution of 0.2 mM DPPH in methanol was prepared and 1 ml of this solution was mixed with 1 ml of extract in methanol (5 to 150 [micro]g/ml). The reaction mixture was vortexed thoroughly and left in the dark at room temperature for 30 min. A control sample containing the same volume of solvent in place of extract was used to measure the maximum DPPH absorbance. The absorbance of the mixture was measured spectrophotometrically at 517 nm. Ascorbic acid and quercetin were used as references. Results were expressed as percentage of inhibition of the DPPH radical according to the following equation:

% Inhibition of DPPH = (Absorbance of control - Absorbance of sample) x 100/Absorbance of control

Determination of reducing power

The reducing power of P. jaubertii leaves extracts was determined according to Oyaizu (Oyaizu., 1986). Different amounts of the extracts were suspended in distilled water and mixed with 2.5 ml of 0.2 M phosphate buffer (pH 6.6), and 2.5 ml of 1% [K.sub.3]Fe[(CN).sub.6]. The mixture was incubated at 50[degrees]C for 20 min, 2.5 ml of 10% TCA was added to the mixture and centrifuged at 3000 rpm for 10 min. 2.5 ml of upper layer of the solution was mixed with 2.5 ml distilled water and 0.5 ml of 0.1% Fe[Cl.sub.3], and the absorbance was measured at 700 nm. Increase in absorbance of reaction mixture indicated reducing power. Ascorbic acid and quercetin were used as references.

Inhibition of lipid peroxide formation induced by [Fe.sub.2+]/ascorbic acid system

The reaction mixture containing rat liver homogenate (0.1 ml, 25% w/v) in Tris-HCl (30 mM), ferrous ammonium sulfate (0.16 mM), ascorbic acid (0.06 mM) and different concentrations of the extract (from 50 to 600 [micro]g/ml) in a final volume of 0.5 ml was incubated for 1h at 37[degrees]C and the resulting thiobarbituric reacting substance (TBARS) was measured. A 0.4 ml aliquot of the reaction mixture was treated with sodium dodecyl sulfate (0.2 ml, 8.1%), thiobarbituric acid (1.5 ml, 0.8%), and acetic acid (1.5 ml, 20%, pH 3.5), made to a total volume of 4 ml by adding distilled water, and kept in a water bath at 95[degrees]C for 1 h. After cooling, 4 ml of n-BuOH was added. After shaking and centrifuging, the organic layer was separated and the absorbance measured at 532 nm (Ohkawa et al., 1979). Ascorbic acid and quercetin were used as references.

Determination of O[H.sup.o] scavenging

Scavenging of O[H.sup.o] was determined by the method of Halliwell et al(. Halliwell et al., 1987). O[H.sup.o] were generated by incubating the following reagents in a final volume of 1.2 ml 10 mM K[H.sub.2]P[O.sub.4]-KOH buffer (pH 7.4) at 37[degrees]C for 60 min: 1.4 mM [H.sub.2][O.sub.2], 100 [micro]M Fe[Cl.sub.3] and 2.8 mM deoxyribose, 100 [micro]M EDTA, and 100 [micro]M ascorbic acid in presence or absence (control) of the extract. Ascorbic acid was added in the end to start the reaction. Degradations of deoxyribose sugar induced by O[H.sup.o] was determined by addition of 1 ml TBA (1% w/v) and 1 ml TCA (5.0% w/v) and heating at 100[degrees]C for 20 min. The pink chromogen formed was determined by measuring its absorbance at 535 nm. Quercetin was used as reference.

Ferrous-chelating ability

The chelating of ferrous ions by P. jaubertii extract was estimated by the method of Dinis et al. (2006). Briefly, 50 [micro]l of 2 mM Fe[Cl.sub.2] was added to the extract (1 ml). The reaction was initiated by the addition of 0.2 ml of 5 mM ferrozine solution. The mixture was vigorously shaken and left to stand at room temperature for 10 min. The absorbance was measured spectrophotometrically at 562 nm. EDTA was used as reference.

Determination of total phenolic contents

Total phenolic content was determined using Folin-Ciocalteu reagent as adapted from Singleton and Rossi (Oyaizu, 1986), with slight modifications. 100 [micro]l of extract was mixed with 250 [micro]l of Folin-Ciocalteu reagent (1N) and allowed to stand at room temperature for 2 min. 1250 [micro]l of sodium carbonate (20%) was added, and the mixture was mixed and allowed to stand at room temperature in the dark for 2 h. The absorbance was read at 765 nm, and the total polyphenols concentration was calculated from a calibration curve, using gallic acid as standard (50-1000 mg/L). The results were expressed as gallic acid equivalents (GAE)/g extract.

Determination of flavonoids

Total flavonoid content was determined using the method of Ordon Ez et al. (Ordon Ez et al., 2006). A volume of 0.5 ml of 2 % Al[Cl.sub.3] ethanol solution was added to 0.5 ml of sample solution. After one hour at room temperature, the absorbance was measured at 420 nm. A yellow color indicated the presence of flavonoids. Extract samples were evaluated at a final concentration of 0.1 mg/ml. Total flavonoids were calculated as quercetin (mg/g) using the calibration curve. Results were expressed as mg quercetin equivalents (QE) / g extract.

Statistical analysis

All assays were carried in triplicates and results expressed as means [+ or -] standard deviation. [IC.sub.50]-value ([micro]g extract/ml) is the effective concentration which proves 50% of activity, was calculated for each assay. Statistical comparisons were done with Student's test. Differences were considered to be highly significant at P < 0.01 and significant at P< 0.05.

Results and discussion

Determination of antioxidant activity

Scavenging effect on DPPH radical.

The antioxidants react with [DPPH.sup.o], a stable purple colored free radical and convert it into colorless a- adiphenyl-[beta]-picryl hydrazine. The extent discoloration indicates the amount of DPPH scavenged (Ohinishi et al., 1994). As shown in Figure 1, the DPPH radical scavenging activities of various investigated extracts from leaves of P. jaubertii were in order of AcOEt extract (96.87%) > n-BuOH extract (63.62%) > CH[Cl.sub.3] extract (33.78%) at concentration 50 [micro]g/ml. These data suggested that both AcOEt and BuOH extracts of P. jaubertii have a remarkable ability to scavenge radicals with [IC.sub.50]-value (7.17 [+ or -] 0.82 [micro]g/ml and 20.06 [+ or -] 1.86 ng/ml respectively) (Table 1). The AcOEt extract (96.45%) exhibited potent radical scavenging activity even at lower concentration 20 Lg/ml which was the dose dependent manner.

[FIGURE 1 OMITTED]

Reducing power assay

The reducing power assay measures the electron-donating capacity of antioxidant using potassium ferricyanide reduction method (Hollman, 2001). The reducing power results of various extracts of leaves of P. jaubertii and standard references which are presented in Figure 2, followed the order : ascorbic acid (1.7) > quercetin (1.3) > AcOEt extract (1.24) > n-BuOH extract (0.9) > CH[Cl.sub.3] extract (0.15) at 400 [micro]g/ml. Regarding to [IC.sub.50]-values (233.45 [+ or -] 1.66 [micro]g/ml and 275.07 [+ or -] 17.43 [micro]g/ml) both AcOEt extract and n-BuOH extract reduced potentially the ferric ion/ferricyanide to the ferrous form ([Fe.sup.2+]). Previous study reported that reducing power of medicinal plants prevents liver injury by inhibiting formation of lipid peroxides (Seeram and Nair., 2002).

Inhibition of lipid peroxide formation induced by [Fe.sup.2+]/ascorbic acid system

Free radicals (O[H.sup.o.] and [O.sup.o..sub.2]) mediated peroxydation unsaturated fatty acid within in the membrane lipid bilayer (Heijnen et al., 2002). which can be induced in liver homogenate by [Fe.sup.2+]/ascorbate system. The results shown in Figure 3, revealed that both AcOEt (89.34 %) and n-BuOH (65.64 %) extracts proved a good protection and reduce MDA generated by [Fe.sup.3+]/ascorbate at concentration 200 [micro]g/ml. The AcOEt extract (89.34 %) was found to be a better inhibitor of lipid peroxidation compared to the reference standard ascorbic acid (72.34%). Investigated CH[Cl.sub.3] extract showed a moderate protection (45.69 %) activity but even at the highest concentration (600 [micro]g/ml). The propagation of lipid peroxydation is broken by either enzymatic inactivation of reactive oxygen species involved in chain reaction or non-enzymatic reactions (Heijnen et al., 2002). due to the intervention of free radical scavenger and antioxidant compounds probably present in the investigated extracts.

Hydroxyl radical scavenging activity

OH radical is the most reactive free radical in biological system and it can be formed from superoxide anion and hydrogen peroxide in the presence of metal ions, such as copper and iron (Valko et al., 2006). The OH radical scavenging activity was carried out by measuring the competition between deoxyribose and the various extracts from leaves of P. jaubertii for hydroxyl radicals generated from [Fe.sup.3+]/ascorbate/EDTA/[H.sub.2][O.sub.2] system. Figure 4 showed that both extracts AcOEt (63.3 - 84.13 %) and n-BuOH (50.94 - 72 %) at the concentration ranged from 200 to 400 [micro]g/ml, were considerably more active than CH[Cl.sub.3] extract (11.65 -28.66 %). The hydroxyl radical scavenging capacity of the investigated extracts compared to standard references was in order to quercetin (83.51%) > AcOEt (63.32 %) > n-BuOH (50.94 %) > CH[Cl.sub.3] (11.65 %) at concentration 200 [micro]g/ml. The ability of both AcOEt and n-BuOH extracts of leaves of P. jaubertii to quench hydroxyl radicals which are implicated in some diseases, revealed the presence of antioxidant compounds in this plant.

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

Ferrous-chelating ability

The iron-chelating capacity test measures the ability of antioxidants to compete with ferrozine in chelating ferrous ion (Afanas'ev et al., 1989). This assay as shown in Figure 5, indicated that both AcOEt and n-BuOH extracts of P. jaubertii interfered with the formation of activity and captured ferrous ions before ferrozine. As it can be deduced from Figure 5, these two extracts, AcOEt (81.46 %) and n-BuOH extract (63.65 %) had the highest ferrous ion chelating activity at a concentration 400 [micro]g/ml. Although the CH[Cl.sub.3] extract did not show ion chelator activity even at the highest concentration, the antioxidant compounds contained in AcOEt and nBuOH extracts of P. jaubertii probably inhibited interaction between metal and lipid through formation of insoluble complexes with ferrous ion (Heijnen et al., 2002).

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

According to the [IC.sub.50]-values presented in Table 1, the AcOEt extract from leaves of P. jaubertii have an important role in scavenging abilities of various radicals and [IC.sub.50]-values of antioxidant activities followed the order : [DPPH.sup.o] (7.17 [micro]g/ml) > LPO (31.19 [micro]g/ml) > iron-chelating (79.4 [micro]g/ml) > O[H.sup.o] (105.63 [micro]g/ml) > reducing power (233.45 [micro]g/ml) compared to the [IC.sub.50] values of antioxidant activities of n-BuOH extract : [DPPH.sup.o] (20.06 [micro]g/ml) > LPO (148.87 [micro]g/ml) > iron-chelating (216.58 [micro]g/ml) > O[H.sup.o] (259.84 [micro]g/ml) > reducing power (275.07 [micro]g/ml). The AcOEt extract which had the highest content of polyphenols and flavonoids was the most powerful compared to n-BuOH extract. Previous investigations reported that the beneficial effect of plants is mainly associated with the antioxidant activity of their phenolic compounds (Pietta., 2000). It was also revealed that the extracts obtained by polar organic solvents (acetone and methanol) were potentially active than those obtained by umpolar organic solvents (chloroform and petroleum ether) (Cakir et al., 2006). This supports the idea that the polar compounds (flavonoids) present in the extract are mainly responsible for its antioxidant activity (Bravo, 1998).

Conclusion

The results obtained in this study clearly showed that both AcOEt and n-BuOH extracts from the leaves of Pulicaria jaubertii possess antioxidant activity. The AcOEt extract exhibited a strong antioxidant activity and had the most potent scavenging abilities of various radicals which may be caused by the high content of polyphenols and flavonoids. The very strong antioxidant activity of the P. jaubertii suggests that the extracts obtained by polar solvents from the leaves could be used as an effective natural source of antioxidant and food additives.

Acknowledgements

The authors are grateful to to Pr. Abdellah Amine (Sana'a University, Yemen) for identification of the plant material and MESRS (Ministry of Scientific Research, Algeria) for financial support.

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(1) M.N. Algabr, (1) R.Mekkiou, (2) S. Ameddah, (2) A. Menad, (3) O. Boumaza, (1) R. Seghiri, (3) S.Benayache, (1) F.Benayache

(1) Laboratoire de Phytochimie et Analyses Physico-Chimiques et Biologiques, Universite Mentouri, Route de Ain El Bey, 25 000 Constantine, Algeria, fax: 213 31 81 88 83;

(2) Laboratoire de biologie et environnement, Universite Mentouri, Route de Ain El Bey, 25 000 Constantine, Algeria.

(3) Laboratoire de Valorisation des Ressources Naturelles et Synthese de Substances Bioactives, Universite Mentouri, Route de Ain El Bey, 25 000 Constantine, Algeria.

Corresponding Author: R.Mekkiou,, Laboratoire de Phytochimie et Analyses Physico-Chimiques et Biologiques, Universite Mentouri, Route de Ain El Bey, 25 000 Constantine, Algeria, fax: 213 31 81 88 83; Email: mekkiou_ratiba@yahoo.fr
Table 1: Polyphenol contents and [IC.sub.50]-values of
antioxidant activities of extracts from leaves of P. jaubertii.

Extract and               [IC.sub.50] ([micro]g/ml)
standard
reference       DPPH [degrees]          Iron-chelating

AcOEt           7,17 [+ or -] 0,82 **   79,45 [+ or -] 3,59 **
n-BuOH          20,06 [+ or -] 1,86 *   216,58 [+ or -] 31,70 *
CH[Cl.sub.3]    457,55 [+ or -] 31,86   22794,077 [+ or -] 9911.69
Quercetin       2,47 [+ or -] 0,05 **   --
Ascorbic acid   3,74 [+ or -] 0,02 **   --
EDTA            --                      29.16 [+ or -] 1.71* *

Extract and                 [IC.sub.50] ([micro]g/ml)
standard
reference       OH [degrees]              LPO

AcOEt           105,63 [+ or -] 2,36 **   31,19 [+ or -] 3,74 **
n-BuOH          259,84 [+ or -] 14,90 *   148,87 [+ or -] 9,58 *
CH[Cl.sub.3]    2889,08 [+ or -] 877,33   xxx
Quercetin       50,0 [+ or -] 80,70 **    39,67 [+ or -] 1,71 **
Ascorbic acid   --                        74,10 [+ or -] 2,16 **
EDTA            --                        --

                      [IC.sub.50]
Extract and          ([micro]g/ml)         Total Polyphenols
standard                                   (mgGAE/g)
reference       Reducing Power

AcOEt           233.45 [+ or -] 1.66 **    322,98 [+ or -] 33,76 **
n-BuOH          275.07 [+ or -] 17.43 **   77,83 [+ or -] 6,79 *
CH[Cl.sub.3]    256 [+ or -] 2.73          1,08 [+ or -] 0,07
Quercetin       124.49 [+ or -] 0.37 **    --
Ascorbic acid   50.05 [+ or -] 11.33 **    --
EDTA            --                         --

Extract and     Total flavonoids (mgQE/g)
standard
reference

AcOEt           1 159,80 [+ or -] 22,11 **
n-BuOH          19,52 [+ or -] 3,68 **
CH[Cl.sub.3]    0,19 [+ or -] 0,01
Quercetin       --
Ascorbic acid   --
EDTA            --

Comparison between extracts, ** highly significant at P < 0.01,
* significant at P<0.05

(GAE)/g extract : mg gallic acid equivalents / g extract, (QE)/g
extract : mg quercetin equivalents / g extract,

AcOEt compare to n-BuOH and CH[Cl.sub.3] , * significant at P <
0.05, n-BuOH compare to CH[Cl.sub.3]
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Title Annotation:Original Article
Author:Algabr, M.N.; Mekkiou, R.; Ameddah, S.; Menad, A.; Boumaza, O.; Seghiri, R.; Benayache, S.; Benayach
Publication:Advances in Natural and Applied Sciences
Article Type:Report
Geographic Code:6ALGE
Date:Jan 1, 2010
Words:3885
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