In course of investigation on natural antioxidants, the present study was aimed to report the antioxidant activities, both in vitro and in vivo, of the crude methanolic extracts of the whole plant of Oxalis corniculata Linn along with its various organic fractions. The different assay methods, including total antioxidant activity, scavenging free radical, authentic peroxynitrite, nitric oxide and reducing power assessment were used to evaluate the antioxidant potential of the crude extract and its organic fractions. The ethylacetate (EtOAc) fraction, showed strong activity in all the model systems tested and in peroxynitrite model this fraction (IC50 value of 2.29±0.18 μg mL-1) exerted three-fold stronger activity than standard penicillamine (IC50 value of 6.20±0.32 μg mL-1). The reducing power of the extract was found to be concentration dependent. The administration of the extract/fractions at a dose of 250 and 500 mg kg-1 body weight to the male Wistar rats increased the percentage inhibition of reduced glutathione, superoxide dismutase and catalase significantly. Whereas, lipid peroxidation level in hepatotoxic rats markedly decreased at a dose of 500 mg kg-1 body weight after 7 days. The total phenol and flavonoid content were also measured in the crude extract along with its organic fractions. The Brine shrimp lethality bioassay was used to determine the toxicity of the extracts and Vincristin sulphate was used as positive control. The dichloromethane (CH2Cl2) fraction showed highest activity (LC50 value of 29.02±1.16 μg mL-1) and other showed activity in the order of: EtOAc fraction >n-BuOH fraction> MeOH extract > aqueous fraction. Taken together, these results suggest that O. corniculata extract has strong antioxidant properties and further validate the traditional use of this plant.
PDF Abstract XML References Citation
How to cite this article
Oxidation of food boosts up energy production for living beings. However, paradoxically Reactive Oxygen Species (ROS) are formed as by products including superoxide anion radical (•O2¯), hydrogen peroxide (H2O2), hydroxyl radical (•OH), singlet oxygen (1O2) and free radicals of lipids such as alkoxyl radical (RO•) and peroxyl radical (ROO•) (Gulcin et al., 2002; Yildirim et al., 2000). In addition, Peroxynitrite (ONOO¯), the reactive nitrogen species (RNS), a product of the reaction of nitric oxide (NO) with superoxide anion (O-2), is formed within tissues with perfusion injury and inflammation. These ROS and RNS, the main reprobate, are capable of damaging several cellular components such as proteins, lipids and DNA (Koneru et al., 2011). Also, these reactive species are likely to be involved in diseases such as Alzheimers disease and cancer, aging, arteriosclerosis, rheumatoid arthritis and allergies (Sohal, 2002; Squacrito and Peyer, 1998; Choi et al., 2002). Undoubtedly, in vivo suppression of these reactive species is important for the human body to eliminate the toxicity induced by these reactive species. Now a days, research have been carried out to find powerful and nontoxic antioxidants from natural sources, especially edible or medicinal plants to prevent the above reactive species related disorders in human as well as replace the synthetic compounds which are in use may have carcinogenic activity and harmful to the lungs and liver (Rechner et al., 2002).
The plant Oxalis corniculata (creeping wood sorrel) also called procumbent yellow sorrel belongs to family oxalidaceae. It is very popular perennial herb and distributed in all over Bangladesh. The leaves of wood sorrel are quite edible with a tangy taste and well known for its medicinal value as a good appetizer (Peterson, 1977). The entire plant is rich in Vitamin-C and leaves possess three major C-glycosyl flavones namely isoorientin, isovitexin and swertisin (Mizokami et al., 2008). Oxalis corniculata used in wound healing (Taranalli et al., 2004), Abortifacient antimplantation (Sharangouda and Patil, 2007). Antibacterial activity (Satish et al., 2008) anti fungal activity (Iqbal et al., 2001) relaxant activity (Achola et al., 1995) and other traditionally used in anaemia, dyspepsia, cancer, piles, dementia, convulsionis (Chetty et al., 2008). It is also reported to exhibit hypoglycemic, antihypertensive, antipsychotic, CNS-stimulant and posses chronotropic and inotropic effect (Achola et al., 1995; Raghavendra et al., 2006).
Recently, Sakat et al. (2010) have suggested only in vitro antioxidant property of methanolic extract of Oxalis corniculata. Taking this in view and as a part of our ongoing search on Bangladeshi medicinal plants (Alam et al., 2010) the present study aimed at evaluating the antioxidant potential of the Methanol (MeOH) extract and its organic solvent soluble fractions, such as dichloromethane (CH2Cl2), ethyl acetate (EtOAc), n-butanol (n-BuOH) and the aqueous (H2O) fraction, of the O. corniculata through various in vitro and in vivo models. In addition, the toxic potentialities of these fractions were also investigated.
MATERIALS AND METHODS
Plant materials: The whole plant of Oxalis corniculata Linn. was collected from the village Kachuria under Mollahat thana of Khulna district, Bangladesh during the month of August 2009. The plants were mounted on paper and the sample was identified by Mrs. Mahmuda Begum, Senior Scientific Officer, Bangladesh National Herbarium, Dhaka, where the voucher specimen has been deposited. Its DACB Accession No. is 32930.
Chemicals: Ammonium molybdate, Folin-chiocaltu phenol reagent, sodium nitroprusside, were purchased from E. Merck (Germany). 1,1-diphenyl- 2-picryl-hydrazyl (DPPH), ascorbic acid, quercetin and potassium ferric cyanide and DL-penicillamine (DL- 2- amino- 3- mercapto- 3- methylbutanoic acid) were purchased from Sigma Chemical Company (St. Louis, MO, USA). The high quality DCFH-DA and DHR 123 (dihydrorhodamine 123) and ONOO- were purchased from Molecular Probes (Eugene, Oregon, USA) and Cayman (Ann Arbor, MI, USA), respectively. All other chemicals and reagents were of analytical grade.
Preparation of plant extract: The plant material was shade-dried with occasional shifting and then powdered with a mechanical grinder, passing through sieve No. 40 and stored in a tight container. The dried powder material (1.5 kg) was refluxed with MeOH for three hours. The total filtrate was concentrated to dryness, in vacuo at 40°C to render the MeOH extract (490 g). This extract was suspended in H2O and then successively partitioned with dicholoromethane (CH2Cl2), ethylacetate (EtOAc) and normal butanol (n-BuOH) to afford the CH2Cl2 (200 g), EtOAC (60 g), and n-BuOH (110 g) fractions and the H2O residue (120 g).
In vitro antioxidant activity
The amount of phenolic compounds and flavonoids: The total phenolic and flavonoid content of methanolic extract and several organic fractions were determined using Folin-Ciocalteu reagent (Yu et al., 2002) and aluminium chloride colorimetric method (Chang et al., 2002), respectively.
Determination of total antioxidant activity: The antioxidant activity of the MeOH extract and several fractions were evaluated by the phosphomolybdenum method according to the procedure of Prieto et al. (1999). The assay is based on the reduction of Mo(VI)-Mo(V) by the extract and subsequent formation of a green phosphate/Mo(V) complex at acid pH. The antioxidant activity is expressed as the number of equivalents of ascorbic acid using the following formula:
Antioxident activety = C = (cxV)/m
where, C is total antioxidant activity in mg g-1 plant extract, in Ascorbic acid; c is the concentration of ascorbic acid established from the calibration curve in mg mL-1; V is the volume of extract in mL and m is the weight of pure plant extract in g.
Free radical scavenging activity measured by 1,1-diphenyl-2-picryl-hydrazyl (DPPH): The free radical scavenging activity of MeOH extract and fractions, based on the scavenging activity of the stable 1,1-diphenyl-2- picrylhydrazyl (DPPH) free radical, was determined by the method described by Braca et al. (2001). The percentage inhibition activity was calculated from:
% inhibition = [(A0A1)/A0]x100
where, A0 is the absorbance of the control and A1 is the absorbance of the extract/standard. IC50 value was calculated from the equation of line obtained by plotting a graph of concentration (μg mL-1) versus % inhibition.
Measurement of the ONOO-scavenging activity: The ONOO-scavenging activity was measured by monitoring the oxidation of DHR 123, by modifying the method of Kooy et al. (1994).
Nitric oxide radical scavenging assay: The procedure is based on the method (Sreejayan and Rao, 1997) where sodium nitroprusside in aqueous solution at physiological pH spontaneously generates nitric oxide which interacts with oxygen to produce nitrite ions that can be estimated using Greiss reagent. Scavengers of nitric oxide compete with oxygen leading to reduced production of nitrite ions.
Reducing power activity: The reducing power of O. corniculata was determined according to the method previously described by Oyaizu (1986).
In vivo antioxidant activity
Animals: Male Wistar rats with a mean weight of 175±5.2 g were collected from the animal research branch of the International Center for Diarrheal Disease and Research, Bangladesh (ICDDR,B). Animals were maintained under standard environmental conditions (temperature: (24.0±1.0°), relative humidity: 55-65% and 12 h light/12 h dark cycle) and had free access to feed and water ad libitum. The animals were acclimatized to laboratory condition for one week prior to experiments. All protocols for animal experiment were approved by the institutional animal ethical committee.
Animal grouping and extract administration: Twenty five male rats were randomized into five groups consisting of five each. Group 1 served as normal control and was given distilled water alone (0.5 mL) per day for seven days with the aid of oropharyngeal cannula. Groups 2 animals served as hepatotoxic control, treated with CCl4 in a single dose of 0.5 mL administered orally for seven days. Groups 3 animals served as positive control, treated with silymarin in a single dose of 25 mg/kg/day orally for seven days while the animals in group 4 and 5 were treated like the normal control except that they received 0.5 mL of the extract corresponding to 250 and 500 mg kg-1 body weight respectively. Again group 3-5 was given 0.5 mL of CCl4 on the seventh day after 6 h of extract administration. All the animals from each group were sacrificed by ether anesthesia 24 h after their respective 21 daily doses of the extract and distilled water. The liver from each animal was excised, rinsed in ice cold 0.25 M sucrose solution and 10% w/v homogenate was prepared in 0.05 M phosphate buffer (pH 7) and centrifuged at 5000 rpm for 60 min at 4°C. The supernatant obtained was used for the estimation of catalase, superoxide dismutase, lipid peroxidation (TBARS) and reduced glutathione.
Determination of catalase activity: The activity of catalase was assayed according the method described by Pari and Latha (2004).
Determination of reduced glutathione activity: Reduced glutathione was determined using the modified method of Ellman (1959).
Estimation of lipid peroxidation: Lipid peroxidation in the liver was estimated colorimetrically by thiobarbituric acid reactive substances (TBARS) using the modification method of Niehaus and Samuelson (1968).
Brine shrimp lethality bioassay: The toxic potentiality of the different fractions of the plant was evaluated using Brine Shrimp lethality bioassay method (Meyer et al., 1982), where 6 graded doses (viz,. 5, 10, 20, 50, 100 and 200 μg mL-1) were used.
Statistical analysis: All values were expressed as the Mean±Standard error of three replicate experiments. The analysis was performed by using students t test. The p<0.001 and <0.005 were considered to be statistically significant.
In vitro antioxidant activity
Total phenolic and flavonoid contents: The content of total phenols in the extract and fractions of O. corniculata was determined using the Folin-Ciocalteu assay, calculated from regression equation of calibration curve (y = 0.013x+0.127, r2 = 0.988) and is expressed as Gallic Acid Equivalents (GAE). The content of the total phenols in the fractions decreased in the order of EtOAc > n-BuOH > MeOH > CH2Cl2 > aqueous fractions and the flavonoid contents of the whole plant extract and fractions in terms of quercetin equivalent (the standard curve eqation: y = 0.009x-0.036). The flavonoid content in the fractions decreased in the order of EtOAc > n-BuOH > MeOH > aqueous fractions > CH2Cl2 (Table 1).
Total antioxidant activity: Percentage yield of methanol extract and different organic fractions of O. corniculata and their total antioxidant capacity are given in Table 1. Total antioxidant capacity of O. corniculata is expressed as the number of equivalents of ascorbic acid. Total antioxidant capacity of EtOAc fractions showed the highest and was found to be 224.5±0.45 mg g-1 equivalent of ascorbic acid, followed by n-BuOH, MeOH, Aqueous fraction and CH2Cl2 125.4±0.21, 113.9±0.69, 20.4±0.12 and 14.0±1.01 mg g-1 equivalent of ascorbic acid, respectively.
DPPH radical scavenging activity: All the fractions of O. corniculata demonstrated H-donor activity. EtOAc fractions showed the highest DPPH scavenging activity with the IC50 value of 4.04±0.08 μg mL-1, followed by n-BuOH, MeOH and aqueous extract/fractions with the IC50 value of 12.32±0.16, 17.37±0.22 and 48.49±0.72 μg mL-1, respectively. CH2Cl2 had no activity within the experimental concentration range. EtOAc fractions showed the three fold higher activity than the standard ascorbic acid (IC50 12.30±0.11μg mL-1) (Table 2).
Peroxynitrite (ONOO¯) scavenging activity: The ONOO-scavenging activity was measured by monitoring the oxidation of DHR 123. The MeOH extract and its organic soluble fractions exhibited significant ONOO¯ scavenging effects in a dose-dependent manner, with IC50 values of 2.29±0.18 μg mL-1 for EtOAc fraction and exerted activity three-fold stronger than a well known ONOO¯ scavenger, penicillamine, with an IC50 value of 6.20±0.32 μg mL-1. n-BuOH came in second with respect to IC50 values, 8.85±0.28, followed by MeOH, aqueous and CH2Cl2 extrac/fractions with IC50 values of 15.16±0.61, 58.08±2.41 and 82.08±2.41 μg mL-1, respectively (Table 2).
|Table 1:||Yield, total amount of plant phenolic compounds, flavonoids and total antioxidant capacity of methanolic extract and soluble organic fraction of Oxalis corniculata|
|aGallic acid equivalents (GAE, mg g-1 of each extract) for the total phenolic content. b Quercetin equivalents (mg g-1 of each extract) for the total flavonoid content. c Ascorbic acid equivalents (mg g-1 of each extract) for the total antioxidant capacity. The GAE, QA and ASC values are expressed as Means±SEM of triplicate experiments|
|Table 2:||Antioxidant activities of the O. corniculata extract on DPPH, ONOO¯ and NO|
|aDPPH is the free radical scavenging activity (IC50: μg mL-1). bONOO- is the inhibitory activity of authentic peroxynitrite (IC50: μg mL-1). cNO is the inhibition of NO production (IC50: μg mL-1). *p<0.001 by students test for values between the sample and the control. **p<0.005 by students test for values between the sample and the control. # Not significant|
Nitric oxide (NO) radical scavenging activity: The MeOH extract and its organic soluble fractions of O. corniculata effectively reduced the generation of NO from sodium nitroprusside. As stated in Table 2, The EtOAc fraction showed the highest scavenging activity (IC50 values of 8.21±0.07 μg mL-1) which was similar than the standard ascorbic acid (IC50 values of 8.22±0.22 μg mL-1). n-BuOH (15.10±0.33 μg mL-1), MeOH (58.23±0.15 μg mL-1), aqueous (97.69±0.57 μg mL-1) and CH2Cl2 (109.19±0.72 μg mL-1) also showed good scavenging activity.
Reducing power ability: For the measurement of the reductive ability, transformation of Fe3+ to Fe2+ was investigated in the presence of extract and organic fractions. Like the antioxidant activity, the reducing power of O. corniculata increased with increasing concentration of the sample. Figure 1 shows the reductive capabilities of the O. corniculata compared with quercetin. All O. corniculata extract and fractions concentrations tested showed higher activities and these differences were statistically significant (p<0.001).
In vivo antioxidant activity
Estimation of lipid peroxidation (LPO), enzymic (CAT, SOD) and non enzymic (GSH) antioxidant system: Reduced activities of enzymic (CAT, SOD), non enzymic (GSH) antioxidant system and lipid peroxidation (LPO) level of liver homogenate were summarized in Table 3. There was a significant decrease in the percentage inhibition of CAT, SOD and GSH in CCl4 treated rats than the normal control group. However, the percentage inhibition of SOD, CAT and GSH were significantly increased after oral administration of extract/fractions at 250 and 500 mg kg-1 body weight in a dose dependent manner. EtOAc fraction at a dose of 500 mg kg-1 body weight showed the highest percentage inhibition activity in both enzymic (69.12±0.11% for CAT and 75.22±0.22% for SOD) and non enzymic (70.45±0.53% for GSH) antioxidant system. Since aqueous and CH2Cl2 fractions showed lower activity in in vitro model, test for in vivo model were not done.
In vivo lipid peroxidation study of rats treated with CCl4 showed a significant increase (p<0.001) in TBARS when compared with normal control group. Treatment with O. corniculata extract/fractions for 7 days were able to lower the rise in TBARS level dose dependently as shown in Table 3. EtOAc showed the highest lowering effect in TBARS level (89.17±0.17) at dose of 500 mg kg-1 body weight than the standard Salymarin (72.97±0.27) at dose of 25 mg kg-1 body weight.
|Fig. 1:||Reducing power of MeOH extract and fractions of O. corniculata and standards by spectrophotometric detection of Fe3+ to Fe2+ transformation. Results are Mean±SEM of three parallel measurements|
|Table 3:||Effect of MeOH extract and its organic soluble fractions of O. corniculata on LPO, antioxidant enzymes and GSH in CCl4 induced liver damage in male wistar rats|
|Values are Mean±SEM, (n = 5). **p<0.001 by students test for values between the sample and the CCl4 control. M: Methanolic extract, C: Dicholoromethane (CH2Cl2) fraction, E: Ethylacetate (EtOAc) fraction, B: n-Butanol (BuOH) fraction and A: Aqueous (H2O) fraction. 1: 250 mg kg-1 body weight and 2: 500 mg kg-1 body weight. ND: Note done|
|Table 4:||LC50 data of test samples of O. corniculata and vincristine sulphate|
|aValues of toxicity (LC50) were expressed as the Mean±SE of three experiments|
Assay for toxicity of Oxalic corniculata extract: As summarized in Table 4, the toxicity exhibited by the crude MeOH extract as well as the organic soluble fractions of the plant showed potent activity against the positive control (vincristine sulphate). The toxicity of the MeOH extract and its fractions on the BSLA increased in the order of CH2Cl2 < EtOAc < n-BuOH < MeOH < H2O and LC50 values were 29.02±1.16, 34.92±1.56, 54.65±3.13, 85.32±1.63 and >200 μg mL-1, respectively.
Phenolic compounds are commonly found in both edible and nonedible plants, and they have been reported to have multiple biological effects, including antioxidant activity. The antioxidant activity of phenolic compounds is mainly due to their redox properties, which can play an important role in adsorbing and neutralizing free radicals, quenching singlet and triplet oxygen, or decomposing peroxides (Soares et al., 1997). Phenolic compounds are understood to induce the cellular antioxidant system; increase approximately 50% cellular glutathione concentration. Flavonoids are important in the modulation of γ-glutamylcysteine synthase in both cellular antioxidant defenses and detoxification of xenobiotics (Muchuweti et al., 2007). In this study EtOAc fractions possessed the highest amount of phenolic and flavonoid compounds i.e., 340±0.02 mg g-1 in GAE and 112.73±0.23 mg g-1 in QA, respectively, followed by n-BuOH and MeOH extract/fractions.
The phosphomolybdenum method was based on the reduction of Mo (VI) to Mo (V) by the compounds having antioxidant property and the formation of a green phosphate/ Mo (V) complex with a maximal absorption at 695 nm. This assay is successfully used to quantify vitamin E in seeds. This method is simple and independent on other antioxidant measurements and is commonly employed for plant extracts (Prieto et al., 1999).
The stable DPPH radical model is widely used and was found relatively quick method for the evaluation of free radical scavenging activity. DPPH• is a stable free radical that accepts an electron or hydrogen radical to become a stable diamagnetic molecule (Nakayama, 1994). DPPH• is usually used as a substrate to evaluate the antioxidant activity of a compound (Chang et al., 2002). Based on the data obtained from this study, DPPH radical scavenging activity of EtOAc fractions of O. corniculata was significantly lower than standard. It was revealed that organic soluble fraction of O. corniculata did show the proton donating ability and could serve as free radical inhibitor or scavenger, as well as a primary antioxidant that reacts with free radicals, which may limit free radical damage occurring in human body.
Suppression of NO● release may be partially attributed to direct NO● scavenging, at all concentrations of crude methanolic extract and organic fractions of O. corniculata which decreased the amount of nitrite generated from the decomposition of sodium nitroprusside in vitro. The plant products may have the property to counteract the effect of NO• formation and in turn may be of considerable interest in preventing the ill effects of excessive NO• generation in the human body. Further, the scavenging activity may also help to arrest the chain of reactions initiated by excess generation of NO• that are detrimental to the human health. Nitric oxide is implicated for inflammation, cancer and other pathological conditions (Duh, 1998).
Formation of reactive peroxynitrite (ONOO¯) form the combination of NO• and O●¯2 leads to serious toxic reactions with biomolecules such as protein, lipids and nucleic acids. High concentration of Nitric Oxide (NO) has deleterious effects, so it is necessary to regulate the production of NO strictly (Beasley et al., 1991). When NO is produced by macrophages, the nitric oxide radical can be converted into peroxynitrites, which will cause diverse chemical reactions in a biological system including nitration of tyrosine residue of protein, triggering lipid peroxidation, inactivation of aconites, inhibition of mitochondrial electron transport and oxidation of biological thiol compound.
The reducing capacity of a compound may serve as a significant indicator of its potential antioxidant activity (Beckman et al., 1990). At the concentration of the extract/fractios tested, reducing power of the extract/fractions was higher than that of some commonly consumed green leafy vegetable (Oboh, 2008). The reducing properties are generally associated with the presence of reductones which have been shown to exert antioxidant action by breaking the free radical chain by donating a hydrogen atom (Beckman and Koppenol, 1996). Present data on the reducing power of the tested extracts suggested that it is likely to contribute significantly towards the observed antioxidant effect.CCl4 Is one of the most commonly used hepatotoxin in the experimental study of liver damage (Lee et al., 2001). The toxic effects of CCl4 in vivo is well known to be mediated through radical reactions. The CCl3O* and/or CCl3OO* redicals produced as a result of the metabolic conversion of CCl4 is reported to initiate lipid peroxidation (Gupta et al., 2006). In the present study, a single dose of CCl4 developed significant hepatic damage and oxidative stress, leads to increase lipid peroxidantion. The treatment with different fractions of O. corniculata was able to reduce the level of lipid peroxides in a dose dependent manner as compared with the hepatotoxic group.
Superoxide dismutase has been reported as one of the most important enzymes in the enzymatic antioxidant defense system (Curtis et al., 1972). It removes superoxide anion by converting it to hydrogen peroxide and prevent the toxic effect caused by this radical. CCl4 Induced hepatic damage lead to decrease in percentage inhibition of SOD and after administration of plant extract/fractions increased the percent inhibition of SOD, revealed the efficient protective mechanism of this plant.
Catalase, another antioxidant enzyme, is widely distributed in the animal tissues and decomposes H2O2 and protects the cells from highly reactive hydroxyl radicals (Chance et al., 1952). Yeh and Yen (2006), reported that four different phenolic acids induced antioxidant enzymes SOD, catalase and glutathione peroxidase. Thus increased the percentage inhibition of catalase after administration of extract/fractions probably due to the presence of the phenolic compounds in the extract/fractions.
Reduced Glutathione (GSH) is a tripeptide, non enzymatic biological antioxidant present in the liver and are important for maintaining the structural and functional integrity of different organs. Glutathione reductase and NADH stricly maintain the cellular GSH levels (Ganie et al., 2010). Moreover, GSH protects cellular proteins against reactive oxygen species generated from exposure to CCl4 (Arivazhagan et al., 2000). The ability of plant extracts to reactivate the hepatic glutathione reductase was reflected by decreasing the level of lipid peroxidation. This result agrees with the earlier report of Bhandarkar and Khan (2004).
The Brine Shrimp Lethality Assay (BSLA) has been used routinely in the primary screening of the crude extracts to assess the toxicity towards brine shrimp, which could also provide an indication of possible toxicity of the test materials. A number of novel antitumor and pesticidal natural products have been isolated using this bioassay (Meyer et al., 1982). The variation in BSLA results (Table 4) may be due to the difference in the amount and kind of toxic substances (e.g., tannins, flavonoids, triterpenoids, or coumarins) present in the crude extracts. Moreover, this significant lethality of the crude plant extracts (LC50 values less than 100 ppm or μg mL-1) to brine shrimp is indicative of the presence of potent toxic and probably insecticidal compounds which warrants further investigation. BSLA results may be used to guide the researchers on which crude plant extracts/fractions to prioritize for further fractionation and isolation of these bioactive compounds.
In conclusion, the results of the present study indicate that the MeOH extract and its various fractions extract exhibit interesting antioxidant properties via various in vitro and in vivo model and also show potent toxicity. These results of the investigation do not reveal that which chemical compound is responsible for aforementioned activity. To explore the lead compounds liable for aforementioned activity from this plant are in progress.
- Achola, K.J., J.W. Mwangi and R.W. Munenge, 1995. Pharmacological activity of Oxalis corniculata. Pharm. Biol., 33: 247-249.
- Braca, A., N. De Tommasi, L. Di Bari, C. Pizza, M. Politi and I. Morelli, 2001. Antioxidant principles from Bauhinia tarapotensis. J. Nat. Prod., 64: 892-895.
- Mizokami, H., K. Tomita-Yokotani and K. Yoshitama, 2008. Flavonoids in the leaves of Oxalis corniculata and sequestration of the flavonoids in the wing scales of the pale grass blue butterfly, Pseudozizeeria maha. J. Plant Res., 121: 133-136.
- Naskar, S., A. Islam, U.K. Mazumder, P. Saha, P.K. Haldar and M. Gupta, 2010. In vitro and in vivo antioxidant potential of hydromethanolic extract of Phoenix dactylifera fruits. J. Sci. Res., 2: 144-157.
- Oyaizu, M., 1986. Studies on products of browning reaction. Antioxidative activities of products of browning reaction prepared from glucosamine. Jpn. J. Nutr. Dietetics, 44: 307-315.
- Rechner, A.R., G. Kuhnle, P. Bremner, G.P. Hubbard, K.P. Moore and C.A. Rice-Evans, 2002. The metabolic fate of dietary polyphenols in humans. Free Radic. Biol. Med., 33: 220-235.
- Sakat, S.S., A.R. Juvekar and M.N. Gambhire, 2010. In vitro antioxidant and anti-inflammatory activity of methanol extract of Oxalis corniculata linn. Int. J. Pharm. Pharm. Sci., 2: 146-155.
- Satish, S., M.P. Raghavendra and K.A. Raveesha, 2008. Evaluation of the antibacterial potentials of some plants against human pathogenic bacteria. Adv. Biol. Res., 2: 44-48.
- Sharangouda, J.P. and S.B. Patil, 2007. Antiimplantation and abortifacient activity of Oxalis corniculata (whole plant) in albino rats. Niger. J. Natl. Prod. Med., 11: 58-60.
- Sohal, S.R., 2002. Role of oxidative stress and protein oxidation in the aging process. Free Radical Biol. Med., 33: 37-44.
- Squadrito, G.L. and W.A. Pryor, 1998. Oxidative chemistry of nitric oxide: The roles of superoxide, peroxynitrite and carbon dioxide. Free Radical Biol. Med., 25: 392-403.
- Taranalli, A.D., S.V. Tipare and S. Kumar, 2004. Wound healing activity of Oxalis corniculata whole plant extract in rats. Ind. J. Pharm. Sci., 66: 444-446.
- Yeh, C.T. and G.C. Yen, 2006. Induction of hepatic antioxidant enzymes by phenolic acids in rats is accompanied by increased levels of multidrug resistance-associated protein 3 mRNA expression. J. Nutr., 136: 11-15.
- Yildirim, A., A. Mavi, M. Oktay, A.A. Kara, O.F. Algur and V. Bilaloglu, 2000. Comparison of antioxidant and antimicrobial activities of tilia (Tilia argentea Desf ex DC), sage (Salvia triloba L.) and black tea (Camellia sinensis) extracts. J. Agric. Food Chem., 48: 5030-5034.