Introduction

Nature still serves as the man's primary source for the cure of his ailments. The majority of the rich diversity of Indian medicinal plants is yet to be scientifically evaluated for such properties. However, the potential of higher plants as source for new drugs is still largely explored (Oke et al., 2002). The free radicals are chemical species, capable of independent existence; posses an unpaired electron on an orbital. They occur in the form of Superoxide, Hydroxyl radical (OH) and Peroxide ion (HO₂-).They are also known as Reactive Oxygen Species (ROS) or Reactive Oxygen Metabolite (ROM). These radicals are produced by body's normal use of oxygen and are also generated through environmental pollutants, cigarette smoke, automobile exhaust fumes, radiation, air pollution, pesticides, etc (Tiwari, 2001& Aqil et al.,2006). Mammalian cells possess elaborate defense mechanisms for radical detoxification. Key metabolic steps are superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX), which destroy toxic peroxides. In addition to antioxidant enzymes, nonenzymatic molecules, including thioredoxin, thiols, and disulfide-bonding play important roles in antioxidant defense systems. Some of the compounds are of an exogenous nature and are obtained from food, such as a-tocopherol, b-carotene, and ascorbic acid, and such micronutrient elements as zinc and selenium (Aqil et al .,2006). The medicinal properties of plants have been investigated in the recent scientific developments throughout the world ,due to their potential antioxidant activities, no side effects and economic viability (Auudy et al .,2003).The majority of the active antioxidant compounds flavonoids, isoflavones, flavones, anthocyanins, coumarins, lignans, catechins, and isocatechins. In addition to the above compounds found in natural foods, vitamins C and E, b-carotene, and a-tocopherol are known to possess antioxidant potential (Prior RL., 2003, Luo et al., 2004, Kapoor et al., 2002).Recently there has been an upsurge of interest in the therapeutic potentials of medicinal plants as antioxidants in reducing such free radical induced tissue injury (Pormouard et al., 2006). This paper reports screening of the antioxidant assay of certain indigenous medicinal plants of Western Ghats of India.

Materials and Methods

Plant Material

Preparation of extracts

Antioxidant assay

DPPH Radical scavenging activity:

DPPH scavenging activity was carried out by the method of Blois, (1957).Different concentrations (1000,500,250,125,62.5 and 31.2 mg/ml) of A.longifolia,P.edulis and Delonix elata extracts (Methanol) were dissolved in DMSO (dimethyl sulfoxide) and taken in test tubes in triplicates . Then 5 ml of 0.1mM ethanol solution of DPPH (1, 1, Diphenyl-2- Picrylhydrazl) was added to each of the test tubes and were shaken vigorously. They were then allowed to stand at 370 C for 20 minutes. The control was prepared without any extracts. Methanol was used for base line corrections in absorbance (OD) of sample measured at 517nm. A radical scavenging activity was expressed as 1% scavenging activity and was calculated by the following formula.

Figure 1

IC 50 Value was also calculated.

Reducing power

Results and Discussion

Scavenging activity for free radicals of 1,1-diphenyl 1-2-picryl hydrazyl (DPPH) has been widely used to evaluate the antioxidant activity of natural products from plant and microbial sources. Plant extracts from 3 medicinal plants listed in table.1.were prepared for investigation of their antioxidant activities. Free radical scavenging activity of methanolic extract from the 3 medicinal plants was quantitatively determined using DPPH and reducing power assay. Table 1-3 shows the result of antioxidant assay.

Figure 2

Table 1a: Antioxidant activity of methanolic extracts of leaves.

Figure 3

Table 1b: Antioxidant activity of methanolic extracts of

Figure 4

Tables 1c: Antioxidant activity of methanolic extracts of

All the medicinal plant materials used contain varying degrees of antioxidants. It is well recognized that free radicals are critically involved in various pathological conditions such as cancer, cardiovascular disorders, arthritis, inflammation and liver diseases (Martin et al. 1993). Under normal physiological conditions low concentrations of lipid peroxidation products are found in tissues and cells. In the presence of oxidative stress more lipid peroxidation products are formed due to cell damage. Cellular antioxidant enzymes such as superoxide dismutase, glutathione peroxidase and catalase normally challenge oxidative stress (Agbor et al. 2002). In this study, a methanol solution of DPPH free radical was found to be stable for more than 30 mins by spectrophotometry at 517nm of an (0.1mM) solution (Blois, 1958). The radical scavenging effect of 3 medicinal plant extracts and fractions of them were then measured spectrophotometrically for DPPH free radical. The control intensity (absorbance of extracts, fractions and pure compounds) was taken as 100% and the percentage intensity was calculated. The concentration for 50% inhibition (IC₅₀) as well as the plant extracts examined in this study for scavenging effects on DPPH free radical is shown in Tables 1-3.

Figure 5

Table 2a: Reducing power of methanolic extracts of

Figure 6

Table 2b: Reducing power of methanolic extracts of

Figure 7

Table 2c: Reducing power of methanolic extracts of

Values are expressed as mean ±S.D

Values are taken as a mean of three individual experiments

Conclusion

Against the backdrop of many known medicinal properties of these plants, results from the present work suggest that relatively low values of antioxidant and reducing power may not imply a low medicinal value. Emerging trends in antioxidant research point to the fact that low levels of phenolics (and other phytochemicals) and low value of antioxidant indices in plants do not translate to poor medicinal properties. The radical scavenging effects of Asteracantha longifolia were higher than all others in tested plants. Asteracantha longifolia found that major criteria for the evolution of anti-inflammatory activity in which it is caused a statistically significant suppression of ROS (Reactive Oxygen Species).

Acknowledgements

Correspondence to

A.Doss Department of Microbiology RVS College of Arts and Science Coimbatore, Tamilnadu, India dossandro@gmail.com