Comparison of antioxidant activity, Phenolic and Flavonoid contents of selected medicinal plants in Sri Lanka

Oxidative stress related diseases are as a result of accumulation of free radicals in the cellular organs. Plant based antioxidants play a defensive role by preventing the generation of free radicals and therefore the main focus of this study was to screen twenty five Sri Lankan medicinal plants for comparison of antioxidant capacity. Aqueous extracts of twenty five plants were screened for antioxidant activity by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Six plants that gave high antioxidant activity Terminalia chebula Retz., Punica granatum L., Flueggea leucopyrus Willd., Cassia fistula L., Piper betle L. and Phyllanthus amarus were selected for further analysis. Methanol extracts of the selected plants were subjected to assess IC50 by DPPH assay. Total phenolic and flavonoid contents were analyzed by Folin Ceocalteu method and Aluminium Colorimetric method respectively. Statistical analysis was done by Minitab 17 package using regression analysis techniques to identify the effect of IC50 by phenolics and flavonoids. Seeds of T. chebula Retz. showed high antioxidant activity with 102 mg/ml of IC50 value. Antioxidant activity of rest of the plants in the descending order was F. leucopyrus Willd. (twigs) > C. fistula L. (bark) > P.granatum L. (leaves) > P. betle L. (leaves) >P. amarus (twigs). The relationship between IC50 by phenolic and flavonoid content was statistically significant. Further IC50 has a strong negative relationship between phenolics and flavonoids. Data from present study revealed that Terminalia chebula Retz., Punica granatum L., Flueggea leucopyrus Willd., Cassia fistula L., Piper betle L. and Phyllanthus amarus possess high antioxidant capacity compared to other medicinal plants.