Isolation of Gallic Acid and Estimation of Total Phenolic Content in Some Medicinal Plants and Their Antioxidant Activity

Gallic acid was isolated from ethylacetate soluble portion of the methanol extract of fruit pulp of Terminalia chebula and characterized by comparing the melting point, Rf values, UV and IR spectra with authentic gallic acid. Quantitative determination of phenolics from different extracts of medicinal herbs such as Adhatoda vasica Nees, Bergenia ciliata (Haw) Sternb, Phyllanthus emblica Linnaeus, Terminalia bellirica (Gaerth) Roxb, Terminalia chebula Retzius and Vitex negundo Linnaeus which are commonly used as home herbal remedies for the primary health care was carried out using Folin-Ciocalteu colorimetric method. Gallic acid was used as the standard for the estimation of phenolics. All the investigated plant extracts contained high amount of phenolics but the highest amount was detected in 70 % acetone extract of B. ciliata (357.08 mg GAE/g sample) and the lowest amount was detected in 50% aqueous methanol extract of T. bellirica (108.69 mg GAE/g sample). The antioxidant activity of selected extracts was determined by 1,1-diphenyl-2-picryl-hydrazyl (DPPH) assay. The extract having the highest phenolic content showed the lowest IC50 demonstrating the positive correlation between radical scavenging activity and total phenolic content. Key words: antioxidant activity, gallic acid, medicinal herbs, total phenolic conten