Abstract:
A wide array of Sri Lankan medicinal plants has been used for the treatment of many chronic diseases such as diabetes mellitus, liver diseases and arthritis in Ayurvedic medicine. Antioxidants are reported to play central roles in reducing or preventing free radical damage in the above oxidative stress related diseases. The present study was conducted to evaluate the antioxidant activities of hot water extracts of 20 Sri Lankan medicinal plants. The total polyphenol content was determined by Folin-Ciocalteu method. The antioxidant activities were determined by three methods namely 2,2-diphenyl-2picrylhydrazyl hydrate (DPPH) radical scavenging activity, ferric reducing power (FRAP) and nitric oxide (NO) inhibition. Gallic acid and L-ascorbic acid were the reference compounds in expressing the polyphenol content and the antioxidant activities by the three assays, respectively. The total polyphenol content varied from 1.84 to 26.25 mgGAE /gm. The antioxidant activities ranged from IC50 of 19.48-245.68 µg/mL for DPPH radical scavenging, 103.35-484.60 µg/mL for NO inhibition and 1.14-26.06 µM for Ferric reducing antioxidant power (FRAP). A significant positive correlation was found between total polyphenol content and antioxidant activities indicating polyphenol compounds contribute significantly to the total antioxidant properties of medicinal plant extracts.
