Abstract
Stevia (Stevia rebaudiana), a well-known sweet herb, has been reported to have potent antioxidant activity. Methanolic extract of Stevia was fractionated and subsequently purified according to the results of DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assay, producing three active compounds. Structural analysis of these compounds revealed that they were 3,4-dicaffeolylquinic acid, 3,5-dicaffeolylquinic acid and quercetin-3-O-α-rhamnopyranoside. Their antioxidant activity was measured using a radical initiator AAPH 2,2′-azobis(2-amidinopropane)hydrochloride -induced lipid oxidation system. While their activity was not as high as that of trolox, the three isolated compounds exhibited potent antioxidant activity at a concentration of 60μmol/l.
