2,2-diphenyl-1-picrylhydrazyl radical-scavenging active components from Polygonum multiflorum Thunb.

An activity-directed fractionation and purification process was used to identify the antioxidative components of Polygonum multiflorum Thunb. (PM). Dried root of PM was extracted with 95% ethanol and then separated into water, ethyl acetate, and hexane fractions. Among these only the ethyl acetate phase showed strong antioxidant activity by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) test when compared with water and hexane phases. The ethyl acetate fraction was then subjected to separation and purification using silica gel column chromatography and Sephadex LH-20 chromatography. Three compounds showing strong antioxidant activity were identified by spectral methods (H-1 NMR, C-13 NMR, and MS) and by comparison with authentic samples to be gallic acid, catechin, and 2,3,5,4'-tetrahydroxystilbene 2-O-beta-D-glucopyranoside.