Abstract: This paper investigated the effect of water extract,separated parts of ethanol extract from processed Polygonum multiflorum and the monomer components including emodin, physcion, emodin-8-O-β-D-glucoside and 2,3,5,4′-tetrahydroxystilbene-2-O-β-D-glucoside (THSG) on the tyrosinase activity in vitro by measuring the oxidation rate of L-DOPA.The results showed that none of the tested substance could activate the tyrosinase activity effectively.Conversely,50% ethanol and 95% ethanol eluted components from the ethanol extract of processed Polygonum multiflorum, water extract of processed Polygonum multiflorum and THSG inhibited the tyrosinase activity in a concentration dependent manner.THSG exhibited a significant tyrosinase inhibitory activity (reached 46.72%) at the concentration of 48 μg/mL,which indicated that THSG has potential value in developing skin whitening product.

Key words: Tyrosinase activity, Extracts from processed Polygonum multiflorum, emodin, physcion, emodin-8-O-&beta, -D-glucoside, 2,3,5,4&prime, -tetrahydroxystilbene-2-O-&beta, -D-glucoside