Abstract: The aim of this study was to explore the mechanism of processed Polygonum multiflorum induced hair blackening.The effects of water extract of processed P.multiflorum (PWE),crude polysaccharide from processed P.multiflorum, 2,3,5,4′-tetrahydroxystilbene-2-O-β-D-glucoside (THSG) and emodin on tyrosinase activity in B16F10 cells were assayed by measuring the oxidation rate of L-DOPA and Dopa staining testing.The impact of PWE,THSG and emodin on the tyrosinase mRNA expression in B16F10 cells was also examined using qRT-PCR.The results showed that none of the tested substance activated the tyrosinase activity effectively,though PWE (500 μg/mL) stimulated tyrosinase mRNA expression significantly.Then,the antioxidant capacity of PWE,emodin and THSG was determined using DPPH radical scavenging assay and the HepG2C8 cells.It showed that PWE and THSG eliminated DPPH free radical in a dose-dependent manner in vitro and elevated the expression of ARE in HepG2C8 cells.Therefore,the results in this report indicated that the strong antioxidant activity might be the reason for processed P.multiflorum to cause hair blackening.

Key words: water extract of processed Polygonum multiflorum;crude polysaccharide of processed Polygonum multiflorum, emodin;2,3,5,4′-tetrahydroxystilbene-2-O-β-D-glucoside, tyrosinase;antioxidant