The effect of chlorophorin and its derivative on melanin biosynthesis

By means of bioassay-guided fractionation using mushroom tyrosinase, a geranylated stilbene, chlorophorin, was characterized as the principal tyrosinase inhibitor in the heartwood of Chlorophora excelsa (Moraceae). It inhibited the oxidation Of L-tyrosine and (DL)-3,4-dihydroxyphenylalanine ((DL)-DOPA) due to mushroom tyrosinase and melanin biosynthesis on B16 melanoma cells. Chlorophorin, which is a slight yellowish compound, has previously been reported as an unstable compound in light. On the basis of this finding, a chlorophorin derivative [4-(3",7"-dimethyloctyl)-2 ',3,4 ',5-tetrahydroxydihydrostilbene; hexahydrochlorophorin] which is colorless, obtained by the hydrogenation of chlorophorin with Pd/ C, was also tested to develop a superior material for practical use. Hexahydrochlorophorin showed more potent inhibitory activity on tyrosinase and melanin biosynthesis, and lower cytotoxicity towards B16 melanoma cells than chlorophorin.