Enos Tangke Arung, 1. Department of Forest and Forest Products Sciences, Faculty of Agriculture, Kyushu University, Fukuoka, Japan
1 Keisuke Yoshikawa, 2. Department of Forest and Forest Products Sciences, Faculty of Agriculture, Kyushu University, Fukuoka, Japan
2 Kuniyoshi Shimizu, 3. Department of Forest and Forest Products Sciences, Faculty of Agriculture, Kyushu University, Fukuoka, Japan
3 Ryuichiro Kondo4. Department of Forest and Forest Products Sciences, Faculty of Agriculture, Kyushu University, Fukuoka, Japan
4 Corresponding author. Department of Forest and Forest Products Sciences, Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka, 812-8581, Japan Tel./Fax: +81-92-642-2811
Abstract
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.
