Phenylacylphenol derivatives with anti-melanogenic activity from Stewartia pseudocamellia

Three new phenylacylphenol derivatives, stewartianol (1), deoxystewartianol-4'-O-arabinoglucoside (2), and stewartianol-3-O-glucoside (3), along with nine known compounds, methylesculin (4), fraxoside (5), fraxetin (6), scopletin (7), (+)-dihydromyricetin (8), (+)-taxifolin-7-O-β-D-glucose (9), (+)-taxifolin (10), (+)-dihydrokaempferol-7-O-β-D-glucose (11), and 3-acetyl-ursolic acid (12), were isolated from the twigs of Stewartia pseudocamellia; commonly used as folk medicine in Korea. The structures of the isolated compounds were identified using spectroscopic analysis, including 1D, 2D NMR, MS and compared with published data. The compounds were tested for their anti-melanogenic activity in cultured murine B16 melanoma cells. Stewartianol (1) and stewartianol-3-O-glucoside (3) showed an inhibitory effect significantly on melanogenesis in a concentration-dependent manner.