Melanogenesis Inhibitory Activities of Diarylheptanoids from Alnus hirsuta Turcz in B16 Mouse Melanoma Cell

Four diarylheptanoids, (5R)-1,7-bis (3,4-dihydroxyphenyl)-heptane-5-O-$\beta$-D-glucoside (1), (5R)-1,7-bis (3,4-dihydroxyphenyl)-heptane-5-ol (2), oregonin (3), hirsutanonol (4), were isolated from the bark of Alnus hirsuta Turcz and its inhibitory effects on melanogenesis by measuring the melanin level and tyrosinase activity in B16 melanoma cell were examined. Melanin level and tyrosinase activity were reduced to 75 to 85% by addition of diarylheptanoids to incubation medium of the melanoma cell. On the other hand, melanin level and tyrosinase activity were reduced to 13 to 43% by the addition of diarylheptanoids to incubation medium of the melanoma cell treated with melanogenesis stimulator, $\alpha$-MSH and forskolin. These melanogenesis inhibitory effects were significantly different compared with control.