Studies of cuticle drugs from natural sources. III. Inhibitory effect of Myrica rubra on melanin biosynthesis.

The inhibitory effect of a 50% ethanolic extract obtained from the dried leaves and the bark of Myrica rubra, was investigated in vitro on melanin biosynthesis which is closely related to hyperpigmentation. These extracts inhibited tyrosinase activity which converts dopa to dopachrome in the biosynthetic process. Furthermore, the extracts inhibited the production of melanin from dopachrome by autoxidation and also showed superoxide dismutase (SOD)-like activity. After bioassay-guided fractionation, quercetin, myricetin and myricetin 3-O-rhamnoside were isolated from the leaves. As they showed the inhibitory effect on tyrosinase activity, the activity is partially attributable to them in the extract of M. rubra. These results suggested that the leaves or the bark of M. rubra might be used as a whitening agent for the skin.