STUDIES OF CUTICLE DRUGS FROM NATURAL SOURCES .2. INHIBITORY EFFECTS OF PRUNUS PLANTS ON MELANIN BIOSYNTHESIS

The inhibitory effects of 50% ethanolic extracts from dried leaves of 38 plants collected in the herbal. garden of Kinki University were investigated in vitro on melanin biosynthesis which is closely related to hyperpigmentation. Of the 38 extracts, Prunus yedoensis, P. zippeliana, P. amygdalus, P. persica, P. armeniaca, Thea sinensis and Chaenomeles sinensis showed a potent inhibition of tyrosinase, the enzyme which converts 3-(3,4-dihydroxyphenyl)alanine (dopa) to dopachrome in the biosynthetic process. Furthermore, the extracts from the leaves of P. yedoessis and P. zippeliana among the Prunus plants used in this experiment inhibited the production of melanin from dopachrome by autoxidation. These inhibitory effects of P. zippeliana on melanin biosynthesis were observed in cultured B-16 mouse melanoma cells. These results suggest that the leaves of P. zippeliana inhibit melanin biosynthesis which is involved in hyperpigmentation and could be used as a whitening agent for the skin.