Melanogenesis inhibition by an oolong tea extract in b16 mouse melanoma cells and UV-induced skin pigmentation in brownish guinea pigs.

To investigate the new physiological functions of oolong tea, the effects on melanogenesis were studied. An oolong tea extract inhibited melanogenesis without affecting cell growth in B16 mouse melanoma cells. However, the oolong tea extract hardly showed any inhibitory effect on mushroom tyrosinase in a cell-free system. The effects of an oolong tea extract on the intracellular tyrosinase level in B16 cells were therefore studied. All the levels of activity, protein and mRNA were decreased in the oolong tea extract-treated cells. We also investigated the inhibitory effects of oolong tea on the pigmentation induced by ultraviolet B (UVB) by using brownish guinea pigs in vivo. The number of 3,4-dihydroxyphenylalanine (DOPA)-positive melanocytes increased by UVB was repressed by an oral administration of oolong tea. These results imply that oolong tea might be effective in whitening and that its inhibitory effect on melanogenesis was involved in the decrease of intracellular tyrosinase at the mRNA level.