摘要：In Vitro Studies on the Depigmenting Activity of 4-( p -Hydroxyphenyl)-2-Butanone: Yoshiharu FUKUDA, et al. Department of Public Health, Kumamoto University School of Medicine -The aim of this study is to investigate the enzymatic properties and the depigmenting activity of 4-( p -hydroxyphenyl)-2-butanone (HPB) in vitro. The activity of HPB as a substrate of tyrosinase, its effect on tyrosinase enzymatic reactions, and its inhibition of the growth and the melanogenesis of cultured melanoma cells were examined. The HPB-tyrosinase reaction and the effect of HPB on tyrosine-tyrosinase and dopa-tyrosinase reactions were followed spectrophotometrically. Fifty percent growih inhibition concentrations (IC50) of several chemicals for melanoma cells and non-pigmented cells were measured. Melanogenic activities in HPB-treated melanoma cells were assayed. The results showed that HPB was oxidized by tyrosinase and stimulated tyrosinetyrosinase and dopa-tyrosinase reactions. The IC50 of HPB for melanoma cells was higher than those of the established depigmenting agents but it was lower than that of HPB for non-melanotic cells. Tyrosine hydroxylase in HPB-treated melanoma cells was stimulated comparecl with the control, but melanin product in HPB-treated cells was almost similar to the control. The results showed that HPB acts as a good substrate for tyrosinase and it stimulates tyrosinase enzymatic reactions, but it inhibits pigmented cell growih selectively. This study suggests that HPB-induced depigmentation is due to a selective cytotoxic effect on pigmented cells rather than to the inhibition to melanogenesis.
