Depigmentory Effects of Keishibukuryogankayokuinin in Human Epidermal Melanocytes

摘要

Keishibukuryogankayokuinin (KBY) is a traditional Japanese herbal medicine widely used to treat skin pigmentation. The scientific basis for its use is, however, unclear, and studies evaluating its mechanism and effectiveness are sparse. In this study, we compared the tyrosinase inhibitory effects of KBY and Keishibukuryogan (KB, which has the same composition of KBY, except Coix Seed [CS]) and CS under exposure to UV radiation as well as under non-exposure conditions. Neonatal human epidermal melanocytes obtained from a darkly pigmented donor were used. These cells were cultured in a final concentration of 500 μg/ml or 1000 μg/ml, to which KBY, KB, and CS were added. After incubation for 72 h, cells were stained with Fontana-Masson stain and counted. Tyrosinase activity was measured by its dopa oxidase activity, and tyrosinase expression was estimated using real-time PCR. For UV radiation, cells were exposed to UVB radiation for 90 s per day for 3 days. Under non-exposure conditions, tyrosinase activity significantly increased with both KBY and KB but significantly decreased with CS, regardless of the concentration. In addition, tyrosinase expression significantly decreased but only with KBY at both concentrations. Under UV radiation exposure, tyrosinase activity significantly increased with KBY and KB at both concentrations while tyrosinase expression significantly decreased with KBY and KB; a significant increase was, however, observed with CS at both concentrations. These results suggest that taking KBY after sunburn is effective against skin pigmentation, and the combination of KB and CS is useful for skin depigmentation.