Involvement of p38 MAPK signaling pathway in the anti-melanogenic effect of San-bai-tang, a Chinese herbal formula, in B16 cells

Aim of the study San-bai-tang (SBT), a Chinese herbal formula, is traditionally used as a skin whitener in China. In our previous screening assays, SBT was identified as an effective tyrosinase inhibitor. In this study, we aim to investigate the anti-melanogenic effect and mechanisms of SBT in B16 cells. Materials and methods Cell viability was examined by the MTT assay. Cellular tyrosinase activity and melanin content were determined using spectrophotographic methods. Protein expression was analyzed by immunoblotting. Results SBT inhibited tyrosinase activity with an IC50 of 215.6 ± 10.3 μg/ml, and decreased cellular melanin content with an IC50 of 254.8 ± 14.5 μg/ml at 48 h. MTT assay demonstrated that 48-h SBT (50–400 μg/ml) treatment did not show obvious cytotoxicity. Immunoblot analysis showed that SBT (100, 200 or 400 μg/ml) treatment for 48 h down-regulated the expression levels of phosphorylated-p38, MITF, tyrosinase, TRP-1 and TRP-2 in a dose-dependent manner. Conclusions SBT inhibited melanogenesis in B16 cells, and suppression of p38 MAPK signaling pathway contributed to the anti-melanogenic effect of SBT by down-regulating the expression of MITF and melanogenic enzymes. These novel findings demonstrated the anti-melanogenic effect and mechanisms of SBT, and provide pharmacological basis for the traditional use of SBT.