Anti-melanogenic effect of the aqueous ethanol extract of Ginkgo biloba leaf in B16F10 cells

Objective Ginkgo biloba leaf extract (GLE) shows diverse biological effects, and it is used as an ingredient in some skincare products. GLE and a few purified compounds are known to inhibit melanogenesis. However, there are very few reports on the molecular mechanisms underlying the regulation of melanogenesis by GLE. We investigated the anti-melanogenic effect of a GLE, an aqueous ethanol extract of Ginkgo biloba leaves, and the molecular mechanisms involved. Methods B16F10 murine melanoma cells were treated with various concentrations of GLE (0-100 mu g/mL), together with 0.1 nM alpha-melanocyte stimulating hormone (alpha-MSH), which was used to induce melanogenesis. Cell proliferation, total melanin content, cellular reactive oxygen species (ROS) content, and cellular tyrosinase activity were measured. The cellular levels of microphthalmia-associated transcription factor (MITF), tyrosinase, and tyrosinase-related protein 1 (TYRP1), and the phosphorylation levels of Akt, glycogen synthase kinase 3 beta (GSK3 beta), and beta-catenin were analyzed. Results GLE inhibited alpha-MSH-induced melanogenesis and ROS generation, without causing cytotoxicity. GLE decreased cellular tyrosinase activity and the levels of MITF, tyrosinase, and TYRP1. GLE decreased the phosphorylation of Akt (Ser473) and GSK3 beta (Ser9) and increased the phosphorylation of beta-catenin (Ser33/37/Thr41). Conclusions Our results suggest that GLE can inhibit alpha-MSH-induced melanogenesis in B16F10 cells by downregulating the expression of melanogenic proteins, i.e., MITF, tyrosinase, and TYRP1. The downregulation of melanogenic protein expression appears to result from stimulating beta-catenin degradation, which is induced by phosphorylation by GSK3 beta that is activated via inhibition of Akt. GLE's antioxidant activity can also play a role in its anti-melanogenic effect.