Abstract
Hyperpigmentation resulting from the overactivation of tyrosinase leads to darker spots or patches on the human skin. Although these phenomena are harmless, there is still great demand for melanogenesis inhibitors to prevent hyperpigmentation by inhibiting the tyrosinase, a rate-limiting enzyme in melanogenesis. Although Lepisorus thunbergianus has been used in folk remedies as a diuretic and hemostatic agent, its effect on melanogenesis has not yet been reported. In this study, we prepared an L. thunbergianus extract and its solvent fractions and evaluated their biological activity against free radical and melanin synthesis. The extract of L. thunbergianus inhibited mushroom tyrosinase activity more efficiently than, and with similar antioxidant activity to, arbutin in vitro. Comparative evaluation of the anti-melanogenesis and anti-tyrosinase activity of L. thunbergianus solvent fractions demonstrated that, by inhibiting tyrosinase activity, the butanol fraction has the highest potential for the inhibition of melanogenesis in melanoma cells. We found by structural analysis using high-performance liquid chromatography (HPLC) and NMR spectroscopy that the major compounds in butanol fraction were three caffeoylquinic acid derivatives. The three derivatives had similar radical scavenging and anti-tyrosinase activities in vitro, while only 5-caffeoylquinic acid had an inhibitory effect on α-MSH-induced melanogenesis. The inhibitory effect of 5-caffeoylquinic acid was verified by the determination of the melanin content and tyrosinase activity in melanoma after treating the cells with a commercial compound. Further, we revealed that 5-caffeoylquinic acid inhibited melanogenesis by chelating a copper cation from a copper-tyrosinase complex. Thus, 5-caffeoylquinic acid or butanol fraction isolated from L. thunbergianus might be useful in cosmetics as a skin-whitening agent.