GA 2017

Leonurus japonicus (Lamiaceae), a traditional Chinese medicine (TCM), could inhibit the melanin synthesis on B16F10 melanoma cells. No anti-melanogenesis phytochemical study of this TCM has been reported to date. Therefore, the species was selected as a lead candidate of anti-melanogenesis drugs developments to investigate its active components and mechanism of action. The methanol extracts (LJM) of dried L. japonicus showed anti-melanogenesis effects, and then the LJM were partitioned into EtOAc (LJME) and aqueous extracts (LJMW). The LJME fraction has significant inhibitory effects against B16F10 cells at the concentrations of 50 and 100 μg/mL, but cytotoxicity at concentration of 200 μg/mL. Additionally, the LJMW fraction showed anti-melanogenesis effects in a dose-dependent manner. The LJME fraction was further isolated into 95%MeOH (LJMEM)- and hexane- (LJMEH) soluble fractions. Chromatographic fractionation of the LJMEM led to isolation 24 compounds, nine diterpenes 1-9, four monoterpenes 10-13, four flavones 14-17, four benzenoids 18-21, and two lignans 22-23. The isolates 1-7 were elucidated as new compounds via various spectroscopic data. Anti-melanogenesis effects of 1-23 (IC50 < 50 μg/mL) were evaluated to clarify the potential activity of L. japonicus. Overall, our studies identified L. japonicus as a promising plant source of new agents for whitening drugs and cosmetic research.