RESUMEN
Six new diterpenes, leojaponins G-L (1-6) along with 19 known compounds (7-25) were isolated from Leonurus japonicus. Their structures were elucidated by NMR, MS, IR, UV, and ECD spectroscopic data. Anti-melanogenesis assay indicated that 7 could safely and dose-dependently decrease melanin production in B16F10 melanoma cell with an IC50 value of 59.1⯵M, but moderately inhibit tyrosinase activity. Without cytotoxicities at 20⯵M, compounds 11, 14, 15, and 17-21 showed significant melanogenesis stimulation activities at the percentages of 7.7-48.2. Antioxidants 19 and 24 could notably inhibit ROS production in a dose-dependent manner with percentages of 24.7-42.2 and 27.9-40.2, respectively among the concentrations of 0.16 to 100⯵M. Our results demonstrated L. japonicus and its constituents could be potential botanical resources of cosmeceutical development for treatment and prevention of skin disorders.