New diterpenes leojaponins G-L from Leonurus japonicus

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 μM, but moderately inhibit tyrosinase activity. Without cytotoxicities at 20 μM, 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 μM. Our results demonstrated L. japonicus and its constituents could be potential botanical resources of cosmeceutical development for treatment and prevention of skin disorders.