New labdane diterpenoids from Leonurus japonicus and their anti-inflammatory activity

Abstract Two new, 16-oxo-leoheteronone A ( 1 ) and 15-methoxyleoheteronin B ( 2 ), and four known, 8,9-secohispanolone ( 3 ), galeopsin ( 4 ), hispanone ( 5 ), and leoheteronin B ( 6 ), labdane diterpenoids were isolated from the aerial parts of Leonurus japonicus . Compound 3 was isolated for the first time as a naturally occurring compound. Structures of the two compounds were determined on the basis of extensive spectroscopic techniques, including 1D, 2D NMR, and HREIMS. In addition, compounds 1 – 3 , 5 and 6 were examined for inhibition of superoxide anion generation and elastase release, and the results suggested that compound 5 possesses anti-inflammatory activity.