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

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. (C) 2014 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved.