Two new labdane diterpenoids from aerial parts of Leonurus japonicus and their anti-inflammatory activity.

Two new labdane diterpenoids, Leojaponin E (1) and F (2), together with three known compounds were isolated from the dried herb of Leonurus japonicus Houtt., Lamiaceae. Their structures were determined based on extensive spectroscopic analyses. The absolute configurations of 1 and 2 were elucidated on the basis of experimental and calculated electronic circular dichroism spectra. In addition, compounds 1 and 2 exerted inhibition of LPS-induced PGE2 production in a dose-dependent manner at concentrations ranging from 5 to 20 µM.