A new diepoxy-ent-kauranoid, rugosinin, from Isodon rugosus.

A new diterpenoid, rugosinin (1), isolated from Isodon rugosus, with absolute configuration was proved by single-crystal X-ray diffraction analysis, to be the member of a rare class of C-20/C-7 and C-20/C-14 diepoxy- ent-kauranoids. Effusanin A (2), effusanin B (3), effusanin E (4), lasiokaurin (5) and oridonin (6) were found as known constituents of the genus Isodon with C-20/C-7 epoxy function. These compounds have exhibited DNA-damaging activity in assay which employed DNA-repair deficient (RAD 52Y) and repair proficient (RAD +) yeast strains.