Dimeric ent-Kaurane Diterpenoids from Isodon excisus

Five new dimeric ent-kauranoids, biexcisusins A–E (1–5), were isolated from the aerial parts of Isodon excisus. The structures and relative configurations of these compounds were determined on the basis of spectroscopic data interpretation. Of these, biexcisusins C–E (3–5) are dimeric ent-kaurane diterpenoids exhibiting an unprecedented linkage through a nine-membered lactone ring between two ent-kaurane subunits. Compounds 1–5 showed no inhibitory effects on the LPS-induced production of nitric oxide in murine macrophage RAW264.7 cells, up to a dose of 50 μM.