ent-kaurene diterpenoids from Isodon adenanthus

Three new ent-kaurene diterpenoids, adenanthins N, 0 and P (1-3), and four known diterpenoids, leucophyllin E (4), glabcensin C (5), adenanthin A (6), leucophyllin B (7), together with a highly unsaturated fatty acid, 9,16-dioxo-10,1 2,14-octadeca-trienoic acid (8), were isolated from Isodon adenanthus (Diels) Kudo. The structure of compound 4 was revised accordingly. Compound I showed significant cytotoxic activity against K562 cells with IC50 = 0.45 mug/mL.