New 4,5-seco-20(10→5)-abeo-Abietane Diterpenoids with Anti-Inflammatory Activity from Isodon lophanthoides var. graciliflorus (Benth.) H.Hara.

Three new 4,5-seco-20(10→5)-abeo-abietane diterpenoids, 16-hydroxysalvilenone (1), 15-hydroxysalprionin (2), and 11β,15-dihydroxysalprionin-12-one (3), and nine known abietane diterpenoids, 4-12, along with one known sempervirane diterpenoid, hispidanol A (13), were isolated from the aerial parts of Isodon lophanthoides var. graciliflorus. The structures of compounds 1-3 were determined on the basis of spectroscopic methods including extensive analysis of NMR and mass spectroscopic data. All diterpenoids were tested for their TNF-α inhibitory effects on LPS-induced RAW264.7 cells. Compound 9 (16-acetoxyhorminone) was the most potent with an IC₅₀ value of 3.97±0.70 μm.