Four New Cembrane Diterpenes Isolated from an Okinawan Soft Coral Lobophytum crassum with Inhibitory Effects on Nitric Oxide Production

Four new cembrane diterpenes (1-4) and fifteen known cembranoids (5-19) were isolated from an Okinawan soft coral Lobophytum crassum. The structures of these four new cembranoids were determined on the basis of spectroscopic evidence. In particular, the absolute stereochemistry of I, 2, 5 and 6 were elucidated by the application of the modified Mosher's method and circular dichroism (CD) spectral data. The inhibitory effects of some isolates were evaluated on nitric oxide (NO) production against a murine macrophage-like cell line (Raw 264.7). Cembranoids consisting of alpha-methylene-gamma-lactone, exhibited the significant effect on NO production.