Simplexins A-I, eunicellin-based diterpenoids from the soft coral Klyxum simplex.

Nine new eunicellin-based diterpenoids, simplexins A-I (1-9), were isolated from a Dongsha Atoll soft coral, Klyxum simplex. The structures of these compounds were established by detailed spectroscopic analysis (IR, MS, 1D and 2D NMR) and by comparison with the physical and spectral data of related known compounds. The absolute configuration of 1 was determined by a modified Mosher's method. Compounds 1, 4, and 5 were found to be cytotoxic toward a limited panel of cancer cell lines. Compound 5 was shown to significantly inhibit the accumulation of the pro-inflammatory iNOS and COX-2 proteins in LPS-stimulated RAW264.7 macrophage cells.