Isolation and Structure Elucidation of Cembranoids from a Dongsha Atoll Soft Coral Sarcophyton stellatum

Six new polyoxygenated cembrane-based diterpenoids, stellatumolides A-C (1-3), stellatumonins A and B (4 and 5), and stellatumonone (6), were isolated together with ten known related compounds (7-16) from the ethyl acetate (EtOAc) extract of soft coral Sarcophyton stellatum. The structures of the new compounds were established by extensive spectroscopic analyses, including 1D and 2D nuclear magnetic resonance (NMR) spectroscopy and data comparison with related structures. Compounds 8 and 14 were isolated from a natural source for the first time. The isolated metabolites were shown to be not cytotoxic against a limited panel of cancer cells. Compound 9 showed anti-inflammatory activity by reducing the expression of proinflammatory cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) proteins in lipopolysaccharide (LPS)-stimulated mouse leukaemic monocyte macrophage (RAW 264.7) cells.