In order to discover bioactive secondary metabolites, we have studied the chemical constituents from the organic extracts of soft coral Sinularia flexibilis. This study had led to the isolation of eighteen natural compounds 1¡V18, including seven new cembrane-type diterpenoids, flexibilisolides C¡VG (1, 2, 3, 6, 7), flexiblilisin C (5), 11,12-secoflexibillin (4) along with eleven know compounds. The structure of compounds 1¡V18 were established by detailed spectral data analysis (IR, MS, 1D, 2D NMR) and by comparison of the spectral data with those of the related known compounds. The cytotoxicity of compounds 1¡V6, 8¡V14, 16¡V18 against the Hela (human cervical epitheloid carcinoma), SK-Hep1 (human liver carcinoma), and B16 (human melanin carcinoma) tumor cell lines were screened. Compounds 1, 9, 12, and 13 showed moderate activity toward the Hela and SK-Hep1 tumor cells. Compound 12 also showed moderate activity toward the B16 cells, and compound 14 showed activity toward the Hela cells. On the other hand, compounds 1, 9, 13, and 17 were found to show significant activity against the accumulation of the pro-inflammatory iNOS and COX-2 protein at 10 £gM. Compounds 2¡V4, 7, 8, 10, 14, 16 were found to show activity against the accumulation of the pro-inflammatory iNOS protein at 10 £gM.

Investigation on the chemical constituents of the EtOH extract of the soft coral Lobophytum sarcophytoides, collected off the coast of Dongsha Atoll, Taiwan, has led to the isolation of ten natural compounds 1¡V10, including four new cembrane-type diterpenoids, Sarcophytolins A¡VD (1¡V4) and one new polyhydroxylated steroid 23, 24-Dimethyl-cholesta-5, 16-diene-3£], 20£\-diol (5) along with five know compounds 6¡V10¡CThe structure of compounds 1¡V10 were established by detailed spectral data analysis (IR, MS, 1D, 2D NMR) and by comparison of the spectral data with those of the related known compounds. The relative stereochemistries of compound 5 was further confirmed by X-ray single-crystal diffraction analysis. The cytotoxicity of compounds 1¡V10 against the Daoy (human medulloblastoma), Hep-2 (human laryngeal carcinoma), MCF-7 (human breast adenocarcinoma), CCRF-CEM (human T-cell acute lymphoblastic leukemia), and DLD-1/WiDr (human colon adenocarcinoma) tumor cell lines were determined. Compounds 6, 8, 9, and 10 exhibited moderate cytotoxicities against the tested tumor cells. Furthermore, compounds 1, 2, 4, 6, and 10 were found to show significant activity against the accumulation of the pro-inflammatory iNOS protein at 10 £gM.

Soft corals of the genus Lobophytum (Alcyoniidae) have been well recognized as a rich source of various secondary metabolites that have attracted much interest for the natural products chemists due to their structural complexity and remarkable pharmacological activities such as cytotoxicity, antibacterial activities, anti-inflammatory properties, and antiviral activity. Twelve cembrane diterpenes including six new secondary metabolites 1−6 were isolated organic extracts of soft coral Lobophytum durum collected at Dongsha Atolls. The structures of these six new cembranolides were determined by 1H, 13C, DEPT, COSY, HMBC, HSQC, NOESY, IR and Mass spectra. Furthermore, these six new secondary metabolites 1−6 were evaluated in vitro for the cytotoxicity against A-459 (human lung carcinoma), HT-29 (human colon adenocarcinoma), and P-388 (mouse lymphocytic leukemia) cancer cell lines, and antiviral activity against HCMV (human cytomegalovirus) cells.