Several sesquiterpenes isolated from a Formosan gorgonian coral Isis hippuris have shown significant cytotoxic activity against various cancer cell lines. In order to search other active components, we have investigated the chemical constituent of I. hippuris from a Green Island specimen. In the cytotoxcity assay, the EtOAc extract showed potent cytotoxic response toward P-388, A549 and HT-29 cancer cell lines. Thus, the investigation on the chemical content of this extract was carried out.
This study finally led to the isolation of twelve steroids(1-12). Nine metabolites, hippuristerone G (1)、hippuristerone H (2), hippuristerone I (3)、hippuristerone J (4)、hippuristerol E (5)、2a,3a-diacetoxy-24-methyl-
11b,18; 18,20b; 22,25-triepoxy-5a-furostane (7)、2a,3a-diacetoxy-11b-
furostane (11) and 2a,3a-diacetoxy-11b,18a-dihydroxy-24-methyl-18,
20b; 22,25-diepoxy-5a-furostane (12) are new compounds, whereas hippuristerone A (6), 3a-acetoxy-24-methyl-11b,18; 18,20b; 22,25-
triepoxy-5a-furostane (7) and 3a-acetoxy-11b-hydroxy-24-methyl-22,25-
epoxy-5a-furostan-18,20b-lactone (9) are known compounds. The structures of 1-12 were elucidated by spectroscopic evidences (IR, MS, 1D NMR, 2D NMR) and chemical method. The stereochemistries of compounds 7 and 9 were further confirmed by single-crystal X-ray diffraction analyses. Cytotoxicity test revealed that hippuristerone I (3) exhibited moderate inhibition toward NCI cancer cell line.