New Eunicellin Diterpenes And 9,10-Secosteroids From The Gorgonian Muricella Sibogae

Bioactivity-guided isolation of the rare gorgonian Muricella sibogae (Nutting) yielded the two new eunicellin diterpenes sibogin A and B (1 and 2), the three new 9,10-secosteroids sibogol A-C (6-8), together with the three known eunicellin diterpenes 3-5 and the five known 9,10-secosteroids 9-13. Their structures were established by extensive spectral analysis (1D- and 2D-NMR, IR, and MS). The cytotoxicity of the isolates 1-13 was evaluated in vitro against the selected tumor cell lines P388 and BEL-7402. All the compounds showed only weak activity against P388 cell lines, with an inhibition rate ranging from 10 to 60% at a concentration of 50g/ml, whereas the were inactive against BEL-7402 cell lines.