Cytotoxic ketosteroids from the Red Sea soft coral Dendronephthya sp.

A marine specimen of the Red Sea soft coral Dendronephthya sp. was extracted with a mixture of n-hexane, diethyl ether, and methanol. One new cytotoxic steroid dendronestadione (1), five known steroids: dendronesterones A-C (2-4), dendrotriol (5), and cholesterol (6) along with 4-oxo-pentanoic acid (7) and a polyhydroxy alkane hexitol (8) were isolated from the Dendronephthya sp. extract. The chemical structures of the isolated metabolites were elucidated by the application of several spectroscopic techniques (1D, 2D NMR, IR, and UV) and mass spectrometry. The antiproliferative effect of the isolated compounds was assessed against a panel of human cancer cell lines including HepG2, HT-29, and PC. The obtained results indicated that compounds 1-4 (dendronesterones A-C) exhibited a higher cytotoxic effect than that of the other co-isolated ones. Among all examined dendronesterones, dendronesterone C showed the highest IC50 values of 19.1 +/- 1.81, 32.4 +/- 2.84, and 7.8 +/- 0.80 mu M against the three cancer cells under investigation. Interestingly, all isolated ketosteroids showed potent effects against prostate cancer cells. These findings highlight the role of ketosteroids as an antiproliferative agent against the examined cells in this study.