Polyhydroxylated steroids have four carbon-based rings and are adorned with several hydroxyl groups, giving these molecules a high oxidation level and making them very difficult to synthesise and modify using simple methods. “Ouabagenin has six of these hydroxyl groups, which also exist in a lopsided orientation,” said Hans Renata, a graduate student in the Baran laboratory who was first author of the study. “This confers a strong directionality on ouabagenin molecules, so that they tend to stick even to inorganic material such as laboratory glassware, especially on small scale.”
In previous studies on the secondary metabolites of the Taiwanese octocoral Isis？hippuris, specimens have always been collected at Green Island. In the course of our studies on bioactive compounds from marine organisms, the acetone-solubles of the Taiwanese octocoral I. hippuris collected at Orchid Island have led to the isolation of five new polyoxygenated steroids: hipposterone M–O ( 1– 3), hipposterol G ( 4) and hippuristeroketal A ( 5). The structures of these compounds were determined on the basis of their spectroscopic and physical data. The anti-HCMV (human cytomegalovirus) activity of 1– 5 and their cytotoxicity against selected cell lines were evaluated. Compound 2 exhibited inhibitory activity against HCMV, with an EC 50 value of μg/mL.