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Five new steroids, norselic acids A-E (1-5), were isolated from the sponge Crella sp. collected in Antarctica. The planar structures of the norselic acids were established by extensive NMR spectroscopy and mass spectrometry studies, and the configuration of norselic acid A (1) was elucidated by X-ray crystallography. Norselic acid A displays antibiotic activity against methicillin-resistant Staphylococcus aureus (MRSA), methicillin-sensitive S. aureus (MSSA), vancomycin-resistant Enterococcus faecium (VRE), and Candida albicans and reduces consumption of food pellets by sympatric mesograzers. Compounds 1-5 are also active against the Leishmania parasite at low micromolar levels.

Seven new steroids, compounds 1-7, were isolated from the Antarctic octocoral Anthomastus bathyproctus. The structures of the new metabolites have been established by analysis of their spectroscopic data. The in vitro cytotoxicity has been tested against three human tumor cell lines.

The chemical study of the Antarctic octocoral Dasystenella acanthina has led to the isolation of the new polyoxygenated steroids (24R,22E)-24-hydroxycholest-4,22-dien-3-one (1), 23-acetoxy-24,25-epoxycholest-4-en-3-one (2), 12beta-acetoxycholest-4-en-3,24-dione (3), 12beta-acetoxy-24,25-epoxycholest-4-en-3-one (4), (22E)-25-hydroxy-24-norcholest-4,22-dien-3-one (5), 3alpha-acetoxy-25-hydroxycholest-4-en-6-one (6), and 3alpha,11alpha-diacetoxy-25-hydroxycholest-4-en-6-one (7), whose structures have been established by spectroscopic analysis. The absolute stereochemistry at C-24 in compound 1 has been determined through the 1H NMR study of the corresponding (R)- and (S)-MPA esters. All the new compounds showed significant activities as growth inhibitors of several human tumor cell lines. In addition, cytostatic and cytotoxic effects were also observed on selected tumor cell lines.