Plakinamines C and D and three other new steroidal alkaloids from the sponge Corticium sp.

Five new steroidal alkaloids, plakinamines C (1) and D (2), and the related compounds 3-5 have been isolated from the Vanuatu sponge Corticium sp. The ir structures have been elucidated by a detailed spectroscopic analysis, :i ncluding 2D-HMBC and ROESY correlation experiments. The new compounds show significant in vitro cytotoxicity against human bronchopulmonary non-small- cell lung carcinoma cells (NSCLC-NG) with IC50 values of < 3.3-5.7 mu g/mL. When tested against T leukemia virus type one (HTLV-I), compounds 1, 4 and 5 were found to exhibit slight anti-HIV activity.