Cortistatins E, F, G, and H, four novel steroidal alkaloids from marine sponge Corticium simplex

Four novel steroidal alkaloids named cortistatins E ( 1), F ( 2), G ( 3), and H ( 4) have been isolated from the marine sponge Corticium simplex. The chemical structures of these four cortistatins, which are unique abeo-9(10–19)-stigmastane-type steroidal alkaloids having oxabicyclo[3.2.1]octene and N-methyl piperidine or 3-methylpyridine units in the side chain, were elucidated by the detailed 2D-NMR analysis. These four compounds showed only weak anti-proliferative activity against human umbilical vein endothelial cells (HUVECs) at 0.35–1.9 μM concentrations in contrast to cortistatin A ( 5), which was isolated as a highly selective inhibitor of proliferation of HUVECs from the same marine sponge. [Display omitted] Four novel steroidal alkaloids, cortistatins E, F, G, and H were isolated from the marine sponge Corticium simplex and their chemical structures were elucidated by 2D-NMR analysis.