New cytotoxic polyacetylene amides from the Egyptian marine sponge Siphonochalina siphonella.

Four new polyacetylene amides, siphonellamides A-D (1-4), and one new fatty amide, siphonellamide E (5), together with a known indole fatty amide (6) and callyspongamide A (7), were isolated from the Red Sea marine sponge Siphonochalina siphonella. The structures of 1-5 were elucidated by extensive analyses of their 1D- and 2D-NMR spectra and MS. The isolated compounds were assessed for their cytotoxicity against HeLa, MCF-7, and A549 cancer cell lines. Compounds 1 and 2 exhibited cytotoxic activities with IC50 values ranging from 9.4 to 34.1 µM, while 5 was only cytotoxic to HeLa cells, with an IC50 value of 78.4 µM. Compound 7 showed moderate cytotoxicity against all tested cell lines.