RESUMO
Dereplication of the antiproliferative ethyl acetate fraction of the Madagascan sponge Carteriospongia sp. led to the detection and isolation of the two known homoscalarane-type sesterterpenes 1 and 2. Investigation of a similar sponge containing closely related compounds afforded the four new antiproliferative homoscalarane sesterterpenes (3 and 5-7). The structures of all isolated compounds were elucidated by spectroscopic methods, including UV, IR and 1D and 2D NMR. Compounds 1, 3 and 5 displayed submicromolar antiproliferative activity against the A2780 ovarian cell line with IC50 values of 0.65, 0.26 and 0.28 µM, respectively, while compounds 6 and 7 showed moderate activity (4.5 and 8.7 µM, respectively). Compounds 3 and 5 also displayed anti-proliferative activity against the H522-T1 non-small cell lung and A2058 human melanoma cancer cell lines.