The new bioactive diterpenes cyanthiwigins E–AA from the Jamaican sponge Myrmekioderma styx

Twenty-seven diterpenes, cyanthiwigins A–AA (), were isolated from the Jamaican sponge Myrmekioderma styx. Cyanthiwigins E–AA () are unreported natural products and their structures were elucidated by detailed analysis of 1H, 13C, DEPT, COSY, NOESY, HMQC and HMBC NMR spectra. Cyanthiwigins are 5,6,7-tricarbocyclic diterpenes, in which the chemical shift of the β-olefinic carbon of the cyclopentenone resonates at a low field of 195 ppm. Cyanthiwigins A (), B (), C () and D () were assayed against hepatitis B virus (HBV), human immunodeficiency virus (HIV-1), and Mycobacterium tuberculosis (Mtb). Cyanthiwigin C () exhibited activity against HBV and Mtb with an EC50 of 43 μg/mL and 50% inhibition at 6.25 μg/mL, respectively. Cyanthiwigin B () exhibited activity against HIV-1 with an EC50 of 42.1 μM. Cyanthiwigins A, C–F, I and Z (, , , ) are active against human primary tumor cells (IC50<18 μM) with cyanthiwigin F exhibiting the strongest activity (IC50 3.1 μM).