Formamido-Diterpenes from the South China Sea Sponge Acanthella cavernosa

Seven new formamido-diterpenes, cavernenes A–D (1–4), kalihinenes E and F (5–6), and kalihipyran C (7), together with five known compounds (8–12), were isolated from the South China Sea sponge Acanthella cavernosa. Structures were established using IR, HRESIMS, 1D and 2D NMR, and single X-ray diffraction techniques. The isolated compounds were assessed for their cytotoxicity against a small panel of human cancer cell lines (HCT-116, A549, HeLa, QGY-7701, and MDA-MB-231) with IC(50) values in the range of 6–18 μM. In addition, compound 9 showed weak antifungal activity against Trichophyton rubrum and Microsporum gypseum with MIC values of 8 and 32 μg/mL, respectively, compound 10 displayed weak antifungal activity against fungi Candida albicans, Cryptococcus neoformans, T. rubrum, and M. gypseum with MIC values of 8, 8, 4, and 8 μg/mL, respectively.