Monanchoxymycalin C with anticancer properties, new analogue of crambescidin 800 from the marine sponge <i>Monanchora pulchra</i>

<p>A new pentacyclic guanidine alkaloid, monanchoxymycalin C (<b>1</b>) was isolated from a new collection of marine sponge <i>Monanchora pulchra</i> along with the known monanchoxymycalin A (<b>2</b>). The structure of <b>1</b> was elucidated on the basis of spectroscopic data. Monanchoxymycalin C exhibits cytotoxic activity against human cancer HeLa cells at low micromolar concentrations, induces apoptosis-related death of malignant cells and inhibits cancer cell colony formation. In addition, synergistic and additive effects have been observed in combination with cisplatin.</p>