Cytotoxic Irciniastatin Analogs and a New Thiazole Lipid from Sarcotragus spinosulus

Chemical investigation of the cytotoxic extract from the marine sponge Sarcotragus spinosulus led to the isolation of four irciniastatin derivatives (1-4), eight meroterpenes (5-12), and one thiazole-bearing fatty acid (13). Among these, three irciniastatins (2-4) and the thiazole derivative (13) were identified as previously undescribed metabolites. Notably, compound 13 features a 2-substituted thiazole ring, a structural motif rarely encountered in sponge-derived fatty acids. The structures were elucidated by extensive spectroscopic analysis, including 1D and 2D NMR and HR-ESIMS. The irciniastatin derivatives (1-4) exhibited exceptional cytotoxicity against a panel of six human cancer cell lines, identifying them as the primary bioactive constituents, whereas the meroterpenes (5-12) displayed differential potency, and compound 13 was found to be inactive.