Sulfated steroids isolated from the marine sponge Petrosia (Strongylophora) strongylata and their antimicrobial activity.

The extract of Petrosia (Strongylophora) strongylata was separated to trace sulfated terpenoids, which were expected to be present in the crude extract based on its 1H NMR spectrum. As a result, seven sulfated (1-7) sterols and one highly oxygenated steroid (8), including two unreported analogs (4 and 7), were isolated and identified. The MIC measurement of all isolated compounds against six bacterial cell lines demonstrated that compounds 1-7 efficiently inhibit the growth of Gram-positive bacteria. Compound 8, which lacks the sulfate group in the structure, displayed no activity even at a concentration of 128 µM. This study demonstrated that the sulfate groups in the structures of sterols play a critical role in the growth inhibition of Gram-positive bacteria, suggesting the potential of sulfated sterols for use as antimicrobial agents. The modes of action of these compounds and their molecular -targets are currently under investigation.