Isolation, biological activity, and preliminary chemical characterization of a secretory bioactive fraction from the cyanobacterium Neowestiellopsis persica

The growing challenge of antimicrobial resistance has intensified the search for novel bioactive compounds from natural sources. In this study, a bioactive fraction (pS10) was isolated from the culture supernatant of the cyanobacterium Neowestiellopsis persica . The antibacterial, antibiofilm, antioxidant, and cytotoxic activities of this fraction were evaluated using standard in vitro assays. pS10 exhibited antibacterial activity against Staphylococcus aureus , producing a clear inhibition zone and a minimum inhibitory concentration (MIC) of 7.8 µg/mL. The fraction also reduced S. aureus biofilm biomass under the tested conditions and showed weak antioxidant activity, while exhibiting no cytotoxic effects on the tested mammalian cell lines at the evaluated concentrations. Preliminary chromatographic, spectroscopic, elemental, and mass spectrometric analyses provided evidence for a nitrogen-containing bioactive fraction. CHNS analysis confirmed the presence of nitrogen and the absence of detectable sulfur. Although the combined analytical findings supported the successful recovery and enrichment of the bioactive fraction, complete structural elucidation of its active constituent(s) was not achieved. Further high-resolution mass spectrometric and advanced multidimensional NMR analyses will be required to determine the precise molecular structure. Overall, these findings highlight the biological potential of pS10 and support its further investigation as a source of anti-staphylococcal compounds.