Sortase A-Inhibitory Metabolites from a Marine-Derived Fungus Aspergillus sp.

Seven alkaloidal compounds (2-8) and one polyketide (1) were isolated from a semisolid rice culture of the marine-derived fungusAspergillussp. F452. Structures of the isolated compounds were elucidated based on spectroscopic data and comparisons with previously reported data. The alkaloidal compounds (2-8) displayed weak to moderate inhibitory activities againstStaphylococcus aureus-derived sortase A (SrtA) without affecting cell viability. Aspermytin A (1) strongly inhibited SrtA activity, with an IC(50)value of 146.0 mu M, and significantly reduced bacterial adherence to fibronectin-coated surfaces. The present results indicate that the underlying mechanism of action of compound1is associated with the inhibition of SrtA-mediatedS.aureusadhesion to fibronectin, thus potentially serving as an SrtA inhibitor.