New pyranonaphthazarin and 2-naphthoic acid derivatives from the mangrove endophytic fungus Leptosphaerulina sp SKS032

Two new compounds, named leptospyranonaphthazarin A (1) and leptosnaphthoic acid A (2), together with four known compounds (3-6) were isolated from an endophytic fungus Leptosphaerulina sp. SKS032. Their structures were assigned using spectroscopic methods, computational methods, and single-crystal X-ray diffraction analysis. In the antibiotic assay, compounds 1, 2, and 6 exhibited antibacterial activities against Staphylococcus aureus with minimal inhibitory concentration (MIC) values of 25.0, 50.0, and 50.0 mu g/mL, respectively.