Abstract
Four 4-hydroxy-α-pyrones including three new ones named nipyrones A-C (1-3) together with one known analogue germicidin C (4) were discovered from a marine sponge-derived fungus Aspergillus niger cultivated in a solid rice culture. Their structures and absolute configurations were elucidated through a combination of spectroscopic data and electronic circular dichroism (ECD) calculations as well as comparison with literature data. Compounds 1-4 were evaluated for their antibacterial activities against five pathogenic bacteria (Staphylococcus aureus, Escherichia coli, Bacillus subtilis, methicillin-resistant Staphylococcus aureus, and Mycobacterium tuberculosis). Compound 3 showed promising activity against S. aureus and B. subtilis, with minimum inhibitory concentration (MIC) values of 8 μg/mL and 16 μg/mL, respectively, and displayed weak antitubercular activities against M. tuberculosis, with MIC value of 64 μg/mL, while compounds 1 and 2 exhibited moderate antibacterial efficacy against four pathogenic bacteria with MIC values of 32-64 μg/mL.