The rise of methicillin-resistant Staphylococcus aureus (MRSA) and the ineffectiveness of current antibiotics make new treatments critically urgent. Fungi represent a promising source of anti-MRSA drug leads. In this study, three new compounds, including (1R,3S,4R,10R)-3,4,10,11-tetrahydroxybisabol-7-ene (1), 15β-hydroxy methyl nortricycloalternarate (2), and 2,9α,10β,11α-tetrahydroxy-4-methoxy-13-methyl-9,10,11,12-tetrahydro-6,8-biphenyl-1-carboxylic acid (5), along with 11 known compounds (3, 4, and 6-14) were isolated from the endophytic fungus Alternaria alternata LZU-183. The structures of three new compounds were determined by a comprehensive analysis of the spectroscopic data. All 14 isolates were evaluated for their antibacterial activity against two strains of MRSA. Among them, the dibenzo-α-pyrones (5-9, 11-12, and 14) showed anti-MRSA activity with MIC values ranging from 8.0 to 128.0 µg/mL. Compound 8 demonstrated the most potent activity, with MIC values of 8.0 and 16.0 µg/mL against the two MRSA strains, respectively.
Zhang et al. (Wed,) studied this question.