OBJECTIVE To find lead compounds of antibacterial activity from secondary metabolites of endophytic fungus Diaporthe arengae M2 in Camellia oleifolia.

METHODS The secondary metabolites of D. arengae M2 were isolated and purified by traditional column chromatography and semi-prep HPLC. The structure of the compounds was identified by NMR, IR, HR-ESI-MS and other spectroscopic instruments. Finally, the antibacterial activity of these compounds was evaluated by broth dilution method.

RESULTS A total of 8 compounds were isolated and identified from the secondary metabolites of D. arengae M2: xylariphthalide A (1), cytosporone B (2), cytosporone E (3), cytosporone C (4), pestalotiopsone A (5), pestalotiopsone C (6), ergosterol (7), 7, 8-dimethyl-3, 10-dimethyl-iso-alloxazine (8). The antibacterial activity evaluation showed that the minimum inhibitory concentration(MIC) values of compound 3 against the three Gram-positive strains were 2 μg·mL⁻¹, and the MIC values against Escherichia coli and Pseudomonas aeruginosa were 32 and 64 μg·mL⁻¹, respectively. The MIC values of compound 2 against four strains of Fusarium oxysporum ranged from 8 to 16 μg·mL⁻¹. Compound 4 against Staphylococcus aureus, methicillin-resistant Staphylococcus aureus and Bacillus subtilis with MIC ranged from 8 to 16 μg·mL⁻¹.

CONCLUSION Compounds 2, 3 and 4 show better antibacterial activity.