Antimicrobial activity of an endophytic Xylaria sp.YX-28 and identification of its antimicrobial compound 7-amino-4-methylcoumarin.

An endophytic Xylaria sp., having broad antimicrobial activity, was isolated and characterized from Ginkgo biloba L. From the culture extracts of this fungus, a bioactive compound P3 was isolated by bioactivity-guided fractionation and identified as 7-amino-4-methylcoumarin by nuclear magnetic resonance, infrared, and mass spectrometry spectral data. The compound showed strong antibacterial and antifungal activities in vitro against Staphylococcus aureus [minimal inhibitory concentrations (MIC) 16 microg.ml(-1)], Escherichia coli (MIC, 10 microg.ml(-1)), Salmonella typhia (MIC, 20 microg.ml(-1)), Salmonella typhimurium (MIC, 15 microg.ml(-1)), Salmonella enteritidis (MIC, 8.5 microg.ml(-1)), Aeromonas hydrophila (MIC, 4 microg.ml(-1)), Yersinia sp. (MIC, 12.5 microg.ml(-1)), Vibrio anguillarum (MIC, 25 microg.ml(-1)), Shigella sp. (MIC, 6.3 microg.ml(-1)), Vibrio parahaemolyticus (MIC, 12.5 microg.ml(-1)), Candida albicans (MIC, 15 microg.ml(-1)), Penicillium expansum (MIC, 40 microg.ml(-1)), and Aspergillus niger (MIC, 25 microg.ml(-1)). This is the first report of 7-amino-4-methylcoumarin in fungus and of the antimicrobial activity of this metabolite. The obtained results provide promising baseline information for the potential use of this unusual endophytic fungus and its components in the control of food spoilage and food-borne diseases.