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 mu g center dot ml(-1)], Escherichia coli (MIC, 10 mu g center dot ml(-1)), Salmonella typhia (MIC, 20 mu g center dot ml(-1)), Salmonella typhimurium (MIC, 15 mu g center dot ml(-1)), Salmonella enteritidis (MIC, 8.5 mu g center dot ml(-1)), Aeromonas hydrophila (MIC, 4 mu g center dot ml(-1)), Yersinia sp. (MIC, 12.5 mu g center dot ml(-1)), Vibrio anguillarum (MIC, 25 mu g center dot ml(-1)), Shigella sp. (MIC, 6.3 mu g center dot ml(-1)), Vibrio parahaemolyticus (MIC, 12.5 mu g center dot ml(-1)), Candida albicans (MIC, 15 mu g center dot ml(-1)), Penicillium expansum (MIC, 40 mu g center dot ml(-1)), and Aspergillus niger (MIC, 25 mu g center dot 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.