Isolation and Identification of the Antimicrobial Agent Beauvericin from the EndophyticFusarium oxysporum5-19 with NMR and ESI-MS/MS
Endophytic microbe has been proved to be one of rich sources of bioactive natural products with potential application for new drug and pesticide discovery. One cyclodepsipeptide, beauvericin, was firstly isolated from the fermentation broth ofFusarium oxysporum5-19 endophytic onEdgeworthia chrysanthaLinn. Its chemical structure was unambiguously identified by a combination of spectroscopic methods, such as HRESI-MS and1H and13C NMR. ESI-MS/MS was successfully used to elucidate the splitting decomposition route of the positive molecule ion of beauvericin. Antimicrobial results showed that this cyclodepsipeptide had inhibitory effect on three human pathogenic microbes,Candida albicans,Escherichia coli, andStaphylococcus aureus. In particular, beauvericin exhibited the strongest antimicrobial activity againstS. aureuswith MIC values of 3.91 μM, which had similar effect with that of the positive control amoxicillin.