Biodiscovery of Potential Antibacterial Diagnostic Metabolites from the Endolichenic Fungus Xylaria venustula Using LC–MS-Based Metabolomics

Three species of the lichen Usnea (U. baileyi (Stirt.) Zahlbr., U. bismolliuscula Zahlbr. and pectinata Stirt.) nine associated endolichenic fungi (ELF) were evaluated using a metabolomics approach. All investigated crude extracts afforded antibacterial activity against Staphylococcus aureus (minimum inhibitory concentration (MIC): 0.0625 mg/mL), but none was observed Escherichia coli, while ELF extract Xylaria venustula found to be most active S. (MIC: 2.5 mg/mL) E. coli 5 mg/mL). X. fractionated tested for determine its activity. Fractions XvFr1 displayed bioactivities both test bacteria. Selected fractions subjected analyses high-resolution LC–MS. Multivariate showed presence five secondary metabolites unique bioactive 3, which identified as responsible venustula. The p-values these at margin significance level, with methyl xylariate C (P_60) being significant. However, their high variable importance projection (VIP) scores (>5) suggest are potential diagnostic “dual” bioactivity coli. statistical models also distinctiveness produced by lichens ELF, thus supporting our hypotheses functionality similar plant endophytes.