Bioactivity screening of endophytic fungi from Sterculia urens and GC–MS metabolites profiling of the potent isolate Chaetomium meridiolense

Endophytic fungi associated with medicinal plants are recognized as promising sources of bioactive secondary metabolites. In this study, fungal endophytes were isolated from healthy leaves of Sterculia urens, an ethnomedicinal plant with documented therapeutic relevance, and evaluated for their phytochemical composition and biological activities. Nine endophytic fungi were screened for antioxidant potential using DPPH and ABTS radical scavenging assays and for antibacterial activity against Staphylococcus aureus, Escherichia coli, and Salmonella typhi through minimum inhibitory and bactericidal concentration analyses. Among the isolates, Chaetomium meridiolense exhibited comparatively higher antioxidant and antibacterial activities and was therefore selected for detailed metabolic investigation. This isolate also showed elevated phenolic and flavonoid contents, suggesting a chemical basis for its bioactivity. Gas chromatography-mass spectrometry analysis revealed a metabolite profile enriched with terpenoid- and phenolic-derived compounds. Multivariate statistical analyses indicated positive associations between phenolic enrichment and observed antioxidant and antibacterial effects. Overall, this study provides new insight into the bioactive potential of C. meridiolense associated with S. urens and supports the relevance of endophytic fungi as potential sources of biologically active metabolites for further exploration.