Metabolites from Alternaria citri: Chemical Profiling and Biological Activity Evaluation

Fungal extracts have garnered considerable attention in recent years due to their diverse pharmaceutical potential. The present study investigates the secondary metabolite profile and biological activities of Alternaria citri, a fungal strain associated with citrus fruits. Metabolites were extracted from A. citri grown in Potato Dextrose Broth (PDB) using ethyl acetate and subsequently evaluated for antimicrobial, antioxidant, and cytotoxic activities, alongside gas chromatography–mass spectrometry (GC–MS) profiling. GC–MS analysis identified 14 bioactive compounds in the fungal extract. The extract exhibited antimicrobial activity against Aspergillus flavus, Trichoderma hamatum, Staphylococcus aureus, and Escherichia coli. Moderate total phenolic and flavonoid contents were observed, which correlated with concentration-dependent antioxidant activity as determined by the DPPH assay. Cytotoxic evaluation using NIH/3T3 cells demonstrated potential anticancer activity, with an IC50 value of 126.63 µg/mL. A. citri is an interesting source of bioactive metabolites with potential therapeutic applications. These findings further strengthen the evidence that Alternaria species can serve as promising sources of natural antioxidants and antimicrobials, thereby supporting their potential applications in pharmaceutical and biomedical formulations. This study expands current knowledge of fungal metabolite diversity and establishes A. citri as a potential source of novel therapeutic agents.