Extract of endophytic fungus Cepalotheca foveolata (N11) inhibits lytic bacteriophage: a study on activity, cytotoxicity, and chemical profiling

Viral infections are one of the leading causes of disease worldwide. The continuous emergence of new viruses has limited the effectiveness and availability of antiviral drugs. Fungal endophytes are considered important sources for the discovery of novel antiviral agents. In this study, a bacteriophage was used as a safe and economical viral model to screen for antiviral compounds from endophytic fungi. Bacteriophage AU-1 and its host bacteria (Escherichia coli) were isolated from sewage water. The endophytic fungus Cepalotheca foveolata (N11) was screened using a plaque reduction assay. The fungal extract was fractionated via liquid-liquid partition, and its antiphage activity was evaluated against the isolated lytic bacteriophage using a plaque reduction assay. Cytotoxicity was assessed using the Artemia salina model, and chemical profiling of active fractions was performed using Gas Chromatography-Mass Spectrometry (GC-MS). C. foveolata crude extracts exhibited strong anti-phage activity, showing 100% plaque reduction at 1 mg/100 µL. Following pilot-scale cultivation, the extract was purified by silica-gel column chromatography. Active pooled fractions (F31–F40) showed > 93% plaque inhibition at 0.4 mg/100 µL. GC-MS analysis revealed four major compounds, including benzophenone, a known antiviral agent. The results demonstrate the utility of bacteriophage-based assays for the preliminary screening of antiviral compounds from fungal extracts. This approach is simple, safe, and cost-effective, and the identified extracts warrant further investigation for the isolation of potential antiviral agents.