Endophytic Fungi Associated with Annona senegalensis: Identification, Antimicrobial and Antioxidant Potential

Background: The endophytes of African medicinal plants are largely underexplored despite their potential as repositories of bioactive compounds. Objective: To identify the endophytic fungi associated with Annona senegalensis and evaluate the antimicrobial and antioxidant potential of their crude ethyl acetate extracts. Method: The surface sterilization technique (using ethanol and sodium hypochlorite) was used to isolate the endophytic fungi that were identified by rDNA sequencing of the ITS region. The extracts were screened for antimicrobial activity using the agar diffusion method and evaluated for antioxidant activity using a commercial kit. The total phenolic content of the extracts was determined using the Folin- Ciocalteu method and functional groups present in the extracts were predicted using Fourier-transform infrared spectroscopy. Results: Eight fungal isolates identified as Phoma species, Epicoccum nigrum, Epicoccum sorghinum, Alternaria alternata, Alternaria tenuissima, Phaeosphaeria species and Penicillium chloroleucon were isolated from the tissues of Annona senegalensis. The extracts did not exhibit any potential antimicrobial activity and the extract obtained from Epicoccum sorghinum demonstrated both the highest total phenolic content (28.85±1.14 mg GAE/g dry weight) and total antioxidant capacity (593.46 ± 1.86 μM CRE). A strong positive linear correlation (r = 0.9556) was found between antioxidant capacity and phenolic content. The Fourier- transform infrared spectral analysis of the crude extracts from Epicoccum sorghinum confirmed the presence of molecules carrying bonded hydroxyl functional groups characteristic of phenolic compounds. Conclusion: The preliminary results indicate that the isolated fungal endophytes from Annona senegalensis belong to the phylum Ascomycota and have potential as sources of natural antioxidants.