Evaluation of the antimicrobial and antiviral potentials of extracts of endophytic fungi from Azadirachta indica

Endophytic fungi are known to inhabit the internal tissues of plants. The neem plant is one of the medicinal plants cultivated in Nigeria on large scale for its therapeutic potential. Endophytic fungi are producers of important bioactive compounds. In the present study, endophytic fungi were isolated from healthy leaves of Azadirachta indica, fermented and ethyl acetate were used to extract the secondary metabolites produced. The crude extracts were subjected to antimicrobial and antiviral assays adopting standard procedures. Following the isolation and purification stages, five (5) AIE1, AIE2, AIE3, AIE4, and, AIE5 endophytic fungi were differentiated using morphological characteristics. The ethyl acetate crude extract of the fungi exhibited microbial growth-inhibitory potentials when tested at a concentration of 1 mg/mL. Secondary metabolites of AIE1, AIE2, AIE4, and, AIE5 exhibited broad-spectrum antimicrobial potentials, inhibiting at least one Gram-positive and Gram-negative bacteria respectively. At 1 mg/mL, AIE1 extract showed good microbial growth inhibitory effects against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and, Candida albicans. Low antiviral activity was recorded for each of the fungal crude extracts. When tested at 1 mg/mL, AIE1 and AIE2 crude extract recorded 21 and 15% reverse transcriptase inhibition respectively in vitro. Our findings highlight the bioactivity of secondary metabolites and also validate the chemo-biosynthetic capacities of fungal endophytes associated with Azadirachta indica.