Antimicrobial activity of endophytic fungi from the medicinal plants Mammea americana (Calophyllaceae) and Moringa oleifera (Moringaceae).

Introduction: Infectious diseases represent one of the leading causes of death worldwide. Considering the growing global challenge of antimicrobial resistance, research into new sources of potentially effective antimicrobial agents from natural origins is of great importance for world health. Objective: To evaluate the antimicrobial activity of endophytic fungi from Mammea americana and Moringa oleifera upon Staphylococcus aureus (ATCC 29213), S. aureus (resistant strain USb003), Escherichia coli (ATCC 25922), and E. coli (resistant strain USb007). Materials and methods: We isolated endophytic fungi from the leaves, seeds, and stems of the two plants under study. We evaluated their antimicrobial activity through the formation of sensitivity haloes in dual tests in vitro, as well as in trials using crude ethanolic extracts from the endophytes. The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and cytotoxicity o the substances were analyzed. Results: Three ethanolic extracts of Penicillium sp., Cladosporium (001), and Cladosporium (002) exhibited the greatest inhibition halos in sensitive and resistant strains of E. coli and S. aureus. The MIC and CBM found were statistically significant (p≤0.05) compared with the gentamicin control. Furthermore, the cytotoxicity test results of CC50>1,000 demonstrated that the endophytic fungi studied exhibit bactericidal characteristics without causing unintended damage. Conclusion: The endophytic fungi M. oleifera and M. americana represent a source of active secondary metabolites with antimicrobial and non-toxic properties. In light of these findings, further research should proceed with chemical identification of the compounds and the study of their mechanisms of action, especially given the paucity of current scientific knowledge concerning the isolation of endophytes in these plants.