Atividade biológica do extrato da fermentação do fungo endófito de café Alternaria alternata

Abstract

The search for new active components of microorganisms is one of the areas of greatest investment in developed countries. Among these microorganisms, fungi are distinguished by their ability to produce diverse metabolites for pharmacological purposes. Endophytes are all microorganisms, cultivated or not, that live inside plant tissue, without causing harm to the host and without developing external structures, excluding nodule bacteria and mycorrhiza. Considering the importance of coffee production in the state of Minas Gerais, studies of endophytic fungi in coffee allow for greater understanding of the diversity of these fungi. In this study, a total of 22 endophytic fungi isolated from coffee (Coffea arabica L.) were cultivated in vitro. The screening was conducted using the agar diffusion method against Gram-positive and Gram-negative bacteria and yeast. The most effective isolated fungus among all of the tested microorganisms was the lineage Alternaria alternata, and subsequently, its extract was assayed. The total phenolic content was 3.44 μgGAE/mg of the crude extract. For the antimicrobial activity assays, the minimum inhibitory concentration (MIC) and minimum bactericidal and fungicidal concentration (MBFC) against Staphylococcus aureus, Escherichia coli and Candida albicans were determined. The ranges of MIC values were 50-100 μg/mL for S. aureus and 800-1000 μg/mL for E. coli. The crude extract did not show activity in the tested concentrations for C. albicans. Through these tests, the antioxidant activity of the fungus was assayed through its ability to scavenge DPPH radicals and through β-carotene/linoleic acid system oxidation, both of which were not significant. Antitumour activity was studied by the MTT assay. At a dilution of 400 μg/mL, the extract displayed a cytotoxic activity of approximately 50% towards HeLa cells in vitro. These results indicate that endophytic fungi could be a promising source of antimicrobial compounds and are worthy of further study.