Bioprospecção e caracterização de fungos endofíticos produtores de compostos bioativos isolados de Dalbergia ecastaphyllum L. Taub

Abstract

Secondary metabolites of endophytes are known for their bioactive activities and biotechnological use. Dalbergia ecastaphyllum (L). Taub is the main source of the resin used for the production of Brazilian red propolis, a product with medicinal properties, its endophytes are attractive sources for the bioprospecting of biologically active compounds. This work aimed to isolate endophytic fungi from D.ecastaphyllum to evaluate them in in vitro biological assays of amylolytic, antimicrobial, antioxidant, antiproliferative activity, determination of compounds by HPLC-FR from crude extracts and morphological characterization of microorganisms. A total of 150 endophytic fungi were obtained through the leaves of D. ecastaphyllum collected in Canavieiras-BA. An effective protocol was established for the first time to obtain endophytic fungi for this plant species. The endophytes were submitted to amylolytic and antimicrobial activity screening by block agar method, 12.67% were able to synthesize the amylase enzyme in vitro and 23.33% presented antimicrobial activity in the screening method. Eleven endophytes were selected according to the size and specificity of the zones of inhibition in the screening, and were submitted to fungal fermentation to obtain their crude extracts. The ethanolic extracts of the endophytes were evaluated by the microdilution method in broth against Gram-positive, Gramnegative bacteria and yeasts of the genus Candida spp. All the extracts presented antimicrobial activity, mainly against bacteria of the family Enterobacteriaceae. Inhibitory concentrations ranged from 50 μg / mL to 800 μg / mL. The extracts were evaluated in an antioxidant assay of DPPH, in which all had sequestering capacity of free radicals with statistically distinct averages, three extracts being more active than the commercial synthetic BHT butilated hydroxytoluene standard. The MTS cell viability assay of five extracts showed no significant decrease in cell proliferation in MCF-7, A549 and Hep-G2 tumor cells. The analysis by HPLC-FR indicated that the secondary metabolites produced by endophytes have polar characteristics, and the previous morphological characterization by the microculture technique showed fungi with hyaline, septate hyphae and ascospore production suggestive of the Ascomycota phylum. This is the most complete survey of the endophytic microbiota of D.ecastaphyllum present in the literature, the first report of antimicrobial activity of its endophytes, and the confirmation of its potential as sources of bioactive substances of biotechnological interest.