Caracterização de fungos endofíticos bioativos associados às espécies vegetais longínquas presentes em fragmento de Mata Atlântica do estado de Minas Gerais com potencial para aplicação contra doenças tropicais negligenciadas e de importância na agricultura

Abstract

Tropical endophytic fungi, known to inhabit different plant tissues without causing apparent damage to their hosts, are considered promising sources of biologically active natural products, which can be applied in different segments of biotechnology. These microorganisms are studied as to their ability to produce different bioactive metabolites of interest in medicine and agriculture. Among the plants targeted for studies of the community of endophytic fungi, those considered distant, endemic and with “particular biology” have shown to represent promising sources for the characterization of species producing bioactive molecules. In this context, plant species native to the Atlantic Forest of Brazil represent interesting targets for bioprospecting of associated endophytic fungi producing bioactive metabolites. From the above, this thesis aimed to know the potential of endophytic fungi associated with distant plant species of an Atlantic Forest fragment of Minas Gerais Swietenia macrophylla, Lecytis pisonis and Joannesia princeps capable of producing bioactive secondary metabolites of interest in medicine and agriculture. Fragments of leaves and adventitious roots of the target plants were sampled and used to isolate endophotic fungi. A total of 372 isolates of filamentous fungi were obtained, of which 201 were obtained from the tissues of S. macrophylla, 52 of L. pisonis and 119 of J. princeps. The fungi obtained were submitted to the solid fermentation process to obtain their secondary metabolites. Of these, 12 fungi were shown to be producers of herbicide substances. Pyricularia sp. isolates UFMGCB 17499 and Diaporthe sp. UFMGCB 17510 exhibited broad-spectrum herbicide activity by inhibiting the seeds of the targets Allium schoenoprasum (monocotyledon) and Lactuca sativa (dicotyledonea). Four extracts obtained from taxa of the genus Colletotrichum (UFMGCB 17500, 174511, 17482 and 18126) exhibited selective activity against A. schoenoprasum, while the isolates UFMGCB 17496 and 17485 exhibited herbicide effect only for L. sativa. In addition, the fungi obtained were evaluated to produce metabolites capable of inhibiting the parasites Trypanosoma cruzi (Chagas disease), Leishmania amazonensis (leishmaniasis) and Plasmodium falciparum (malaria), recognized agents causing neglected tropical diseases (NTD). Seven fungi have been shown to be producers of active metabolites against the parasites causing NTD. The fungal extract produced from the fungus Fusarium sp. UFMGCB 17514 showed trypanosyactivity with IC50 = 4.39 μg mL-1. The active substance identified in Fusarium sp. UFMGCB 17514 corresponded to the mycotoxin beauvericin that exhibited activity (IC50 = 1.6 μg mL-1). The extract of the fungus Fusarium sp. UFMGCB 18279 was able to inhibit P. falciparum (IC50 = 5.1 μg mL-1) and the putative analysis in syl suggested that cyclosporine is the antimalarial substance produced by the fungus. The extract of the fungus Colletotrichum sp. UFMGCB 17511 inhibited amastigote forms of L. amazonensis (IC50 = 0.02 μg mL-1) and in syphilic analyses suggested that the bioactive substance belongs to the glycerophosphocholine class. In addition, the endophytic fungi obtained from the roots of S. macrophylla were evaluated for the ability to stimulate the development of soybean seedlings and beans in vivo. The isolates Fusarium sp. UFMGCB 18289 and 18290 were able to induce the dry biomass gain and stem length of Phaseolus vulgaris (beans) seedlings by adding the fermented liquid medium. On the other hand, lints identified as Fusarium and Dactylonectria species were able to inhibit seed towning in seedlings of P. vulgaris (beans) and Glycine max (soybean). Based on the results obtained, the present work contributed to the knowledge of the biotechnological potential of the community of endophytic fungi associated with distant plants of the Atlantic Forest of the state of Minas Gerais, which are shown to be good candidates as producers of metabolites for use against NTDs and with potential application in agriculture. Although the bioactive metabolites of the Fusarium and Colletotrichum are known, the results of this thesis suggest that the evaluated fungi can be considered promising eukaryotic "factories" producing bioactive metabolites. In addition, endophytic fungi of distant plants were also able to produce metabolites of interest in agriculture, either by their herbicide activity or by the ability to stimulate the development of seedlings of economic interest. Furthermore, the results also demonstrated that some fungi present in equilibrium at the root of S. macrophylla were able to cause negative effects in bean and soybean seedlings in vivo, this draws attention to the non-devastation of natural ecosystems, including native plants that have an endophytic community in symbiosis in their tissues.