Bioprospecting of endophytic fungi isolated from the Amazonian guarana

Colletotrichum fungi are considered one of the main pathogens in the world, affecting different cultures and causing social and economic damage to several countries, including Brazil. Despite control measures already being employed, these are not always effective, which is why the search for new control options that can act in the integrated management is necessary. Among these, the secondary metabolites produced by endophytes are involved in the production of compounds of biotechnological interest, with applications in several areas, including the agronomic. In this context, this study aimed to explore the biological and chemical potential of secondary metabolites produced by endophytic fungi isolated from the Amazonian guarana, evaluating their antifungal activity \"in vitro\" to Colletotrichum gloeosporioides, isolated from the culture of guarana and C. acutatum and C. gloeosporioides, isolated from the red pepper crop. For this purpose, 16 strains of endophytic fungi were evaluated in biological assay of dual culture and disk diffusion method against Colletotrichum spp. Four strains of these strains presented promising results which were selected for bioprospecting. From the crude extract of the endophyte Aspergillus flavus (272) was isolated the active compound asperfuran, which showed inhibitory activity to three pathogens, with IC50 <100 &mu;g disk-1, similar to the commercial fungicide difenoconazole. From the crude extract of Xylaria sp. (214) was isolated the active compound cytochalasin D, which showed inhibitory activity against C. gloeosporioides isolated from guarana (IC50> 500 &mu;g disk-1). From the crude extract of Xylaria sp. (249) was isolated the active compound piliformic acid, which showed inhibitory activity against C. gloeosporioides isolated from guarana (IC50 of 500 &mu;g disk-1) and C. acutatum isolated from red pepper (IC50 of 300 &mu;g disk-1). And from the crude extract of Talaromyces aculeatus (507) were isolated three compounds, of phthalate esters class, one of them with activity. The predecessor fraction of these three compounds showed inhibitory activity against C. gloeosporioides isolated from guarana (IC50> 500 &mu;g disk-1). From the crude extract of T. aculeatus it was also isolated a partially identified active compound and a semi-purified active compound. The predecessor fraction of these two compounds showed inhibitory activity to both C. gloeosporioides (IC50> 300 &mu;g disk-1) and to C. acutatum (IC50 around 150 &mu;g disk-1). The antifungal activity of the compounds isolated in this study is being reported for the first time against fungus of the genus Colletotrichum. (AU)