Identificação de substâncias produzidas pelos fungos Cercospora brachiata, Beauveria bassiana e Verticillium sp e avaliação da atividade antibacteriana.

Abstract

Among the organisms studied in the chemistry of natural products, fungi can be highlighted due to the various applications beneficial to man, such as antibacterial activity. Fungi differ by their physical characteristics and by the type of host they use for their survival. The fungi studied in this work were Beauveria bassiana and Verticillium sp., which are classified as entomopathogenic, and Cercospora brachiata which is phytopathogenic. The damages that these fungi cause in their hosts are directly related to the metabolites produced. In order to know more about these compounds, the objective of this work was to identify, isolate and characterize the substances present in extracts of broths of growths and mycelia of these fungi, using chromatography techniques (CC: column chromatography and GC-MS: gas chromatography coupled to mass spectrometry) and nuclear magnetic resonance (NMR). The antibacterial activity of the extracts was also evaluated. Among the identified compounds, fatty acids, esters and steroids stand out because they are associated with several biological activities. Among the identified acids, those that were identified in the highest concentrations in the extracts were: hexadec-9-enoic acid, hexadecanoic acid, oleic acid, octadecanoic acid, lauric acid, myristic acid, palmitic acid, docos-13-enoic acid, stearic acid, linoleic acid and nonadecanoic acid. In addition to the identified acids, ergoster-6,22-dien-3β,5α,8α-triol and brassicasterol steroids were isolated. The antibacterial activity was evaluated by the broth microdilution method. Prominent values of the minimum inhibitory concentration (MIC) were found for the ethyl acetate extract of the mycelia of C. brachiata against the Actinomyces naeslundii (MIC = 100 μg mL-1) and the ethyl acetate extract of the growth broth of B. bassiana against the Porphyromonas gingivalis and Fusobacterium nucleatum (MIC = 100 μg mL-1).