Bioprospecção da atividade antimicrobiana de extratos brutos de fungos endofíticos isolados da espécie Oryctanthus alveolatus (Kunth) Kuijt

Abstract

The plants belonging to the family Loranthaceae are popularly known as ervas-de- passarinho. Among the various plants known belonging to this family, there is Oryctanthus alveolatus, which sparked interest due to the few phytochemicals and microbial studies with this plant. Microorganisms are mostly seen as pathogenic agents, especially fungi and bacteria. However, they are also useful in the production of chemicals such as antibiotics and antitumor. Among the existing fungi, endophytic fungi are microorganisms that inhabit the interior of plants bringing benefits to them. So the aim of this study was to obtain and evaluate the antimicrobial activity of crude extracts of 29 isolated endophytic fungi of the leaves and stems of Oryctanthus alveolatus species, in the face of pathogenic Gram-positive Staphylococcus aureus and Staphylococcus epidermidis and Gram-negative Pseudomonas aeruginosa and Escherichia coli. All extracts were subjected to antimicrobial assay using agar diffusion test at concentrations of 0,5 μg.μL-1 and 1000 μg.mL-1. Only three extracts; Coa 007, 009a and 014, were able to inhibit bacterial growth of one or more strains tested at 1000 μg.mL-1. Subsequently, the active extracts were tested at concentrations of 200, 500, 700, 800 and 900μg.mL-1, and the Coa 007 extract showed the CIM values of 900 μg.mL-1 for the bacteria E. coli and P. aeruginosa and CIM of 1000 μg.mL-1 for the bacteria S. aureus. The Coa 009a extract showed CIM of 1000 μg.mL-1 for S. aureus and E. coli bacteria and Coa 014 extract showed CIM in the amount of 900 μg.mL-1 for E. coli and 1000 μg.mL-1 for the bacteria P. aeruginosa and S. aureus. The other fungi tested did not inhibit bacterial growth. Fungi in the extracts were active, they were also evaluated the morphological point of view. The Coa 007 and Coa 014 fungi presented macromorfológicas initially similar characteristics: both possessed white coloring, with algodonosa and opaque texture. Over time, the Coa 007 now presents beige-pink color reverse, differentiating Coa 014 that pasou to present pink pigmentation spots, with reverse part of beige. The Coa 009a initially presented black color, becoming black-gray, cotton wool spots, and reverse the black colony.