Santos, Elizeu Antunes dosMoura, Geovanna Maria de Medeiros2025-06-242025-06-242024-12-04MOURA, Geovanna Maria de Medeiros. Bioprospecção de compostos do fungo Langermannia bicolor: potencial modulador de antibióticos, atividade antioxidante e avaliação de toxicidade. Orientador: Dr. Elizeu Antunes dos Santos.. 2024. 117f. Tese (Doutorado em Bioquímica e Biologia Molecular) - Centro de Biociências, Universidade Federal do Rio Grande do Norte, Natal, 2024.https://repositorio.ufrn.br/handle/123456789/64026The emergence of multidrug-resistant bacteria has driven the search for new therapeutic agents and adjuvants. In this study, we investigated the properties of an extract from the mushroom Langermannia bicolor as a modulator of antibiotics (gentamicin, norfloxacin, and ampicillin) against multidrug-resistant strains of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, as well as its antioxidant activity and toxicity. The crude aqueous extract of L. bicolor was fractionated using increasing volumes of acetone, resulting in three fractions (F0.5, F1, and F2), which exhibited different biochemical profiles. Tests with human erythrocytes revealed that the extract and its fractions did not exhibit hemolytic activity, while MTT reduction assays in fibroblast cells (NHI/3T3) showed that the crude extract reduced viability by 50%. In vivo tests with zebrafish embryos, up to young larvae (Danio rerio), confirmed the absence of toxicity of the fractions through embryotoxic analyses, heart rate measurements, and behavioral tests. Although none of the fractions demonstrated direct antibacterial activity, all exhibited significant modulatory effects when combined with conventional antibiotics against the tested multidrug-resistant bacteria. Notably, fraction F2, rich in proteins with higher proteolytic and hemagglutinating activities, reduced the Minimum Inhibitory Concentration (MIC) of gentamicin across all tested strains. The fractions also displayed potent antioxidant properties both in vitro and in vivo. Fraction F0.5, enriched with phenolic compounds and flavonoids, exhibited the broadest spectrum of antioxidant activities, including metal chelation (Fe²⁺ and Cu²⁺), free radical scavenging (•OH and O₂⁻•), and both concurrent and preventive cellular protection against hydrogen peroxide (H₂O₂) induced oxidative stress in 3T3 cells. Meanwhile, fraction F1, which was carbohydrate-rich, was able to repair oxidative damage following H₂O₂ stress. In vivo, all fractions protected zebrafish embryos exposed to H₂O₂. When quantifying reactive oxygen species (ROS) using a fluorescent probe (DCFH), zebrafish larvae treated with F0.5 followed by H₂O₂ significantly reduced ROS production in their cells, yielding values even lower than those of larvae not exposed to the oxidizing agent. To a lesser extent, F1 and F2 also protected zebrafish cells by reducing ROS production. By pioneering the therapeutic potential of L. bicolor, our study paves the way for future investigations into the bioactive composition of this mushroom and its respective molecular mechanisms involved in the observed properties: antibiotic potentiation and protection against oxidative stress.pt-BRAcesso AbertodoctoralThesisCIENCIAS BIOLOGICAS