Atividade antimicrobiana da Buchenavia tomentosa e dos seus fungos endofíticos e atividade anticancerígena da Eleutherine Plicata

Abstract

Endophytic fungi live in symbiosis with the host plant, and many may produce the same active metabolites as their hosts, thereby becoming a reservoir for an infinite number of antimicrobial or anticancer natural products, among others. This study was divided into three chapters. In the first chapter Buchenavia tomentosa, a plant not well established as medicinal in the literature, was used to assess the growth inhibition capacity of pathogenic bacteria by the aqueous extract of the plant and alcoholic extract of isolated endophytic bacteria, and evaluate the antagonistic activity of these endophytes against the phytopathogen Rhizopus stolonifier. Of the 11 bacterial strains tested, Salmonella typhimurium, Staphylococcus epidermidis and Shigella flexneri were sensitive to the active compounds of the plant. A total of 22 fungal isolates were obtained from leaves, seven of which showed antimicrobial activity against S. typhimurium, S. epidermidis and S. flexneri. Two isolates (FC12 and FC31) displayed antimicrobial activity against three bacteria, and all the fungi inhibited at least one of the bacteria tested at a concentration of 25 μg/ml (lowest concentration obtained in the test). In antagonist activity, only FC123 inhibited 53% of R. stolonifer growth by substance diffusion, and no result was observed with the production of volatile compounds. The endophytic isolates tested are potential sources of antimicrobial substances, but new studies should be conducted to identify the endophytic species and microbial substances they produce. Chapter two investigated the anticancer activity of the plant Eleutherina plicata. Previous studies demonstrated that there are three main naphthoquinone compounds involved: eleutherine, isoeleutherine and eleutherol, but their mechanism of action remains undefined. Eleutherine stands out among the other naphthoquinones and its mechanisms of action have been investigated in the rat C6 glioma cell line. In vivo cytotoxicity was assessed by the MTT assay, and morphological changes were evaluated by phase-contrast microscopy. Apoptosis was determined by annexin V- FITC/propidium iodide staining and the antiproliferative effects were assessed by wound migration and colony formation assays. Protein kinase B expression B (AKT/pAKT) was measured by western blotting, and mRNA from telomerase reverse transcriptase by real time PCr (qRT-PCR). Eleutherine reduced dose-dependent C6 cell proliferation, suppressed migration and invasion, induced apoptosis and decreased AKT phosphorylation and telomerase expression. In short, the results suggest that eleutherine has clinical potential in the treatment of glioma. Chapter three discusses a number of techniques used to investigate the production of plant-derived anticancer substances by endophytic fungi, which is a subsequent part of chapter two to be carried out (investigation of eleutherine production by E. plicata endophytes). In general, both plants studied are interesting sources of biotechnological products in the area of antimicrobial and anticancer substances.