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.
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