Estudo fitoquímico das cascas de Maytenus guianensis Klotzsch ex Reissek e seu potencial sobre Bactérias

Abstract

Maytenus guianensis Klotzsch ex Reissek is a Brazilian Amazonian plant widely used in folk medicine against diseases such as malaria, leishmaniasis, and cancer. It is believed that this pharmacological action may be related to terpenoids present in species belonging to the Maytenus genus. Due to the increase in the number of microorganisms resistant to antimicrobial substances already known, various herbal extracts have been tested in order to find new compounds with recognized antimicrobial activity. Thus, this research aimed to carry out a phytochemical study and evaluate the antimicrobial potential effect of isolated compounds from the bark of M. guianensis on bacteria and fungi. The barks were collected in the Adolpho Ducke Forest Reserve, in Manaus, the state capital of Amazonas, Brazil. Subsequently, they were properly dried and ground, and subjected to extraction in Soxhlet apparatus with different solvents according to the degree of polarity. The isolation and purification of the chemical constituents of the extract from the barks were performed through column chromatography, using silica gel as fixed phase. The development of the chromatographed substances in Thin Layer Chromatography was made by exposing the cromatoplates to ultraviolet light (250 nm) and by pulverization using a universal indicator, followed by heating in an oven at 100 °C. The structural identification of the isolated chemical constituents of M. guianensis was performed using spectroscopic methods of nuclear magnetic resonance Hydrogen-1 (1H-NMR) and Carbon-13 (13C-NMR), one- and two-dimensional, mass spectroscopy, and spectroscopy in the infrared region. To evaluate the antimicrobial potential effect on ATCC bacteria, pathogenic bacteria, and fungi, it was applied the agar well diffusion technique using specific protocols for the experiments. The design was completely randomized with three replicates per treatment. The test evaluation consisted of measuring the growth of bacteria and fungi colonies, 24 hours after the beginning of the experiment. The results obtained from this phytochemical study, until now, allowed the isolation of four substances: two friedelin and friedelanol triterpenes (triterpene 3-oxo-29-hydroxyfriedelane and triterpene 3-oxo-16β-hydroxyfriedelane) and quinonamethide triterpenes (tingenine B and tingenone). Phytochemicals results of this work in conjunction with the data described in literature clearly show that M. guianensis is a rich source of triterpenes classes of fridelanos and quinonamethide, they are restricted to Celastraceae family. In addition, extracts and compounds isolated from the bark of M. guianensis presented inhibitory effect against at least four of the five tested bacteria and fungi ATCC, noting satisfactory inhibition halos being novel antimicrobial testing. However, negative results were found for pathogenic bacteria. Thus, M. guianensis plant is a promising for the development of new antimicrobial herbal, and further studies must be made on the chemical composition and understanding of activity on virulence factors of multiresistant bacteria. The results indicate the antimicrobial potential of this plant, which may be promising for drug development studies.