Bioprospecção de metabólitos secundários de Aniba spp. (Lauraceae) da Amazônia para o desenvolvimento de novos antimicrobianos

Abstract

Due to the spread of multiresistant strains and limitations of commercially available drugs for the treatment of infectious diseases, studies aimed at finding molecules that can serve for the development of new drugs are essential. Plants of the genus Aniba are related to the production of secondary metabolites of chemical classes known for their bioactivities. The aim of the present study was to perform a phytochemical study of bioactive ethanolic extracts of A. panurensis, A. parviflora and A. ferrea, for the isolation of bioactive compounds. Ethanolic extracts and phases of liquid-liquid partition were tested against 23 gram-negative bacteria, 9 gram-positive bacteria and the parasite Plasmodium falciparum (FRC3 strain). The isolated compounds were tested for their antibacterial, antifungal, anti-Plasmodium, antichagasic and anti-Leishmania activity. The ethanolic extracts and Hex and CHCl3 phases of A. panurensis leaves and branches had good activity against Bacillus subtilis, Staphylococcus simulans, Staph. aureus, methicillin-resistant Staph. aureus (MRSA) and Streptococcus mutans (7.8 ≤ MIC ≤ 250 µg / mL). The bioactive phases were submitted to bioautography assays and the CHCl3 phase of A. panurensis branches was selected for the bioguided chemical fractionation by the same technique. Flash column chromatography was used for the isolation of compounds which were identified by spectrometric and spectroscopic methods as: 5,6 dehydrokawaina (compound 1); 4-methoxy-11,12-methylenedioxy-6-trans-styryl-pyran-2-one (compound 2); 6.6 - (2,4-Bis (3,4-dimethoxyphenyl) cyclobutane-1,3-diyl) bis (4-methoxy-2H-pyran-2-one) (compound 3); and 2- Furanacetic acid, 4-dodecyltetrahydro-5-oxo-, (compound 4). Only compound 4 exhibited antibacterial activity, with MICs values of 7.8 µg / mL for Staphylococcal strains, 125 µg / mL for B. subtilis and 31.25 µg / mL for Strep. mutans. Time-kill curve showed bactericidal behavior of compound 4 at 4-fold of their respective MIC against Staph. aureus and MRSA at 12 hours and 9 hours, respectively. Against Strep. mutans, compound 4 was bactericidal at its corresponding MIC within 6 hours. The antibacterial modes of action of substance 4 were taken by Scanning (SEM) and Transmission (TEM) Electron Microscopy, in which it was possible to observe the separation of the cytoplasm from the cell wall of Staph. aureus, interference with MRSA cell wall synthesis, and several changes in Strep. mutans cells, such as partial separation of cell wall and cytoplasm, cell wall disintegration, extravasation of cytoplasmic content and loss of electrodense cell material. Compounds 1 and 4 exhibited good antifungal activity against Trichophyton rubrum, with MICs values of 62.5 and 7.8 μg / mL, respectively, and moderate and poor activity against C. albicans (125 and 500 µg/mL, respectively). Compound 1 exhibited the best result against P. falciparum strain (IC50 14 µM). Compound 4 further exhibited low potential against T. cruzi epimastigote (IC50 92 µM) and trypomastigote (IC50 64 µM). In cytotoxicity test against VERO cells, only compound 4 caused cell death at the concentrations tested, with CC50 value of 148 µg / mL. These results contribute to the pharmacological knowledge of the Amazonian plant A. panurensis and provide possible structural models for the development of new antimicrobial drugs.