Isolamento de substâncias ativas, atividade antimalárica in vitro e antioxidante da Bertholletia excelsa Bonpl. (castanha-do-Brasil)

Abstract

This work aimed to study the chemical composition and evaluate the in vitro antiplasmodic activity of extracts and substances from Bertholletia excelsa, through bioguided study. Root residues, root bark, stem bark and bark of this species were collected, from Fazenda Aruanã in Itacoatiara – AM. The extracts were prepared based on an experimental design of mixtures of the simplex-centroid type, with three different components (Group 1: hexane, dichloromethane and ethyl acetate, and group 2: acetone, ethanol and water). A chemometric study was carried out, based on mass spectrometry data of these extracts, where the obtained data were treated and interpreted in the Chemoface program. The analysis was carried out by the plant, in order to identify extracts with components with m/z associated with antiplasmodic activity. The extracts were tested for antimalarial activity in vitro against the P. falciparum K1 strain initially by initial screening in two concentrations (50 and 5 µg/mL). Of the forty-one (41) extracts that were prioritized to determine the 50% inhibitory concentration (IC50), in the concentrations of 100 to 1.56 µg/mL, four (4) of the root extracts were partially active (10.3 - 12.3 µg/mL) and thirty-seven (37) were considered active (1.7 - 8.2 µg/mL), highlighting the extract obtained from the B. excelsa bark in the acetone/ethanol/water mixture (E56) as the most active (1.7 µg/mL). The chemometric data were worked to find a relationship between the active extracts and the chemical profile, noting the presence of three (3) main peaks: 301; 447; 469 in active extracts. These results, when correlated with activity and yield of the extracts, helped to define the choice of extract E56 for separation by HPLC, so a new extraction on a larger scale was performed. The methanolic fraction of E57, obtained by column solid phase extraction, was analyzed by HPLC, resulting in the collection of 6 substances. The identification/characterization of the substances obtained was carried out by analyzing the 1H and 13C NMR spectra (mono and two-dimensional) and LC-MS, according to the structural characteristics, observing that the characteristic signs correspond to ellagic acid and derivatives (valoneic acid dilactone, ellagic acid hexoside, ellagic acid pentoside, eschweilenol C and methyl ellagic acid ramnopyranoside), with antiplasmodic activity (IC50 = 2.08 - 9.47 µM) and antioxidant (IC50 = 15.58 - 35.47 µM) important. Bioguided fractionation proved to be efficient in the isolation of substances with antiplasmodial activity in vitro.