Estudo fitoquímico e investigação das propriedades citotóxicas das cascas dos ramos de Annona amazonica (ANNONACEAE)

Abstract

Annona amazonica R. E. Fries, is an Amazonian species belonging to the Annonaceae family, which occurs in dryland forests and is distributed throughout Brazil, mainly in the states of Amazonas and Pará. In addition to its great economic importance for the food industry, phytochemical and biological studies have been carried out on this family of plants and have revealed important pharmacological properties. The aim of this research was to carry out a phytochemical study of the bark of the branches of A. amazonica and to investigate its cytotoxic properties by testing the extracts, fractions and isolated substances. The crude methanolic extract of the bark of the branches was obtained by maceration at room temperature and indicated the presence of alkaloids using Dragendorff's reagent, after which it was subjected to acid-base treatment and the alkaloid fraction was obtained. The chemical profile of the methanolic extract and the alkaloid fraction was investigated by mass spectrometry (MS) and, through chemical prospecting of both, substances of even m/z were identified, indicative of possible nitrogen compounds such as alkaloids. 1H and 13C 1D/2D NMR spectroscopy and mass spectrometry (MS) techniques were used to identify these constituents. The study of the bark of the branches of A. amazonica resulted in the isolation of six substances, five of which belong to the alkaloid class: liriodenine and N-methyl-actinodafinine (already described in the species), discretamine reported for the first time in the species, dicentrinone and nordicentrin, and a terpene belonging to the sesquiterpene subclass known as 1β, 6α-Dihydroxy-4 (15)-eudesmene, described for the first time in the genus and species under study. Among the extracts and fractions that were submitted to the in vitro cytotoxicity test, the alkaloid fraction (from the methanolic extract) showed an inhibition percentage of 67% for HCT116 tumor cells (human colon carcinoma) and 54% for HepG2 (human hepatocellular carcinoma), which were considered moderate activities. Among the isolated alkaloids evaluated, N-methyl-actinodafinin showed the best results against the HCT116, B16-B10 and MRC-5 cell lines, with CI50 values of 4.27, 10.01 and 12.16 μg.mL-1, respectively. The results obtained in this work are described for the first time in the bark of the branches of A. amazonica and, with the exception of the alkaloids liriodenine and N-methyl-actinodafinine, all the other substances are recorded for the first time in the species, corroborating the chemical potential of Brazilian Annonaceae species, particularly those occurring in Amazonas, and contribute to the expansion of chemical knowledge of the species under study and justify the continuation of its study in future projects in search of substances with cytotoxic properties.