Estudo químico e avaliação da atividade antioxidante de Diplotropis racemosa (Hoehne), resíduo madeireiro do Médio Amazonas.

Abstract

Diplotropis racemosa (Hoehne) belongs to the Leguminosae family, popularly known as Sucupira preta, has dispersion throughout Brazil and is widely used in degraded areas. Studies carried out in the Amazon Region indicate the presence of active substances such as flavonoids, terpenes, saponins and alkaloids in the bark and heartwood of species of the family. The phytochemical prospecting aimed to identify groups of secondary metabolites present in the crude extract and fractions of the D. racemosa bark, whose chemical constitution is unknown. The peel was dried, crushed and the crude extract was obtained under reflux with 70% ethanol. The crude extract was fractionated by liquid-liquid partition, obtaining the following fractions: hexane, chloroform, ethyl acetate, butanolic and hydroalcoholic. The chemical constitution of the extracts was evaluated before reaction in tubes and chromatographic plates. The antioxidant activity was analyzed against the radicals DPPH and ABTS, and the content of total phenols was determined. The butanolic fraction was fractionated in the HPCCC using solvent systems composed of: ethyl acetate - butanol - water. Chromatographic and spectroscopic methods were used to obtain the chemical profile of the purified samples. Phytochemical prospecting showed qualitatively the presence of the following classes of secondary metabolites: condensed tannins, flavones, flavonoids, xanthones, flavanone, flavanones, pentacyclic triterpenes, saponins and alkaloids. CCD analysis showed the presence of flavonoids in the following samples: crude extract, ethyl acetate fraction and butanolic fraction. In addition, it allowed to monitor the entire process of isolation and antioxidant activity against DPPH, which in the in vitro assay the ethyl acetate fraction showed an IC50 of 49.27 µg / mL and a higher concentration of total phenols. However, the fraction yield in ethyl acetate was low, so the isolation was directed to the second most active fraction, considering the antioxidant test of ABTS. The HPCCC technique allowed for fast and effective targeting for the fractionation and purification of substances. In the present study, it was possible to purify and identify 4 novel C-glycosylated flavones in the species D. racemosa, namely: violantine (8.4 mg), isoviolantine (12.1 mg), vitexin (12 mg) and isovitexine (7.7 mg). This research was a pioneer in the phytochemical characterization of wood residue D. racemosa, collected in the Middle Amazon region. These results demonstrate a possibility for the use of residues by the industry, supplying substances with technological potential, contributing to the environment. This work contributes to the phytochemical knowledge of the genus Diplotropis and should be continued to find new substances present with biological potentials, yet to be explored.