Contribuição ao conhecimento da composição fenólica e avaliação do potencial antioxidante das cascas de Endopleura uchi (Huber) Cuatrec.

Abstract

Endopleura uchi (Huber) Cuatrec. (Humiriaceae), popularly known as “uxi amarelo” or “uxi liso”, is a native tree of the Brazilian Amazon rainforest found throughout the Amazon basin. It has been a constant target of new research over the years, particularly for its popular use, phytochemical potential and biological activities. Its bark is commonly used as natural medicine for the treatment of many diseases. Although widely investigated from the phytochemical viewpoint, the knowledge regarding the phenolic content remains unexplored. In order to access the phenolic composition of E. uchi bark, an integrative approach based on simplex centroid design, direct infusion electrospray ionization mass spectrometry (ESI-MS) and chemometric analysis was adopted. In addition, the extracts were evaluated for total phenolic content and antioxidant activity. The multivariate analysis pointed to the ethanol-based extracts containing as the most containing phenolic compounds, with 3,5-di-O-galloylquinic acid (2), gallic acid (4), 5-galloylquinic acid (5) and gallocatechin gallate (6) tentatively identified by MS analysis. All are described for the first time in E. uchi. Besides, pure ethanol extract presented highest total phenolic content (TPC = 133.61 ± 0.3 mg of gallic acid equivalent per 100 g of dry extract) and antioxidant activity (half-maximal inhibitory concentration, IC50 = 9.32 ± 0.15). In vitro cytotoxicity and an antioxidant activity by iron reduction (FRAP) of the selected extractor were applied and a simplified protocol for selective extraction of the target compounds and a quantitative study by HPLC-MS/MS were applied. The integrative approach proposed to this work provided an effective way to assess the phenolic compounds of E. uchi bark, therefore, improving the knowledge regarding phenolic content in this Amazonian medicinal plant. In addition, the quantitative study of quinic acid, gallic acid and gallocatechin gallate were first reported in the species.