Otimização de métodos extrativos, investigação fitoquímica e biológica de Arachis repens HANDRO (Fabaceae)

Abstract

The vegetal species Arachis repens, commonly known as peanut grass, was studied and, for the first time, we detected the presence of the bioactive compound trans-resveratrol (t-RSV). We compared the efficiency of three different methodologies (conventional Maceration [CM], ultrasound [UAE] and microwave [MAE] assisted extractions) concerning total phenolics (TP) and resveratrol (t-RSV) content, followed by antioxidant activity (AA) evaluation. By CM, at 1 h, it was found the highest RSV content (1.024 ± 0.036 mg / L) and, correspondly, the highest DPPH capture (23.90 ± 0.04%). The TP contents, at 1h, presented the highest value (27.26 ± 0.26 mg/g GAE). By the UAE, the maximum yield of TP (357.18 mg/g GAE) and RSV (2.14 mg/L), as well as, the highest AA (70.95%), were obtained by 5 min after a maceration pre-treatment, on the solid-solvent ratio 1:40 w/v. For MAE, a central composite rotatable design (CCRD) was applied followed by the FFD design in order to evaluate the statistical effects of four independent variables on the extraction of RSV. The optimal conditions established for obtaining the highest recovery (2.516 mg/g) were: 20 min; 90% MeOH aq.; 120 rpm; 60°C and, solid-solvent ratio: 1:35 w/v. Relevant correlations were established considering the TP and RSV contents, as well as, the AA, corroborating obvious advantages of such techniques in terms of high extraction efficiency in shorter times. The identification of the constituents by GC / MS revealed the presence of novel allelochemical substances in the species. Substances isolated in mixture or do not indicate the presence of steroids such as sitosterol, stigmasterol and lupeol in the hexanic extract of A. repens stems. These substances are attributed to the allelopathic activity known in the literature. The dichloromethane partition of the methanolic extract of stems and leaves showed an inhibitory allelopathic effect for both hypocotyls as in L. sativa radicles and in the weeds Commelina benghalenses and Panicum maximum