Atividade antioxidante de flavonóides e terpenóides obtidos das folhas e da casca do tronco de Scutia buxifolia Reissek

Abstract

The Rhamnaceae family is composed of some 58 genera and about 900 species. Scutia buxifolia Reissek species, popularly known as coronilha, is a local plant from South America, with a dispersion that comprise Rio Grande do Sul state in Brazil, Argentina and Uruguay. The stem bark and leaves decoction are popularly used as cardiotonic, antihypertensive and diuretic. This work aims to isolate and identify flavonoids and triterpenes present in Scutia buxifolia and analyze ability to capture free radicals. Stem bark and leaves of S. buxifolia were collected in October 2007 in Dom Pedrito-RS (coordinates 30º 59'09''S and 54º27'44''W). The material is deposited in the herbarium of the Department of Biology UFSM cataloged under the registration number SMBD 10919. The dried plant material was ground and macerated using ethanol: water (70:30, v/v) as solvent. The crude extract was fractionated with solvents of increasing polarity (CH2Cl2, AcOEt, n-BuOH). In AcOEt fraction of the leaves was characterized quercetin, quercetin 3-0-rhamnosíde, quercetin 3-0-β-Dglucopyranoside and rutin, and the CH2Cl2 fraction of stem bark the steroids β-sitosterol and stigmasterol, and the triterpene lupeol. The compounds were analyzed by 1H-NMR and 13CNMR and spectroscopic data were compared with those obtained from the literature. The compounds were quantified by HPLC in the fraction used for insolation. The crude extract and fractions of S. buxifolia were investigated for lipid peroxidation, antioxidant activity and total content of phenols. The total phenolic content ranged from 141.09 ± 0.71 to 323.47 ± 2.62 mg/g for stem bark and 72.09 ± 0.50 to 383.34 ± 2.31 mg/g for leaves of S. buxifolia. Crude extract and fractions caused a sharp fall in TBARS production with IC50 from 2.93 ± 2.17 to 40.46 ± 2.51 μg/mL for the leaves and 0.66 ± 0.17 to 27.3 ± 1.23 μg/mL for the stem bark. The order of capture of free radicals was: AcOEt > n-BuOH > CH2Cl2 > crude extract, for the two parts of the plant.