The redox thermodynamics and kinetics of flavonoid rutin adsorbed at glassy carbon electrodes by stripping square wave voltammetry

The adsorptive accumulation of rutin (RU) at glassy carbon (GC) electrodes in 10% ethanol + 90% 1 mol dm-3 HClO4 aqueous solution is studied by using cyclic (CV) and square wave (SWV) voltammetries. The Frumkin adsorption isotherm best described the specific interaction of rutin with carbon electrodes. By fitting the experimental data, values of -31.9 kJ mol -1 and 0.54 ± 0.02 were obtained for the Gibbs free energy of adsorption and the interaction parameter, respectively. SWV fully characterized the thermodynamics and kinetics of the surface redox process, using a combination of the "quasi-reversible maximum" and the "splitting of SW peaks" methods. Average values of 0.644 ± 0.003 V and 0.44 ± 0.02 were obtained for the formal potential and the anodic transfer coefficient, respectively. Moreover, a formal rate constant of 6.1 × 102 s-1 was obtained. SWV was also employed to generate calibration curves. The lowest concentration of RU experimentally measured for a signal-to-noise ratio of 3:1 was 2 × 10-8 mol dm-3 (12 ppb).Fil: Catunda Jr., Francisco Eduardo Aragão. Universidade Federal Rural do Rio de Janeiro; BrasilFil: De Araujo, Marcelo Francisco. Universidade Federal Rural do Rio de Janeiro; BrasilFil: Granero, Adrian Marcelo. Universidad Nacional de Río Cuarto. Instituto para el Desarrollo Agroindustrial y de la Salud. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto para el Desarrollo Agroindustrial y de la Salud; ArgentinaFil: Arevalo, Fernando Javier. Universidad Nacional de Río Cuarto. Instituto para el Desarrollo Agroindustrial y de la Salud. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto para el Desarrollo Agroindustrial y de la Salud; ArgentinaFil: De Carvalho, Mario Geraldo. Universidade Federal Rural do Rio de Janeiro; BrasilFil: Zon, María Alicia. Universidad Nacional de Río Cuarto. Instituto para el Desarrollo Agroindustrial y de la Salud. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto para el Desarrollo Agroindustrial y de la Salud; ArgentinaFil: Fernandez, Hector. Universidad Nacional de Río Cuarto. Instituto para el Desarrollo Agroindustrial y de la Salud. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto para el Desarrollo Agroindustrial y de la Salud; Argentin

Chemical and Biological insights of <i>Ouratea hexasperma</i> (A. St.-Hil.) Baill.: a source of bioactive compounds with multifunctional properties

<p>The study aimed to evaluate <i>in vitro</i> antioxidant, anticholinesterase and antidiabetic properties of <i>Ouratea hexasperma</i> (A. St.-Hil.) Baill. The inflorescence methanol extract and the ethyl acetate fraction of leaves and stems reported the highest Relative Antioxidant Capacity Index (RACI), whereas the dichloromethane fraction of leaves was the best inhibitor of <i>α</i>-amylase and <i>α</i>-glucosidase. T<i>rans</i>-3-<i>O</i>-methyl-resveratrol-2-<i>C</i>-<i>β</i>-glucoside, lithospermoside, 2,5-dimethoxy-<i>p</i>-benzoquinone, lup-20(30)-ene-3β,28-diol, 7-<i>O</i>-methylgenistein, apigenin and luteolin and amentoflavone were isolated from <i>O. hexasperma</i>. Resveratrol derivative was isolated for the first time in Ochnaceae family. Luteolin, followed by apigenin, reported the highest Relative Antioxidant Capacity Index and they were also the best inhibitors of α-glucosidase enzyme.</p