Potencial bioativo de sucos de uva Vitis labrusca L.: caracterização química e atividade antioxidante, influência de sementes de uva e de pectinases na composição fenólica, e bioatividade do trans-resveratrol em células humanas

The bioactive properties of polyphenols are extensively studied in wines and grapes from V. vinifera L. However, the V. labrusca L. varieties, widely cultivated in Brazil and mainly destined to grape juice production, represent an attractive source of phenolic compounds. The objectives of this study were to evaluate the influence of the addition of grape seeds and pectinolytic enzymes on the polyphenols content, antioxidant activity in vitro and on the macro and microelements contents in grape juices from different V. labrusca L. varieties grown in the South region of Brazil; and to evaluate their bioactive properties in vitro and in vivo. In the experimental preparation of juices, the effects of grape seed addition and pectinases were evaluated in Bordo, Concord and Isabel grape juices. Industrialized grape juices produced in the Serra Gaúcha Region, RS, Brazil, were used to investigate the bioactive potential. Characterization of the phenolic and elemental composition and in vitro antioxidant activity was performed in red and white grape juices. The effect of acute consumption of organic and conventional grape juices on antioxidant activity and oxidative stress markers in healthy subjects was evaluated through a randomized controlled intervention trial. In human cells studies, the bioactive effects of transresveratrol (RSV) towards oxidative mechanisms related to endothelial dysfunction were investigated through a co-culture of intestinal Caco-2 cells and endothelial EA.hy926 cells. Grape seed addition significantly increased the total phenolics and antioxidant capacity of juices, and was positively correlated with minerals Ca, Mg, Na, K, Mn e Zn. The optimization of pectinolytic activity through response surface methodology led to an increased extraction of minerals and phenolics in juices, and depicted a positive correlation among the variables. The optimized conditions for polyphenols extraction were estimated by the model at enzyme concentrations of 1.30 and 1.57 g L -1 , at 46.8 and 54.8 oC, respectively. The characterization of industrialized grape juices showed higher concentration of total phenolics, monomeric anthocyanins, trans-resveratrol, Mg and Mn, and higher antioxidant activity in vitro in the organic grape juice. The acute consumption of V. labrusca L. juices promoted significant reductions on levels of hydroperoxides (LOOH) in serum and thiobarbituric acid reactive substances (TBARS) in plasma of healthy individuals. The consumption of juices significantly augmented serum antioxidant capacity and enzymatic activities of catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase (SOD) in erythrocytes. The interventions with grape juices did not affected significantly the glycaemic status and uric acid levels. The multivariate analysis confirmed the influence of the main phenolic classes on biological responses. However, the chemical differences associated with organic and conventional juices were not a predictive factor for its effects in vivo. In cell culture, RSV treatment significantly reduced the tumor necrosis factor α (TNF-α)-induced levels of vascular endothelial growth factor (VEGF), reactive oxygen species (ROS), interleukin 8 (IL-8) and intercellular adhesion molecule 1 (ICAM-1) and increased the endothelial production of nitric oxide (NO). The UPLC-MS/MS E analysis revealed the presence of RSV and four conjugated metabolites. The bioactivity of RSV and its metabolites towards inflammatory mechanisms was demonstrated in a co-culture for the first time. The chemical characterization and the in vitro and in vivo results have demonstrated that V. labrusca L. grape juices are rich sources of macro and microelements and phenolic compounds, with bioactive potential in human health.