IJCS | Volume 32, Nº2, May/June 2019

241 Figure 1 - Graphical representation of the results of antioxidant tests DPPH (A), ABTS (B) and total content of phenolic compounds by Folin-Ciocalteu reaction (C), expressed in μg gallic acid equivalent (GAE/mL). The letters on the bars represent the statistical difference (p < 0.05) between the indicated groups. Gallic acid equivalent ( µ g/mL) Britto Junior et al. Antioxidant and vasodilatory action of grape juices Int J Cardiovasc Sci. 2019;32(3)238-246 Original Article The ABTS technique (Figure 1B) confirmed the best antioxidant activity of the RJ sample (CE 50 : 0.59 ± 0.11 µL). The SP sample had a lower antioxidant potential (CE 50 : 1.25 ± 0.19 μL), being statistically different (p < 0.05) from the best sample (RJ). In turn, the other samples presented similar results (p > 0.05). The order of activity for the ABTS TEST was RJ > RS (1) (0.83 ± 0.1 μL) > RS (2) (0.91 ± 0.18 μL) > GO (0.65 ± 0.01 μL) > PR (0.90 ± 0.13 μL) > SP. In Figure 1C, we can see the number of phenolic compounds (expressed in μg equivalents of gallic acid/ mL of the sample) present in the samples. The results are according to the antioxidant activity (Figures 1A, B), and the sample with the highest antioxidant potential presenteda higher concentrationof phenolic compounds (RJ: 2.25 ± 0.06 µg/mL). The lowest concentration of phenolic compounds was observed in the SP sample (1.26 ± 0.08 μg/mL), being different (p < 0.05) from all others. Electrochemical analyses Figure 2A shows the results of the electroanalytical analyses of the samples. Although the electrochemical indices showed a higher activity for the RJ sample (21.7 ± 2.1 μA/V), the samples from RS (1) , RS (2) , GO and PR presented equivalent electrochemical indices (p > 0.05) (18.8 ± 1.9; 16.3 ± 1.5; 19.8 ± 2.5; 17.2 ± 3.3 μA/V, respectively). Only the SP sample (11.3 ± 0.5 μA/V) showed a statistical difference (p < 0.05) compared to most effective sample (RJ). The IE values ​are calculated from the main electrochemical parameters, that is, an anode peak potential — E pa . The lower the anode peak potential the higher the thermodynamic capacity of the species to reduce others, and anodic peak current intensity — I pa — which in addition to being related to concentration, also concerns the speedwithwhich the reduction process occurs. The presence of electroactive compounds in both the most effective sample (RJ) and in the least effective sample (SP), which presented two oxidation peaks (1 a and 2 a ). The oxidation peak of the RJ sample occurs at a lower voltage than the SP sample, showing its greater reducing potential. (Figure 2B). Vasodilator effect Vasodilator activity was demonstrated in vitro for the 6 juice samples tested and the red wine sample (for comparison purposes). All 6 juice samples induced concentration-dependent relaxation, whose efficacy was variable among them (Figure 3A). The RJ sample (as well as in the antioxidant activity tests) was the most effective one, inducing maximum relaxation of 88.2 ± 4.8%. This sample was the only one that had a similar maximum relaxation (p > 0.05) compared to red wine induced relaxation (112.9 ± 5.1%). The other samples (except RJ) showed lower relaxation (p < 0.05) than that produced by red wine. The RS (2) sample was the least effective one in inducing vascular dilatation (19.5 ± 6.1%), being significantly (p < 0.05) different from the RS (1) (71.6 ± 9.6%), RJ (88.2 ± 4.8%) and GO (53.6 ± 7.2%) samples. The PR and SP samples induced relaxation in similar magnitudes (39.8 ± 7.4 and 39.9 ± 10.4%, respectively) and only showed a significant difference (p < 0.05) over the RJ sample. These results are presented in figure 3B.