IJCS | Volume 32, Nº2, May/June 2019

243 Figure 3 - Vascular relaxation curve induced by different juice samples in aortas of rats precontracted with phenylephrine (A) and maximal vascular relaxation (B). Red wine was used for comparison. The dots represent means ± SEM of the relaxing effect expressed in % relaxation. * Significant difference (p < 0.05) vs. red wine. % Relaxation Maximal relaxation (%) Wine Wine Britto Junior et al. Antioxidant and vasodilatory action of grape juices Int J Cardiovasc Sci. 2019;32(3)238-246 Original Article as red wines, which have different properties depending on the brand and place of manufacture. 12 In fact, the juice sample obtained from RJ was the most powerful in the tests of antioxidant activity and the one from SP was the worst one. With regard to the DPPH radical elimination activity, it was found that the juice from RJ had the highest antioxidant potential, with similar results for the RS (1) , RS (2) and GO samples. The samples produced in SP and PR were the worst ones, presenting the same potential compared to each other, and lower than the others. Similar resultswere obtainedwith theABTS technique, where the best and the worst antioxidant activity was found in the RJ and SP samples, respectively. Grape juices are sources of different antioxidant substances, mainly polyphenols, which includes them in the range of foods with high antioxidant potential. 1,5,13 As expected, the sample of highest antioxidant capacity (RJ) also presented the highest concentration of polyphenols. Likewise, the sample of lowest antioxidant activity also had the lowest concentration of polyphenols (SP). This different concentration of polyphenols may be responsible for the antioxidant capacity of the samples, as it was also found in other foods and beverages. 13,14 Antioxidant substances are electroactive compounds. Therefore, the electrochemical analysis can be considered