IJCS | Volume 32, Nº2, May/June 2019

239 Britto Junior et al. Antioxidant and vasodilatory action of grape juices Int J Cardiovasc Sci. 2019;32(3)238-246 Original Article the elderly, children and pregnant women. However, studies have found that the consumption of grape juice also has positive results, often comparable to wine consumption, such as an antioxidant and vascular relaxation action. 5,6 Despite the existence of several studies with red wine from different parts of the world, including Brazil, a smaller number of information exists regarding the biological properties of red grape juice. Research on the functional properties of grapes was boosted by the benefits derived from wine consumption, encouraged by the “French paradox”, an expression that is known worldwide. Moreover, there is an increasing number of studies that demonstrate that grape juice has beneficial functional properties similar to wine, especially on the cardiovascular system. 7,8 In Brazil, the consumption and production of whole- grape juice has increased by around 15% per year. 9 However, the quantity and quality of the functional ingredients of grapes may be largely influenced by the climate, soil and geographic region of the crops. 10,11 As Brazil is an enormous country, the juices produced in different regions may contain different antioxidant potentials and chemical compositions, which would certainly modify their functional properties. In this study, we evaluated the antioxidant properties and the vasodilatory capacity of grape juice of various brands produced in different regions across Brazil. Methods Sourcing of the juices analyzed Samples of 6 whole-grape juices produced in a few regions in Brazil, marked with the acronym of the state where they were produced, have been purchased. The acronyms are the following: RS (2 samples: RS (1) and RS (2) ), RJ, GO, PR and SP. The eligibility criteria were: i) whole red grape juice; (ii) no added preservatives, stabilizers or antioxidants; (iii) no added water; (iv) no added sugar; and v) samples whose ingredients were only “100% grape juice”. The juice samples were selected at random from the main producer states. We did not have access to any samples produced in the North and Northeast regions. For the spectrophotometric and electroanalytical experiments, each samplewas diluted in the concentration of 10% in an ethanolic solution. All tests were performed in triplicate. Reagents Th e r a d i c a l s ABT S . + ( 2 , 2 a z i n o - b i s - ( 3 - ethylbenzothiazoline-6-sulfonate), DPPH (2,2-diphenyl- 1-picrylhydrazyl) and the reagents used in the analyzes were all analytically pure and sourced from Sigma Chemical Co. (St. Louis, MO, USA). All electrolytic solutions were prepared with purified water using the Millipore Milli-Q system, conductivity ≤ 0.1μS.cm -1 (Millipore S.A., Molsheim, France). Other reagents were purchased off-the-shelf. Evaluation of antioxidant action by theDPPH radical sequestration method The purple radical DPPH (2,2-diphenyl-1- picrylhydrazyl), when reduced by the antioxidant, is discolored and turns yellow. Reduction of radical DPPH is followed by a decrease in absorbance by 517 nm. The amount of analyte in μL required to reduce the DPPH absorbance by 50% (Efficient Concentration, EC50) is calculated to evaluate the antioxidant capacity of each sample and the free radical sequestering activity or percentage of discoloration. The analytes were solutions of 10% whole juices and the standard solution of gallic acid evaluated at different concentrations. Absorbance was monitoredwith a UV-Vis spectrophotometer (Jasco ® V-530) and all tests were performed in triplicate. Evaluation of the antioxidant activity by the ABTS radical method T h e r a d i c a l ABT S . + ( 2 , 2 ’ a z i n o - b i s - ( 3 - ethylbenzthiazoline-6-sulfonate) is formed from the ABTS reaction (7 mM) with 88 μl of potassiumpersulfate (140mM) in the absence of light. To perform the analyses, a volume of 300 μL of the ethanolic analyte solution was placed in a test tube with 2.7 mL of the ABTS radical, then the tubes were covered with Parafilm ® and kept in the dark for 20minutes and the absorbance was monitored at 734 nmusing a UV-Vis spectrophotometer (Jasco ® V-530) and all tests were performed in triplicate. Determination of total phenols The method Folin-Ciocalteau (FC) allows the quantification of phenolic compounds by evaluating the reduction of the FC reagent by these antioxidants with the formation of a blue complex whose intensity increases linearly at 765 nm. The total amount of phenols was obtained by constructing a standard curve prepared