Grape is one of the world‘s largest fruit crops widely cultivated because of its economic importance in making wine, juice, jam, and raisins [1]. Grapes have been found to possess notable antioxidant capacities mostly due to the abundance in polyphenols [1], as well as due to the presence of several antioxidants that are known to have protective effects against many diseases [2]. Grape phenolic compounds are mainly found in skins, pulps, and seeds that are partially extracted during processing. In grapes, they have a special significance because they contribute to the color, taste and aroma of fresh fruit and also to the color, taste and quality of wines, juices and other products. Such a complex system like the one found in grapes assumes the occurrence of synergic or anti-synergic interactions between its compounds. According to Tsao [3], synergistic combination of compounds with antioxidant activity can be advantageous, as long as it increases the individual antioxidant effects when two or more compounds are combined. From a technological and ecological point of view, this phenomenon is favorable due to the significant increase in the effectiveness of food preservation, the reduction of the amount of food additives required and, in particular, due to the decrease in the application of synthetic antioxidants that can be toxic [3]. In this study, the influence of tartaric, citric and gallic acids on the antioxidant activity of some grape polyphenols is reported. The experiments were performed using the DPPH method [4] that involves the interaction of the antioxidant compounds with the free radical 2,2-diphenyl-1-picrylhydrazyl. The results are expressed as g-equivalents of ascorbic acid per liter. The half maximal effective concentration, which can be defined as the concentration required to obtain a 50% free radical annihilation effect, was determined in order to ensure an easier comparison between each antioxidant. The synergic and anti-synergic effects were calculated for each sample tested, using the equations described in the literature [5].