There is increasing evidence that reactive oxygen species arising from several enzymatic reactions are mediators of inflammatory events. Plant preparations have the potential for scavenging such reactive oxygen species. Flavans and procyanidins are bioavailable and stable during the process of cooking. This study used conditions that mimicked digestion of Vitis vinifera seed powder in the stomach (acidic preparation) and small intestine (neutral preparation). The flavonoids of these two preparations were released during simulated digestion and were determined with HPLC analysis. Biochemical model reactions relevant for the formation of reactive oxygen species in vivo at inflammatory sites were used to determine the antioxidant properties of the two preparations. The inhibition of the indicator reaction for the formation of reactive oxygen species represents a potential mechanism of the physiological activity of the corresponding preparation. The results of this work show clearly that the polyphenols released during the simulated digestion of the two preparations have good scavenging potential against superoxide radicals, hydroxyl radicals, and singlet oxygen. They protect low-density lipoprotein against copper-induced oxidation due to the copper-chelating properties and their chain-breaking abilities in lipid peroxidation.