Antioxidant/prooxidant activity of a polyphenolic grape seed extract

The oxidative potential of a polyphenolic grape seed extract, with the idea of using this extract as a nutritive supplement, was evaluated. Data presented in this work provide in vitro (primary leukocyte culture) UV–Vis spectral evidence, indicating that quinones, as oxidation products, are involved in the modulation of the antioxidant/prooxidant balance at cellular level in the case of catechin-type compounds (pure catechin (CS) and polyphenolic extract (PE)), in the absence or presence of lipoxygenase (pure (LS) or in raw soybean extract (LE)) as oxidative stress inducers. The study shows, to some extent, the grape seed extract tested, considered as an antioxidant nutritive supplement, may have prooxidant activity as well, depending on the dose, duration of administration, and other dietary components. The UV–Vis analysis confirms that the antioxidant activity of this extract might be mediated by prooxidant quinones and oxidation products of the polyphenols from grape seeds.