Intracellular antioxidant activities of polyphenolic compounds (single and in mixture): resveratrol and quercitin

Under physiopathological conditions reactive oxygen species can be over produced evoking an intracellular state of oxidative stress. Dietary polyphenols are known to have potent antioxidant activity by various mechanisms. While a number of data is available on the antioxidant behavior of single polyphenolic compounds, little is known about possible interactions among them, which could influence the “quality” of their intracellular antioxidant activity when present in mixture. This study was aimed to assess the intracellular antioxidant activity of two red wine polyphenols, resveratrol and quercetin, both single and in mixture. HeLa cells charged with the ROS-sensitive cell permeant dye, CM-H2DCFDA, were used as model. Spectrofluorimetric and confocal microscopy analysis was performed. In the range of concentration tested (5-50 µM) quercetin alone exhibited a dose-dependent intracellular antioxidant activity against an oxidative stress induced by H2O2 used as pro-oxidant agent. On the other hand resveratrol showed a pro-oxidant intracellular activity. When the cells were exposed to equimolar mixtures of the two compounds, an intracellular interaction among them was highlighted, with a non-predictable behavior on the basis of the analysis conducted on the single compounds. In conclusion results demonstrated that antioxidant properties of polyphenolic compounds depend not only on the nature of the compound itself, but also on the type of their interaction in a cellular system.