Effect of caffeic acid on tert-butyl hydroperoxide-induced oxidative stress in U937.

Nonvitamin phenolic compounds are ubiquitous in food plants and therefore potentially present in human plasma in a diet-dependent concentration. The aim of this study was to evaluate the ability of caffeic acid, a phenolic acid with antioxidant activity, to affect cellular response in U937 human monocytic cells to t-butyl hydroperoxide-induced oxidative stress. In our experimental conditions caffeic acid was incorporated into cells without any cytotoxic effect. Caffeic acid-treated cells showed an increased resistance to oxidative challenge, as revealed by an higher percent of survival and the maintenance of an higher proliferative capacity in respect to control cells. This effect seems to be due to the ability of caffeic acid to reduce glutathione depletion and to inhibit lipid peroxidation during tBOOH treatment. It can be concluded that caffeic acid exerts an antioxidant action inside the cell, responsible for the observed modulation of the cellular response to oxidative challenge. Due to its presence in the diet, therefore, caffeic acid may play a role in the modulation of oxidative processes in vivo.