Antioxidant effects of dietary polymeric grape seed tannins in tissues of rats fed a high cholesterol-vitamin E-deficient diet

Effects of dietary monomeric and polymeric grape seed tannins on the activity of antioxidant enzymes, total glutathione and level of lipid peroxidation in various tissues were investigated in rats fed a high cholesterol diet poor in vitamin E. They were compared with those in rats receiving a high cholesterol-vitamin E-sufficient diet without addition of tannins. Four groups of rats were studied for 10 weeks: Group 1, sufficient vitamin E diet; Group 2, deficient vitamin E diet; Group 3, deficient vitamin E diet + monomeric tannins (71 mg/kg); Group 4, deficient vitamin E diet + polymeric tannins (71 mg/kg). Compared with a normal vitamin E diet (Group 1), aortic, cardiac, hepatic, intestinal, muscular and renal catalase, glutathione peroxidase and superoxide dismutase activities were significantly lower in rats receiving the deficient vitamin E diet (Group 2); polymeric tannins (Group 4), but not monomeric tannins, were able to restore all these enzymic activities. In all tissues and in blood, total glutathione concentration, which was significantly lowered by vitamin E deficiency, was brought to the normal level only with polymeric tannins. Furthermore, the lipid peroxidation in plasma and tissues was significantly reduced in the presence of supplemented polymeric tannins as much as in the presence of vitamin E. It is therefore likely that polymeric grape seed tannins function as antioxidants in vivo, negating the effects of the oxidative stress induced by both vitamin E deficiency and atherogenic diet.