Abstract
The tea catechin EGCG has been postulated to provide health benefits in humans, to some extent, as an antioxidant. The dose-response effect of dietary EGCG (0, 30, 60, or 120 mg/kg diet) was tested in rats under high versus low oxidative stress conditions that were created by feeding diets adequate in vitamin E and Se (Lox), or deficient in both (Hox) for six weeks. Effects on growth, quinone reductase (NQO1) activity, F2-isoprostanes and nutrient antioxidant amounts in the liver were evaluated as markers of nutrient deficiency and oxidative status. Under Hox conditions consumption of EGCG only at the lowest dose was partially associated with a protection against oxidative stress, reflected by a delay in growth deceleration, but no protection against lipid oxidation. Elevated liver NQO1 activity was observed in this group (>4-fold) increasing with the dose; but it was not associated with antioxidant protection. In contrast, under Lox conditions consumption of EGCG was associated with antioxidant activity reflected in a reduction (>30%) in F2-isoprostanes and protection of CoQ reduced status in the liver. Overall these results suggest that the antioxidant effect of EGCG in vivo depends on the level of oxidative stress and the presence of other nutrient antioxidants.
Highlights
Aerobic organisms are in constant interaction with molecular oxygen as part of the energy yielding processes in cells
A low dose of EGCG was loosely associated with antioxidant protection in animals under high oxidative stress diet (Hox) conditions; supported by the delay in growth deceleration and lower function of NQO1 in the liver, but not from accumulation of lipid peroxidation products or antioxidant molecules
Consumption of higher amounts of dietary EGCG did not provide additional antioxidant protection and this was only associated with higher NQO1 activities in the liver
Summary
Aerobic organisms are in constant interaction with molecular oxygen as part of the energy yielding processes in cells Because this process is not perfect, this adaptation to use oxygen as the final acceptor of electrons in the process of trapping energy is translated in the accumulation of oxygen free radicals or reactive oxygen species (ROS). Consumption of diets rich in plant foods, such as fruits, vegetables and herbs, has been negatively correlated with the risk for a variety of chronic diseases, cardiovascular disease and some types of cancer [3] These beneficial effects have largely been attributed to their high content of dietary fiber and non-nutrient plant chemicals such as flavonoids and terpenes. The main stated hypothesis is that flavonoids, to some extent, mediate the beneficial effects derived from an enriched fruit and vegetable diet in part by their multiple antioxidant properties [4]
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