Characterisation of the free radical chemistry in physicochemical conditions of the digestive tract
Abstract
The free radical reactions were evaluated in an aqueous model system which mimics the physicochemical conditions of the digestive tract (37°C and pH 3.5, 5, 6.5). Oxidants (Fe2+/H2O2) and antioxidants were added in concentrations which can be found in a bolus after ingestion of a balanced meal composed of meat and vegetables. Detection of the free radicals was achieved using two specific probes (Nitroblue Tetrazolium for superoxide radicals, O2°-, and Terephthalate for hydroxyl radicals, OH°). The level of the detected radicals increased with increasing oxidant concentrations. The pH effect varied according to the free radical. Detected O2°- decreased with increasing pH while a biphasic effect of pH was observed with OH°, with a maximum of detected OH° at pH 5. Antioxidants had various impacts on the free radicals. Plant-derived antioxidants; -carotene and polyphenols (caffeic acid, rutin, chlorogenic acid and quercetin) had antagonist effects on the two radicals. They increased the level of detected O2°- and decreased OH° detection. Trolox C (a water soluble analogue of vitamin E) did not significantly impact the free radical detection. From these data a predictive mathematic model of oxidations in the digestive tract will be built.
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