Abstract
BackgroundRedox active minerals in dietary supplements can catalyze unwanted and potentially harmful oxidations.MethodsTo determine if this occurs in vivo we employed electron paramagnetic (EPR) imaging. We used 1-hydroxy-3-carboxy-2,2,5,5-tetramethylpyrrolidine (CPH) as a reporter for one-electron oxidations, e.g. free radical-mediated oxidations; the one-electron oxidation product of CPH, 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxy (CP•), is a nitroxide free radical that is relatively persistent in vivo and detectable by EPR. As model systems, we used research formulations of vitamin mineral supplements (RVM) that are typical of commercial products.ResultsIn in vitro experiments, upon suspension of RVM in aqueous solution, we observed: (1) the uptake of oxygen in the solution, consistent with oxidation of the components in the RVM; (2) the ascorbate free radical, a real-time indicator of ongoing oxidations; and (3) when amino acid/oligosaccharide (AAOS; glycinate or aspartate with non-digestible oligofructose) served as the matrix in the RVM, the rate of oxidation was significantly slowed. In a murine model, EPR imaging showed that the ingestion of RVM along with CPH results in the one-electron oxidation of CPH by RVM in the digestive system. The resulting CP• distributes throughout the body. Inclusion of AAOS in the RVM formulation diminished the oxidation of CPH to CP• in vivo.ConclusionsThese data demonstrate that typical formulations of multivitamin/multimineral dietary supplements can initiate the oxidation of bystander substances and that AAOS-complexes of essential redox active metals, e.g. copper and iron, have reduced ability to catalyze free radical formation and associated detrimental oxidations when a part of a multivitamin/multimineral formulation.
Highlights
Redox active minerals in dietary supplements can catalyze unwanted and potentially harmful oxidations
research multivitamin/multi mineral formulations (RVM) formulation It is not possible to compare directly the potential oxidative chemistry of different multivitamins/minerals supplements that are on the market due to interferences from the different matrices of the formulations
We have clearly demonstrated the value of using the oxidation of 1Hydroxy-3-carboxy- 2 (CPH) to CP● as a reporter for oneelectron oxidations in vitro and in vivo
Summary
Redox active minerals in dietary supplements can catalyze unwanted and potentially harmful oxidations. Rabovsky et al BMC Nutrition (2015) 1:32 ascorbate, referred to as the Udenfriend system, is a standard approach to oxidize organic substances [12] These metals could bring about the loss of antioxidants as well as initiate potentially harmful oxidation reactions in cells and tissues before absorption by the digestive system. We prepared research multivitamin/multi mineral formulations (RVM) based on RDA guidelines with minerals as typical inorganic complexes or with amino acid/oligosaccharide (AAOS; glycinate or aspartate with non-digestible oligofructose) serving as the coordinating ligands and matrix for the minerals in the RVM The abilities of these formulations to initiate oxidation processes in vitro and in vivo were examined. We used EPR imaging to determine if formulations of multivitamin/multimineral supplements can initiate free radical oxidations in vivo
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