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      Ethoxyquin: An Antioxidant Used in Animal Feed

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          Abstract

          Ethoxyquin (EQ, 6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline) is widely used in animal feed in order to protect it against lipid peroxidation. EQ cannot be used in any food for human consumption (except spices, e.g., chili), but it can pass from feed to farmed fish, poultry, and eggs, so human beings can be exposed to this antioxidant. The manufacturer Monsanto Company (USA) performed a series of tests on ethoxyquin which showed its safety. Nevertheless, some harmful effects in animals and people occupationally exposed to it were observed in 1980's which resulted in the new studies undertaken to reevaluate its toxicity. Here, we present the characteristics of the compound and results of the research, concerning, for example, products of its metabolism and oxidation or searching for new antioxidants on the EQ backbone.

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          Most cited references81

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          Plant phenolic antioxidant and prooxidant activities: phenolics-induced oxidative damage mediated by metals in plants.

          Y Sakihama (2002)
          Plant phenolic compounds such as flavonoids and lignin precursors are important constituents of the human diet. These dietary phytophenolics have been recognized largely as beneficial antioxidants that can scavenge harmful active oxygen species including O(2)(.-), H(2)O(2), .OH, and (1)O(2). Here we review our current understanding of the antioxidant and prooxidant actions of phenolics in plant cells. In plant systems, phytophenolics can act as antioxidants by donating electrons to guaiacol-type peroxidases (GuPXs) for the detoxification of H(2)O(2) produced under stress conditions. As a result of such enzymatic as well as non-enzymatic antioxidant reactions, phenoxyl radicals are formed as the primary oxidized products. Until recently, phenoxyl radicals had been difficult to detect by static electron spin resonance (ESR) because they rapidly change to non-radical products. Application of Zn exerts spin-stabilizing effects on phenoxyl radicals that enables us to analyze the formation and decay kinetics of the radicals. The ESR signals of phenoxyl radicals are eliminated by monodehydroascorbate radical (MDA) reductase, suggesting that phenoxyl radicals, like the ascorbate radical, are enzymatically recycled to parent phenolics. Thus, phenolics in plant cells can form an antioxidant system equivalent to that of ascorbate. In contrast to their antioxidant activity, phytophenolics also have the potential to act as prooxidants under certain conditions. For example, flavonoids and dihydroxycinnamic acids can nick DNA via the production of radicals in the presence of Cu and O(2). Phenoxyl radicals can also initiate lipid peroxidation. Recently, Al, Zn, Ca, Mg and Cd have been found to stimulate phenoxyl radical-induced lipid peroxidation. We discuss the mechanism of phenoxyl radical prooxidant activity in terms of lifetime prolongation by spin-stabilizing agents.
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            Chemistry and antihypertensive effects of tempol and other nitroxides.

            Nitroxides can undergo one- or two-electron reduction reactions to hydroxylamines or oxammonium cations, respectively, which themselves are interconvertible, thereby providing redox metabolic actions. 4-Hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (tempol) is the most extensively studied nitroxide. It is a cell membrane-permeable amphilite that dismutates superoxide catalytically, facilitates hydrogen peroxide metabolism by catalase-like actions, and limits formation of toxic hydroxyl radicals produced by Fenton reactions. It is broadly effective in detoxifying these reactive oxygen species in cell and animal studies. When administered intravenously to hypertensive rodent models, tempol caused rapid and reversible dose-dependent reductions in blood pressure in 22 of 26 studies. This was accompanied by vasodilation, increased nitric oxide activity, reduced sympathetic nervous system activity at central and peripheral sites, and enhanced potassium channel conductance in blood vessels and neurons. When administered orally or by infusion over days or weeks to hypertensive rodent models, it reduced blood pressure in 59 of 68 studies. This was accompanied by correction of salt sensitivity and endothelial dysfunction and reduced agonist-evoked oxidative stress and contractility of blood vessels, reduced renal vascular resistance, and increased renal tissue oxygen tension. Thus, tempol is broadly effective in reducing blood pressure, whether given by acute intravenous injection or by prolonged administration, in a wide range of rodent models of hypertension.
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              Phenolics: prooxidants or antioxidants?

              A. Decker (1997)
              Both essential and nonessential dietary antioxidants have been suggested to be beneficial for health. However, studies show that many antioxidants can also exhibit prooxidant behavior under certain conditions. The antioxidant/prooxidant activity of phenolics is dependent on such factors as metal-reducing potential, chelating behavior, pH, and solubility characteristics. These factors, in addition to bioavailability and stability in tissues, should be considered when evaluating the potential bioactivity of dietary phenolics.
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                Author and article information

                Journal
                Int J Food Sci
                Int J Food Sci
                IJFS
                International Journal of Food Science
                Hindawi Publishing Corporation
                2314-5765
                2013
                30 April 2013
                : 2013
                : 585931
                Affiliations
                1Department of General Genetics, Molecular Biology and Plant Biotechnology, Faculty of Biology and Environmental Protection, University of Łódź, Banacha 12/16, 90-237 Łódź, Poland
                2Department of Organic Chemistry, Faculty of Chemistry, University of Łódź, Tamka 12, 91-403 Łódź, Poland
                Author notes

                Academic Editor: Ángel Medina-Vayá

                Article
                10.1155/2013/585931
                4745505
                26904606
                4203ed35-1f5a-4a65-a4a1-34a5214dde06
                Copyright © 2013 Alina Błaszczyk et al.

                This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 15 January 2013
                : 2 April 2013
                Categories
                Review Article

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