Antioxidants Ethylenediaminetetraacetic

Certain compounds, known as chelating agents (qv), react synergisticaHy with many antioxidants. It is beheved that these compounds improve the functional abiUties of antioxidants by complexing the metal ions that often initiate free-radical formation. Citric acid and ethylenediaminetetraacetic acid [60-00-4] (EDTA), C2QH2gN20g, are the most common chelating agents used (22). 

Secondary antioxidants, i.e., sequestrants or chelators, are important compounds in the prevention of lipid oxidation. The effect of chelators tested varied with the different compounds. Of those chelators tested, ethylenediaminetetraacetic acid (EDTA, tetrasodium salt) and sodium phytate were the most effective inhibitors of lipid oxidation (so indicated by low hexanal and TEARS values) and MFD (as seen by high CBB and low PIT and CBD intensity values), see Table 5. Sodium phytate was previously shown to chelate iron and thus, was proposed as a food antioxidant(7J). Sodium citrate at a concentration of 500... 

EDTA, Ethylenediaminetetraacetic acid TAS, total antioxidant status TRAP, total peroxyl-radical-trapping antioxidant capability of plasma ABAP, 2,2 -azobis(2-amidopropane) FRAP, ferric-reducing activity of plasma H2-DCF-DA, 2, 7 -dichlorofluorescein diacetate ORAC, oxygen-radical-absorbing capacity ABTS, 2,2 -azinobis(3-ethylbenzthiazoline-6-sulfonic acid). 

There are various synthetic antioxidants, such as butylated hydroxytoluene (BHA), propyl gaUate (PG), ethylenediaminetetraacetic acid (EDTA), etc. that are used in commercial oils TBHQ is known to produce the best results in frying applications. 

Buffers can also be provided in parenteral formulations to ensure the required pH needed for solubility and/or stability considerations. Other excipients included in parenteral products are preservatives (e.g., benzyl alcohol, p-hydroxybenzoate esters, and phenol), antioxidants (e.g., ascorbic acid, sodium bisulfite, sodium metabisulfite, cysteine, and butyl hydroxy anisole), surfactants (e.g., polyoxyethylene sorbitan monooleate), and emulsifying agents (e.g., polysorbates). An inert gas (such as nitrogen) can also be used to enhance drug stability. Stability and solubility can also be enhanced by the addition of complexation and chelating agents such as the ethylenediaminetetraacetic acid salts. For a more detailed list of approved excipients in parenteral products, the reader should consult the monographs within the USP. 

Since there are synergistic effects between antioxidants, commercial preparations usually contain mixtures of these antioxidants. As oxidative rancidity is strongly catalyzed by some heavy metal ions, in particular QT+, antioxidant mixtures often contain sequestrants (e.g., citric acid and ethylenediaminetetraacetic acid (EDTA)) in order to complex these ions. Reductants such as ascorbic acid, which decrease the local concentration of oxygen, are also able to decrease the formation of peroxy radicals. 

The antioxidant synergists enhance the effect of antioxidants. Chelating agents like ethylenediaminetetraacetic acid (EDTA) are commonly added to parenterals. They may reduce oxidative damage by forming complexes with oxidative metal ion catalysts. Chelating agents are further discussed in Section 14.2.6. 

Metal deactivators chelate the transition metal ions, which otherwise would catalyze the oxidation reaction. Some effective chelating agents for latexes are ethylenediaminetetraacetic acid and its salts, and citric acid. A list of commercial antioxidants is given in ref. 115. 

The antioxidant activity of these DHPM(s) (103) was evaluated, and some of these compounds exhibited potent activity against lipid peroxidation induced by Fe and ethylenediaminetetraacetic acid (EDTA) (Stefani et al. 2006). 

Retardation rather than acceleration of rancidity occurs if the level of tocopherol or other phenolic antioxidant in the fat is raised sufficiently high (Krukovsky, 1949 Watts and Wong, 1951) or if various compounds such as ethylenediaminetetraacetic acid or polyphosphates (Lehmann and Watts, 1951), which have in common the ability to complex metal ions, are added with the ascorbic acid. Frequently the antioxidant effect of the ascorbic acid will be evidenced later after an initial period of acceleration, suggesting that the inhibitor is an intermediate in the oxidative decomposition of the ascorbic acid. 

Metal ion assisted electron transfer reactions are important when considering the roles of sequesterants and enzymes in antioxidant protection (8). Compounds like ethylenediaminetetraacetic acid (EDTA), phytic acid, and polyphenols can sequester transition metal ions and thereby inhibit oxidation. Binding the metal ions essentially prevents them from regenerating hydroxy radicals through the Fenton reaction. 

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