Vitamin ascorbate, interaction with

McCay PB. Vitamin E interactions with free radicals and ascorbate. Armu Rev Nutr 1985 5 323. 

McCay, P. B., 1985, Vitamin E Interactions with free radicals and ascorbate, Anna. Rev. Nutr. 5 323-340. 

Mirvish (53,54) discovered that vitamin C could inhibit ni-trosation reactions. The purely chemical interaction of ascorbic acid with nitrite has been studied for theoretical reasons and because of its importance in the preservation of foods. This interaction has received increased attention for minimizing the presence of nitrosamines and nitrosamides in the environment, and especially in foods. We have studied the relationship in gastric carcinogenesis between high levels of nitrite, including pickling, and of vitamin C as a protective and inhibiting element. 

This suggests that either the P-CAR +, which is more polar than the parent p-CAR, can efficiently reorientate so as to interact with the vitamin C in the aqueous phase, or that the ascorbic... 

Thus, vitamin C is able to replenish vitamin E, making the latter a much more efficient free radical inhibitor in lipid membranes. In addition, it has been suggested [9] that ascorbic acid can directly interact with the plasma membrane giving electrons to a trans-plasma membrane oxidoreductase activity. This ascorbate reducing capacity is apparently transmitted into and across the plasma membrane. 

Both vitamin E and vitamin C are able to react with peroxynitrite and suppress its toxic effects in biological systems. For example, it has been shown [83] that peroxynitrite efficiently oxidized both mitochondrial and synaptosomal a-tocopherol. Ascorbate protected against peroxynitrite-induced oxidation reactions by the interaction with free radicals formed in these reactions [84]. 

Partial silylation of the highly disperse silica surface enhances the adsorption of vitamin E from ethanol solution, and provides the ability to obtain water-soluble nanocomposites containing vitamin E. Immobilization of vitamin C on the silica surface prevents its oxidation. Its interaction with the adsorbent surface leads to a decrease in proton-donor ability of the OH-groups involved in the oxidation of ascorbic acid. Elydrophobized silica nanocomposites are characterized by a prolonged desorption of immobilized vitamins. It has been shown that vitamin C does not lose its antioxidant properties after desorption. 

Antioxidant compounds are an important defense for immediate detoxication of highly reactive intermediates. They act as competing nucleophiles and can bind to the intermediate, forming a less reactive species. Glutathione is one antioxidant molecule that can directly interact with free radicals. Other chemical antioxidants include vitamins A (retinol), C (ascorbic acid), and E. Ascorbic acid, for example, may react directly with reactive intermediates by hydrogen abstraction, resulting in the formation of dehydroascorbic acid. 

Low molecular weight antioxidants react with ROS in cell compartments which for some reasons are lack of antioxidant enzymes. Thus, suppression of bifurcate chain reactions of lipid peroxidation in hydrophobic core of cell membrane is mostly effectively performed by vitamin E (a-tocopherol). Interaction of lipid molecules with hydroxyl radical in the absence of vitamin E results in bifurcation of oxidative processes and formation of peroxyl and alcoxyl radicals. They are quickly accumulated in the restricted volume of the membrane and reaction began to be uncontrolled. a-Tocopherol interacts with peroxyl radicals with high affinity, reduces them and is then oxidized itself into relatively nonactive phenoxyl radical [8]. The latter can be accumulated within the bilayer until it will be returned to initial state by reduction by ascorbate [9]. Pair Vitamin E - Vitamin C is a good example of a mutual interaction between hydrophobic and hydrophilic low molecular weight antioxidants. Recently, tight relations were demonstrated for several natural antioxidants which interaction balances the red/ox state of the cell [3.5.10-12]. Figure 4 demonstrates such interaction between some of them. 

In the diet and at the tissue level, ascorbic acid can interact with mineral nutrients. In the intestine, ascorbic acid enhances the absorption of dietary iron and selenium reduces the absorption of copper, nickel, and manganese but apparently has little effect on zinc or cobalt. Ascorbic acid fails to affect the intestinal absorption of two toxic minerals studied, cadmium and mercury. At the tissue level, iron overload enhances the oxidative catabolism of ascorbic acid. Thus, the level of dietary vitamin C can have important nutritional consequences through a wide range of inhibitory and enhancing interactions with mineral nutrients. 

Such ascorbate free radicals are important intermediates in a wide variety of in vitro reactions involving oxidation and reduction and there is evidence that ascorbate radicals also have an important role in living systems. Vitamin C is known to interact with the tocopheroxyl radical... 

Both CoQ and ascorbate have been proposed to have a role as free radical chain-breaking antioxidants especially through their interaction with vitamin E, in protecting lipids from peroxidation (Buettner, 1993). This property could be due to redox reactions that reduce quinones in the membranes (Nakamura and Hayashi, 1994). 

Due to the potency of the redox system of vitamin C s two forms, several further interactions with readily oxidizable nutrients exist. The redox system is able to protect sulfhydryl groups of proteins as well as polyunsaturated fatty acids from oxidation. The close relationship of the nutritive antioxidants vitamin C, vitamin E, and P-carotene can be seen not only in cellular antioxidative metabolism but also during absorption. In the presence of ascorbic acid the absorption of these antioxidants is improved due to the protecting characteristics of vitamin C. 

The ascorbic acid-vitamin E interaction is also important to maintain the protease-antiprotease balance in the lung. Ascorbic acid reacts with glutathione, and through antioxidant synergism it can increase the effectiveness of vitamin E. The following series of enzymatic reduction reactions that occur in the cells illustrates the participation of ascorbic acid in the inhibition of lipid peroxidation. 

Two techniques for sorption-spectroscopic determination of ascorbic acid have been proposed. The first one is the recovery by silica modified with tetradecyl ammonium nitrate of blue form of molibdophosphoric HPA in the presence of vitamin C. And the second one is the interaction between the ascorbic acid in solution and immobilized on silica ion associate of molibdophosphoric acid with lucigenine. The detection limits of vitamin C are 0.07 and 2.6 mg respectively. The techniques were successfully applied to the determination of ascorbic acid in fmit juices. 

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