Ascorbic acid interaction

Ascorbic acid interacts as a donor with nicotinamide to produce a temperature-dependent 1 1 yellow complex [128], the color increasing with decreasing temperature. The absorbance of this complex is pH-dependent peaking at pH 4, in contrast to the pH-independent N -methyl nicotinamide, suggesting an interaction between the protonated nicotinamide base and the ascorbic cation. 

An interesting pesticide-ascorbic acid interaction in fish has been studied by Mayer and coworkers (140-143). Several species of fish were continuously exposed to toxaphene on diets with and without ascorbic acid. The toxaphene reduced the ascorbic acid content of the vertebrae but not of the liver, leading the investigators to believe that this reduction unfavorably affects collagen formation. Diets containing the higher levels of L-ascorbic acid reduced toxaphene residues and increased the tolerance to the chronic effect of toxaphene on growth, bone development, and skin lesions. 

During the past two decades ascorbic acid free radicals have become recognized and their kinetics studied (281-287) in the oxidation of ascorbic acid. Interactions between certain of the vitamins or ingredients... 

Adversed nutritional effects of high doses of ascorbic acid have been reported to lover vitamin 8 2 levels (Hines, 1975 Herbert and Jacob, 1974 Herbert, 1980). In contrast, others (Nevmark and Schelner, 1976) have suggested that methodology problems explain the vitamin 6 2 to ascorbic acid Interaction. Ascorbic acid has also been reported to elevate the excretion of urinary 4-pyridoxic acid, the major metabolite of vitamin Bg (Scllvanova, 1960). Other Interactions between ascorbic acid and vitamin Bg have also been reported (Baker et al, 1971 Baker et al, 1964). More recently, Shultz and Leklem (1982) concluded that short-term ascorbic acid supplementation did not alter vitamin Bg metabolism. 

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. 

Solid-phase basic dyes ai e also used for the study of their interaction with medical products nicotinic, aminocaproic, acetylsalicylic and ascorbic acids and for the establishing of the new methods of SPS determination in known medical products. 

Ascorbic acid is a reasonably strong reducing agent. The biochemical and physiological functions of ascorbic acid most likely derive from its reducing properties—it functions as an electron carrier. Loss of one electron due to interactions with oxygen or metal ions leads to semidehydro-L-ascorbate, a reactive free radical (Figure 18.30) that can be reduced back to L-ascorbic acid by various enzymes in animals and plants. A characteristic reaction of ascorbic acid is its oxidation to dehydro-L-aseorbie add. Ascorbic acid and dehydroascor-bic acid form an effective redox system. 

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. 

The addition of celite or HyfloSupercel to increase the contact surface with the extraction solvent and help filtration is often utilized during extraction. In case of interaction of such filter aids with the food, treated sand can be employed instead. Weak bases such as NaHCOj, MgC03, or CaC03 (1 g/10 g sample) to neutralize acids liberated from tissues and antioxidants (0.1% BHT, 5% pyro-gallol, ascorbic acid, and sodium ascorbate) to avoid oxidation can be added during extraction. ... 

Adams, J.B., Food-additive interactions involving sulphur dioxide and ascorbic acids a review. Food Chem., 59, 401, 1997. 

Kalyanaraman, B., Darley-Usmar, V.M., Wood, J., Joseph, J. and Parathasarathy, S. (1992). Synergistic interaction between the probucol phenoxyl radical and ascorbic acid in inhibiting the oxidation of LDL. J. Biol. Chem. 267, 6789—6795. 

Vitamin B12 generally is well tolerated and exhibits minimal adverse effects. Injection-site pain, pruritus, rash, and diarrhea have been reported. Drug interactions have been observed with omeprazole and ascorbic acid that decrease oral absorption. 

The synergistic effect observed in the presence of all three antioxidants implies that there is an interaction between the individual antioxidant components. The direct interaction of the a-tocopherol radical and ascorbic acid is already well established (Bisby and Parker 1995) and a study by Mayne and Parker (1989) on chicks deficient in vitamin E and selenium showed that the... 

Kostic, D. et al. (1995). Intestinal absorption, serum clearance, and interactions between lutein and beta-carotene when administered to human adults in separate or combined oral doses. Am. J. Clin. Nutr. 62 604—610. Kuo, S. M. et al. (2001). Dihydropyridine calcium channel blockers inhibit ascorbic acid accumulation in human intestinal Caco-2 cells. Life Sci. 68(15) 1751-1760. 

The electrochemical response of analytes at the CNT-modified electrodes is influenced by the surfactants which are used as dispersants. CNT-modified electrodes using cationic surfactant CTAB as a dispersant showed an improved catalytic effect for negatively charged small molecular analytes, such as potassium ferricyanide and ascorbic acid, whereas anionic surfactants such as SDS showed a better catalytic activity for a positively charged analyte such as dopamine. This effect, which is ascribed mainly to the electrostatic interactions, is also observed for the electrochemical response of a negatively charged macromolecule such as DNA on the CNT (surfactant)-modified electrodes (see Fig. 15.12). An oxidation peak current near +1.0 V was observed only at the CNT/CTAB-modified electrode in the DNA solution (curve (ii) in Fig. 15.12a). The differential pulse voltammetry of DNA at the CNT/CTAB-modified electrode also showed a sharp peak current, which is due to the oxidation of the adenine residue in DNA (curve (ii) in Fig. 15.12b). The different effects of surfactants for CNTs to promote the electron transfer of DNA are in agreement with the electrostatic interactions... 

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. 

Flavonoids exhibit protective action against LDL oxidation. It has been shown [145] that the pretreatment of macrophages and endothelial cells with tea flavonoids such as theaflavin digallate diminished cell-mediated LDL oxidation probably due to the interaction with superoxide and the chelation of iron ions. Quercetin and epicatechin inhibited LDL oxidation catalyzed by mammalian 15-lipoxygenase, and are much more effective antioxidants than ascorbic acid and a-tocopherol [146], Luteolin, rutin, quercetin, and catechin suppressed copper-stimulated LDL oxidation and protected endogenous urate from oxidative degradation [147]. Quercetin was also able to suppress peroxynitrite-induced oxidative modification of LDL [148],... 

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