Effect of Ascorbate

Iron Absorption. A very important effect of ascorbic acid is the enhancement of absorption of nonheme iron from foods. Ascorbic acid also enhances the reduction of ferric iron to ferrous iron. This is important both in increasing iron absorption and in its function in many hydroxylation reactions (140,141). In addition, ascorbic acid is involved in iron metaboHsm. It serves to transfer iron to the Hver and to incorporate it into ferritin. 

FIGURE 18.30 The physiological effects of ascorbic acid (vitamin C) are the result of its action as a reducing agent. A two-electron oxidation of ascorbic acid yields dehy-droascorbic acid. 

Table II. Effect of Ascorbic Acid on the Color of Applesauce Stored at 75°F in Various Types of Cans0...

Figure L Effect of ascorbic acid on NDELA formation.

Choi, M.H., Kim, G.H., and Lee, H.S., Effects of ascorbic acid retention on juice color and pigment stability in blood orange Citrus sinensis) juice during refrigerated storage, Food Res. Int, 35, 753, 2002. 

Meister A. (1992). On the antioxidant effects of ascorbic acid and glutathione. Biochem. Pharmacol. 44, 1905-1915. 

It has long been recognized that ascorbate levels are low in patients with RA (Lunec and Blake, 1985) and ascorbate is predominantly found in the dehydro form. The presence of increased dehydroascorbate has been suggested to indicate its rapid oxidation by stimulated PMNs (Halliwell and Gutteridge, 1990). When ascorbate concentrations are lower than about 20 /tmol/1, as can occur in rheumatoid synovial fluid, the Fe(III) reducing effects of ascorbate outweigh its radical-scavenging effects. Ascorbate then causes increased OH formation and promotes lipid peroxidation (Blake et al., 1981). 

Malo, J.L., Cartier, A., Pineau, L., Archeveque, J., Ghezzo, H. and Martin, R.R. (1986). Lack of acute effects of ascorbic acid on spirometry and airway responsiveness to histamine in subjects with asthma. J. Allergy Clin. Immunol. 78, 1153-1158. 

Takahama, U. Oniki, T. Effects of ascorbate on the oxidation of derivatives of hydroxycinnamic acid and the mechanism of oxidation of sinapic acid by cell wall-bound peroxidases. Plant Cell Physiol. 1994, 35, 593-600. 

Rababah, TM, Ereifej, KI and Howard, L. 2005. Effect of ascorbic acid and dehydration on concentrations of total phenolics, antioxidant capacity, anthocyanins, and color in fruits. J Agric Food Chem 53(ll) 4444-4447. 

Tominaga et al. [682,683] studied the effect of ascorbic acid on the response of these metals in seawater obtained by graphite-furnace atomic absorption spectrometry from standpoint of variation of peak times and the sensitivity. Matrix interferences from seawater in the determination of lead, magnesium, vanadium, and molybdenum were suppressed by addition of 10% (w/v) ascorbic acid solution to the sample in the furnace. Matrix effects on the determination of cobalt and copper could not be removed in this way. These workers propose a direct method for the determination of lead, manganese, vanadium, and molybdenum in seawater. 

Classic antioxidants, vitamin E, vitamin C, and others can suppress the activation of apoptosis. For example, ascorbic acid prevented cytochrome c release and caspase activation in human leukemia cells exposed to hydrogen peroxide [128], Pretreatment with A -acctylcystcinc, ascorbate, and vitamin E decreased homocysteine thiolactone-induced apoptosis in human promyelocytic leukemia HL-60 cells [129]. Resveratrol protected rat brain mitochondria from anoxia-reoxygenation damage by the inhibition of cytochrome c release and the reduction of superoxide production [130]. However, it should be mentioned that the proapoptotic effect of ascorbate, gallic acid, or epigallocatechin gallate has been shown in the same human promyelocytic leukemia cells [131]. 

Recently, Carr and Frei reviewed studies on the antioxidant and prooxidant effects of ascorbic acid [8]. These authors pointed out that a highly controversial work by Podmore and coworkers [71] who found that the prooxidant effect of ascorbic acid supplementation to healthy volunteers is much questionable. These authors demonstrated that of the 44 in vivo studies, 38 showed the antioxidant effect of ascorbic acid, 14 showed no change, and only six showed the enhancement of oxidative damage after ascorbate supplementation. It was concluded that ascorbic acid is an antioxidant in biological fluids, animals, and humans, both with and without iron supplementation. 

Inhibitors of nitrosation generally function by competing with the amine for the nitrosating agent. An inhibitor would thus react with nitrite at a faster rate than with amines. The inhibition reaction has recently been reviewed ( 35). The ability of ascorbate to act as a potent inhibitor of nitrosamine formation has resulted in the use of the vitamin in nitrite-preserved foods and pharmaceuticals. Furthermore, the effectiveness of ascorbate in inhibiting nitrosamine formation is dependent on (1) the concentration of ascorbate (an excess is required) (2) pH (ascorbate is nitrosated 240 times more rapidly than ascorbic acid) (3) the reactivity of the amine toward nitrosation and (4) the extent of oxygenation of the system. 

Peng, Z., Duncan, B., Pocock, K. F., and Sefton, M. A. (1998). The effect of ascorbic acid on oxidative browning of white wines and model wines. Aust. ]. Grape Wine Res. 4,127-135. 

Hermel, M., Heckelen, A., Kirchhof, B., Schrage, N.F. Inhibitory effect of ascorbic acid on human retinal pigment epithelial cell proliferation compared to cytostatic drugs-influence of histamine. Inflamm Res 50(Suppl 2), S93-S95... 

In its biochemical functions, ascorbic acid acts as a regulator in tissue respiration and tends to serve as an antioxidant in vitro by reducing oxidizing chemicals. The effectiveness of ascorbic acid as an antioxidant when added to various processed food products, such as meats, is described in entry on Antioxidants. In plant tissues, the related glutathione system of oxidation and reduction is fairly widely distributed and there is evidence that election transfer reactions involving ascorbic acid are characteristic of animal systems. Peroxidase systems also may involve reactions with ascorbic acid In plants, either of two copper-protein enzymes are commonly involved in the oxidation of ascorbic acid. 

Chen, T.S.. R.G, Cooper "Thermal Destruction of Folacin Effect of Ascorbic Acid. 

Kamm, J.J, et al. Protective Effect of Ascorbic Acid on Hepatotoxicity Caused by Sodium Nitrite plus Aminopyrine, Proc., Nat. Acad. Sci., 70, 74 (1973). 

Vitamin C (ascorbate) (Fig. 9.5) has the ability to act as a reducing agent, i.e. it will tend to reduce more reactive species. This ability to reduce Fe3+ to Fe2+may be important in promoting iron uptake in the gut. Oxidation of ascorbate by reaction with reactive oxygen species or reactive nitrogen species seems to lead to its depletion. In vitro, vitamin C can also exert pro-oxidant properties. Fe3+ can react with ascorbate to form Fe2+ and the semi-dehydroascorbate or ascorbyl radical. The latter can react with hydrogen peroxide to form Fe3+, the hydroxyl radical and a hydroxide anion. A key question with regard to the pro- or anti- oxidant effects of ascorbate may therefore be the availability of transition metal ions. Neurons main-... 

Sandnes, K, Ulgenes, Y., Braekkan, O.R. and Utne, F. (1984). The effect of ascorbic acid supplement in broodstock feed on reproduction of rainbow trout (Salmo gairdneri). Aquaculture 43,167-177. 

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