Ascorbic acid protection against

Fraga, C.G., Motchnik, P.A., Shigenaga, M.K., Helbock, H.J., Jacob, RA. and Ames, B.N. (1991). Ascorbic acid protects against endogenous oxidative DNA damage in human sperm. Proc. Natl Acad. Sci. USA 88, 11006-11033. 

Norepinephrine Blood circulation increase blood pressure peripheral vasoconstrictor without change or slight decrease in output and heart rate. No flow increase in brain, liver, or muscle Ascorbic acid protects against oxidation of norepinephrine... 

Review of Ascorbic Acid Mechanisms of Action. Ascorbic acid and AP have antioxidant activity in fats, oils, vitamin A, and carotenoids. In these systems AP is a better antioxidant than are the phenolic antioxidants BHT and BHA, both from these data and others (29,35). Ascorbic acid protects against oxidation of flavor compounds in wine, beer, fruits, artichokes, and cauliflower (29) presumably by oxygen scavenging. The well-known formation of nitric oxide from nitrites by ascorbic acid is used not only for inhibition of nitrosamine fortnation, but also to promote... 

Ascorbic acid has also been suggested to be neuroprotective by inhibiting NMDA receptor activity via a redox modulatory site on the receptor (Section 4). Theoretically, high levels of ascorbic acid in the central nervous system could be neuroprotective, as inhibition of the NMDA receptor protects neurons from ischemic damage (Simon et al., 1984). In fact, ascorbic acid protects against NMDA-mediated neurotoxicity in cortical cell cultures (Majewska and Bell, 1990), although the required concentration is relatively high (1-3 mM). 

F13. Frei, B. Ascorbic acid protects lipids in human plasma and low density lipoprotein against oxidative damage. Am. J. Clin. Nutr. 54, 1113S-1118S (1991). 

Ascorbic acid is the major water-soluble antioxidant present in cells and plasma. It will quench reactive oxygen species as 02 (Nishikimi 1975), HO (Bielski et aL 1975), and O2 (Bodannes and Chan 1979). On the other hand, it reduces Fe to Fe and thus will stimulate Fenton catalysis of H2O2 —> HO. Hydroperoxide-dependent lipid peroxidation in rat liver microsomes was enhanced by ascorbic acid (Laudicina and Marnett 1990). Ascorbic acid protected cardiac microsomes against lipid peroxidation and oxidative damage (Mukhopadhyay et al. 1993). It diminished both luminol- and lucigenin-amplified H2O2 derived chemiluminescence in concentrations > 10" (Klinger et al. 1996). 

Seregi, A., Schafer, A., and Komlos, M., 1978, Protective role of brain ascorbic acid content against lipid peroxidation, Experientia 34 1056-1057. 

Eberlein-Konig B, Placzek M, Pryzbilla B (1998) Protective effect against sunburn of combined systemic ascorbic acid (vitamin C) and d-alpha-tocopherol (vitamin E). J Am Acad Dermatol 38 45-48... 

Vitamin C occurs as L-ascorbic acid and dihydroascorbic acid in fruits, vegetables and potatoes, as well as in processed foods to which it has been added as an antioxidant. The only wholly undisputed function of vitamin C is the prevention of scurvy. Although this is the physiological rationale for the currently recommended intake levels, there is growing evidence that vitamin C may provide additional protective effects against other diseases including cancer, and the recommended dietary allowance (RDA) may be increased in the near future. Scurvy develops in adults whose habitual intake of vitamin C falls below 1 mg/d, and under experimental conditions 10 mg/d is sufficient to prevent or alleviate symptoms (Bartley et al., 1953). The RDA is 60 mg per day in the USA, but plasma levels of ascorbate do not achieve saturation until daily intakes reach around 100 mg (Bates et al., 1979). Most of the ascorbate in human diets is derived from natural sources, and consumers who eat five portions, or about 400-500 g, of fruits and vegetables per day could obtain as much as 200 mg of ascorbate. 

Nowadays, consumers would like those antioxidants present in food products not only to stabilise food lipids, but also to be absorbed through the intestinal wall and protect the lipids of blood plasma against oxidation. This effect is relatively evident in the case of tocopherols (which are liposoluble) or ascorbic acid (which is hydrophilic), but much less evidence is available on antioxidants of medium polarity, such as flavonoids, rosemary oleoresins or green or black tea catechins. 

Khan, S.G., Ali, S. and Rahman, Q. (1990). Protective role of ascorbic acid against asbestos induced toxicity in rat lung in vitro study. DrugChem. Toxicol. 13, 249-256. 

HOCl is one of the oxidants that activated phagocytes have in their arsenal. Hu et al. (1993) have shown that plasma albumin sulphydryl and ascorbic acid both protect against oxidant injury from HOCl. Neutrophils, interestingly, contain about 25 times more ascorbic acid than plasma. This su ests an endogenous self-protection role. This work is important because of the biological emphasis of reactive chlorine by the neutrophil. 

The results on the cellular protection against N()2 can be interpreted as the N()2 reacting with the three antioxidants to produce their radicals, with ascorbic acid reacting least efficiently, probably due to the lower reduction potential of its radical. Moreover, Arroyo et al. (1992) reported that NO - and N02 -induced mutations in Salmonella typhimurium TA1535 were inhibited efficiently by P-CAR and tocopherols, but not at all by ascorbic acid. 

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