Ascorbic acid in animals

Saccharoascorbic acid, 35, has been proposed as a minor metabolite of ascorbic acid in animals (57-60). The isolation of ascorbic acid 2-0-sulfate, 18, in a variety of animal species and the remarkable oxidative stability of the 2-0-sulfate substituted enonolactone moiety have prompted suggestions (60) that saccharoascorbic acid 2-0-sulfate, 34, is a catabolite of 18 in vivo. 

The effects of age and development on the distribution of ascorbic acid in animals is not striking. During pregnancy and during the rapid... 

This system cannot now be fitted into known pathways of electron transport, principally because a system that oxidizes ascorbic acid in animal tissues is unknown. The fact is clear, however, that ascorbic acid is oxidized to dehydroascorbic acid in animal tissues and that dehydro-ascorbic add can be reduced. At the very least, this system emphasizes the potential eflBciency of a form of ascorbic acid as an electron acceptor (K3). 

The distribution of ascorbic acid in animal tissues has been reviewed by Giroud (1939). Cellular tissues contain a greater concentration of the... 

Selected methods for the determination of ascorbic acid in animal cells, tissues, and fluids, 1 "Methods in Enzymology, D. B. McCormick and L. D. Wright, eds., Academic Press, New York, Vol. 62, Part D, pp. 3-11. 

Shimazono, N., and Mano, Y., 1961, Enzymatic studies on the metabolism of uronic and aldonic acids related to L-ascorbic acid in animal tissues, Ann. N.Y. Acad. Sci. 92 91-104. 

The synthesis of ascorbic acid in animals has also been linked with thiamine and riboflavin (Kennaway and Daff, 1946 Roy et al., 1946). With both these deficiencies the ascorbic acid content of the tissue of rats and mice has been shown to be low. The stimulation of synthesis shown by a normal animal after chloretone treatment was not observed in animals deficient in either thiamine or riboflavin. The claim was made... 

G Barja de Quiroga, M Ldpez-Torres, R Perez-Campo, C Rojas. Simultaneous determination of two antioxidants, uric and ascorbic acid, in animal tissue by high-performance liquid chromatography. Anal Biochem 199 81-85, 1991. 

Carr, R.S., Bally, M.B., Thomas, P., and Neff, J.M., Comparison of methods for determination of ascorbic acid in animal tissues. Anal. Chem., 55, 1229-1232, 1983. 

Methods for the preparation of L-ascorbic acids having isotopic C, H, O in various positions have been described and reviewed (104,105). Labeled L-ascorbic acid has played an important role in the elucidation of the metaboHc pathway of L-ascorbic acid in plants and animals. 

Buu Hoi and Ratsimamanga116 found that kojic acid protected the adrenal ascorbic acid in test animals during the reversible period of scurvy, without itself showing vitamin C action. 

Biosyntheses of hexuronic acids and L-ascorbic acid in plants and animals are closely related. Hexuronic acids, L-ascorbic acid, and L-tartaric acid (a possible precursor of dihydroxyfumaric acid) commonly occur together in plants. If a rat is given chloretone (an antispasmodic), both L-ascorbic acid and D-glucuronic acid are excreted in increased quantity.244 Unlike humans, rats can synthesize their own vitamin C, and are therefore independent of outside sources. Here, D-glucose and D-galactose can be utilized, but not D-mannose. 

Adrenocortical Steroids, Determination of Individual (Neher), 1, 127 Amino Aciduria (Bigwood, Crokaert, Schram, Soupart and Vis), 2, 201 Ammonia, Blood (Bessman), 2, 135 Ascorbic Acid in Man and Animals (Knox and Goswami), 4, 122 Automation (Marsh), 2, 201 Bile Pigments in Jaundice (Billing), 2, 268... 

Until the 20th century, it was thought that scurvy was confined to humans. Most plants and animals have the ability to synthesize ascorbic acid, but it was discovered that a limited number of animals, including primates, guinea pigs, the Indian fruit bat, and trout, also lack the ability to produce ascorbic acid. In vertebrates, ascorbic acid is made in the fiver from glucose in a four-step process. Each step requires a specific enzyme and humans lack the enzyme required for the last step, gulonolactone oxidase. 

To some extent the vitamin E requirement may be lessened by the presence in the diet of synthetic antioxidants and by selenium. Much evidence supports a relationship between the nutritional need for selenium and that for vitamin E. Lack of either causes muscular dystrophy in many animals as well as severe edema (exudative diathesis) in chicks. Since vitamin E-deficient rats have a low selenide (Se2 ) content, it has been suggested that vitamin E protects reduced selenium from oxidation.) Vitamin C (ascorbic acid), in turn, protects vitamin E. 

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. 

As a number of excellent articles have been published that review various aspects of the biological roles of L-ascorbic acid,8 the biosynthesis of L-ascorbic acid in plants and animals,7-11 and radicals derived from L-ascorbic acid,12 these topics will not be treated. Likewise, the methods by which L-ascorbic acid is assayed13 and the uses of L-ascorbic acid and related molecules in a wide variety of assays and oxidation-reduction systems will not be discussed. 

As indicated in Figure 2, when minces of tumor obtained from normal and ascorbic acid-deficient animals were incubated with C14-pro-line, much more radioactivity was incorporated into the collagen of the normal tissue. When the specific radioactivities of the isolated imino acids were examined (Table HI), several conclusions were possible. In the experiments with granuloma from normal animals and C14-proline, the values for hydroxyproline were not far from those of proline. With the scorbutic granulomas, the specific activity of the isolated proline was not greatly reduced, compared to that obtained from the normal granuloma. In contrast, the specific activity of the hydroxyproline isolated from the deficient tissues was markedly reduced. Similar results were obtained in the studies with tritiated proline. Thus, the specific activity of the proline isolated from the deficient granuloma was only moderately reduced, whereas the specific activity of the hydroxyproline was extremely low. This observation may be explained in terms of a dual-pathway mechanism of proline incorporation, considered below. 

Ascorbic acid is a vitamin in primates. In most other animals, it can be synthesized by a branch of the glucoronic acid pathway (Chapter 18). It is apparently not changed into any coenzyme in the human being and participates as a vitamin in a reducing capacity in several biochemical reactions. These include the post-translational hydroxylation of proline in collagen biosynthesis (Chapter 8) and in tyrosine metabolism (Chapter 20). Ascorbic acid is oxidized to dehydroascorbic acid, a diketo derivative of ascorbate. Scurvy is a deficiency disease caused by a shortage of dietary ascorbic acid. In children, this results in defective bone formation in adults, extensive bleeding occurs in a number of locations. Scurvy is to be suspected if serum ascorbic acid levels fall below 1 jug/mL. 

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