Metabolism, ascorbic acid

Carbon dioxide, 4 803-822. See also CO2 entries Ionic liquid/CC>2 mixtures Supercritical carbon dioxide in acid gas stream, 23 605 adsorption of mixtures with ethane on zeolite 5A, 7 603 from anaerobic digestion, 3 701 from ascorbic acid metabolism, 25 771 in beer, 3 582t... 

SmirnoffN (2000) Ascorbic acid metabolism and functions ofamulti-facettedmolecule. Current Opinion Plant Biology 3,229-35. 

Chatterjee IB (1978) Ascorbic acid metabolism. World Review of Nutrition and Dietetics 30, 69-87. 

Horio F and Yoshida A (1982) Effects of some xenobiotics on ascorbic acid metabolism in mts. Journal of Nutrition 112, 416-25. 

His published work covered many fields and included diverse subjects such as the chemistry of amino acids and peptides, especially glutathione mineral metabolism, with special reference to calcium melanin pigment metabolism ascorbic acid metabolism metabolic aspects of cardiac muscle and analytical techniques for lipids, nitrogenous compounds, and cortisol. He was an extraordinarily meticulous analyst who, from the first, maintained that the standards of technique in the service laboratory should be the same as those required for research purposes. He maintained that the fulfillment of clinical chemistry demanded equal collaboration between physician and chemist. The function of the latter was not to usurp that of the former but to assist the clinician by helping to shed light on the nature of an illness. 

The desire to prepare radiolabeled material for use in the study of L-ascorbic acid metabolism in plants, fish, animals, and humans. 

The grape is a seasonal plant. Moreover, conversion of ascorbate to tartrate, as noted above, is limited to certain stages of growth and development. EflForts to find an alternative species of Vitaceae more amenable to research led us to Virginia Creeper (Parthenocissus quinque-folia). In a controlled environment, this plant retains its leaves and continues to lengthen its vines indefinitely, an ideal system for study of Vitaceae-type ascorbic acid metabolism on a year-around basis. 

Three cases that demonstrate the value of additional research are the eflFects of smoking on the rate of ascorbic acid metabolism, as described in chapter 16 in this book the increase in the RDA for vitamin C in 1980 over that in 1974 on the basis of the significant improvement in iron absorption (40) and the blocking of nitrosamine production as described in chapter 24 in this book. 

Effects of Excess Tissue Iron on Ascorbic Acid Metabolism. Epidemiological observations among the Bantu of South Africa showed an apparent association of clinical scurvy in adult males with hemosiderosis common to this group. Both plasma clearance of ascorbic acid and urinary excretion of ascorbic acid were altered in severe iron overload plasma clearance was increased and urinary excretion was decreased in siderotic subjects (40,41), The evidence was interpreted as a demonstration of enhanced oxidative catabolism of ascorbic acid in the presence of excess tissue iron. 

Zinc and Ascorbic Acid Metabolism and Excretion. Iron has an oxidizing effect on ascorbic acid, reducing its urinary excretion therefore, Keltz et al. (61) questioned whether zinc would show a similar effect. Human subjects were fed a diet containing either 11.5 or 19.5 mg of zinc/d for 7-d balance periods. Daily ascorbic acid intake was 100 mg. Consistent with the findings from iron-loaded Africans, the higher zinc intake caused a significant 30% decrease in urinary ascorbate excretion. No explanation for the zinc-related reduction in ascorbic acid beyond the analogy with the iron-loaded individuals is readily available. 

Another part of the urinary oxalate is of endogenous origin. It is a product of ascorbic acid metabolism in rats (C19) and in man (H14, L3). The metabolic pathway leading from ascorbic to oxalic acid is unknown. 

In planning this review the writer quickly persuaded himself that it was arduous and fortunately unnecessary to scan the whole exhaustive and exhausting literature on ascorbic acid. Many aspects of the vitamin— such as its relation to immune reactions and the interpretation of its excretion following a test dose—have been very well summarized in past reviews, some of which are listed below (Section I, 3). Instead it was decided to concentrate chiefly on those aspects of ascorbic acid metabolism that seem to he of special current interest to research workers. 

The question of the effect of ascorbic acid on adrenocortical hormone production has proved hard enough (see Section XI) the question of the influence of adrenocortical hormones on ascorbic acid metabolism seems likely to be still more difficult. 

This question, though not a new one, is by far the most interesting present aspect of ascorbic acid metabolism. The evidence, for and against, deserves study in detail. 

Studies on the excretion of 17-ketosteroids by female rats on a diet deficient in pantothenate have not been reported. These data would be interesting because of the observations of Dorfman (1947), who reported a sharp decrease in the excretion of 17-ketosteroids in female monkeys and guinea pigs following adrenalectomy. It was also observed that in the scorbutic female guinea pig (Dorfman, 1947 Banerjee and Deb, 1952) there was a sharp decrease in the excretion of 17-ketosteroids. These observations indicate that the adrenal is the source of these steroids and that diets deficient in ascorbic acid, which affects the adrenals, will also decrease the synthesis of these steroids. In view of the fact that there is a disturbance of ascorbic acid metabolism in pantothenate-deficient rats, it may well be that this would contribute to a disturbance in the synthesis of the 17-ketosteroids in the pantothenate deficiency. 

ABSTRACT Ascorbic acid metabolism is associated with a number of mechanisms known to be involved in host resistance to malignant disease. Cancer patients are significantly depleted of ascorbic acid, and in our opinion this demonstrable biochemical characteristic indicates a substantially increased requirement and utilization of this substance to potentiate these various host resistance factors. 

We have advanced arguments elsewhere indicating that one important factor in host resistance is the free availability of ascorbic acid (1-3). These arguments are based upon the demonstration that cancer patients have a much greater requirement for this substance than normal healthy individuals, on the realization that ascorbic acid metabolism can be implicated in a number of mechanisms known to be involved in host resistance, and finally, and most convincingly, on the published evidence that ascorbic acid can sometimes produce quite dramatic remissions in advanced human cancer (4, 5). 

Host resistance to neoplastic growth and invasiveness is recognized to be an important factor in determining the occurrence, the progress, and the eventual outcome of every cancer illness. The factors involved in host resistance are briefly reviewed, and the relationship between these factors and ascorbic acid metabolism is presented in detail. It is shown that many factors involved in host resistance to neoplasia are significantly dependent upon the availability of ascorbate. 

The ability safely to enhance host resistance to maximum levels in every patient would vastly improve cancer treatment. It is our intention to show that ascorbic acid metabolism is implicated in all these resistance mechanisms and that ingestion of this substance in adequate amounts could provide a simple and safe method of achieving this desirable goal. 

Chatterjee. A. K., Basu, J.. Suradis, Datta, S. C., Sengupta, K., and Ghosh, B. Effects of L-lysine administration on certain aspects of ascorbic acid metabolism. Intern. J. Vitam. Nutr. Res., 46 286-290, 1976. 

Kakar. S., and Wilson. C. W. M. Ascorbic acid metabolism in human cancer. Abstract. Proc. Nutr. Soc. 33 110,1974. 

Sokoloff B, Hori M, Saelhof CC, Wrzolek T, Imai T. Aging, atherosclerosis and ascorbic acid metabolism. J AmGerSoc 1966 14 1239-1260. 

Foyer, C. H., and B. Halliwell The presence of glutathione and glutathione reductase in chloroplasts a proposed role in ascorbic acid metabolism. Planta 133, 21 (1977). 

Loewus, F. A. L-Ascorbic acid metabolism, biosynthesis, function. In The Biochemistry of Plants, Vol. 3, Carbohydrates Structurje and Function (J. Preiss, ed.), pp. 77-99. Academic Press, New York 1980... 

Scruvy and Ascorbic Acid Metabolism 279 Clinicopathology of Scurvy Vitamin C—Sources and Requirements Vitamin C and Metabolism... 

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