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PubMedDate not supplied

Physiological role of dehydroascorbic acid.

Dehydroascorbic acid is present in insignificant amounts in plant and animal tissue but appears in considerable amounts under various physiological and pathological conditions. It is found increased: in blood of patients suffering from infectious diseases; in blood and tissues of thyrotoxic patients; in blood after injection of thyroxin, corticotropin and cortisone. In all the above conditions there is concomitant decrease in L-ascorbic acid and glutathione values of blood and tissues. Dehydroascorbic acid, however, disappears after continued administration of a high dose of ascorbic acid. The accumulation of dehydroascorbic acid seems to be an indication of ascorbic acid deficiency. The extreme sensitivity of the ascorbate system to physiological changes is suggestive of a major biochemical role for this redox system. Accumulated evidences indicate that dehydroascorbic acid possible control cell division.

Animals↗
PubMed1975

[Simplification of the dinitrophenylhydrazine method for the photometric determination of ascorbic acid and dehydroascorbic acid in fruit juices. I. Application to juice of black current (author's transl)].

The photometric determination of ascorbic acid and dehydroascorbic acid by preparing the 2,4-dinitrophenylhydrazone derivative of dehydroascorbic acid and purifying it by thinlayerchromatography was simplified and adapted to the microliter system of Eppendorf Gerätebau, Hamburg, Germany. Using this method with juice of black current, quite reproducible results for vitamin C contents were obtained. Compared with the method of the International Federation of Fruit Juice Producers (titration with 2,6-dichlorphenolindophenol) the contents of vitamin C found with nine different commercial juices of black current were lower from 13 to 30%.

Ascorbic Acid↗
PubMed1978

Ascorbic acid and dehydroascorbic acid in HeLa cells: their effect on the collagen-peptidase activity of glucose-deficient cultures.

HeLa cells in culture do not accumulate ascorbic acid unless ascorbic acid or dehydroascorbic acid is available in the medium. Collagen peptidase corresponding to the activity found in the invasive zone of tumours, and acid phosphatase, in HeLa cells cultured under normal conditions, are unaffected by ascorbic acid, but are reduced in cells deprived of carbohydrate. These reduced collagen-peptidase levels, but not acid phosphatase, are restored to the values of normal HeLa cells by ascorbic acid. The relevance of these findings is considered in the context of tumour growth and spread.

Acid Phosphatase↗
PubMed1976

In vitro effects of ascorbic acid and dehydroascorbic acid on diphosphopyridine nucleotide diaphorase in toad testis.

The enzyme diphosphopyridine nucleotide diaphorase (DPND) was demonstrated histochemically in both the tubular and Leydig cells of the toad testis. Addition of 200 mug of dehydroascorbic acid (DHA) to 100 mg of testicular slices in the incubating medium increased the activity of DPND, while a similar dose of ascorbic acid failed to do so. The evidence indicates that DHA is involved in the oxidation of reduced DPND in toad testis.

Animals↗
PubMed1979

Uptake of L-ascorbic acid and L-dehydroascorbic acid by human erythrocytes and HeLa cells.

Uptake of AsA and DAsA by human cells, i.e., erythrocytes and HeLa cells, was examined in vitro. AsA was taken up very slowly, but DAsA was taken up very rapidly by erythrocytes to establish equilibrium after 1 minute. Uptake of the vitamins by HeLa cells was similar to that by erythrocytes, except there was an uptake of DAsA that reached saturation after 5 minutes. The DAsA taken up was reduced in part to AsA and the concentrations of DAsA inside and outside the cells became almost equal. GSH was responsible for this reduction. Although DAsA was evidently a more permeant form than AsA in the case of human cells, the relevance of this to the uptake of vitamin C by the tissues in vivo remains uncertain.

Ascorbic Acid↗
PubMed1976

Volatile degradation products of l-dehydroascorbic acid.

Volatile degradation products were isolated from a solution of L-dehydroascorbic acid in phosphate buffer solution of pH 2,4,6 and 8 heated under reflux for 3 h or left at 25 degrees C for 200 h. The products were identified by comparison of their gas chromatographic retention data, infra-red and mass spectra with those of authentic compounds. Fifteen products were identified, among which 12 had not yet been reported as degradation products of L-dehydroascorbic acid. Concentrations of 5 main degradation products, i.e. 3-hydroxy-2-pyrone, 2-furancarboxylic acid, 2-furaldehyde, acetic acid and 2-acetylfuran depended on the pH values and temperature; the presence of oxygen had no pronounced effect.

Acetates↗
PubMed1979

[The amount of L-dehydroascorbic acid on total-vitamin C of vegetable products (author's transl)].

Spectrophotometric determinations of vitamin C were carried out on different kinds of vegetable products in raw state, after steam-cooking and freezedrying. Indicators used were in part 2,6-dichlorophenol-indophenol (DIP) and in part N-bromosuccinimide (NBS) and starch iodide, which at the same time allows a determination of other reducing interfering substances. The amount of L-dehydroascorbic acid (DAS), which together with L-ascorbic acid (AS) becomes vitamin C or total-vitamin C (VC), proved to be of special interest. During homogenisation of the vegetable samples in oxalic oxid solution AS was not oxidized. Other precautions like cooling or on oxygen-free atmosphere were not required. DAS was not found in raw vegetable products or after cooking. A high proportion of interfering substances especially when estimating VC was considered the cause for the normally measured amount of DAS. In freeze-dried samples of vegetable products a small amount DAS could be identified depending on the freezing process.

Ascorbic Acid↗
PubMed1976

Effects of tetraacetyl-bis-dehydroascorbic acid, a derivative of ascorbic acid, on Ehrlich cells and HeLa cells (human carcinoma cells).

Derivatives of ascorbic acid were synthesized, and the studies were made on their effects in Ehrlich ascites carcinoma cells, in regard to the inhibition and the prolongation of survival time as well as on the morphological degeneration in HeLa cells. In a model infection study carried out by using tetraacetyl-bis-dehydroascorbic acid in dd mice infected with Ehrlich cells, it was proved that the prolongation of survival time was nearly double in comparison to the control group mice. Also, it was noted that hypertrophy due to abdominal dropsy and body weight were reduced much more than in the control group. From these results, the inhibiting effect of tetraacetyl-bis-dehydroascorbic acid was confirmed. While in the case of DHA and other derivatives, almost no inhibition and prolongation of survival time were observed. As for HeLa cells in a tissue culture, tetraacetyl-bis-DHA, in a dosage of 125-250 mug/ml, demonstrated definitely its morphological degeration. After 125 mug/ml of tetraacetyl-bis-DHA was added to a tissue culture solution of HeLa cells, the cells were washed and recultured. No growth of the cells was observed. Consequently, this substance was confirmed to be anti-HeLa substance with a low toxicity.

Animals↗
PubMed1975

Determination of vitamin C (ascorbic and dehydroascorbic acids) in foods and feeds.

Ascorbic acid (ASC) is separated by percolating the extract solution through an anionic Sephadex column. After one or two washings with water, the vitamin is oxidized on the column by a p-benzoquinone solution to dehydroascorbic acid (DASC). This latter being actually no acid is eluted as it is formed. The DASC containing eluate is treated with a new colorimetric reagent: 4-Nitro-1,2-Phenylenediamine (NPD). After extraction of the excess reagent with ethyl acetate, the optical extinction is measured at 375 nm. DASC, if present in the extract solution, can be reduced to ASC by dimercaptopropanol prior to chromatography. The method is very specific. The rather simple chromatographic purification can be effected semi-automatically with series of 10 colums (or more).

Ascorbic Acid↗