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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↗
PubMed1991

Assay for both ascorbic and dehydroascorbic acid in dairy foods by high-performance liquid chromatography using precolumn derivatization with methoxy- and ethoxy-1,2-phenylenediamine.

A procedure for the simultaneous determination of both ascorbic and dehydroascorbic acid in dairy foods by high-performance liquid chromatography using precolumn derivatization with 4-methoxy- and 4-ethoxy-1,2-phenylenediamine is presented. The derivatives are isolated by solid-phase extraction and analysed by fluorescence detection on a resin-type reversed-phase column at pH 9. Retention times are 2 and 3.2 min for the derivatives of ascorbic and dehydroascorbic acid, respectively. Relative standard deviations of the within- and between-assay tests are 7.1 and 5.5%, respectively, for ascorbic and 11 and 9%, respectively, dehydroascorbic acid. The limits of detection are 50 and 70 fmol per 5-microl injection for ascorbic and dehydroascorbic acid, respectively.

Animals↗
PubMed1989

Ascorbic and dehydroascorbic acids status in rats fed diets varying in vitamin E levels.

Vitamin E, ascorbic and dehydroascorbic acids were determined in plasma and selected tissues of rats fed for 2-3 months different diets varying in vitamin E content. The diets contained as low as 5 IU for group LE, a normal amount of 50 IU for group NE and as high as 250 IU of vitamin E for group HE. Small increases in total vitamin C were observed only in liver, kidney, spleen and plasma with increased dietary levels of vitamin E, however, this was not followed by a substantial increment in the ascorbate/dehydroascorbate ratio. These differences were only observed between diets LE and HE; there was no correlation between vitamin E and vitamin C levels in the tissue. These data suggest that the interactions that readily take place in vitro between these two vitamins do not occur in vivo, probably due to the complexity of natural membranes.

Administration, Oral↗
PubMed1989

Liquid chromatographic and fluorescent derivative aerobic degradation studies of dehydroascorbic acid in aqueous solution at elevated temperatures.

The aqueous degradation of dehydroascorbic acid (DHA) has been studied in the temperature range 52-90 degrees C. The DHA was determined by reversed-phase liquid chromatography and by derivatisation of DHA with o-phenylenediamine to form the fluorescent quinoxaline. The pseudo-first-order degradation of DHA has been verified and rate constants for the process are presented. The role of DHA in the degradation of ascorbic acid and previous DHA solution stability studies are discussed.

Ascorbic Acid↗
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↗