Showing papers on "Dehydroascorbic acid published in 1984"
90 citations
TL;DR: The electron spin resonance technique can be used for discrimination between the epimers of vitamin C by restoring the original electronic configuration at C(4) without changing the electroneutral bicyclic structure.
Abstract: The four O-H bands of ascorbic acid could be assigned by means of infrared investigations It could be shown by electron spin resonance and nuclear magnetic resonance measurements that the radical sodium ascorbate is formed by a cyclic side-chain structure resulting in a loss of C(6)-OH and C(3)-OH The C(2) = C(3) double bond is still maintained as could be shown by infrared and ultraviolet absorption spectroscopy In the case of complete oxidation of ascorbic acid to dehydroascorbic acid, C(6)-OH is reestablished (indicating the reopening of the furanoid ring), while C(2)-OH as well as the C(2) = C(3) double bond have disappeared due to the deprotonation of C(2)-OH and C(3)-OH In the case of isoascorbic acid and its radical potassium isoascorbate similar results are obtained with one distinct difference: in the case of isoascorbic acid, C(2)-OH does not appear while C(3)-OH exhibits a shoulder
52 citations
TL;DR: Lower limits of detection for both forms of vitamin C are well below the levels found in the usual food sources of this vitamin.
Abstract: A high performance liquid chromatographic (HPLC) procedure has been developed for the analysis of ascorbic acid and dehydroascorbic acid in complex matrices. Separation is accomplished with an anion-exchange resin and fluorescent detection is achieved through post-column inline chemistry, involving oxidation of ascorbic acid to dehydroascorbic acid followed by reaction with o-phenylenediamine to form a fluorescent product. Lower limits of detection for both forms of vitamin C are well below the levels found in the usual food sources of this vitamin. The extraction procedures developed yield clean samples for analysis with minimal loss of the vitamers during the analytical procedures. Recoveries are in the range of 90-107%. The results obtained with this HPLC procedure agree well with those obtained with a modified version of the classical procedure of Deutsch and Weeks. A variety of foods including fruit juices, vegetables, and fruits were analyzed.
35 citations
TL;DR: By this procedure the contents of uric and ascorbic acids in human serum and urine were estimated and the oxidation of urIC acid to allantoin and asCorbic acid to dehydroascorbic acid could be readily monitored.
33 citations
TL;DR: It is concluded that either vitamin C and trace element injections containing copper should not be added to the same bag, or an adequate coverage of ascorbic acid must be included to allow for losses by oxidation before and during administration.
Abstract: Ascorbic acid stability in TPN infusions in 3-litre plastic bags was examined. Vitamin C was found to degrade slowly in mixtures which do not contain trace elements. In the presence of copper, degradation proceeds rapidly until dissolved oxygen is depleted. Reducing the copper concentration had only a minor influence on degradation rate. However, this copper-catalyzed reaction was prevented if cysteine was present in the TPN regimen. The amount of ascorbic acid degraded depended on the dissolved oxygen content of the infusion, the amount of residual air in the bag after filling and the permeability of the plastic to oxygen. In the absence of copper, 20-30 mg ascorbic acid was broken down within 24 h at ambient temperatures, but if copper was present, 150-200 mg was degraded within 2-4 h. The contribution of dehydroascorbic acid to the amount of vitamin C delivered to the patient was negligible. It is concluded that either vitamin C and trace element injections containing copper should not be added to the same bag, or an adequate coverage of ascorbic acid must be included to allow for losses by oxidation before and during administration.
31 citations
TL;DR: Studies on the effect of high doses of AA and DHA added to the culture medium in single or fractionated doses revealed that fractionated administration is more efficient in inhibiting cell multiplication than single administration.
Abstract: The effects of AA and DHA on ATP C+ cell multiplication in vitro were studied by measuring incorporation of 3H thymidine into DNA. The results obtained demonstrate that both AA and DHA have the same effects: they favor cell multiplication at low doses and inhibit it at high doses. Experiments carried out with serial doses of both these substances revealed that AA is more efficient in determining both stimulating and inhibiting effects. The lesser efficiency of DHA may be attributed to its limited stability in culture medium. Studies on the effect of high doses of AA and DHA added to the culture medium in single or fractionated doses revealed that fractionated administration is more efficient in inhibiting cell multiplication than single administration.
29 citations
TL;DR: The levels of the two biologically active forms of vitamin C, ascorbic acid and dehydroascorbic acid (DHAA), were determined in individual fruits, in fruit blends and in model systems over a 3-h incubation period at room temperature.
Abstract: The levels of the two biologically active forms of vitamin C, ascorbic acid (AA) and dehydroascorbic acid (DHAA), were determined in individual fruits, in fruit blends and in model systems over a 3-h incubation period at room temperature. There was essentially no reduction in the AA content in the orange juice sample and in the model solution of analytical l-ascorbic acid. A rapid decrease in the AA content was observed in the banana, apple and guava samples and in blends consisting of orange juice-banana-apple or L-ascorbic acid-banana-apple blends. However, the reduction in AA was concomitant with a quantitative increase in DHAA content.
22 citations
TL;DR: The hypothesis of free radical damage to the central nervous system after certain types of injury (trauma, ischemia, and tumors) may provide a satisfactory explanation for the findings of this work.
Abstract: The ascorbic acid/dehydroascorbic acid system was analyzed in the cerebrospinal fluid (CSF) of 41 patients with different neurological disorders. The chi-square test of covariance analysis revealed in this sample significant differences in the CSF levels of total ascorbic acid when patients were classified by diagnostic categories. The population analyzed contained a group of 18 patients (back pain/sciatica group) in whom no overt neurological abnormalities were disclosed upon evaluation. Taking the CSF levels of total ascorbic acid and dehydroascorbic acid in these patients as the reference (3.57 +/- 0.87 (SD)/100 ml and 0.53 +/- 0.19 mg/100 ml, respectively), it was found that head-traumatized patients showed a significant reduction in the concentration of total ascorbic acid in the CSF. CSF ascorbic acid levels were also significantly lower in patients with increased intracranial pressure (noninfected hydrocephalus group) and in patients with cerebral tumors. Although the CSF concentration of dehydroascorbic acid did not correspondingly increase over the reference values in these three groups of patients, the tendency existed for dehydroascorbic acid to represent in them a higher percentage of total ascorbic acid. After examining different alternatives, it is concluded that the hypothesis of free radical damage to the central nervous system after certain types of injury (trauma, ischemia, and tumors) may provide a satisfactory explanation of our findings. A rationale for the use of vitamin C in the management of some neurological patients is also derived from this work.
15 citations
TL;DR: No evidence that diabetic patients have higher plasma dehydroascorbic acid levels than nondiabetics is found, and some possible reasons are considered for the discrepancy between this finding and those of earlier reports.
Abstract: Recent reports of high dehydroascorbic acid levels in Asian subjects suffering from diabetes mellitus have led us to examine plasma dehydroascorbic acid levels in diabetic and non-diabetic Europeans. We can find no evidence that diabetic patients have higher plasma dehydroascorbic acid levels than nondiabetics, and consider some possible reasons for the discrepancy between this finding and those of earlier reports.
15 citations
01 Jan 1984
TL;DR: The results show that blood histamine is increased both in the moderate and severe form of pre-eclampsia, and ascorbic acid is increased only in the severe form.
Abstract: Levels of histamine and total ascorbic acid (L-ascorbic acid plus dehydroascorbic acid) in the peripheral blood of women in pre-eclampsia have been measured. The results show that blood histamine is increased both in the moderate and severe form of pre-eclampsia. Blood ascorbic acid on the other hand is increased only in the severe form of pre-eclampsia. The rise in histamine values may be in response to the rising blood pressure in pre-eclampsia. The rise in ascorbic acid values may reflect the reduced maternal blood volume and/or restricted transport of ascorbic acid from maternal to fetal tissues.
14 citations
TL;DR: It is proposed that superoxide radicals and hydrogen peroxide cooperate in producing hydroxyl radicals, which are directly involved in hemolysis, and reduced the hemolytic action of copper-ascorbate.
TL;DR: A competitive mechanism can be inferred from experiments with phosphate and substrates, which block the activity decay, and the influence of temperature, pH, other inhibitors and tertiary structure modifications on the inactivation process is investigated.
TL;DR: Owing to the possible occurrence of both ascorbic acid and Cu++ ions in beer, partial irreversible inactivation of papain can be expected even at very low oxygen concentrations.
Abstract: The simultaneous presence of ascorbic acid, Cu++ ions and oxygen causes reversible inactivation of proteolytic activity of papain. Low concentrations of ascorbic acid and Cu++ ions have no effect on their own. Ascorbic acid at concentrations higher than 2 × 10−4 m inactivates papain irreversibly in the presence of Cu++ ions. Papain inactivation is not accompanied by the destruction of papain molecules. Irreversible papain inactivation does not occur in solutions free of oxygen and the intermediates of ascorbic acid oxidation, i.e. dehydroascorbic acid and hydrogen peroxide, do not cause papain inactivation. The irreversible inactivation of papain is most probably due to free radicals formed during ascorbic acid oxidation. Owing to the possible occurrence of both ascorbic acid and Cu++ ions in beer, partial irreversible inactivation of papain can be expected even at very low oxygen concentrations.
Journal Article•
TL;DR: Evidence is provided showing that addition of ascorbic acid in a reaction mixture results in a spontaneous decrease in nitrite concentration, suggesting that ascorBic acid may be involved in the reduction of nitrite to nitrogen oxide.
Abstract: Nitrite is known to react with free amines to form nitrosamines which may have carcinogenic activity. The present study provides evidence showing that addition of ascorbic acid in a reaction mixture results in a spontaneous decrease in nitrite concentration. The nitrite lowering effect of ascorbic acid appears to correlate with the rate of oxidation of the vitamin to dehydroascorbic acid, suggesting that ascorbic acid may be involved in the reduction of nitrite to nitrogen oxide.
Journal Article•
TL;DR: Quercetin and hesperidin were found to be responsible for lysosomal stability, probably by reducing the content of dehydroascorbic acid to a normal level in the hypercholesterolemic condition.
Abstract: Possible mechanisms responsible for hepatic lysosomal fragility in hypercholesterolemic rats have been investigated. It was found that certain factor(s) present in the intracellular environment of liver were required for the release of lysosomal enzymes. Elevated hepatic dehydroascorbic acid content in hypercholesterolemic rats is thought to render the lysosomes fragile in this pathological state, since this compound was found to labilise the lysosomes in vitro. Quercetin and hesperidin were found to be responsible for lysosomal stability, probably by reducing the content of dehydroascorbic acid to a normal level in the hypercholesterolemic condition.
TL;DR: Quantitation of ascorbate at concentrations normally found in biological samples and foods has previously been shown to be possible by HPLC analysis and resulted in a more discrete peak in the elution of dehydroascorbic acid and more complete recovery of the total [14C]activity.
Journal Article•
Patent•
12 Jun 1984TL;DR: In this article, a novel process for decomposing ascorbic acid to produce H2O and dehydroascorbic acid instead of producing H 2O2 was proposed, which comprises mixing a monovalent or divalent copper ion, peroxidase, and at least one compound selected from the group consisting of: (1) 4-aminoantipyrine; (2) 3-methylbenzothiazolinone hydrazone; (3) 2,2'-azinobis(3-ethylbenzman-6-
Abstract: A novel process for decomposing ascorbic acid to produce H2O and dehydroascorbic acid instead of producing H2O2, which comprises mixing a monovalent or divalent copper ion, peroxidase, and at least one compound selected from the group consisting of: (1) 4-aminoantipyrine; (2) 3-methylbenzothiazolinone hydrazone; (3) 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid); (4) triphenylmethane leuco dyes; (5) phenolic compounds; (6) aniline compounds; and (7) naphthol compounds.
Patent•
21 May 1984TL;DR: In this article, polycondensed ester derivatives of ascorbic acid are described and prepared by the polycondensation of asbic acids and/or its derivative dehydroascorbic acid in a sealed container in the presence of water to form the respective self esters or self-ester and co-ester mixtures.
Abstract: Polycondensed ester derivatives of ascorbic acid are described and prepared by the polycondensation of ascorbic acids and/or its derivative dehydroascorbic acid in a sealed container in the presence of water to form the respective self esters or self-ester and co-ester mixtures. Alternatively ascorbic acid is partly converted to its calcium salt and polycondensed in the absence of oxygen to form its self-ester or in the presence of oxygen to form dehydroascrobic acid selfesters or mixtures of self-esters and co-esters of the two acids.
Journal Article•
TL;DR: The quenching effects displayed by the ascorbic system on alkaline phosphatase can supply an interesting insight into other aspects of the inhibitor-enzyme interaction.
Abstract: Ascorbic acid, isoascorbic acid and dehydroascorbic acid quench the tryptophyl fluorescence of alkaline phosphatase. The quenching is protein aspecific, although its extent reflects the different inhibitory efficiency of the compounds. The kinetic inactivation and emission deactivation of alkaline phosphatase isoenzymes present also striking similarities. The fluorescence modifications, moreover, show a particular pattern, indicative of a transition phenomenon. The quenching effects displayed by the ascorbic system on alkaline phosphatase can then supply an interesting insight into other aspects of the inhibitor-enzyme interaction.
01 Jan 1984
TL;DR: In this article, a pre-column reaction of dehydroascorbic acid with 1,2-phenylenediamine was used to separate acyclic acid and deodorized acid.
Abstract: Ascorbic acid and dehydroascorbic acid may be separated by High Performance Liquid Chromatography (HPLC) after pre-column reaction of dehydroascorbic acid with 1,2-phenylenediamine. Two methods are described, viz. reversed-phase ion-pairing HPLC, and the use of a CN column for the separation. When both methods were applied to the analysis of orange juice and powdered orande drink, the reversed-phase ion-pairing method was found to be subject to interference problems and variability in retention times. The Cn column method was more successful, particularly for powdered orange drink. Recovery and precision data are presented.
TL;DR: In this paper, the decrease in the ultraviolet absorption of aqueous solutions of ascorbic acid brought about by large doses of gamma radiation has been investigated as a means of developing a new chemical dosimeter.
Journal Article•
TL;DR: Levels of certain metabolites of peroxidation of lipids such as diene conjugates malonic dialdehyde, ascorbic acid, dehydroascorbic acid and diketogulonic acid appeared to be increased in cases of gastric ulcer and cancer.
Abstract: Levels of certain metabolites of peroxidation of lipids such as diene conjugates malonic dialdehyde, ascorbic acid, dehydroascorbic acid and diketogulonic acid were compared in 39 cases of gastric ulcer, 25 patients with gastric cancer and 14 healthy subjects. Diene conjugates and malonic dialdehyde levels appeared to be increased in cases of gastric ulcer and cancer. This was matched by a decrease in ascorbic acid and dehydroascorbic acid levels. Ulcer patients revealed enhanced diketogulonic acid concentration.
Journal Article•
TL;DR: It seems that thyroxine has no direct role on ascorbic acid metabolism in rats, and activities of the degrading enzymes were found to increase significantly in the liver, with no remarkable change in their activities in kidney.
Abstract: Thyroidectomized rats showed a decrease in ascorbic acid and dehydroascorbic acid, with almost no alterations in the diketogulonic acid in liver and kidney. Total ascorbic acid in urine was found to be increased, whereas glucuronic acid in urine decreased significantly. There were no significant changes in the activities of ascorbic acid synthesizing enzymes. Activities of the degrading enzymes were found to increase significantly in the liver, with no remarkable change in their activities in kidney. Daily administration of thyroxine for 10 days to thyroidectomized rats normalized the activities of dehydroascorbatase and 2,3 diketoaldonate decarboxylase in the liver, whereas single administration of thyroxine on the 7th day after thyroidectomy could not bring about such restoration. It seems that thyroxine has no direct role on ascorbic acid metabolism in rats.
01 Jan 1984
TL;DR: The relation between the type of diet and incidence of scurvy was recognized early, however the notion of accessory food factors or vitamins had not been clearly formulated in 1912 by Hopkins and Funk as discussed by the authors.
Abstract: The relation between the type of diet and incidence of scurvy was recognized early, however the notion of accessory food factors or vitamins had been clearly formulated in 1912 by Hopkins and Funk (see: Aberg, 1958). This disease was recognized due to deficiency of a specific dietary factor, ‘Vitamin C’ only in 1917 (Rangaswami and Seshadri, 1952; Aberg, 1958; Florkin and Stotz, 1963; Fieser and Fieser, 1965). Attempts to isolate this factor began in 1920 by Drummond. Later, Zilva and Tillmans made intensive studies but the decisive step was taken by Szent Gyorgyi (1928), who isolated a strongly reducing substance of the molecular formula C6H8O6 from adrenal cortex, oranges, and cabbage and named it as ‘Hexuronic acid’. The new name, ‘Ascorbic acid (AA) was later coined (Szent Gyorgyi and Haworth, 1933) and the following terminology was adopted: — Vitamin C — Ascorbic acid (AA) + Dehydroascorbic acid (DHA).
Journal Article•
TL;DR: In vitro additions of ASA in physiological concentration to the enzyme assay medium inhibited the AChE activity significantly and the inhibition was an un-competitive type.
Abstract: Unilateral-sciatectomy for three months in the frog, Rana cyanophlictis resulted in a substantial increase on unit weight basis in the ascorbic acid (ASA) and dehydroascorbic acid (DHA) contents of the sciatectomized gastrocnemius muscle. Diketogulonic acid (DKA) levels did not vary. On whole muscle-weight basis only the ASA level increased. The AChE activity in sciatectomized muscle is significantly lower than that of the control. Partially purified preparation of the AChE from the sciatectomized muscle showed different kinetics compared to that from innervated control. In vitro additions of ASA in physiological concentration to the enzyme assay medium inhibited the AChE activity significantly and the inhibition was an un-competitive type. Reduced activity of the enzyme has been correlated to the increased concentration of ASA in the sciatectomized muscle.