Showing papers on "Dehydroascorbic acid published in 1991"
TL;DR: Because circulating ascorbic acid is free and is detected only as reduced vitamin, ascorBic acid may be available without intermediates for peripheral utilization.
240 citations
TL;DR: In this paper, the changes of ascorbic acid, dehydroascorbic acid and glutathione content and related enzyme activities were studied in apple buds during dormancy and thidiazuron-induced bud break.
Abstract: The changes of ascorbic acid, dehydroascorbic acid, and glutathione content and related enzyme activities were studied in apple buds during dormancy and thidiazuron-induced bud break. An increase in ascorbic acid, reduced form of glutathione (GSH), total glutathione, total non-protein thiol (NPSH) and non-glutathione thiol (RSH) occurred as a result of induction by thidiazuron during bud break, whereas dehydroascorbic acid and oxidized glutathione (GSSG) decreased during the same period. Thidiazuron also enhanced the ratio of GSH/GSSG, and activities of ascorbate free radical reductase (AFR; EC 1.6.5.4), ascorbate peroxidase (EC 1.11.1.11). dehydroascorbate reductase (DHAR; EC 1.8.5.1) and glutathione reductase (GR; EC 1.6.4.2). The ascorbic acid content and the activities of AFR, ascorbate peroxidase, and DHAR peaked when buds were in the side green or green tip stage just prior to the start of rapid expansion, and declined thereafter. The GSH, NPSH, RSH, ratio of GSH/GSSG, and activities of GR increased steadily during bud development.
200 citations
TL;DR: High expression of ascorbic acid oxidase at a stage when rapid growth is occurring (in both fruits and leaves), and localization of the enzyme in the fruit epidermis, suggest that asCorbic Acid oxidase might be involved in reorganization of the cell wall to allow for expansion.
Abstract: The expression of ascorbic acid oxidase was studied in zucchini squash (Cucurbita pepo L.), one of the most abundant natural sources of the enzyme. In the developing fruit, specific activity of ascorbic acid oxidase was highest between 4 and 6 days after anthesis. Protein and mRNA levels followed the same trend as enzyme activity. Highest growth rate of the fruit occurred before 6 days after anthesis. Within a given fruit, ascorbic acid oxidase activity and mRNA level were highest in the epidermis, and lowest in the central placental region. In leaf tissue, ascorbic acid oxidase activity was higher in young leaves, and very low in old leaves. Within a given leaf, enzyme activity was highest in the fast-growing region (approximately the lower third of the blade), and lowest in the slow-growing region (near leaf apex). High expression of ascorbic acid oxidase at a stage when rapid growth is occurring (in both fruits and leaves), and localization of the enzyme in the fruit epidermis, where cells are under greatest tension during rapid growth in girth, suggest that ascorbic acid oxidase might be involved in reorganization of the cell wall to allow for expansion. Based on the known chemistry of dehydroascorbic acid, the end product of the ascorbic acid oxidase-catalyzed reaction, we have proposed several hypotheses to explain how dehydroascorbic acid might cause cell wall "loosening."
136 citations
TL;DR: In this paper, the authors determined serum ascorbic acid and its metabolite, dehydroascorbic acid, as indices of antioxidant status, and as an index of oxidative stress in 20 matched diabetic patients with and 20 without microangiopathy and in 22 age-matched control subjects.
Abstract: Abnormalities of ascorbic acid metabolism have been reported in experimentally-induced diabetes and in diabetic patients. Ascorbate is a powerful antioxidant, a cofactor in collagen biosynthesis, and affects platelet activation, prostaglandin synthesis and the polyol pathway. This suggests a possible close interrelationship between ascorbic acid metabolism and pathways known to be influenced by diabetes. We determined serum ascorbic acid and its metabolite, dehydroascorbic acid, as indices of antioxidant status, and the ratio, dehydroascorbate/ascorbate, as an index of oxidative stress, in 20 matched diabetic patients with and 20 without microangiopathy and in 22 age-matched control subjects. Each study subject then took ascorbic acid, 1 g daily orally, for six weeks with repeat measurements taken at three and six weeks. At baseline, patients with microangiopathy had lower ascorbic acid concentrations than those without microangiopathy and control subjects (42.1±19.3 vs 55.6±20.0, p<0.01, vs 82.9±30.9 μmol/l, p<0.001) and elevated dehydroascorbate/ascorbate ratios (0.87±0.46 vs 0.61±0.26, p<0.01, vs 0.38±0.14, p<0.001). At three weeks, ascorbate concentrations rose in all groups (p<0.0001) and was maintained in control subjects (151.5± 56.3 μmol/l), but fell in both diabetic groups by six weeks (p<0.01). Dehydroascorbate/ascorbate ratios fell in all groups at three weeks (p<0.0001) but rose again in the diabetic groups by six weeks (p<0.001) and was unchanged in the control subjects. Dehydroascorbate concentrations rose significantly from baseline in all groups by six weeks of ascorbic acid supplementation (p<0.05). No significant changes were observed in fructosamine concentrations in any group during the study. Diabetes mellitus is associated with a major disturbance of ascorbic acid metabolism which is only partially corrected by ascorbate supplementation.
112 citations
TL;DR: It is suggested that ascorbic acid is secreted into the gastric lumen so that gastric juice concentrations are often greater than those in plasma, leading to values in gastric Juice that are lower than plasma levels.
107 citations
TL;DR: It was concluded that ascorbate and other reductant(s) derived from dehydroascorbic acid (DHA) in the presence of thiols are the only significant reducing agents for nitroxides.
101 citations
TL;DR: The method is highly specific for the determination of ascorbic acid in the presence of dehydroascorbic acid and all other vitamins normally encountered with it in pharmaceutical dosage forms and can also be applied to the determination in some fresh fruit juices without interference from coloured and other substances present in the fruit extracts.
Abstract: A simple and selective method for the determination of ascorbic acid in pharmaceutical preparations and fresh fruit juices is described. The procedure is based on the reaction of ascorbic acid with the zinc chloride salt of diazotized 1-aminoanthraquinone (Fast Red AL salt) in an acidic medium, followed by development of a blue colour (λmax 630 nm) in alkaline solution. Different variables affecting the colour development were studied and optimized. The method was used to determine between 5 and 25 µg ml–1 of ascorbic acid in the final measured solution. The simplicity of the method permits rapid analysis, suitable for routine control. The method is highly specific for the determination of ascorbic acid in the presence of dehydroascorbic acid and all other vitamins normally encountered with it in pharmaceutical dosage forms. Moreover, the proposed method can also be applied to the determination of ascorbic acid in some fresh fruit juices without interference from coloured and other substances present in the fruit extracts. The reliability of the method was established by parallel determinations against the official British pharmacopoeial method.
53 citations
TL;DR: A recent survey of foods that constitute the major sources of vitamin C in the American diet yielded information on the total content of this vitamin as well as the amount of its two forms, ascorbic acid and dehydroascorbic acid.
45 citations
TL;DR: The results imply that whole blood has the capacity to maintain a constant ascorbic-dehydroascorbic acid ratio and suggest that this ratio may be of physiological significance.
32 citations
TL;DR: Tests proved that cobalt ascorbate plus vitamin C also inhibited tumor cells, and in vitro findings revealed inhibition of mitoses in L1210 leukemia cells, but not in normal L929 cells.
32 citations
TL;DR: It is concluded that BBdp rats have an altered metabolism of AA, DHAA, and vitamin E, before the onset of diabetes, which could be due to genetic and physiological factors operating during development of this rat strain.
Abstract: Ascorbic acid (AA), dehydroascorbic acid (DHAA), and vitamin E were measured in tissues and plasma of 30 control and 30 spontaneously diabetic BioBreeding rats (BBdp) during development and before the onset of diabetes. At weaning, rats were fed an AIN-76 semisynthetic diet for 30, 64, or 113 days, after which plasma and tissues from 10 rats of each group were collected and analysed for AA, DHAA, and vitamin E. AA and DHAA levels were significantly increased in plasma and spleen of the diabetes-prone rats compared with those of the control group at 30 and 64 days, but the difference disappeared by 113 days. No differences were observed in liver, adrenals, thymus, and pancreas at any of the time periods. However, lower levels of vitamin E were observed in adrenal gland, thymus, and pancreas of the diabetes-prone rats. It is concluded that BBdp rats have an altered metablolism of AA, DHAA, and vitamin E, before the onset of diabetes. These changes could be due to genetic and physiological factors operating during development of this rat strain.
TL;DR: This work has suggested that a mechanism involving concerted proton-electron transfer rather than electron transfer alone would permit reduction of the cytochrome by the abundant ascorbate monoanion but would circumvent formation of unfavorable intermediates.
TL;DR: The removal of oxygen from the reaction mixture had no effect on either protein glycation, protein crosslinking or the modification of lysine residues, provided DHA was used as the glycating agent, confirming that oxygen is required only to convert ASA to DHA.
TL;DR: In this article, the formation of an intermediate ruthenium(III) ascorbate complex (1) by the interaction of L -ascorbic acid and dichlorotetraquorutheniam(III), was reported in the temperature range 25-40°C.
TL;DR: A simple, single-step HPLC assay for the simultaneous detection of both AA and dehydroascorbate was developed without the burden of derivatization of either compounds, and should be applicable to a wide variety of biological samples.
TL;DR: The present work shows that pancreatic islet cells prepared from overnight cultures of isolated islets from 5-7-day-old rats accumulate 14C-labelled ascorbic acid by a Na(+)-dependent active transport mechanism which involves a saturable process.
Abstract: Several amidated biologically active peptides such as pancreastatin, thyrotropin-releasing hormone, pancreatic polypeptide and amylin are produced in endocrine pancreatic tissue which contains the enzyme necessary for their final processing, i.e. peptidylglycine alpha-amidating mono-oxygenase (EC 1.14.17.3). The enzyme needs ascorbic acid for activity as well as copper and molecular oxygen. The present work shows that pancreatic islet cells prepared from overnight cultures of isolated islets from 5-7-day-old rats accumulate 14C-labelled ascorbic acid by a Na(+)-dependent active transport mechanism which involves a saturable process (estimated Km 17.6 microM). Transport was inhibited by ouabain, phloridzin, cytochalasin B, amiloride and probenecid. Glucose inhibited or stimulated uptake, depending on the length of incubation time of the cells. The uptake of dehydroascorbic acid was linearly dependent on concentration. Dehydroascorbic acid was converted to ascorbic acid by an unknown mechanism after uptake. The uptake of both ascorbic acid and dehydroascorbic acid was inhibited by tri-iodothyronine, and uptake of ascorbic acid, but not of dehydroascorbic acid, was inhibited by glucocorticoids. Isolated secretory granules contained a fairly low concentration of iron but a high concentration of copper.
TL;DR: In this article, it was shown that ascorbic acid and dehydroascorbic acid can be derived to the compounds having a maximum absorption wavelength of 300nm under alkaline conditions, and that derivatization of DHAA is accelerated in the presence of reducing agent such as sodium borohydride.
Abstract: It has been found that ascorbic acid (AA) and dehydroascorbic acid (DHAA) can be derivatized to the compounds having a maximum absorption wavelength of 300nm under alkaline conditions, and that derivatization of DHAA is accelerated in the presence of a reducing agent such as sodium borohydride. This reaction has been applied to post-column derivatization in high performance liquid chromatography (HPLC) for the simultaneous determination of AA and DHAA. In this system, AA in the range of 1ng 2μg and DHAA in the range of 2ng 2μg have been determined simultaneously with good reproducibility, C.V 1.5% (n=10).
TL;DR: Ascorbic acid-2-phosphate (AAP) and ascorbic acid (AA) were infiltrated into apple and potato tissue to control browning as discussed by the authors.
Abstract: Ascorbic acid-2-phosphate (AAP) and ascorbic acid (AA) were infiltrated into apple and potato tissue to control browning. Apple tissue absorbed more AAP and AA than potato under similar conditions. AAP hydrolysis by endogenous acid phosphatase (APase) yielded AA which accumulated or became oxidized to dehydroascorbic acid, depending on the rate of hydrolysis and browning tendencies of samples. APase activity varied greatly with commodity, method of sample preparation and sample pH. Variation in the ability of AAP to inhibit browning in different products could be explained by these factors.
TL;DR: 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.
LGC1
TL;DR: The system showed a linear response to the concentration of L-ascorbic acid in the range 1-200 micrograms ml(-1) and was capable of detecting total vitamin C in a range of foodstuffs at a sample throughput of 15 samples h(-1).
Abstract: A microprocessor controlled flow injection system is described for the determination of vitamin C in foodstuffs. The system is based on amperometric detection at a wall-jet electrode coupled with an ascorbate oxidase packed bed. A commercially available Cartesian robotic auto-sampler-dilutor is used as a means of fully automating the sample handling and dilution. Dithiothreitol (DTT) is used to reduce dehydroascorbic acid to ascorbic acid and to stabilize ascorbic acid standard solutions. Initially, the system was connected in series with a high-performance liquid chromatography column and ultraviolet (UV) detector to allow identification of possible interferents and to allow comparative evaluation of results. The system showed a linear response to the concentration of L-ascorbic acid in the range 1-200 micrograms ml(-1) and was capable of detecting total vitamin C in a range of foodstuffs at a sample throughput of 15 samples h(-1). Correlations to existing methods of 0.98 were obtained.
TL;DR: High-performance liquid chromatography with electrochemical detection was applied to the estimation of glutathione, glutATHione disulphide, ascorbic acid and dehydroascorbic acid in various tissues of man, animal, and plant to exclude interfering substances.
Abstract: High-performance liquid chromatography with electrochemical detection was applied to the estimation of glutathione, glutathione disulphide, ascorbic acid and dehydroascorbic acid in various tissues of man, animal, and plant. The simultaneous determination of glutathione and ascorbic acid in tissues was done by a coulometric method. Separation of glutathione and ascorbic acid and unequivocal substance identifications were performed on a 100×4.6 mm RP-18 Spheri 5 column. As mobile phase 0.015 mol/l o-phosphoric acid, pH 2.3 was used. Retention time of ascorbic acid was 5.0 min and of glutathione 10.0 min. Dehydroascorbic acid was determined after reduction to ascorbic acid with dithiothreitol. Glutathione disulphide was reduced at pH 7.5 by β-nicotinamide-dinucleotide phosphate and glutathione reductase, EC 1.6.4.2., to regenerate glutathione. To exclude interfering substances, several other compounds present in tissues and foods were investigated. This coulometric method is highly sensitive, specific and simple. Very low concentrations of ascorbic acid, glutathione, dehydroascorbic acid, and glutathione disulphide (<500 pg/injection) could be analysed using this HPLC-ECD method.
TL;DR: The fact that isolated nerve endings from ox neurohypophyses took up L-[14C]ascorbic acid showed saturation with increasing concentration of ascorbic acid and a Km value of 97 microM suggests the presence of both a glucose- dependent uptake and a sodium-dependent uptake.
Abstract: Isolated nerve endings (neurosecretosomes) from ox neurohypophyses took up L-[14C]ascorbic acid by a process or processes which showed energy dependence and which could be inhibited by unlabelled ascorbic acid in micromolar concentrations and by isoascorbic acid in millimolar concentrations, whereas dehydroascorbic acid only inhibited in concentrations of about 100 mM. The uptake showed saturation with increasing concentration of ascorbic acid and a Km value of 97 microM. Uptake was inhibited by increasing glucose concentration in the medium or by adding cytochalasin B, phloridzin, ethanol or probenecid to the medium. The uptake was inhibited by lowering the sodium concentration and by lack of calcium. These facts suggest the presence of both a glucose-dependent uptake and a sodium-dependent uptake. Cortisol and tri-iodothyronine inhibited uptake. This effect of cortisol, but not of tri-iodothyronine, was dependent on the presence of sodium in the medium. For both hormones it was still present when phloridzin or probenecid was added to the medium.
Journal Article•
TL;DR: The significance of the antiacidotic component in the mechanism of the cardioprotective action of the energy-supplying agents is concluded.
Abstract: The antiacidotic and cardioprotective effects of dehydro-L-ascorbic acid and fructose-1,6-diphosphate were compared in experiments of rats. It was found that the both compounds exhibit the antiacidotic effect on the model of metabolic acidosis in the isolated hypoxic heart, decrease the excess-lactate degree, increase ATP level in the myocardium and reduce the size of the necrosis area 4 hours after the modelling of myocardial infarction. The significance of the antiacidotic component in the mechanism of the cardioprotective action of the energy-supplying agents is concluded.
TL;DR: It is concluded that dopaminergic activation or cholinergic inhibition both increase striatal AA oxidation, which is correlated with a decrease in DA turnover.
Journal Article•
TL;DR: It is concluded that cadmium, given systemically, reduces dopaminergic system activity in the rat striatum; such impairment occurs together with an increase of AA oxidation and of markers of purinergicSystem activity.
Abstract: Levels of dopamine (DA), 3-4-dihydroxyphenylacetic acid (DOPAC), ascorbic acid (AA), dehydroascorbic acid (DHAA), uric acid (UA) and adenosine (ADO), were determined by HPLC in the striatum of male Wistar rats treated with repeated injections of cadmium (as sulfate) 3 mg/kg/day s.c. for 10 consecutive days. Cadmium treatment significantly reduced DOPAC levels with consequent decrease of the DOPAC/DA ratio; AA levels were significantly reduced, while DHAA levels were significantly increased, with consequent increase of DHAA/AA ratio: levels of UA and ADO were both significantly increased. It is concluded that cadmium, given systemically, reduces dopaminergic system activity in the rat striatum; such impairment occurs together with an increase of AA oxidation and of markers of purinergic system activity. The inhibition of striatal dopaminergic activity could be considered the neurochemical basis of behavioral changes induced by cadmium, while the increase of AA oxidation and of purinergic system activity could be considered an antitoxic metabolic response.
TL;DR: The data are consistent with the hypothesis that cyanide inhibition of vitamin C uptake represents the chemical elimination of extracellular DHA rather than the inhibition of active transport in these cells.
Abstract: 1 1 Cyanide inhibited the uptake of vitamin C by human polymorphonuclear leukocytes (PMNs) 2 2 Preincubation of PMNs with cyanide had no effect on cytochalasin B-inhibitable uptake of dehydroascorbic acid (DHA) (the reversibly oxidized and transportable form of vitamin C) 3 3 Preincubation of DHA with cyanide resulted in inhibition of DHA uptake 4 4 Vitamin C uptake was decreased by cyanide to the same degree as it was by glutathione (GSH), which effectively reduces DHA to ascorbic acid The effects of cyanide and GSH were not additive 5 5 The data are consistent with the hypothesis that cyanide inhibition of vitamin C uptake represents the chemical elimination of extracellular DHA rather than the inhibition of active transport in these cells
01 Jan 1991
TL;DR: The treatment of the intoxicated animals with the antioxidants Trolox C or desferrioxamine, completely prevents both lipid peroxidation and liver necrosis, while not changing at all the extent of the covalent binding of bromobenzene metabolites to liver protein.
Abstract: Previous studies from our laboratory (1–3) have shown that the intoxication of mice with three prototypical glutathione (GSH) depleting agents (bromobenzene, diethylmaleate and allyl alcohol) is followed by the development of lipid peroxidation and liver necrosis after the hepatic GSH depletion has reached critical values. The treatment of the intoxicated animals with the antioxidants Trolox C or desferrioxamine, completely prevents both lipid peroxidation and liver necrosis, while not changing at all the extent of the covalent binding of bromobenzene metabolites to liver protein. In subsequent studies, the relationships among the various antioxidant systems (namely, vit. E, GSH and ascorbic acid) of the liver cell have been investigated under conditions of severe GSH depletion, like those induced by the GSH depleting agents mentioned above. Such an abrupt loss of the GSH antioxidant system could reasonably affect the other antioxidant systems. According to some authors (4,5), in fact, GSH is directly involved in the enzymatic system (“tocopheroxy radical reductase“) that reduces the oxidized form of tocopherol; on the other hand, according to others (6,7) the tocopherol regenerating system consists of ascorbic acid that is converted in the reaction to semidehydroascorbic acid radical and then to dehydroascorbic acid. Even in the latter case GSH may be involved in the reduction of the oxidized form of ascorbic acid (dehydroascorbic acid) (8,9). Alternatively, GSH depletion could affect the other antioxidant systems, by decreasing the disposition of hydrogen peroxide through GSH peroxidase. Vit. E may be consumed as a result of an increased formation of lipid peroxides in cell membranes, while ascorbate may be involved by direct interactions with oxy-radicals, especially with hydroxyl radicals.