The Experts below are selected from a list of 195 Experts worldwide ranked by ideXlab platform
P G Spieckermann - One of the best experts on this subject based on the ideXlab platform.
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Spectrophotometric determination of ascorbic Acid and Dehydroascorbic Acid.
Clinical Chemistry, 1995Co-Authors: T Moeslinger, M Brunner, I Volf, P G SpieckermannAbstract:We present a method for measuring ascorbic Acid in methanol/trichloroacetic Acid extracts prepared from human plasma after enzymatic oxidation of ascorbic Acid to Dehydroascorbic Acid by ascorbate oxidase. Samples were assayed by spectrophotometrically monitoring the kinetics of the concentration-dependent absorbance changes of Dehydroascorbic Acid with phosphate-citrate-methanol buffers. Ascorbic Acid was determined as the difference between Dehydroascorbic Acid and total ascorbic Acid content. The detection limit was 0.995) over the range 0-1000 mumol/L. Analytical recovery of ascorbic Acid added to plasma was 93-105%. The between-day variance was < 7%. Comparison of the spectrophotometric determination (y) with a chromatographic procedure (x) gave y = 1.02x - 0.653 (Sylx = 3.61) over the range of physiologically relevant concentrations. Total analysis time is < 10 min per sample and allows the simultaneous analysis of multiple samples.
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Spectrophotometric determination of ascorbic Acid and Dehydroascorbic Acid.
Clinical chemistry, 1995Co-Authors: T Moeslinger, M Brunner, I Volf, P G SpieckermannAbstract:We present a method for measuring ascorbic Acid in methanol/trichloroacetic Acid extracts prepared from human plasma after enzymatic oxidation of ascorbic Acid to Dehydroascorbic Acid by ascorbate oxidase. Samples were assayed by spectrophotometrically monitoring the kinetics of the concentration-dependent absorbance changes of Dehydroascorbic Acid with phosphate-citrate-methanol buffers. Ascorbic Acid was determined as the difference between Dehydroascorbic Acid and total ascorbic Acid content. The detection limit was < 0.5 mumol/L. The calibration curve was linear (r > 0.995) over the range 0-1000 mumol/L. Analytical recovery of ascorbic Acid added to plasma was 93-105%. The between-day variance was < 7%. Comparison of the spectrophotometric determination (y) with a chromatographic procedure (x) gave y = 1.02x - 0.653 (Sylx = 3.61) over the range of physiologically relevant concentrations. Total analysis time is < 10 min per sample and allows the simultaneous analysis of multiple samples.
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Spectrophotometric determination of Dehydroascorbic Acid in biological samples.
Analytical biochemistry, 1994Co-Authors: T Moeslinger, M Brunner, P G SpieckermannAbstract:We describe a method for accurately and precisely measuring Dehydroascorbic Acid in perchloric Acid extracts prepared from human plasma, lymphocytes, and mammalian cells. Samples were assayed by spectrophotometrically monitoring the kinetics of the concentration-dependent absorbance changes of Dehydroascorbic Acid with phosphate-methanol-containing buffers. The lowest detectable dehydroascorbate concentration using this assay is estimated to be below 0.1 mumol/liter. Total analysis time is less than 10 min and allows the simultaneous measurement of numerous samples. The calibration curve is linear (r > 0.995) over the range 0-200 mumol/liter. The Dehydroascorbic Acid concentrations measured in supplemented samples agree with known concentrations. Interference of ascorbic Acid and 2,3-diketogulonic Acid with this assay was excluded. The correlation with a highly specific chromatographic procedure gave comparable results over the range of physiologically relevant concentrations. The procedure avoids the most commonly applied method of measuring the native ascorbic Acid, then reducing the Dehydroascorbic Acid, and finally measuring the total ascorbic Acid and determining Dehydroascorbic Acid by the difference. Stabilization of ascorbic Acid during assay was achieved by addition of desferrioxamine.
Mark Levine - One of the best experts on this subject based on the ideXlab platform.
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Chemical Transport Knockout for Oxidized Vitamin C, Dehydroascorbic Acid, Reveals Its Functions in vivo
EBioMedicine, 2017Co-Authors: Yu Wang, Lauren R. Brinster, Mark LevineAbstract:Despite its transport by glucose transporters (GLUTs) in vitro, it is unknown whether Dehydroascorbic Acid (oxidized vitamin C, DHA) has any in vivo function. To investigate, we created a chemical transport knockout model using the vitamin C analog 6-bromo-ascorbate. This analog is transported on sodium-dependent vitamin C transporters but its oxidized form, 6-bromo-Dehydroascorbic Acid, is not transported by GLUTs. Mice (gulo-/-) unable to synthesize ascorbate (vitamin C) were raised on 6-bromo-ascorbate. Despite normal survival, centrifugation of blood produced hemolysis secondary to near absence of red blood cell (RBC) ascorbate/6-bromo-ascorbate. Key findings with clinical implications were that RBCs in vitro transported Dehydroascorbic Acid but not bromo-Dehydroascorbic Acid; RBC ascorbate in vivo was obtained only via DHA transport; ascorbate via DHA transport in vivo was necessary for RBC structural integrity; and internal RBC ascorbate was essential to maintain ascorbate plasma concentrations in vitro/in vivo.
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Intracellular Accumulation of Ascorbic Acid Is Inhibited by Flavonoids via Blocking of Dehydroascorbic Acid and Ascorbic Acid Uptakes in HL-60, U937 and Jurkat Cells
The Journal of nutrition, 2000Co-Authors: Jae B. Park, Mark LevineAbstract:In HL-60, U937 and Jurkat cells, the intracellular accumulation of ascorbic Acid occurred via uptakes of both Dehydroascorbic Acid (an oxidized metabolite of ascorbic Acid) and ascorbic Acid (vitamin C). Dehydroascorbic Acid and ascorbic Acid were transported into cells by sodium-independent glucose transporters (GLUT 1 and GLUT 3) and sodium-dependent ascorbic Acid transporters, respectively. Flavonoids inhibited the intracellular accumulation of ascorbic Acid by blocking Dehydroascorbic Acid and ascorbic Acid uptakes in the transformed cells. At flavonoid concentrations of 10-70 micromol/L, approximately 50% of Dehydroascorbic Acid uptake was inhibited in the cells. In Jurkat cells, two potent flavonoids (myricetin and quercetin) competitively inhibited Dehydroascorbic Acid uptake, and K(i) values were approximately 14 and 15 micromol/L, respectively. Because GLUT 1 and GLUT 3 transport Dehydroascorbic Acid, the inhibition of Dehydroascorbic Acid uptake by flavonoids was investigated by using Chinese hamster ovary cells overexpressing rat GLUT 1 or human GLUT 3. Myricetin at concentrations of 22 and 18 micromol/L, respectively, inhibited half of Dehydroascorbic Acid uptake in the cells overexpressing GLUT 1 and GLUT 3. Myricetin also inhibited ascorbic Acid uptake; inhibition was noncompetitive with K(i) = 14 micromol/L in Jurkat cells. These data indicate that flavonoids inhibit both ascorbic Acid and Dehydroascorbic Acid uptake but do so by different mechanisms. These data may contribute to new understanding of the biological effect of flavonoids on the intracellular accumulation of ascorbic Acid in human cells.
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Analysis of ascorbic Acid and Dehydroascorbic Acid in biological samples.
Methods in enzymology, 1999Co-Authors: Mark Levine, Yaohu Wang, Steven C. RumseyAbstract:Publisher Summary This chapter describes the analysis of ascorbic Acid and Dehydroascorbic Acid in biological samples. The chapter focuses on ascorbate assays because these techniques are substantially more advanced than those for Dehydroascorbic Acid and most techniques for the latter are based on those of the former. High performance liquid chromatography (HPLC) with electrochemical (EC) detection is the ascorbate assay technique that provides the highest sensitivity, specificity, and accounts for substance interference. The general separation principles of HPLC are utilized to separate ascorbate from other substances. A mobile phase—or the solution for chromatography—is selected that optimizes both separation and detection. Once separation is accomplished, ascorbate is detected by one of two distinct types of EC detectors, amperometric EC detectors, or coulometric detectors. The principle of both detectors is that they pass a voltage across an area. Current generated by the voltage and the components of the mobile phase are measured. Amperometric EC detectors are “flow by” detectors, in which the solution containing ascorbate and the components of the mobile phase for HPLC separation flow around the detector. Coulometric detectors are “flow through” detectors. The mobile phase and ascorbate flow through the detector, which is porous. Coulometric detectors are preferred over amperometric detectors. The chapter concludes with a discussion of the detection of radiolabeled ascorbate and Dehydroascorbic Acid.
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Purification, cloning and expression of Dehydroascorbic Acid-reducing activity from human neutrophils: identification as glutaredoxin.
Biochemical Journal, 1996Co-Authors: Jae B. Park, Mark LevineAbstract:Dehydroascorbic Acid-reducing activity in normal human neutrophil lysates was characterized and identified by activity-based purification and measurement of newly synthesized ascorbate by HPLC. The initial reducing activity was non-dialysable and could not be accounted for by the activity of glutathione as a reducing agent. The reducing activity was purified to homogeneity as an 11 kDa protein. The protein had a specific activity of 3 mumol/min per mg of protein and was glutathione dependent. Kinetic experiments showed that the protein had a K(m) for glutathione of 2.0 mM and a K(m) for Dehydroascorbic Acid of 250 microM. Dehydroascorbic Acid reduction by the purified protein was pH dependent and was maximal at pH 7.5. Peptide fragments from the purified protein were analysed for amino Acid sequence and the protein was identified as glutaredoxin. By using degenerate oligonucleotides based on the amino Acid sequence, glutaredoxin was cloned from a human neutrophil library. Expressed purified glutaredoxin displayed reducing activity and kinetics that were indistinguishable from those of native purified enzyme. Several approaches indicated that glutaredoxin was responsible for the most of the protein-mediated Dehydroascorbic Acid reduction in lysates. From protein purification data, glutaredoxin was responsible for at least 47% of the initial reducing activity. Dehydroascorbic Acid reduction was at least 5-fold greater in neutrophil lysates than in myeloid tumour cell lysates, and glutaredoxin was detected in normal neutrophil lysates but not in myeloid tumour cell lysates by Western blotting. Glutaredoxin inhibitors inhibited Dehydroascorbic Acid reduction in neutrophil lysates as much as 80%. These findings indicate that glutaredoxin plays a major role in Dehydroascorbic Acid reduction in normal human neutrophil lysates, and represent the first identification of Dehydroascorbic Acid reductase in human tissue by activity-based purification.
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Accumulation of Vitamin C (Ascorbate) and Its Oxidized Metabolite Dehydroascorbic Acid Occurs by Separate Mechanisms
The Journal of biological chemistry, 1995Co-Authors: R W Welch, Yaohui Wang, Arthur Crossman, Jae B. Park, Kenneth L. Kirk, Mark LevineAbstract:It is unknown whether ascorbate alone (vitamin C), its oxidized metabolite Dehydroascorbic Acid alone, or both species are transported into human cells. This problem was addressed using specific assays for each compound, freshly synthesized pure Dehydroascorbic Acid, the specially synthesized analog 6-chloroascorbate, and a new assay for 6-chloroascorbate. Ascorbate and Dehydroascorbic Acid were transported and accumulated distinctly; neither competed with the other. Ascorbate was accumulated as ascorbate by sodium-dependent carrier-mediated active transport. Dehydroascorbic Acid transport and accumulation as ascorbate was at least 10-fold faster than ascorbate transport and was sodium-independent. Once transported, Dehydroascorbic Acid was immediately reduced intracellularly to ascorbate. The analog 6-chloroascorbate had no effect on Dehydroascorbic Acid transport but was a competitive inhibitor of ascorbate transport. The Ki for 6-chloroascorbate (2.9-4.4 μM) was similar to the Km for ascorbate transport (9.8-12.6 μM). 6-Chloroascorbate was itself transported and accumulated in fibroblasts by a sodium-dependent transporter. These data provide new information that ascorbate and Dehydroascorbic Acid are transported into human neutrophils and fibroblasts by two distinct mechanisms and that the compound available for intracellular utilization is ascorbate.
Jens Lykkesfeldt - One of the best experts on this subject based on the ideXlab platform.
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ascorbate and Dehydroascorbic Acid as biomarkers of oxidative stress validity of clinical data depends on vacutainer system used
Nutrition Research, 2012Co-Authors: Jens LykkesfeldtAbstract:Abstract Ascorbate and Dehydroascorbic Acid are frequently used as biomarkers of oxidative stress, but their lack of stability ex vivo and rapid postsampling interconversion continue to result in erroneous reference values. One problem is the large variety of vacutainer devices used for blood sampling purposes and the basic question of plasma vs serum as matrix. This study acquired blood samples by using 9 different and commonly used vacutainer systems followed by Acidic stabilization and analysis by a well-validated method with the purpose of identifying acceptable means of collecting samples for proper ascorbate/Dehydroascorbic Acid analysis. In comparison, K 3 -EDTA vacutainers were superior in maintaining low ex vivo oxidation of vitamin C.
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ascorbate and Dehydroascorbic Acid as reliable biomarkers of oxidative stress analytical reproducibility and long term stability of plasma samples subjected to Acidic deproteinization
Cancer Epidemiology Biomarkers & Prevention, 2007Co-Authors: Jens LykkesfeldtAbstract:Lack of post-sampling stability of ascorbate and Dehydroascorbic Acid and failure to block their in vivo equilibrium have lowered their value as biomarkers of oxidative stress and limited the ability to further investigate their possible role in disease prevention. In the present article, analytic reproducibility was tested by repeated analysis of plasma aliquots from one individual over 4 years. The plasma was subjected to Acidic deproteinization with an equal volume of 10% meta -phosphoric Acid containing 2 mmol/L of EDTA and analyzed for ascorbate and Dehydroascorbic Acid by high-performance liquid chromatography with coulometric detection. In a parallel experiment, the stability of human plasma samples treated as above and stored at −80°C for 5 years was tested in a cohort of 131 individuals. No degradation or shift in the equilibrium between ascorbate and Dehydroascorbic Acid was observed in either of the experiments. In conclusion, ascorbate and Dehydroascorbic Acid could be adequately preserved in plasma stored at −80°C following Acidic deproteinization with meta -phosphoric Acid containing 2 mmol/L of EDTA. (Cancer Epidemiol Biomarkers Prev 2007;16(11):2513–6)
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Measurement of ascorbic Acid and Dehydroascorbic Acid in biological samples.
Current protocols in toxicology, 2002Co-Authors: Jens LykkesfeldtAbstract:Ascorbic Acid and Dehydroascorbic Acid are commonly used biomarkers of oxidative stress in a variety of experimental models. However, the accurate measurement of these labile compounds remains a challenge both in terms of sample collection and analysis. Determination of Dehydroascorbic Acid most commonly involves indirect measurement. The concentration is calculated by subtraction of the measured ascorbic Acid concentration from that of total ascorbic Acid analyzed after reduction of the Dehydroascorbic Acid present; a method referred to as the subtraction method. Consequently, successful determination of Dehydroascorbic Acid is dependent upon proper sample handling, quantitative reduction of the compound, and accurate quantification of both ascorbic Acid and total ascorbic Acid. The unit presents a detailed introduction to ascorbate analysis in biological samples and discusses common problems and pitfalls. The analytical method described is based on reversed-phase HPLC with coloumetric detection. This method includes co-analysis of isoascorbic Acid and uric Acid. Where applicable, uric Acid can conveniently be used as an endogenous intrasample standard that significantly improves the accuracy of the subsequent Dehydroascorbic Acid calculation.
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Current Protocols in Toxicology - Measurement of ascorbic Acid and Dehydroascorbic Acid in biological samples.
Current Protocols in Toxicology, 2002Co-Authors: Jens LykkesfeldtAbstract:Ascorbic Acid and Dehydroascorbic Acid are commonly used biomarkers of oxidative stress in a variety of experimental models. However, the accurate measurement of these labile compounds remains a challenge both in terms of sample collection and analysis. Determination of Dehydroascorbic Acid most commonly involves indirect measurement. The concentration is calculated by subtraction of the measured ascorbic Acid concentration from that of total ascorbic Acid analyzed after reduction of the Dehydroascorbic Acid present; a method referred to as the subtraction method. Consequently, successful determination of Dehydroascorbic Acid is dependent upon proper sample handling, quantitative reduction of the compound, and accurate quantification of both ascorbic Acid and total ascorbic Acid. The unit presents a detailed introduction to ascorbate analysis in biological samples and discusses common problems and pitfalls. The analytical method described is based on reversed-phase HPLC with coloumetric detection. This method includes co-analysis of isoascorbic Acid and uric Acid. Where applicable, uric Acid can conveniently be used as an endogenous intrasample standard that significantly improves the accuracy of the subsequent Dehydroascorbic Acid calculation.
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determination of ascorbic Acid and Dehydroascorbic Acid in plasma by high performance liquid chromatography with coulometric detection are they reliable biomarkers of oxidative stress
Analytical Biochemistry, 1995Co-Authors: Jens Lykkesfeldt, Steffen Loft, Henrik E PoulsenAbstract:Abstract The concentrations of the hydrophilic antioxidants ascorbic Acid and Dehydroascorbic Acid in plasma for some time have been considered possible biomarkers of oxidative stress. However, several problems are associated with the accurate measurement of these two compounds. We have developed and validated a selective and reproducible high-performance liquid chromatographic method for the quantification of ascorbic Acid and Dehydroascorbic Acid in plasma. The method meets the requirements of a reliable routine analysis. The plasma samples are stabilized with 5 mM meta -phosphoric Acid, centrifugated at 4°C before HPLC analysis. For ascorbic Acid analysis, the sample pH is adjusted to 2.6, whereas for total ascorbic Acid measurement Dehydroascorbic Acid is reduced to ascorbic Acid using dithiothreitol for 5 min at pH 6.2 after which the sample pH is adjusted to 2.6. The samples are analyzed on a reversed-phase system using coulometric detection. Dehydroascorbic Acid concentrations are calculated by subtraction. Within- and between-day coefficients of variation for the complete assay were in the range of 4-8 and 3-6% for ascorbic Acid and total ascorbic Acid, respectively. The stability of ascorbic Acid was monitored under various conditions including storage and the implications as well as the reliability of ascorbic Acid as a biomarker are discussed.
T Moeslinger - One of the best experts on this subject based on the ideXlab platform.
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Spectrophotometric determination of ascorbic Acid and Dehydroascorbic Acid.
Clinical Chemistry, 1995Co-Authors: T Moeslinger, M Brunner, I Volf, P G SpieckermannAbstract:We present a method for measuring ascorbic Acid in methanol/trichloroacetic Acid extracts prepared from human plasma after enzymatic oxidation of ascorbic Acid to Dehydroascorbic Acid by ascorbate oxidase. Samples were assayed by spectrophotometrically monitoring the kinetics of the concentration-dependent absorbance changes of Dehydroascorbic Acid with phosphate-citrate-methanol buffers. Ascorbic Acid was determined as the difference between Dehydroascorbic Acid and total ascorbic Acid content. The detection limit was 0.995) over the range 0-1000 mumol/L. Analytical recovery of ascorbic Acid added to plasma was 93-105%. The between-day variance was < 7%. Comparison of the spectrophotometric determination (y) with a chromatographic procedure (x) gave y = 1.02x - 0.653 (Sylx = 3.61) over the range of physiologically relevant concentrations. Total analysis time is < 10 min per sample and allows the simultaneous analysis of multiple samples.
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Spectrophotometric determination of ascorbic Acid and Dehydroascorbic Acid.
Clinical chemistry, 1995Co-Authors: T Moeslinger, M Brunner, I Volf, P G SpieckermannAbstract:We present a method for measuring ascorbic Acid in methanol/trichloroacetic Acid extracts prepared from human plasma after enzymatic oxidation of ascorbic Acid to Dehydroascorbic Acid by ascorbate oxidase. Samples were assayed by spectrophotometrically monitoring the kinetics of the concentration-dependent absorbance changes of Dehydroascorbic Acid with phosphate-citrate-methanol buffers. Ascorbic Acid was determined as the difference between Dehydroascorbic Acid and total ascorbic Acid content. The detection limit was < 0.5 mumol/L. The calibration curve was linear (r > 0.995) over the range 0-1000 mumol/L. Analytical recovery of ascorbic Acid added to plasma was 93-105%. The between-day variance was < 7%. Comparison of the spectrophotometric determination (y) with a chromatographic procedure (x) gave y = 1.02x - 0.653 (Sylx = 3.61) over the range of physiologically relevant concentrations. Total analysis time is < 10 min per sample and allows the simultaneous analysis of multiple samples.
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Spectrophotometric determination of Dehydroascorbic Acid in biological samples.
Analytical biochemistry, 1994Co-Authors: T Moeslinger, M Brunner, P G SpieckermannAbstract:We describe a method for accurately and precisely measuring Dehydroascorbic Acid in perchloric Acid extracts prepared from human plasma, lymphocytes, and mammalian cells. Samples were assayed by spectrophotometrically monitoring the kinetics of the concentration-dependent absorbance changes of Dehydroascorbic Acid with phosphate-methanol-containing buffers. The lowest detectable dehydroascorbate concentration using this assay is estimated to be below 0.1 mumol/liter. Total analysis time is less than 10 min and allows the simultaneous measurement of numerous samples. The calibration curve is linear (r > 0.995) over the range 0-200 mumol/liter. The Dehydroascorbic Acid concentrations measured in supplemented samples agree with known concentrations. Interference of ascorbic Acid and 2,3-diketogulonic Acid with this assay was excluded. The correlation with a highly specific chromatographic procedure gave comparable results over the range of physiologically relevant concentrations. The procedure avoids the most commonly applied method of measuring the native ascorbic Acid, then reducing the Dehydroascorbic Acid, and finally measuring the total ascorbic Acid and determining Dehydroascorbic Acid by the difference. Stabilization of ascorbic Acid during assay was achieved by addition of desferrioxamine.
John C. Deutsch - One of the best experts on this subject based on the ideXlab platform.
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Spontaneous hydrolysis and dehydration of Dehydroascorbic Acid in aqueous solution.
Analytical biochemistry, 1998Co-Authors: John C. DeutschAbstract:The interaction of water with Dehydroascorbic Acid was examined by incubating Dehydroascorbic Acid and ascorbic Acid in 18O-labeled water for various amounts of time and then oxidizing the products with hydrogen peroxide or reducing the products with mercaptoethanol, with analysis by gas chromatography mass spectrometry. Based on mass changes, Dehydroascorbic Acid readily exchanged three oxygen atoms with H218O. When mercaptoethanol was used to reduce Dehydroascorbic Acid (which had been incubated in H218O) to ascorbic Acid, the newly formed ascorbic Acid also contained three labeled oxygen atoms. However, ascorbic Acid incubated in H218O for the same amount of time under identical conditions exchanged only two labeled oxygen atoms. Electron impact mass spectrometry of derivatized ascorbic Acid created a decarboxylation product which had only two labeled oxygen atoms, regardless if 3-oxygen-labeled or 2-oxygen-labeled ascorbic Acid was the parent compound, isolating the extra oxygen addition to carbon 1. These data suggest that Dehydroascorbic Acid spontaneously hydrolyzes and dehydrates in aqueous solution and that the hydrolytic-hydroxyl oxygen is accepted by carbon 1. Ascorbic Acid, on the other hand, does not show this same tendency to hydrolyze.
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Ascorbic Acid and Dehydroascorbic Acid Interconversion without Net Oxidation or Reduction
Analytical biochemistry, 1997Co-Authors: John C. DeutschAbstract:The interconversion of ascorbic Acid and Dehydroascorbic Acid was examined in aqueous solution using unlabeled Dehydroascorbic Acid and nonlabile, stable isotope-labeled ascorbic Acid by gas chromatographic/mass spectrometric analysis. Although the formation of unlabeled ascorbic Acid from unlabeled Dehydroascorbic Acid or labeled Dehydroascorbic Acid from labeled ascorbic Acid did not occur to any significant extent when either solutions of unlabeled Dehydroascorbic Acid or labeled ascorbic Acid were incubated alone, significant amounts of both labeled Dehydroascorbic Acid and unlabeled ascorbic Acid formed when unlabeled Dehydroascorbic Acid was incubated with labeled ascorbic Acid at Acid pH. At alkaline pH, interconversion did not occur to any appreciable extent. Likewise, interconversion did not appear to occur in plasma at physiologic concentrations of ascorbic Acid, but did occur with pharmacologic concentrations. These data show that ascorbic Acid and Dehydroascorbic Acid interconvert in Acidic solution, suggesting the reducing hydrogen atoms are delocalized when ascorbic Acid is paired with Dehydroascorbic Acid under these circumstances. Alkaline pH and plasma inhibit the interconversion.
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Dehydroascorbic Acid undergoes hydrolysis on solubilization which can be reversed with mercaptoethanol
Journal of Chromatography A, 1996Co-Authors: John C. Deutsch, C.r. Santhosh-kumarAbstract:Using gas chromatography-mass spectrometry, we have examined the effect of solubilization, cupric sulfate oxidation and mercaptoethanol reduction of Dehydroascorbic Acid. During solubilization, Dehydroascorbic Acid spontaneously hydrolyzed the lactone ring. The reduction of the Dehydroascorbic Acid hydrolysis product using mercaptoethanol resulted in the formation of ascorbic Acid, suggesting that sulfhydryls are able to effect ring closure of the Dehydroascorbic Acid hydrolysis product. These data suggest that studies of Dehydroascorbic Acid should be interpreted with caution, since properties attributed to Dehydroascorbic Acid may actually be due to another chemical species.