Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Dehydroascorbic Acid”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 937 records · Page 52Linked to original sources
PubMed2000

Phenylethylamine-induced generation of reactive oxygen species and ascorbate free radicals in tobacco suspension culture: mechanism for oxidative burst mediating Ca2+ influx.

In the previous paper [Kawano et al. (2000a) Plant Cell Physiol. 41: 1251], we demonstrated that addition of phenylethylamine (PEA) and benzylamine can induce an immediate and transient burst of active oxygen species (AOS) in tobacco suspension culture. Detected AOS include H2O2, superoxide anion and hydroxyl radicals. Use of several inhibitors suggested the presence of monoamine oxidase-like H2O2-generating activity in the cellular soluble fraction. It was also suggested that peroxidase(s) or copper amine oxidase(s) are involved in the extracellular superoxide production as a consequence of H2O2 production. Since more than 85% of the PEA-dependent AOS generating activity was localized in the extracellular space (extracellular fluid + cell wall), extracellularly secreted enzymes, probably peroxidases, may largely contribute to the oxidative burst induced by PEA. The PEA-induced AOS generation was also observed in the horseradish peroxidase (HRP) reaction mixture, supporting the hypothesis that peroxidases catalyze the oxidation of PEA leading to AOS generation. In addition to AOS production, we observed that PEA induced an increase in monodehydroascorbate radicals (MDA) in the cell suspension culture and in HRP reaction mixture using electron spin resonance spectroscopy and the newly invented MDA reductase-coupled method. Here we report that MDA production is an indicator of peroxidase-mediated generation of PEA radical species in tobacco suspension culture.

Amines↗
PubMed1987

Transport of vitamin C in the lens.

Mediated transport of dehydro-L-ascorbic acid (DAS) occurs in the mammalian ocular lens. At physiological pH, there is negligible cellular uptake of reduced L-ascorbate (AS). In the calf, inhibition by analogues and by cytochalasin B, and saturability with increasing concentration provide evidence of a transport-system for DAS, apparently by facilitated diffusion, since entry was independent of external Na+. The lenticular transporter for DAS evidently is interrelated with that for hexoses, as determined by kinetic studies and inhibition by analogues. Although the two ligands bind initially to separate sites, they probably permeate cellular membranes of this tissue via a common channel. Investigation of AS in the calf's lens over the range, pH 5.0-7.4, showed that uptake increased with increasing acidity in contrast to DAS and D-glucose, whose uptake decreased. This behavior of AS was attributed to back-titration of its enolic hydroxyl group to give the un-ionized moiety, which penetrated as readily as DAS under comparable able conditions, and apparently undergoes mediated transport.

2,3-Diketogulonic Acid↗
PubMed1986

Antiscorbutic effect of dehydro-L-ascorbic acid in vitamin C-deficient guinea pigs.

The antiscorbutic effect of dehydro-L-ascorbic acid (DAsA) was investigated in vitamin C-deficient guinea pigs. Male guinea pigs were fed vitamin C-deficient diets for 16 days to deplete body L-ascorbic acid (AsA) pools and then fed the deficient diet supplemented with DHA and/or AsA intraperitoneally for 14 days. During the repletion period, most of the animals injected with 0.5 mg DAsA/day developed scurvy, their body weights decreased and their mortality rate was higher than that of the other groups injected with 0.5 mg AsA/day or 5 mg DAsA/day. Injecting animals with 0.5 mg AsA/day resulted in the disappearance of the typical scorbutic symptoms and regaining of body weight. These data indicate that DAsA has considerably less antiscorbutic activity than AsA in vitamin C-deficient guinea pigs.

Adrenal Glands↗
PubMed2000

Effect of chemotherapy on ascorbate and ascorbyl radical in cerebrospinal fluid and serum of acute lymphoblastic leukemia.

Ascorbyl radical (ASR) in human cerebrospinal fluid (CSF) of various patients using electron paramagnetic resonance (EPR) at ambient temperature was investigated. Also, effect of chemotherapy on ASR as well as ascorbate (ASA) in CSF and serum of acute lymphoblastic leukemia (ALL) was studied. EPR spectra of various CSF samples showed a characteristic doublet, which was attributed to ASR. ASR in CSF and serum was directly measured without any chemical modification. ASA and ASR concentration in CSF were approximately two times higher than those in serum. ASA and ASR concentrations in CSF and serum were statistically analyzed. The analyses showed that ASR and ASA in CSF and serum had good correlation for patients undergoing chemotherapy but not for patients after the therapy. The correlation for ASR and ASA suggests that ascorbate may play an important role during chemotherapy. In addition, dynamic aspects of ASA and ASR in CSF and serum are discussed.

Adolescent↗
PubMed1986

Mechanism of the inhibition of catalase by ascorbate. Roles of active oxygen species, copper and semidehydroascorbate.

Ascorbate reversibly inhibits catalase, and this inhibition is enhanced and rendered irreversible by the prior addition of copper(II)-bishistidine. In the absence of copper, the inhibition was prevented and reversed by ethanol, but not by superoxide dismutase, benzoate, mannitol, thiourea, desferrioxamine, or DETAPAC. In the presence of the copper complex mannitol, benzoate, and superoxide dismutase still had no effect, but thiourea, desferrioxamine, DETAPAC, or additional histidine decreased the extent of inactivation to that seen in the absence of copper. In the presence of copper, ethanol protected at [ascorbate] less than 1 mM, but was ineffective at [ascorbate] greater than 2 mM, even in the absence of oxygen. Although in the absence of copper, complete removal of oxygen provided full protection against inactivation by ascorbate, this protection was not seen if the catalase was briefly preincubated with H2O2 prior to flushing with nitrogen, or if copper was present. In fact, if copper was present, inactivation was enhanced by the removal of oxygen. Increasing the concentration of oxygen from ambient to 100% slowed the inactivation, whether or not copper was present. It is concluded that the initial reversible inactivation involves reaction with H2O2 to form compound I, followed by one electron reduction of compound I to compound II. In the presence of added copper, the initial (reversible) inactivation allows H2O2 to accumulate sufficiently to permit irreversible inactivation. Since in the presence of copper oxygen is not required, and neither the reversible nor the irreversible inactivation was prevented by conventional scavengers of active forms of oxygen, the inactivation is likely mediated by semidehydroascorbate, and/or it may involve site-specific generation of the damaging intermediates.

Animals↗
PubMed1984

Structure of ascorbic acid and its biological function. I. ESR determination of the ascorbyl radical in biological samples and in model systems.

ESR investigations on lyophilized systems have shown that the signal at g = 2.005 can be explained by an interaction between Na+ or K+ and the anionic ascorbyl radical. The unpaired electron is probably localized near the C(4) region and is produced by a cleavage of an H atom belonging to a water molecule bound tightly to C(4). Experiments on aqueous samples revealed that ascorbic acid in its radical configuration and in its highest concentration exists only at physiological pH and temperature. An additional splitting is obtained by the ring formation between C(3) and C(6)-OH. The coupling constants of the triplets produced by the CH2-6 protons differ between ascorbic acid and isoascorbic acid. Thus, the ESR technique can be applied for an easy distinction between these two epimers.

Ascorbic Acid↗
PubMed1981

Dietary selenium and levels of L-ascorbic acid in the plasma, livers, and lungs of polychlorinated biphenyls-treated rats.

Administration of polychlorinated biphenyls (PCB) (500 mg Aroclor, 1254/kg body weight) intraperitoneally significantly increased the levels of L-ascorbic acid in the plasma and livers, but not in the lungs of one-month-old male rats maintained on a basal low selenium diet with or without 2.0 ppm selenium (as sodium selenite) supplementation for 19 weeks prior to PCB treatment. The levels of L-ascorbic acid were not significantly altered by dietary selenium. In another experiment, 40 days or 15-month-old male rats were fed the same basal selenium diet with or without 1.0 ppm selenium for 1 month prior to PCB treatment. The plasma levels of ascorbic acid were found to increase significantly by PCB treatment, but not by the status of dietary selenium or by animal age. As expected, the activity of selenium dependent glutathione peroxidase was markedly decreased in the plasma, livers, and lungs of rats fed the low selenium diet. However, the enzyme activity was not significantly altered by PCB treatment in plasma, livers, and lungs of animals in both dietary groups.

Animals↗
PubMedDate not supplied

Blood preservation XLIV. 2,3-DPG maintenance by dehydroascorbate better than D-ascorbic acid.

A study was designed to compare the effects of D-ascorbate and dehydroascorbate on red blood cell metabolism during blood storage. Dehydroascorbate increased red blood cell concentrations of 2,3-DPG such that the levels are above normal for four weeks and normal at six weeks of storage. In contrast, there is a gradual decrease in 2,3-DPG levels with D-ascorbate such that the levels are approximately 80 per cent of normal after six weeks. ATP levels were adversely effected such that the worst levels were produced by 10 and 5 mM dehydroascorbate, with 10 mM having a more adversive effect than 5 mM. Intermediate levels of ATP were produced by D-ascorbate, with the 10 mM concentration. The control CPD-adenine preservative maintained near normal ATP levels for the entire six-week storage period. pH values were initially slightly lower with dehydroascorbate compared to the other preservatives early in storage, the difference being slightly over 0.1 pH units.

Ascorbic Acid↗
PubMed1986

Antioxidants in plasma from mice infected with Plasmodium vinckei.

The late stage of infection of mice with the malarial parasite Plasmodium vinckei was accompanied by significant changes in the content of most antioxidants within plasma. The plasma concentrations of uric acid and vitamin C increased, in contrast to those of vitamin E and total plasma proteins, whilst the activity of superoxide dismutase did not change significantly. In contrast to the situation within erythrocytes, the ratio of partly oxidized forms of vitamin C (dehydroascorbate and diketogulonic acid) to reduced ascorbic acid failed to decrease as a result of malarial infection. These results are consistent with earlier findings and add to the idea that malarial infection may result in oxidative tissue damage.

Animals↗
PubMedDate not supplied

Safety and tolerance of ester-C compared with regular ascorbic acid.

The goal of this randomized, double-blind crossover clinical trial in 50 healthy volunteers sensitive to acidic foods was to evaluate whether Ester-C calcium ascorbate causes fewer epigastric adverse effects than are produced by regular ascorbic acid (AA). Volunteers were randomly separated into 2 groups of 25. The study comprised an observation period of 9 days (phase 1 medication for 3 consecutive days, washout phase for 3 consecutive days, phase 2 medication for 3 consecutive days). Participants took 1000 mg vitamin C as Ester-C during phase 1 of the study followed by 1000 mg of vitamin C as AA during phase 2, or vice versa. During the course of the study, 3 examinations for the evaluation of epigastric adverse effects were performed (on days 0, 3, and 9). Participants used a diary to record epigastric adverse effects on a daily basis. In total, 28 (56%) of 50 participants reported 88 epigastric adverse effects of mild to moderate intensity. Of these 88 adverse effects, 33 (37.5%) occurred after intake of Ester-C and 55 (62.5%) were noted after intake of AA. The tolerability of Ester-C was rated "very good" by 72% of participants, whereas AA was rated "very good" by only 54%. This difference is statistically significant (P<.05). Investigators concluded that Ester-C compared with AA caused significantly fewer epigastric adverse effects in participants sensitive to acidic foods and that Ester-C is much better tolerated.

Adult↗
PubMed1994

Generation of thiyl and ascorbyl radicals in the reaction of peroxynitrite with thiols and ascorbate at physiological pH.

Electron spin resonance (ESR) spin trapping was utilized to investigate the reaction of peroxynitrite with thiols and ascorbate at physiological pH. The spin trap used was 5,5-dimethyl-1-pyrroline N-oxide (DMPO). The reaction of peroxynitrite with DMPO generated 5,5-dimethylpyrrolidone-(2)-oxy-(1) (DMPOX). Formate enhanced the peroxynitrite decomposition but did not generate any detectable amount of formate-derived free radicals. Thus, the spin trapping measurements provided no evidence for hydroxyl (.OH) radical generation in peroxynitrite decomposition at physiological pH. Thiols (glutathione, cysteine, and penicillamine) and ascorbate reacted with peroxynitrite to generate the corresponding thiyl and ascorbyl radicals. The one-electron oxidation of thiols by peroxynitrite may be one of the important mechanisms for peroxynitrite-induced toxicity and ascorbate may provide a detoxification pathway.

Ascorbic Acid↗
PubMed1994

Ascorbyl radical as natural indicator of oxidative stress: quantitative regularities.

The intensity of ESR spectrum associated with ascorbyl free radical (A.) was found to be sensitive to various pathologies and intoxications connected with oxidative stress. For this reason, A. has been suggested to be used as a natural noninvasive ESR indicator of oxidative stress. To specify factors controlling [A.] in biological tissues, the kinetic study of ascorbic acid (AH) oxidation in aqueous solutions catalyzed by Fe ions and methylene blue (MB) has been performed by using ESR and Clark electrode techniques. Concentration, temperature, and pH dependences of [A.] and rate of AH oxidation (R(ox)), effects of additives of biological importance (glutathione, uric acid, proteins, glucose, lipid) as well as that of Na dodecylsulfate (SDS) have been studied. The oxidation of 1 mol of AH is accompanied by the consumption of 1 mol of O2 and the generation of 1 mol of A.. [A.] has been found to be proportional to the square root of R(ox), no matter what reason is for R(ox) variation. A. has been shown to be inactive toward all substances tested and free radicals other than A.. It has been concluded that A. decays in biological tissues mostly by self-disproportionation, a value of [A.] gives the definitive quantitative information on the total rate of AH oxidative transformations (oxidation by O2 plus reactions with free radicals). SDS shows the retarding effect on AH oxidation induced by MB.

Ascorbic Acid↗