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PubMed1987

Rapid and sensitive determination of dehydroascorbic acid in addition to ascorbic acid by reversed-phase high-performance liquid chromatography using a post-column reduction system.

An improved procedure for the direct determination of l-dehydroascorbic acid (DHAA), in addition to l-ascorbic acid (AA), has been developed. The two biologically active forms of vitamin C were separated using reversed-phase high-performance liquid chromatography. DHAA was reduced to AA with dithiothreitol (DTT) in a post-column reaction system. Complete conversion was achieved at 50 degrees C using a 1-ml reaction coil. Recoveries were in the range of 95-99% and both forms could be detected spectrophotometrically at 267 nm with high sensitivity. Reproducible results [relative standard deviations 2.4% (DHAA) and 1.0% (AA), n = 5] were obtained when the method was applied to the analysis of rose hip samples.

Ascorbic Acid↗
PubMed1979

Effects of ascorbate on leucocytes: Part II. Effects of ascorbic acid and calcium and sodium ascorbate on neutrophil phagocytosis and post-phagocytic metabolic activity.

The effects of ascorbic acid and calcium and sodium ascorbate at a concentration range of 10(-6)M - 10(-1)M on polymorphonuclear leucocyte (PMN) phagocytosis of Candida albicans and post-phagocytic nitroblue tetrazolium (NBT) reduction, hexose monophosphate shunt (HMS) activity and myeloperoxidase-mediated iodination of ingested protein were investigated. Phagocytosis of C. albicans was unaffected by ascorbate concentrations of 10(-6)M - 10(-2)M; however, progressive inhibition was observed at concentrations of 10(-2)M upwards. Enhancement of resting and stimulated HMS activity and NBT reduction was evident at ascorbate concentrations of 10(-5) M - 10(-2)M. The stimulations of HMS activity and NBT reduction was independent of myeloperoxidase iodination of ingested protein and this latter function was strongly inhibited by ascorbate. Concentrations of ascorbic acid and calcium and sodium ascorbate which caused inhibition of phagocytosis and HMS activity were the same as those which mediated stimulation of cell motility, indicating that independent cellular mechanisms may govern motility and phagocytosis.

Ascorbic Acid↗
PubMed1994

Effect of Helicobacter pylori and its eradication on gastric juice ascorbic acid.

The presence of ascorbic acid in gastric juice may protect against gastric carcinoma and peptic ulceration. This study examined the effect of Helicobacter pylori (H pylori) on the secretion of ascorbic acid into gastric juice by measuring fasting plasma and gastric juice ascorbic acid concentrations in patients with and without the infection and also before and after its eradication. Gastric juice ascorbic acid concentrations in 19 H pylori positive patients were significantly lower (median 2.8, range 0-28.8 micrograms/ml) than those in 10 H pylori negative controls (median 17.8, range 5.6-155.4 micrograms/ml) (p < 0.0005) despite similar plasma ascorbic acid concentrations in both groups. The median gastric juice:plasma ascorbic acid ratio in the H pylori positive patients was only 1.16 (range 0.02-6.67), compared with a median ratio of 4.87 (range 0.76-21.33) in H pylori negative controls (p < 0.01). In the patients with H pylori infection there was a significant negative correlation between the severity of the antral polymorphonuclear infiltrate and gastric juice ascorbic acid concentrations (correlation coefficient -0.52, p = 0.02). After eradication of H pylori in 11 patients, gastric juice ascorbic acid concentrations rose from 2.4 (0-12.8 micrograms/ml) to 11.2 (0-50 micrograms/ml) (p = 0.01). The median gastric juice: plasma ascorbic acid ratio also increased from 1.33 (0.05-6.67) to 2.89 (0.01-166) (p = 0.01). In conclusion, the high gastric juice:plasma ascorbic acid ratio in H pylori negative subjects shows active secretion of ascorbic acid into gastric juice. Secondly, H pylori infection causes a reversible lowering of gastric juice ascorbic acid concentrations, which may predispose to gastric carcinoma and peptic ulceration.

Ascorbic Acid↗
PubMed1994

[The concentration of ascorbic acid, glucose and cortisol in the blood plasma of sheep and the excretion of ascorbic acid in the urine after i.v. administration of the compound].

In lambs, adult female sheep and wethers the influence of the intravenous injection of ascorbic acid (AA) in a dose of 10, 20 or 30 mg/kg body weight (b.w.) on the concentration of AA in the plasma up to 420 minutes thereafter was analysed. Further the concentration of glucose respectively of cortisol in the plasma was determined in some experiments. The results can be used as a basis for investigations in sheep with infectious and parasitic diseases for the determination of the degree of the saturation of the body with AA. For therapeutic purposes the repeated application of a dose of 20 mg AA/kg b.w. is recommended. In wethers a dose dependent excretion of AA in the urine after an i.v. injection of a dose of 10, 20 or 30 mg/kg b.w. was observed. The injection of ACTH, cortisol, adrenaline and noradrenaline had no substantial influence on the concentration of AA in the plasma. In the course of 24 hours there was no alteration in the concentration of AA in the plasma.

Animals↗
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↗
PubMed1995

Investigation of Helicobacter pylori ascorbic acid oxidating activity.

Helicobacter pylori sonicate was shown to oxidize ascorbic acid. Ascorbic acid oxidation was determined by chromatography combined with electrochemical detection. Water soluble ascorbic acid oxidase activity was rather independent of pH with a pH optimum around 2. By gel filtration the oxidizing activity co-eluted with an absorbency peak at 408 nm. The relative molecular mass (Mr) was approximately 14,000. It is suggested that this oxidating activity was caused by a cytochrome c-like molecule. Ascorbic acid oxidating activity could also be extracted from bacterial membranes by detergents. Gel filtration showed several forms, the major one with a Mr = 19,000. pH optimum was 6-7. Other oxidase-positive bacterial strains like Campylobacter coli, Enterobacter cloacae and Pseudomonas aeruginosa could degrade ascorbic acid. Since ascorbic acid oxidation by Helicobacter pylori whole bacterial lysates has a pH optimum in the acidic range corresponding to pH in gastric fluid, the activity of the cytochrome c-like water soluble oxidant of Helicobacter pylori seems to be primarily important for the destruction of ascorbic acid in the gastric juice of infected patients.

Ascorbic Acid↗
PubMed1980

Effect of platelets on apparent leucocyte ascorbic acid content.

The leucocyte ascorbic acid content is widely used as a measure of tissue ascorbic acid status. Standard methods of analysis, however, isolate both leucocytes and platelets (buffy layer), with consequent overestimation, since platelet ascorbic acid is attributed to the leucocytes. Fourteen healthy individuals on ascorbic acid supplements and 11 patients on mega dose ascorbic acid therapy were studied. A significant correlation was demonstrated between the 'leucocyte' ascorbic acid content and the platelet: leucocyte ratio (r = 0.70, P < 0.001). It is suggested that changes in the relative distribution of platelets and leucocytes in the blood will result in an apparent change in the 'leucocyte' ascorbic acid content regardless of any actual change in the ascorbic acid content of the cells.

Adult↗
PubMed1982

Studies on the excretion of ascorbic acid 2-sulfate and total vitamin C into human urine after oral administration of ascorbic acid 2-sulfate.

The excretion of AsS and total vitamin C into urine after oral administration of AsS to humans was investigated. When 10 mmol of AsS was administered to the subjects, the excretion of AsS into urine continued for 60 hr in males and 48 hr in females. The average amount excreted per hour was less than 5 mg. These results differed from those for AsA and DAsA orally administered to humans. The determination of vitamin C after oral administration of AsS to the subjects consisting of ten males and six females showed no vitamin C effect in humans, similarly to the case with the guinea pig and the rhesus monkey.

Adolescent↗
PubMed1993

[The concentration of ascorbic acid, total protein, alpha-amino-N, glucose, 3-hydroxybutyrate and cholesterol and the activity of adenosine deaminase in the blood of sheep in five different periods of pregnancy and the content of ascorbic acid in 14 tissues].

Analyses of different compounds in the plasma of healthy sheep before birth were conducted from day 70 to 43 (group 1), 42 to 22 (group 2), 21 to 15 (group 3), 14 to 8 (group 4) and 7 to 1 (group 5). There were significant differences in the concentration of ascorbic acid, total protein, total alpha-Amino-N, glucose, 3-hydroxybutyrate and of adenosine deaminase in the plasma between several groups, their significance is discussed. There was no difference in the concentration of cholesterol in the plasma of the sheep of the 5 groups. The content of ascorbic acid in 14 different tissues of sheep of the age of 6 and 12 months was analysed. There were significant differences between the 2 groups in the levels of ascorbic acid of the cerebrum and cerebellum, the hypophysis, the lungs, the kidneys and the spleen.

Animals↗
PubMed1989

Ascorbic acid: a factor concentrated in human gastric juice.

1. Concentrations of ascorbic acid (ascorbic and dehydro-ascorbic; A + D; measured by the 2,4-dinitrophenylhydrazine method) of nearly three times those of plasma are present in gastric juice samples from patients with normal gastric histology. 2. A significant reduction in gastric juice ascorbic acid (A + D) was observed in patients with chronic gastritis. This reduction in concentration was independent of the grade of gastritis. 3. Concentrations of ascorbic acid (A + D) in gastric biopsy specimens were consistently higher in the antrum than in the body of the stomach. 4. These data demonstrate that considerable quantities of ascorbic acid (A + D) are normally 'secreted' into the stomach. 5. Ascorbic acid (ascorbic only; A; measured by h.p.l.c.) was present predominantly in its biologically active form in the patients with normal gastric histology. However, in patients with gastritis, independent of grade, ascorbic acid was present predominantly in its oxidized, biologically inactive form.

Adult↗
PubMed1983

Effect of amino acids, peptides and related compounds on the autooxidation of ascorbic acid.

The autooxidation rate of ascorbic acid (AA) at 10(-5) M under aerobic conditions at pH 7.4 was found to be 1.16 mumol/min/l. A number of compounds at low concentrations were found to inhibit this oxidation rate. These were in order of effectiveness: EDTA (10(-6) M) greater than Mercaptoethanol greater than aminoethyl cysteine, oxidized glutathione greater than glycylglycylhistidine greater than glycylhistidyllysine greater than 3-methyl histidine approximately histidine greater than histamine greater than hypertensin greater than cysteic acid greater than imidazole greater than glutamine greater than hydroxyproline, and lysine. All other amino acids and peptides examined had little or no effect on the autooxidation rate of ascorbic acid. Ascorbate solutions, treated with Chelex-100 (divalent chelating resin) or containing low concentrations of EDTA (10(-7) M) did not show a significant reduction of the rate of autooxidation. Of particular interest was the finding that 3-methyl histidine had a significant inhibitory effect on ascorbic acid oxidation whereas 1-methyl histidine had no effect. These data suggest that ascorbic acid forms complexes with certain compounds and that this interaction stabilizes ascorbic acid against auto-oxidation.

Amino Acids↗