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PubMed2006

DNA/Poly(p-aminobenzensulfonic acid) composite bi-layer modified glassy carbon electrode for determination of dopamine and uric acid under coexistence of ascorbic acid.

A nano-composite of DNA/poly(p-aminobenzensulfonic acid) bi-layer modified glassy carbon electrode as a biosensor was fabricated by electro-deposition method. The DNA layer was electrochemically deposited on the top of electropolymerized layer of poly(p-aminobenzensulfonic acid) (Pp-ABSA). Scanning electron microscopy, X-ray photoelectron spectroscopy and electrochemical impedance spectrum were used for characterization. It demonstrated that the deposited Pp-ABSA formed a 2-D fractal patterned nano-structure on the electrode surface, and which was further covered by a uniform thin DNA layer. Cyclic voltammetry and electrochemical impedance spectrum were used to characterize the deposition, and demonstrated the conductivity of the Pp-ABSA layer. The biosensor was applied to the detection of dopamine (DA) and uric acid (UA) in the presence of ascorbic acid (AA). In comparison with DNA and Pp-ABSA single layer modified electrodes, the composite bi-layer modification provided superior electrocatalytic actively towards the oxidation of DA, UA and AA, and separated the originally overlapped differential pulse voltammetric signals of UA, DA and AA oxidation at the bare electrode into three well-defined peaks at pH 7 solution. The peak separation between AA and DA, AA and UA was 176 mV and 312 mV, respectively. In the presence of 1.0 mM AA, the anodic peak current was a linear function of the concentration of DA in the range 0.19-13 microM. The detection limit was 88 nM DA (s/n=3). The anodic peak current of UA was also a linear function of concentration in the range 0.4-23 microM with a detection limit of 0.19 microM in the presence of 0.5 mM AA. The superior sensing ability was attributed to the composite nano-structure. An interaction mechanism was proposed.

Ascorbic Acid↗
PubMed1982

Specific spectrophotometry of ascorbic acid in serum or plasma by use of ascorbate oxidase.

We describe a specific enzymatic spectrophotometric method for ascorbic acid in serum or plasma. Samples are analyzed indirectly by measuring the absorbance at 593 nm of a reaction product, a complex of ferrous ion and 2,4,6-tris(2-pyridyl)-s-triazine (Fe2+-TPTZ). This product is formed by reduction of the corresponding ferric ion complex (Fe3+-TPTZ), which is nonspecifically reduced by various biological reducing agents under acidic conditions. Ascorbic acid is specifically quantified by pretreating one of a pair of replicate samples with ascorbate oxidase (EC 1.10.3.3), to oxidize the ascorbic acid, then reacting both samples with Fe3+-TPTZ and measuring the difference between the absorbances at 593 nm of the treated and untreated samples. This difference is linearly related to ascorbic acid concentrations from 10 to 100 mg/L. Ten repeat determinations of a serum pool with added ascorbic acid yielded a CV of 2.8% and a mean of 47.2 mg/L. The correlation (r) between the proposed method and the dinitrophenylhydrazine method was 0.93 for 32 samples analyzed by both methods. The present method is specific for ascorbic acid and requires no deproteinization.

Ascorbate Oxidase↗
PubMed1993

Relationship between lipid peroxidation, fatty acid composition, and ascorbic acid in the liver during carbohydrate and caloric restriction in mice.

Growing OF1 mice were treated on a short-term basis with ad libitum, caloric-restricted, or carbohydrate-restricted diets, maintaining the same intake of vitamins and minerals in the three groups. Caloric intake was 60% of controls both in the caloric-restricted and in the carbohydrate-restricted groups. Neither global nor carbohydrate restriction changed liver superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, cytochrome oxidase, GSH, uric acid, or malondialdehyde (HPLC). Ascorbate was decreased in both restricted groups. Carbohydrate restriction, but not caloric restriction, increased unsaturation indexes of fatty acids in all lipid classes analyzed and increased sensitivity to peroxidation by one order of magnitude. It is concluded that short-term caloric restriction does not seem to increase antioxidants and decrease peroxidation in the mouse liver whereas long-term restriction can avoid decreases of antioxidants and increases of peroxidation during aging. Our experiments support the prevailing view that the caloric restriction phenomenon is due to a reduction in calories themselves instead of to a reduction in carbohydrates. This last manipulation strongly increases sensitivity to peroxidative damage in the liver. The results show that in vivo fatty acid unsaturation is a main factor in determining the sensitivity to lipid peroxidation.

Animals↗
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↗
PubMed2003

Impaired adrenal catecholamine system function in mice with deficiency of the ascorbic acid transporter (SVCT2).

Ascorbic acid (vitamin C) is a cofactor required in catecholamine synthesis for conversion of dopamine to norepinephrine by dopamine beta-hydroxylase. Mutant mice lacking the plasma membrane ascorbic acid transporter (SVCT2) have severely reduced tissue levels of ascorbic acid and die after birth. We therefore investigated whether these mice might have impaired synthesis of catecholamines. Levels of catecholamines in brain were unaffected by SVCT2 deficiency. In heart, the only evidence for impaired dopamine beta-hydroxylase activity was a twofold increase in tissue dopamine. An influence of the deficiency on tissue catecholamines was most prominent in the adrenals where norepinephrine was decreased by 50% and epinephrine, by 81%. On the ultrastructural level, adrenal chromaffin cells in SVCT2 null mice showed depletion of catecholamine storage vesicles, increased amounts of rough endoplasmic reticulum, signs of apoptosis, and increased glycogen storage. Decreased plasma levels of corticosterone indicated additional effects of the deficiency on adrenal cortical function. These data show that deranged catecholamine system function in SVCT2 null mice is largely restricted to the adrenal medulla and cannot account for the lethality in these animals. The data, however, establish a crucial role for ascorbic acid in adrenal chromaffin cell function.

Adrenal Glands↗
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↗