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PubMed1999

A rapid and selective solid-phase UV spectrophotometric method for determination of ascorbic acid in pharmaceutical preparations and urine.

Ascorbic acid was determined by a solid-phase UV spectrophotometry technique through the sorption of this on a dextran-type anion-exchange resin, Sephadex QAE A-25 and posterior direct measurement of its absorbance on the resin at 267 and 400 nm, packed in a 1-mm cell. The calibration graph was linear over the range 0.3-5.0 microg ml(-1). The sensitivity obtained is more than 50 times higher than that of the corresponding solution method. The detection limit was 0.05 microg ml(-1) and the relative standard deviation 0.74% (n = 10). This method is very rapid and highly selective for determining ascorbic acid in the presence of other species absorbing in the ultraviolet region and which are normally encountered with it. The one-step method proposed was successfully applied in the determination of ascorbic acid in pharmaceutical preparations and urine and the results were of comparable accuracy as indicated by a statistical analysis of the data, using both t- and F-tests.

Ascorbic Acid↗
PubMed1983

Fertility control in vas occluded rats and the biochemical effects of ascorbic acid feeding.

A new approach to rapid male sterilization has been studied by giving a single injection of 95% ethanol directly into the vas deferens. It produced an effective block in the lumen. The mating exposure test showed that the males were sterile. Vas occlusion caused an atrophy of the Cauda epididymis. Extensive necrosis and exfoliation of the seminiferous elements were conspicuous. Reduced succinate dehydrogenase, acid phosphatase, vesicular fructose and altered ascorbate turnover pattern could be restored to normal by simultaneous ascorbic acid feeding. In conclusion ascorbic acid feeding plays a definite beneficial role in vas occluded rats. The antiandrogenic effects of vas occlusion could be reversed by simultaneous ascorbic acid feeding.

Acid Phosphatase↗
PubMedDate not supplied

Concentrations of catecholamines, ascorbic acid, progesterone and oxytocin in the corpora lutea of cyclic and pregnant cattle.

To determine if there are inter-relationships between progesterone, oxytocin (OT), dopamine (DA), noradrenaline (NA) and ascorbic acid, these compounds were measured in the corpus luteum (CL) from cattle at different stages of the oestrous cycle (n = 42) and from 1-5 months of pregnancy (n = 27). They were measured by radioimmunoassay (RIA), high performance liquid chromatography (HPLC) and colorimetric methods. Corpora lutea were collected from heifers and cows within 30 min of slaughter on days 1-5, 6-10, 11-16 and 17-21 of the oestrous cycle. The stage of pregnancy was determined on the basis of foetal size and development. Each CL was divided into four parts and stored in liquid nitrogen. For hormone estimation, the tissue was homogenised/powdered and suspended in phosphate buffer (for OT and progesterone), 0.1 M trichloracetic acid (TCA; for catecholamines) or in ice-cold metaphosphoric acid (for ascorbic acid). There were no significant differences in the measured parameters between cows and heifers, and so the data were combined. The concentration of DA was correlated with NA (r = 0.66; P < 0.001) during the oestrous cycle and was highest in newly formed CL (P < 0.01) as compared with early CL, regressed CL and CL of pregnant females. NA was negatively correlated (P < 0.01) with progesterone (r = -0.53) and OT (r = -0.41). In contrast, progesterone and OT were positively correlated with each other (r = 0.81; P < 0.01) during all stages of the oestrous cycle, but not during pregnancy. The lowest concentrations of ascorbic acid were observed in regressed CL. Ascorbic acid concentrations were correlated (P < 0.01) with those of progesterone (r = 0.68), OT (r = 0.42) and DA (r = -0.37). Luteal concentrations of ascorbic acid, progesterone and OT followed a pattern consistent with the development and regression of the CL. Luteal concentrations of catecholamines were not consistent with this pattern.

Animals↗
PubMed1993

Effect of L-ascorbic acid on the monophenolase activity of tyrosinase.

The effect of ascorbic acid on the monophenolase activity of tyrosinase, using tyrosine as substrate, has been studied. Over the ranges of ascorbic acid concentration used, no direct effect on the enzyme is found. However, a shortening of the characteristic induction period of the hydroxylation reaction is observed. The evolution of the reaction is dependent on the concentration of ascorbic acid. Low concentrations permit the system to reach the steady state when all ascorbic acid is consumed, whereas high concentrations do not. In the light of these results it is proposed that the influence of ascorbic acid on the reaction is due to its ability to reduce the enzymically generated o-quinones. A relationship between the ascorbic acid concentration, and the induction period generated by it, with the diphenolase activity of tyrosinase is established, which can be used as a basis for the determination of trace amounts of this reducing agent.

Ascorbic Acid↗
PubMed2001

Relation of ascorbic acid to bone mineral density and self-reported fractures among US adults.

Ascorbic acid is an essential nutrient involved in collagen formation, and its deficiency is associated with abnormal bone development. To examine the relation of ascorbic acid to bone mineral density and the prevalence of self-reported fractures, the authors analyzed data collected from 13,080 adults enrolled in the Third National Health and Nutrition Examination Survey (NHANES III) during 1988-1994. Because they identified three-way interactions among smoking, history of estrogen use, and dietary and serum ascorbic acid in postmenopausal women, they analyzed these relations stratified by smoking and estrogen use. Dietary ascorbic acid intake was independently associated with bone mineral density among premenopausal women (p = 0.002). Among men, serum ascorbic acid was associated in a nonlinear fashion with bone mineral density (p < 0.05), and dietary ascorbic acid intake was associated in a nonlinear fashion with self-reported fracture (p = 0.05). Among postmenopausal women without a history of smoking or estrogen use, serum ascorbic acid was unexpectedly associated with lower bone mineral density (p = 0.01). However, among postmenopausal women with a history of smoking and estrogen use, a standard deviation increase in serum ascorbic acid was associated with a 49% decrease in fracture prevalence (p = 0.001). Dietary and serum ascorbic acid measures were associated inconsistently with bone mineral density and self-reported fracture among adult participants in NHANES III.

Adult↗
PubMed1996

An automated, specific, spectrophotometric method for measuring ascorbic acid in plasma (EFTSA).

OBJECTIVE: To evaluate an automated enzyme linked, ferric-tripyridyltriazine spectrophotometric assay (EFTSA) for plasma ascorbic acid. DESIGN AND METHODS: Using aqueous ascorbic acid solutions and plasma containing native and/or added ascorbic acid, the following were assessed: reaction kinetics, dose response relationships, recovery of added ascorbic acid, specificity, precision. RESULTS: Performing the test on a Cobas Fara centrifugal analyser, the test is linear at least to 400 micromol/L; within-run CVs at 20, 50, 140, and 300 micromol/L ascorbic acid, in both pure aqueous solutions and in plasma, were <5.5%; 99-105% of added ascorbic acid (from 30-130 micromol/L) was recovered. The reaction of ascorbic acid is virtually instantaneous; other native antioxidants do not appear to interfere, and there is no interference by dehydroascorbic acid when readings are taken within a 15-60-s reaction time window. CONCLUSION: EFTSA appears suitable for the routine measurement of ascorbic acid in plasma.

Adult↗
PubMed1996

Stopped-flow kinetic investigation of the oxidation of ascorbic acid by iron (III) benzohydroxamic acid.

The fast oxidation of ascorbic acid by Fe(III)benzohydroxamic acid complex [Fe(BHA)3] has been investigated by the stopped-flow technique in aqueous ethanol medium at three pH values (4.6, 7.0, and 9.0). The reaction exhibits a first-order dependence of rate each on [ascorbic acid] and [Fe(BHA)3], obeying Michaelis-Menton kinetics. The rate of the reaction was found to be pH-dependent.

Ascorbic Acid↗
PubMed1978

Reassessment of changes in leucocyte and serum ascorbic acid after acute myocardial infarction.

After an acute myocardial infarction, there is an apparent acute fall in leucocyte ascorbic acid associated with an acute rise in white blood cells and serum cortisol. The apparent fall in leucocyte ascorbic acid is the result of the granulocytosis which occurs after the infarction. Estimations of ascorbic acid disclose that the granulocyte contains approximately half the ascorbic acid of the lymphocyte. When the granulocytosis subsides, the new population of white blood cells is depleted of ascorbic acid for at least 56 days, reflecting tissue desaturation which can be corrected by ascorbic acid supplements. Tissue desaturation is also reflected in subnormal serum ascorbic acid levels which persist also unless ascorbic acid supplements are given. Observations on normal subjects given infusions of tetracosactrin (Synacthen) show that adrenal stimulation can produce a similar rise in white blood cells and an apparent fall in leucocyte ascorbic acid concentration with the exception that the serum ascorbic acid remains unaltered. Therefore, while adrenal stimulation can mimic 'stress' with regard to the changes in the white blood cells, tissue depletion of ascorbic acid as reflected in the white blood cells and serum after a myocardial infarction requires a focus of damaged tissue.

Adrenal Glands↗
PubMed2001

[Biological role of reactions of L-ascorbic acid with metals].

L-ascorbic acid (H2Asc) is one of the basic vitamins, necessary to the normal growth and behaviour of organisms. The primary goal of this review is to present the chemical characteristics of this substance and to discussed its relation to various biological functions of vitamin C, mainly as a free radical scavenger. In presented work author analysed of same metals Cu(II), Zn(II), Cd(II), Hg(II), Pb(II) with L-ascorbic acid, showing preventive activity of vitamin C at exposure on metals.

Animals↗
PubMed2000

Ascorbic acid secretion in the human stomach and the effect of gastrin.

AIM:To investigate the changes of gastric mucosal ascorbic acid secretion in patients with nonulcer dyspepsia and the effect of gastrin on it, and to relate any observed changes to H.pylori infection and mucosal histology.METHODS:Ascorbic acid secretions in patients were examined by collecting continuously gastric juice for one hour after having aspirated and discarded fasting gastric juice. Using the clearance rate (mL/min) of ascorbic acid from blood to gastric juice represented ascorbic acid secretion in the gastric mucosa.Ascorbic acid concentrations in plasma and juice were measured by ferric reduced method.RESULTS:Gastric ascorbic acid secretions in H.pylori-positive patients (1.46mL/min,range 0.27-3.78) did not significantly differ from those in H.pylori-negative patients(1.25mL/min, 0.47-3.14)(P>0.05). There were no significant differences in ascorbic acid secretions between patients with mild (1.56mL/min, 0.50-3.30), moderate (1.34mL/min, 0.27-2.93) and severe (1.36mL/min, 0.47-3.78) inflammation (P >0.05). There were no significant differences in ascorbic acid secretions between patients without activity (1.45mL/min, 0.27-3.14) and with mild (1.32mL/min, 0.61-2.93), moderate (1.49mL/min, 0.50-3.78) and severe (1.43mL/min, 0.51-3.26) activity of chronic gastritis either (P>0.05). Ascorbic acid secretions in patients with severe atrophy (0.56mL/min, 0.27-1.20) were markedly lower than those in patients without atrophy (1.51mL/min, 0.59-3.30) and with mild (1.43mL/min, 0.53-3.78) and moderate (1.31mL/min,0.47-3.16)atrophy(P<0.005). There was a significant negative correlation between ascorbic acid secretion and severity of atrophy (correlation coefficient =-0.43, P<0.005). After administration of pentagastrin, ascorbic acid secretions were markedly elevated (from 1.39mL/min, 0.36-2.96 to 3.53mL/min, 0.84-5.91) (P <0.001).CONCLUSION:Ascorbic acid secretion in gastric mucosa is not affected by H.pylori infection. Gastric ascorbic acid secretion is markedly related to the severity of atrophy, whereas not related to the severity of inflammation and activity. Gastrin may stimulate gastric ascorbic acid secretion. A decreased ascorbic acid secretion may be an important factor in the link between atrophic gastritis and gastric carcinogenesis.

Journal Article↗
PubMed1987

Ascorbic acid: the concept of optimum requirements.

Experiments with enzymes in situ that are dependent on ascorbic acid for maximum activity will provide critical information about ascorbic acid requirements. Our work with chromaffin tissue as a model system eventually will result in the determination of two dose-response curves for norepinephrine biosynthesis, representing cytosolic ascorbic acid and intragranular ascorbic acid (Fig. 11). These curves for norepinephrine biosynthesis can be combined with curves for other enzymatic events that are also dependent on ascorbic acid for maximal activity. These dose-response curves (Fig. 2) will allow determination of optimum ascorbic acid requirements based on specific product formation and minimum toxicity. These principles are adaptable to other vitamins as well as ascorbic acid, and could form the basis for a new approach to vitamin requirements.

Adrenal Medulla↗
PubMed1978

Ascorbic acid and dehydroascorbic acid in HeLa cells: their effect on the collagen-peptidase activity of glucose-deficient cultures.

HeLa cells in culture do not accumulate ascorbic acid unless ascorbic acid or dehydroascorbic acid is available in the medium. Collagen peptidase corresponding to the activity found in the invasive zone of tumours, and acid phosphatase, in HeLa cells cultured under normal conditions, are unaffected by ascorbic acid, but are reduced in cells deprived of carbohydrate. These reduced collagen-peptidase levels, but not acid phosphatase, are restored to the values of normal HeLa cells by ascorbic acid. The relevance of these findings is considered in the context of tumour growth and spread.

Acid Phosphatase↗
PubMed1976

Ascorbic acid deficiency in liver disease.

Leucocyte ascorbic acid (LAA) levels were measured in 138 patients with liver disease. Significantly reduced levels were found in 37 patients with alcoholic liver disease (P less than 0-01) and 25 patients with primary biliary cirrhosis (P less than 0-05). In the primary biliary cirrhosis patients, cholestyramine therapy was associated with significantly lower levels of the vitamin (P less than 0-05). Liver ascorbic acid measured in Menghini needle biopsies in 20 patients was significantly correlated with LAA (r=0-807, P less than 0-001). No significant correlation was found between LAA and haematological indices, conventional liver function tests, or cholesterol levels in any group of patients. Patients with LAA levels below 100 nM/10(8) WBC had significantly higher antipyrine half-lives (mean=28-3 h) than patients with LAA levels above this level (mean=18-6 h) (P less than 0-05). Delayed drug metabolism related to low LAA should be considered when drugs metabolised by the liver are prescribed for patients with alcoholic liver disease or primary biliary cirrhosis.

Alcoholism↗
PubMed1984

Ascorbic acid effect on ethanol sensitivity via possible dopaminergic mediation.

Mice were injected with 0, 107, 215, 430, or 1720 mg/kg of ascorbic acid. Thirty min later they were tested for ethanol (3.5 g/kg) induced sleep time. Brain ethanol levels were determined upon awakening. Another group of mice were tested for apomorphine (3 mg/kg) induced locomotor activity also 30 min after ascorbic acid injection. Ascorbic acid in doses above 215 mg/kg augmented ethanol sleep time up to 210% at the highest doses, the increase being significant from 430 mg/kg. Brain ethanol levels upon awakening were reduced by ascorbic acid treatment; this reduction was significant at 1720 mg/kg dose. Ascorbic acid decreased apomorphine-induced locomotor activity in a dose response manner that paralleled the ascorbic acid increase of ethanol sleep time. At the highest dose of ascorbic acid, apomorphine-induced locomotor activity was completely eliminated. It is suggested that ascorbic acid increases brain sensitivity to ethanol by lowering the activity of dopamine receptors.

Animals↗
PubMed1992

Tissue-mediated regeneration of ascorbic acid: is the process enzymatic?

Ascorbic acid's function in animals is attributed in part to the ease with which it reduces potentially damaging components, such as reactive free radicals. After more than six decades of speculation and laboratory efforts, the mechanisms by which ascorbic acid is maintained in the useful, reduced state remain uncertain. Previous attempts to isolate the enzymes that reduce the partially and the fully oxidized metabolites of vitamin C are reviewed. Some speculation on why dehydroascorbate reductase (EC 1.8.5.1) has not been purified from animal tissues is presented.

Animals↗
PubMed2003

Inhibition of liver cancer cell proliferation and migration by a combination of (-)-epigallocatechin-3-gallate and ascorbic acid.

A mixture of (-)-epigallocatechin-3-gallate (EGCG) and ascorbic acid exhibited 73.2% inhibition of SMMC-7721 cell proliferation in a soft agar colony formation assay, which was much higher than EGCG (40.4%) or ascorbic acid (12.4%) alone. In the cell migration assay, the mixture also significantly suppressed the migration of SMMC-7721 cells by 65.9% while EGCG and/or ascorbic acid did by 28.9% and 18.7%, respectively. Ascorbic acid was able to enhance the antioxidant activity of EGCG by decreasing the intracellular oxidative stress according to fluorographic analysis of oxidative stress. In conclusion, the combination of EGCG and ascorbic acid can strongly suppress the proliferation and metastasis of liver cancer cells, possibly with a mechanism associated with the scavenging of reactive oxygen species. All these events add to our knowledge of liver cancer chemotherapy.

Antioxidants↗
PubMed1998

Abolishing cadmium toxicity in Chlorella vulgaris by ascorbic acid, calcium, glucose and reduced glutathione.

Addition of ascorbic acid, calcium (Ca2+), glucose and reduced glutathione (GSH) to the cadmium (Cd2+)-amended Kuhl medium significantly accelerated the growth and chlorophyll content of Chlorella vulgaris. This enhancement was found to be dose dependent. Their relative effectiveness against Cd2+ on growth and chlorophyll content has been arranged as GSH > Ca2+ > glucose > ascorbic acid. However, Ca2+ offered more protection against Cd2+ toxicity on protein contents, followed by ascorbic acid, GSH and glucose. The different concentrations of all amelioratives completely alleviated the toxicity of Cd2+ on total carbohydrates to exceed the control level. Photosynthetic oxygen evolution showed more response to Ca2+ and glucose in alleviating Cd2+ toxicity. On the other hand, at certain concentrations, GSH, Ca2+, ascorbic acid and glucose stimulated respiratory oxygen uptake over the control level. The uptake of Cd2+ dropped significantly in cultures supplemented with 20 microM ascorbic acid, glucose and GSH, while Ca2+ (30 microM) significantly lowered the Cd2+ uptake by 58% indicating that Ca2+ had a more antagonistic effect against Cd2+.

Journal Article↗