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PubMed1991

Spectrophotometric determination of ascorbic acid in pharmaceuticals by background correction and flow injection.

Background correction has been shown to be an effective and indispensable modification in the spectrophotometric determination of ascorbic acid. The decomposition of ascorbic acid in pharmaceutical samples was carried out by incubation with sodium hydroxide to give products that were insensitive to ultraviolet light. The rapid oxidation in air of ascorbic acid, especially in dilute solutions, was avoided by the use of the flow injection principle for spectrophotometric determination and by employing a carrier stream of an anti-oxidizing nature consisting of 6 micrograms ml(-1) of 2-mercaptoethanol in 0.25% sulphuric acid. The optimized method with a single channel manifold made use of a carrier stream flow rate of 1.1 ml min(-1), an injection volume of 50 microl, a delay coil of 50 cm (0.5 mm i.d.) and detection at 245 nm. The throughput was at least 180 injections h(-1). The proposed flow injection method yielded results for the analysis of 0-20 micrograms ml(-1) of ascorbic acid that were 99-102% (relative standard deviation 0.6% or better) in agreement with those produced by comparable methods involving titration with iodine, chloranil or 2,6-dichlorophenolindophenol [4-(2,6-dichloro-4-hydroxyphenylimino)cyclohexa-2,5-dieno ne], and high-performance liquid chromatography. When the agreement was not good (as low as 14% with respect to the method being compared), this was traced to the presence of substances which are known to interfere in one or other of the methods of comparison.

Ascorbic Acid↗

PubMed1986

The role of ascorbic acid in etomidate toxicity.

Etomidate, a short-acting hypnotic used in anaesthesia, has been shown to block steroidogenesis in man. The free imidazole radical in etomidate binds to cytochrome P450. Serious side-effects of etomidate have only been observed in guinea-pigs and in man, both species relying for restoration of ascorbic acid pools upon resynthesis and upon the daily dietary intake of vitamin C. It has been shown that ascorbic acid and not ACTH can increase serum cortisol concentration during etomidate infusion. Ascorbic acid even restores the ACTH/cortisol ratio to pre-operative values. It is therefore suggested that etomidate blocks ascorbic acid metabolism. Resynthesis of ascorbic acid cannot occur because of the blockade of cytochrome P450. Depletion of the ascorbic acid pool would then cause inhibition of steroidogenesis. This is the case in man and probably also in the guinea-pig. All other species can synthesize their own ascorbic acid from alpha ketogluconic acid.

Adrenal Glands↗

PubMed1996

Possible prevention of postangioplasty restenosis by ascorbic acid.

In this preliminary study to assess the possibility of using ascorbic acid to prevent post-percutaneous transluminal coronary angiography (PTCA) restenosis, the incidence of restenosis was significantly less in 50 patients receiving 500 mg/day of oral ascorbic acid than in 51 control patients. Thus, ascorbic acid, a potent natural antioxidant, appeared to be possibly effective in attenuating post-PTCA restenosis.

Adult↗

PubMed2004

Exposure to L-ascorbic acid or alpha-tocopherol facilitates the development of porcine denuded oocytes from metaphase I to metaphase II and prevents cumulus cells from fragmentation.

It is known that alpha-tocopherol (vitamin E) and L-ascorbic acid (vitamin C) can modulate many biochemical processes intracellularly or extracellularly as antioxidants. The objective of the present study was to investigate the effects of alpha-tocopherol and L-ascorbic acid on porcine oocyte meiotic maturation, viability and the functions of cumulus cells. In two independent experiments, porcine oocytes with or free from cumulus cells were exposed to different levels of alpha-tocopherol (0, 10, 100 and 200 microM) or L-ascorbic acid (0, 50, 250 and 750 microM). Cumulus expansion, cumulus cell DNA fragmentation, meiotic maturation and degeneration of oocytes were assessed 48 h after in vitro culture. The results showed that: (1) neither alpha-tocopherol nor L-ascorbic acid influenced cumulus expansion but both prevented cumulus cell DNA fragmentation. (2) Alpha-tocopherol lowered the percentage of denuded oocytes (DOs) arrested at germinal vesicle stage (GV). Among the oocytes undergoing germinal vesicle breakdown (GVBD) proportion, fewer DOs treated by alpha-tocopherol were at metaphase I (MI) and more at metaphase II (MII). L-ascorbic acid caused lower percentage of DOs arrested at GV stage and higher percentage of DOs undergoing GVBD, especially at MII. The influences of alpha-tocopherol and L-ascorbic acid were not obvious in cumulus-enclosed oocytes (CEOs). (3) Both vitamins compromised the viability of CEOs and DOs. These results indicate that exposure to alpha-tocopherol or L-ascorbic acid promotes the development of porcine DOs from MI to MII and prevents cumulus cell DNA fragmentation at certain levels, especially 10 microM alpha-tocopherol or 250 microM L-ascorbic acid.

Animals↗

PubMedDate not supplied

The diffusion of L(+)-ascorbic acid across DPPC vesicle membranes.

The transmembrane diffusion of L(+)-ascorbic acid has been studied by means of 1H-n.m.r. spectroscopy using small unilamellar DPPC vesicles as a model system. It is shown that the electro-neutral form of L(+)-ascorbic acid diffuses faster across the membranes than the anionic form by about two orders of magnitude. The diffusion is influenced by a molecular interaction between L(+)-ascorbate and the membrane surface and depends also on the fluidity of the membrane. The calculated permeation coefficients of neutral L(+)-ascorbic acid are between 6 x 10(-10) and 3 x 10(-8) cm s-1 (35-52 degrees C).

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2006

Effects of ascorbic acid on impaired vascular reactivity in aortas isolated from age-matched hypertensive and diabetic rats.

Impaired vascular reactivity is a hallmark of several cardiovascular diseases that include hypertension and diabetes. This study compared the changes in vascular reactivity in age-matched experimental hypertension and diabetes, and, subsequently, tested whether these changes could be affected directly by ascorbic acid (10 microM). Endothelium-derived nitric oxide (NO) modulation of ascorbic acid effects was also investigated. All the experiments were performed in the presence of a cyclooxygenase inhibitor, indomethacin (10 microM). Results showed that the endothelium-dependent and -independent relaxations induced by acetylcholine (ACh) and sodium nitroprusside (SNP), respectively, were blunted to a similar extent in isolated aortic rings from age-matched spontaneously hypertensive (SHR) (R(max): ACh = 72.83+/-1.86%, SNP = 96.6+/-1.90%) and diabetic (Rmax: ACh = 64.09+/-5.14%, SNP = 95.84+/-1.41%) rats compared with aortic rings of normal rats (Rmax: ACh = 89%, SNP = 104.0+/-1.0%). The alpha1-receptor-mediated contractions induced by phenylephrine (PE) were augmented in diabetic (Cmax = 148.8+/-9.0%) rat aortic rings compared to both normal (Cmax = 127+/-6.9%) and SHR (Cmax = 118+/-4.5%) aortic rings. Ascorbic acid pretreatment was without any significant effects on the vascular responses to ACh, SNP and PE in aortic rings from normal rats. Ascorbic acid significantly improved ACh-induced relaxations in SHR (Rmax = 89.09+/-2.82%) aortic rings to a level similar to that observed in normal aortic rings, but this enhancement in ACh-induced relaxations was only partial in diabetic aortic rings. Ascorbic acid lacked any effects on SNP-induced relaxations in both SHR and diabetic aortic rings. Ascorbic acid markedly attenuated contractions induced by PE in aortic rings from both SHR (Cmax = 92.9+/-6.68%) and diabetic (Cmax = 116.9+/-9.4%) rats. Additionally, following inhibition of nitric oxide synthesis with l-NAME, ascorbic acid attenuated PE-induced contractions in all aortic ring types studied. These results suggest that (1) vascular hyper-responsiveness to alpha(1)-receptor agonists in diabetic arteries is independent of endothelial nitric oxide dysfunction; (2) ascorbic acid directly modulates contractile responses of hypertensive and diabetic rat aortas, likely through mechanisms in part independent of preservation of endothelium-derived nitric oxide.

Acetylcholine↗

PubMed1986

Ascorbic acid specific utilization by some yeasts.

One hundred and eighty strains of yeasts belonging to 17 genus and 53 species were screened for their ability to grow on ascorbic acid and iso-ascorbic acid as the sole carbon source. Most of the tested strains (157) were unable to grow on either compound. Strains of seven species of the genus Cryptococcus, of two Candida species, of Filobasidiella neoformans, Trichosporon cutaneum, Lipomyces starkeyi, Hansenula capsulata, and one strain of Aureobasidium pullulans were able to grow on ascorbic as well as on iso-ascorbic acid. Conversely, four strains of Aureobasidium pullulans, Candida blankii, and Cryptococcus dimennae could use only ascorbic acid for growth.

Ascorbic Acid↗

PubMed1992

Modification of metal-induced micronuclei formation in mouse bone marrow erythrocytes by Phyllanthus fruit extract and ascorbic acid.

The comparative efficacy of Phyllanthus emblica fruit extract, and its main constituent, ascorbic acid, in modifying the cytotoxic action of lead and aluminium was evaluated in vivo in bone marrow cells of Mus musculus. Oral administration of Phyllanthus emblica fruit extract for 7 days before exposure to the metals through intraperitoneal injections reduced the frequency of micronuclei induced by all doses of both metals. Priming with comparable doses of synthetic ascorbic acid reduced micronuclei formation induced by both doses of aluminium and only the lower dose of lead. With the higher dose of lead (20 mg/kg body wt.) priming with ascorbic acid increased the frequency of micronuclei when compared with mice administered lead alone. The greater efficacy of Phyllanthus fruit extract in alleviating metal-induced clastogenicity may be due to the combined action of all ingredients in the crude extract, rather than to ascorbic acid alone.

Aluminum↗

PubMedDate not supplied

[The laser-magnetic phoresis of ascorbic acid in the combined health-resort therapy of osteoarthrosis patients].

In vitro experiments demonstrate stability of ascorbic acid pH solution and a 1.5-fold increase in ascorbic acid mass-transfer through semipermeable membranes in exposure to laser radiation and magnetic field generated by the device Uzor. Bioavailability of ascorbic acid was proved by adaptogenic and antioxidant effects of laser-magnetophoresis of 2% ascorbic acid solution applied to the affected joints in 79 patients with osteochondrosis. The above laser-magnetophoresis compared to reflex-segmental technique of laser-magnetotherapy is more effective and safe as to balneopathological reactions.

Ascorbic Acid↗

PubMed1977

Ascorbic acid transport by a clonal line of pheochromocytoma cells.

A clonal line of rat pheochromocytoma cells was used as a model of noradrenergic tissue to study ascorbic acid transport. These cells were used because, like sympathetic neurons, they synthesize large amounts of noradrenaline in the presence of ascorbate, they respond to nerve growth factor with the production of neurites and they release, store and take up catecholamines. In these cells, both with and without nerve growth factor (NGF) treatment, [14C]ascorbic acid was concentrated by a stereospecific saturable, energy dependent transport system that could be described by a Michaelis-Menten transport model. The Kt and Vmax for ascorbic acid were approximately 0.03 mM and 0.3 nmole per min per mg protein respectively for both untreated and NGF-treated cells. The ability of the cells to concentrate ascorbic acid was not due to intracellular binding. Cells untreated with NGF and loaded with [14C]ascorbic acid to a concentration of 5.6 nmoles per mg protein retained only 6% of the initial intracellular [14C]ascorbic acid after the 24 h in normal growth medium. Thus, although pheochromocytoma cells contain an ascorbate concentrating system, optimal production of noradrenaline requires ascorbate in the medium.

Adrenal Gland Neoplasms↗

PubMed2004

Quantitative assessment of ischemic tissue damage in ovarian cortical tissue with or without antioxidant (ascorbic acid) treatment.

OBJECTIVE: To estimate ischemic tissue damage in ovarian cortex and to evaluate the effectiveness of ascorbic acid, an antioxidant, to protect ovarian tissue from apoptosis caused by ischemia. DESIGN: In vitro laboratory experiments. SETTING: Academic research institute. INTERVENTION(S): Fresh and frozen/thawed cortical sections of bovine ovaries were incubated in MEM medium with or without ascorbic acid for a duration of 3, 24, and 48 hours at 37 degrees C. MAIN OUTCOME MEASURE(S): Oxygen consumption rates, lactate dehydrogenase concentrations, apoptosis rates determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining, and DNA fragmentation analysis. RESULT(S): The oxygen consumption rates were correlated inversely with the duration of incubation. When the rates of apoptosis in primordial follicles with or without ascorbic acid treatment were compared, there was no statistically significant difference between the two groups. However, the ascorbic acid treatment group showed significantly decreased apoptosis in ovarian cortex (stromal cells) with 24 hours of incubation. CONCLUSION(S): The correlation between ischemic tissue damage and the duration of ischemia was verified. Ovarian cortex could tolerate ischemia at least for 3 hours. Ascorbic acid treatment reduced apoptosis in ovarian cortex up to 24 hours of incubation in vitro. It appeared that stromal cells were more vulnerable to ischemia compared to primordial follicles.

Animals↗

PubMed2006

Biosynthesis of ascorbic acid in legume root nodules.

Ascorbic acid (vitamin C) is a major antioxidant and redox buffer, but is also involved in other critical processes of plants. Recently, the hypothesis has been proposed that legume nodules are unable to synthesize ascorbate and have to import it from the shoot or root, thus providing a means by which the plant regulates nodule senescence. The last step of ascorbate biosynthesis in plants is catalyzed by L-galactono-1,4-lactone dehydrogenase (GalLDH). The mRNAs encoding GalLDH and three other enzymes involved in ascorbate biosynthesis are clearly detectable in nodules. Furthermore, an active membrane-bound GalLDH enzyme is present in nodule mitochondria. Biochemical assays on dissected nodules reveal that GalLDH activity and ascorbate are correlated in nodule tissues and predominantly localized in the infected zone, with lower levels of both parameters (relative to the infected tissues) in the apex (87%) and senescent region (43%) of indeterminate nodules and in the peripheral tissues (65%) of determinate nodules. In situ RNA hybridization showed that the GalLDH mRNA is particularly abundant in the infected zone of indeterminate and determinate nodules. Thus, our results refute the hypothesis that ascorbate is not synthesized in nodules and lend support to a previous conclusion that ascorbate in the infected zone is primarily involved in the protection of host cells against peroxide damage. Likewise, the high ascorbate and GalLDH activity levels found in the apex of indeterminate nodules strongly suggest a participation of ascorbate in additional functions during symbiosis, possibly related to cell growth and division and to molecular signaling.

Ascorbate Peroxidases↗

PubMed1980

Histamine and ascorbic acid in human blood.

Analysis of 437 human blood samples has shown that when the plasma-reduced ascorbic acid level falls below 1 mg/100 ml, the whole blood histamine level increases exponentially as the ascorbic acid level decreases. When the ascorbic acid level falls below 0.7 mg/100 ml, there is a highly significant increase in the blood histamine level. Oral administration of ascorbic acid (1 g daily for 3 days) to 11 selected volunteers resulted in a reduction of the blood histamine level in every instance.

Ascorbic Acid↗

PubMed1977

Reduction of gallstone formation by ascorbic acid in hamsters.

The addition of 0.5% of ascorbic acid to the lithogenic diet of golden hamsters whose body pool was labelled with 26-14C-cholesterol, lowered the formation of gallstones, the cholesterol concentration and half-life in blood plasma and in the liver, and accelerated cholesterol transformation to bile acids.

Animals↗

PubMed2006

Plasma concentrations of ascorbic acid and C-reactive protein, and risk of future coronary artery disease, in apparently healthy men and women: the EPIC-Norfolk prospective population study.

High plasma concentrations of ascorbic acid, a marker of fruit and vegetable intake, are associated with low risk of coronary artery disease. Whether this relationship is explained by a reduction in systemic inflammation is unclear. We investigated the relationship between ascorbic acid plasma concentration and coronary artery disease risk, and in addition whether this relationship depended on classical risk factors and C-reactive protein (CRP) concentration. We used a prospective nested case-control design. The study consisted of 979 cases and 1794 controls (1767 men and 1006 women). Increasing ascorbic acid quartiles were associated with lower age, BMI, systolic and diastolic blood pressure, and CRP concentration, but with higher HDL-cholesterol concentration. No associations existed between ascorbic acid concentration and total cholesterol concentration or LDL-cholesterol concentration. When data from men and women were pooled, the risk estimates decreased with increasing ascorbic acid quartiles such that people in the highest ascorbic acid quartile had an odds ratio for future coronary artery disease of 0.67 (95 % CI 0.52, 0.87) compared with those in the lowest quartile (P for linearity=0.001). This relationship was independent of sex, age, diabetes, smoking, BMI, LDL-cholesterol, HDL-cholesterol, systolic blood pressure and CRP level. These data suggest that the risk reduction associated with higher ascorbic acid plasma concentrations, a marker of fruit and vegetable intake, is independent of classical risk factors and also independent of CRP concentration.

Age Distribution↗

PubMed1986

Interaction of dietary carbohydrate, ascorbic acid and copper with the development of copper deficiency in rats.

The effects of dietary carbohydrate and ascorbic acid on the development of copper deficiency were investigated. Male Sprague-Dawley rats (n = 48) were fed one of eight diets in a 2 X 2 X 2 factorial design for 21 d. These diets varied in copper (1.11 or 8.96 micrograms Cu/g diet), carbohydrate (sucrose or cornstarch, 62.3%) and ascorbic acid (0 or 1%). Compared to controls, copper-deficient rats had lower hematocrit and ceruloplasmin levels, lower levels of copper and iron in several tissues, higher heart weights and lower spleen weights. During copper deficiency, liver iron levels were higher than control levels when cornstarch, but not sucrose, was the carbohydrate source, while liver and gastrointestinal tract weights were higher with sucrose compared to cornstarch. Copper-deficient rats fed ascorbic acid had significantly (P less than 0.05) lower hematocrits when fed sucrose compared to starch [29.6 +/- 1.2 vs. 36.8 +/- 1.2 g/dl (mean +/- SEM), respectively]. In copper-deficient rats, sucrose tended to lower the apparent absorption of copper compared to cornstarch, while ascorbic acid reduced the apparent absorption of iron. Thus, sucrose and ascorbic acid appeared to reduce hematocrit levels through effects on mineral absorption.

Absorption↗

PubMed1996

The effectiveness of ascorbic acid in the prevention of calf neonatal diarrhoea.

A trial was conducted to evaluate the effectiveness of ascorbic acid in the prevention of neonatal calf diarrhoea. Ascorbic acid was given orally to 65 calves as follows: one tablet (1000 mg) three times a day for the first week; one tablet twice a day for the second week; and one tablet daily for the third week after birth (test group). Another 65 calves did not receive ascorbic acid (control group). The calves in these two groups were matched on the basis of the stage of lactation of their dams. The number of diarrhoeic calves that received ascorbic acid was significantly (P < 0.005) lower than the number of diarrhoeic calves in the control group that did not receive the drug.

Animals↗

PubMed2006

Genetic and environmental contributions to serum ascorbic acid concentrations: the Stanislas Family Study.

Although numerous environmental factors are documented to influence serum ascorbic concentrations, little is known about the genetic versus environmental contributions to variation of this trait. The aim of this study was to estimate family correlation and, additive genetic heritability and household effects in a variance component analysis for serum ascorbic acid concentrations. In a sample of ninety French families, information was obtained regarding serum ascorbic acid concentrations, usual dietary intake, lifestyle, and other related covariates. Spouse, parent-offspring and offspring-offspring significant correlation coefficients for serum ascorbic acid concentrations, adjusted for age, cigarette consumption and oral contraceptive use, were 0.432, 0.298 and 0.485, respectively, and for adjusted values for additional diet covariates (vitamin C intake and fruit and vegetable consumption), were 0.362, 0.154 and 0.348, respectively. Variance component analysis for serum ascorbic concentrations showed no significant genetic contribution to variability of this trait. Conversely, household common environment accounted for 27.7 and 42.6% in parents and offspring, respectively, after adjustment for age, cigarette consumption and oral contraceptive use. After adjustment for the two additional diet covariates (vitamin C intake and fruit and vegetable consumption) household common variance decreased to 13.6 and 30.5% in parents and offspring, respectively. These results show that serum ascorbic acid concentrations aggregate within healthy families partly due to diet intake but without a significant genetic component.

Adolescent↗