Showing papers on "Ascorbic acid published in 1982"
TL;DR: A new colorimetric technique for the estimation of ascorbic acid by using Folin phenol reagent has been developed and has been found to be stable up to 18 h and almost 100% efficient.
475 citations
TL;DR: Reduced ascorbic acid (RAA) and Vitamin A (carotenoid) contents of six vegetables obtained from six cities in the United States at two seasons of the year were determined.
Abstract: Reduced ascorbic acid (RAA) and Vitamin A (carotenoid) contents of six vegetables obtained from six cities in the United States at two seasons of the year were determined. Mean RAA content (mg/lOOg) of cabbage was 45.2, carrots 7.8, celery 6.0, corn 6.5, onions 8.4, and tomatoes 15.3. Vitamin C in cooked cabbage was 22.1, corn 6.2, and onions 5.7 mg/100g. Mean vitamin A activity (I.U.) of car- rots was 15,228, cabbage 114, celery 133, corn 219, and tomatoes 750. In cooked cabbage and corn, vitamin A content was 89 and 217 I.U., respectively. The RAA and vitamin A content of vege- tables from the six geographical areas varied significantly. Vitamin concentrations were generally lower than tabulated values. Reten- tion of RAA in cooked cabbage was 52%; in onions, 58%; and in corn, 98%. Vitamin A retention in cooked cabbage was 82%, and in cooked corn was 98%. cities, at two different seasons. The vegetables were obtained from six different areas in the United States: West (Seattle and Denver), Midwest (St. Louis and Minneapolis), and East (Boston and Atlanta), at two different times of the year. The source of the vegetables, including the gowing area (when known), and the months they were obtained, are given in Table 1. Produce typical of that being sold in each area was shipped directly to the University of Illinois via air freight to Champaign-Urbana, IL, stored at 4"C, and pre- pared for analysis within 48 hr of shipment. Tomatoes in some cases were held at room temperature (24°C) to ripen. The times and conditions during shipping were similar to what is encountered in transport from warehouses to market outlets. Sampling procedures All vegetables were analyzed raw, and cabbage, corn and onions were also cooked and analyzed. The vegetables were trimmed, peeled if necessary, washed in deionized distilled (DD) water, and blotted dry. Approximately 15-20 kg of each vegetable were sliced (carrots, celery, onions) or cut in eighths (tomatoes, cabbage). The samples for cooking and analyses were drawn from these com- posites. Approximately 7.5-10 kg of each vegetable were cooked by the methods given below. The cooked vegetables were combined and samples drawn from the composite for nutrient assay. Corn was husked, rinsed and blotted dry, and then cut from the cob for the raw samples. Corn was cooked on the cob and the kernels removed for the cooked samples. All cutting implements used were stainless steel, and care was taken to avoid contamination with minerals. Duplicate or triplicate determinations were performed for every nutrient for each raw or cooked vegetable at each sampling period from all of the geographical areas. Cooking methods
375 citations
TL;DR: It is suggested that American elderly consider using a combination of moderate vitamin D supplementation and increased sunlight exposure in order to improve their vitamin D nutriture.
326 citations
TL;DR: The ability of the mononuclear leucocytes to maintain the highest levels of ascorbic acid in the cell types studied, despite variation in plasma availability, warrants further study, particularly in view of the importance of these cells in immunocompetence.
Abstract: 1. A study was undertaken to investigate the distribution of ascorbic acid between various cellular components of blood, in normal individuals, and its relation to the plasma concentration. Forty-one unsupplemented individuals and sixteen supplemented (2 g/d for 5 d) individuals were studied. 2. Granulocytes, mononuclear leucocytes, platelets and erythrocytes were separated by differential sedimentation and centrifugation. Ascorbic acid contents were measured by the dinitrophenylhydrazine method. 3. Ascorbic acid content per cell was higher in mononuclear leucocytes and granulocytes than in platelets and erythrocytes. Intracellular ascorbic acid concentrations, calculated from published values for cell volumes, when compared with the plasma concentration showed a marked ability to concentrate ascorbic acid in mononuclear leucocytes (80 times), platelets (40 times) and granulocytes (25 times). 4. Erythrocytes showed little ability to concentrate ascorbic acid over the normal range of plasma concentration but because of their relative numbers they and the plasma fraction accounted for most of the blood-borne ascorbic acid (greater than 70%). 5. The ascorbic acid content of granulocytes, platelets and erythrocytes showed a significant positive correlation with the plasma concentration and supplementation with ascorbic acid significantly increased the content of these cell types. Mononuclear leucocytes in contrast did not show any such relationship. 6. The ability of the mononuclear leucocytes to maintain the highest levels of ascorbic acid in the cell types studied, despite variation in plasma availability, warrants further study, particularly in view of the importance of these cells in immunocompetence.
217 citations
TL;DR: In this paper, an alternative method to solubilize crystalline Fe oxides that would fit into a scheme including extractants for amorphous Fe and manganese (Mn) oxides was proposed.
Abstract: Since sodium dithionite (Na₂S₂O₄) is often contaminated with zinc (Zn) and can form metal sulfide precipitates, it is not suitable for solubilizing iron (Fe) oxides in fractionation schemes for soil microelements. The objective was to find an alternate method to solubilize crystalline Fe oxides that would fit into a scheme including extractants for amorphous Fe and manganese (Mn) oxides. Three soils were extracted with seven reagents designed to remove amorphous and/or crystalline Fe or Mn oxides [0.1M Na₄P₂O₇, pH 10.0; 0.2M (NH₄)₂C₂O₄ in 0.2M H₂C₂O₄, pH 3.0 (oxalate); 0.1M NH₂OH-HCl, pH 2.0; 1.0M NH₂OH-HCl in 25% acetic acid; 0.1M ascorbic acid in the oxalate solution; 0.1 g SnCl₂ per gram of soil in the oxalate solution; and 1.0 g dithionite per gram of soil in citrate buffer]. The Na₄P₂O₇, an extractant for elements associated with the organic fraction, extracted amounts of Fe similar to that for the oxalate solution. The two NH₂OH-HCl extractants solubilized very little Fe (<1% total), but NH₂OH-HCl alone solubilized as much Mn as most of the other extractants indicating that it is specific for Mn oxides. The ascorbic acid-oxalate and SnCl₂-oxalate experimental methods extracted amounts of Fe similar to the dithionite method and amounts of Al higher than the dithionite method. Of the amorphous Fe-oxide extractants, the oxalate solution solubilized the most Zn and Cu, whereas of the crystalline Fe-oxide extractants, the ascorbic acid-oxalate solubilized the highest amounts of Zn and Cu. The extractants suggested for a fractionation scheme are NH₂OH-HCl for Mn oxides, oxalate solution shaken with the soil in the dark for amorphous Fe oxides, and ascorbic acid-oxalate for crystalline Fe oxides.
211 citations
TL;DR: These studies indicate that either a reversible, localized derangement in folate metabolism may sometimes be misdiagnosed as cervical dysplasia, or else such a derangements is an integral component of the dysplastic process that may be arrested or in some cases reversed by oral folic acid supplementation.
203 citations
01 Jan 1982
TL;DR: The chemistry of ascorbic acid free radicals is reviewed, with particular emphasis on identification and characterization by spectrophotometric and electron paramagnetic resonance techniques and the kinetics of formation and disappearance.
Abstract: The chemistry of ascorbic acid free radicals is reviewed. Particular emphasis is placed on identification and characterization of ascorbate radicals by spectrophotometric and electron paramagnetic resonance techniques, the kinetics of formation and disappearance of ascorbate free radicals in enzymatic and nonenzymatic reactions, the effect of pH upon the spectral and kinetic properties of ascorbate anion radical, and chemical reactivity of ascorbate free radicals.
192 citations
TL;DR: This model system is among others in the CNS which offer distinctive opportunities to study, in vivo, the onset and progression of membrane damaging free-radical reactions within well-defined parameters of time, extent of tissue injury, correlation with changes in membrane enzymes, and correlation with readily measurable in vivo functions.
Abstract: The hypothesis that pathologic free-radical reactions are initiated and catalyzed in the major central nervous system (CNS) disorders has been further supported by the current acute spinal cord injury work that has demonstrated the appearance of specific, cholesterol free-radical oxidation products. The significance of these products is suggested by the fact that: (i) they increase with time after injury; (ii) their production is curtailed with a steroidal antioxidant; (iii) high antioxidant doses of the steroidal antioxidant which curtail the development of free-radical product prevent tissue degeneration and permit functional restoration. The role of pathologic free-radical reactions is also inferred from the loss of ascorbic acid, a principal CNS antioxidant, and of extractable cholesterol. These losses are also prevented by the steroidal antioxidant. This model system is among others in the CNS which offer distinctive opportunities to study, in vivo, the onset and progression of membrane damaging free...
190 citations
TL;DR: The data suggest that ascorbic acid temporarily influenced polyp growth or turnover in patients with polyposis coli and support continued studies of chemoprevention in this and other high risk settings.
Abstract: The possibility of pharmacological control of large bowel adenomas has been suggested by effectiveness of antioxidants in experimental tumor models and by the results of a limited clinical study using ascorbic acid. Over a two year period we tested this hypothesis in a randomized, double-blind study of 49 patients with polyposis coli. Of 36 patients who were evaluable at completion, 19 had received ascorbic acid, 3 g/day, and 17 had received a placebo. We found a reduction in polyp area in the ascorbic acid-treated group at nine months of follow-up (P less than 0.03) and trends toward reduction in both number and area of rectal polyps during the middle of the trial. A labeling study of rectal epithelium with tritiated thymidine also hinted at a treatment effect. Our data suggest that ascorbic acid temporarily influenced polyp growth or turnover. Although these results have no current therapeutic value, our findings support continued studies of chemoprevention in this and other high risk settings.
177 citations
TL;DR: The effects of coumarin and its derivatives on rat platelet lip Oxygenase and cyclooxygenase activities were studied and Esculetin (6,7-dihydroxycoumarin) was found to inhibit the lipoxygen enzyme more strongly than the cyclo oxygengenase.
TL;DR: Reactivity with 2-thiobarbituric acid has been widely used as a test to detect oxidative deterioration in lipid products and can be distinguished from the MDA-TBA adduct following chromatographic separation or characterisation of their fluorescent spectra.
TL;DR: The study provides new data on a number of rat brain regions; the most significant finding is that there are very marked gradients of ascorbate concentrations throughout the various nuclei.
TL;DR: Measurements in the cortex or in the caudate nucleus of animals lesioned by prior injection of 6-hydroxydopamine show that a substance with voltammetric properties identical to those of ascorbic acid also increases in concentration in these areas as a result of amphetamine administration.
TL;DR: In this paper, a procedure is described whereby thin films of an alkylamine-siloxane polymer can be formed on Pt electrode surfaces, and electrocatalytic reaction of trapped ferrocyanide ions can be stably observed.
TL;DR: A new type of enzyme electrode has been developed for in vivo electrochemical measurements which allows discrimination between ascorbic acid and catecholamines and their metabolites and has been tested in brain slice measurements and shown to respond to releases of catechlamines initiated by potassium ion stimulation.
TL;DR: The studies indicate for the first time the possibilities of a hitherto unrecognized role of ascorbate against cataracts and other age-, light- and oxygen-dependent ocular abnormalities and re-emphasizes the role of tissue catalase and superoxide dismutase in the prevention of photoperoxidative damages to the tissue.
Abstract: Exposure of rat lens to fluorescent daylight (150 ft candles) under tissue culture conditions led to a substantial lipid peroxidation as evidenced by the formation of malonaldehyde (MDA). MDA content of lenses incubated overnight in presence of such light was approximately sixfold of that in the control lenses cultured in the dark. These cultures were maintained in physiological medium resembling aqueous humor which does not contain any additional photoactive component. Thus, the lens in its physiological surroundings is susceptible to photoperoxidation by light of wavelengths which freely penetrate the eye. Photoperoxidation could be thwarted by superoxide dismutase, catalase, and ascorbate, suggesting that the observed peroxidative degradation is initiated by photocatalytic generation of superoxide and its subsequent derivation to other potent oxidants. These studies provide for the first time suggestive evidence that senile cataract development may in part be linked to the in vivo photochemical generation of superoxide and other potent oxidants in the aqueous humor and lens derived from the ambient oxygen and light; and ascorbate which is maintained at high levels in this fluid by virtue of its active transport from plasma, is physiologically important in preventing the deleterious action of these potent oxidants. The studies thus indicate for the first time the possibilities of a hitherto unrecognized role of ascorbate against cataracts and other age-, light- and oxygen-dependent ocular abnormalities, In addition, the study re-emphasizes the role of tissue catalase and superoxide dismutase in the prevention of photoperoxidative damages to the tissue.
TL;DR: These studies indicate the importance of biliary iron excretion in monitoring the effectiveness of desferrioxamine and suggest that large chelator doses may remove established iron overload much more rapidly than has previously been realized.
TL;DR: The effect of supplementation with vitamin C in lung-cancer patients on survival should be tested in a clinical trial because of the increasing circumstantial evidence that immune mechanisms exert some measure of control on tumour extension and metastasis in man.
Abstract: Plasma and buffy-coat vitamin C were estimated in 158 samples from 139 lung-cancer patients, at all stages of the disease. Most samples showed hypovitaminosis C in both estimations: 64% had plasma, and 25% buffy-coat values below the thresholds for incipient clinical scurvy (0.3 mg% and 10 micrograms/10(8) cells respectively). Levels were diet-dependent and could be increased by oral supplements. Levels were low both in tumour-bearing patients and in those clinically free of disease after resection. The latter had particularly low values during the first 6 months, indicating the utilization of vitamin C in surgical repair. The vitamin C content of 13 primary lung tumours was assayed: tumours had a higher vitamin C content (mean 111.6 +/- 55.1 micrograms/g tissue) than normal lung (58.5 +/- 20.4 micrograms/g). Mononuclear cells from normal individuals show a higher vitamin C content than polymorphs, but in lung-cancer patients the expected correlation of buffy-coat vitamin C with the proportion of lymphocytes in peripheral blood was obscured by an inverse correlation in patients with relative lymphocytosis (greater than or equal to 25% lymphocytes), confirmed by an inverse correlation of the proportion of lymphocytes in peripheral blood with mononuclear-cell vitamin C in 14 patients in whom this was measured. These correlations were unaffected by controlling for plasma values, and indicate the utilization of vitamin C in lymphocyte-related anti-tumour mechanisms. Vitamin C is necessary for phagocytosis and for the expression of cell-mediated immunity. In view of the increasing circumstantial evidence that immune mechanisms exert some measure of control on tumour extension and metastasis in man, the effect of supplementation with vitamin C in lung-cancer patients on survival should be tested in a clinical trial.
TL;DR: Results reveal that ascorbic acid has a preferential stimulating effect on type I procollagen mRNA, which appears to be independent of its cofactor role in prolyl and lysyl hydroxylation.
TL;DR: A specific enzymatic spectrophotometric method for ascorbic acid in serum or plasma and requires no deproteinization is described.
Abstract: 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.
TL;DR: Lipid peroxidation and haemoglobin degradation were the two extremes of a spectrum of oxidative damage in red cells exposed to t-butyl hydroperoxide, although some synergistic effects between extracellular ascorbate and glutathione were observed.
Abstract: Lipid peroxidation and haemoglobin degradation were the two extremes of a spectrum of oxidative damage in red cells exposed to t-butyl hydroperoxide. The exact position in this spectrum depended on the availability of glucose and the ligand state of haemoglobin. In red cells containing oxy- or carbonmono-oxy-haemoglobin, hexose monophosphate-shunt activity was mainly responsible for metabolism of t-butyl hydroperoxide; haem groups were the main scavengers in red cells containing methaemoglobin. Glutathione, via glutathione peroxidase, accounted for nearly all of the hydroperoxide metabolizing activity of the hexose monophosphate shunt. Glucose protection against lipid peroxidation was almost entirely mediated by glutathione, whereas glucose protection of haemoglobin was only partly mediated by glutathione. Physiological concentrations of intracellular or extracellular ascorbate had no effect on consumption of t-butyl hydroperoxide or oxidation of haemoglobin. Ascorbate was mainly involved in scavenging chain-propagating species involved in lipid peroxidation. The protective effect of intracellular ascorbate against lipid peroxidation was about 100% glucose-dependent and about 50% glutathione-dependent. Extracellular ascorbate functioned largely without a requirement for glucose metabolism, although some synergistic effects between extracellular ascorbate and glutathione were observed. Lipid peroxidation was not dependent on the rate or completion of t-butyl hydroperoxide consumption but rather on the route of consumption. Lipid peroxidation appears to depend on the balance between the presence of initiators of lipid peroxidation (oxyhaemoglobin and low concentrations of methaemoglobin) and terminators of lipid peroxidation (glutathione, ascorbate, high concentrations of methaemoglobin).
TL;DR: Tannic acid, gallic acid and chlorogenic acid suppressed the mutagenicity of the model nitrosation system at concentrations similar to or even lower than ascorbic acid.
Abstract: Several plant phenolics, one instant coffee, one instant decaffeinated coffee, one roasted coffee, one Japanese tea, one black Indian tea, and one Chinese tea were examined for their inhibitory properties on mutagenicity resulting from the nitrosation of methylurea. Mutagenicity was estimated as the number of his+ revertants per survivor of Salmonella typhimurium TA1535 which was exposed in suspension to the nitrosation mixtures and the modulating agents for 20 min. Tannic acid, gallic acid and chlorogenic acid suppressed the mutagenicity of the model nitrosation system at concentrations similar to or even lower than ascorbic acid. The three tested coffees and three tested teas exerted an inhibitory effect on the mutagenicity of the test system at doses at which they are consumed.
TL;DR: A pronounced effect of vitamin C in decreasing the incidence and delaying the onset of the malignant lesions was observed with high statistical significance.
Abstract: We have carried out a study of large malignant skin tumors (squamous cell carcinomas) and other lesions in hairless mice (groups of 38-45) intermittently exposed to ultraviolet light over a period of 15 weeks, beginning when the mice were about 10 weeks old. The several groups were given a standard diet with 0%, 0.3%, 5%, and 10% added L-ascorbic acid (vitamin C) throughout the study. No lesions developed in unirradiated control groups. The lesions were counted every 14 days for 4 months, beginning 4 weeks before the end of the period of irradiation. The observed incidence of lesions of several sizes during successive time periods was analyzed by the statistical method recommended by a committee of the International Agency for Research on Cancer. A pronounced effect of vitamin C in decreasing the incidence and delaying the onset of the malignant lesions was observed with high statistical significance.
TL;DR: The archetype food supplement user was likely to be a young female with some college education, who believes that the nutritional quality of food has decreased in the last 10 yr and in the efficacy of supplements for disease prevention or cure, and primarily receives information concerning food and nutrition from books and health food stores.
TL;DR: Measurements of ascorbic acid concentration in leukocytes by "high-performance" liquid chromatography (HPLC) provides better nutritional assessment, leading to better management, particularly of presymptomatic and critically ill patients.
Abstract: Measurements of ascorbic acid concentration in leukocytes by "high-performance" liquid chromatography (HPLC) provides better nutritional assessment, leading to better management, particularly of presymptomatic and critically ill patients. This procedure includes a simple, reproducible cell-separation technique that requires no more than 2 mL of whole blood. Cell populations are separable with greater than 95% purity and greater than 99% viability. Ascorbic acid is assayed by HPLC. The vitamin can be reproducibly quantified in concentrations as low as 0.1 microgram/mL of cell extract. The chromatographic procedure is very rapid, analysis being completed within 15 min after specimen preparation. The assay is suitable also for urine and protein-free filtrates of plasma and of other biological materials. Reference intervals for plasma, mononuclear leukocytes, and polymorphonuclear leukocytes were established. A preliminary clinical evaluation revealed that hospital patients were at a greater risk of ascorbic acid deficiency than expected.