Showing papers on "Ascorbic acid published in 1977"

Air pollution and ascorbic acid

Abstract: Well-lighted plants may contain considerable amounts of ascorbic acid (AA) particularly in their chloroplasts. AA is known to be a strong reductant which fulfils several functions in photosynthesis. AA may also influence detoxification of polluted plants, e.g. by reducing SO2. AA contents of forest tree species were distinctly decreased by shading, particularly in light demanding species. Continued SO2 fumigation depressed AA contents long before visible symptoms of injury appeared. AA thus deserves more attention in physiological air pollution research.

Determination of Orthophosphate in Aqueous Solutions Containing Labile Organic and Inorganic Phosphorus Compounds

Abstract: A simple and precise colorimetric method of determining orthophosphate in aqueous solutions containing labile organic and inorganic P compounds is described. It involves a rapid formation of molybdenum blue color by the reaction of Orthophosphate with molybdate ions in the presence of ascorbic acid-trichloroacetic acid and citrate-arsenite reagents and complexation of the excess molybdate ions to prevent further formation of blue color from the phosphate derived from hydrolysis of the acid-labile P compounds. The color is stable up to 24 hours. The method is sensitive and accurate, and it permits determination of microgram quantities of Orthophosphate in samples containing large amounts of acid-labile P compounds. Tests with a wide range of condensed phosphate and organic phosphate compounds showed that none of the P compounds studied interfered with this method. Results by this method are compared with those obtained by the method of Murphy and Riley. Additional Index Words: water quality, phosphorus fertilizers. Several methods have been proposed for determination of Orthophosphate in aqueous solutions. These include gravimetric, titrimetric, photometric, spectrophotometric, chromatographic, and radioactivation analysis (15). Some of these methods are tedious and time consuming, and others require special equipment and do not give reproducible results. Among the methods mentioned, however, the spectrophotometric heteropoly blue (molybdenum blue) color method is the most simple, sensitive, and accurate, especially for analysis of Orthophosphate at low concentrations. This method was developed by Osmond in 1887 (13), and since then, it has been modified by many workers. It involves the reaction of an acid ammonium molybdate solution with Orthophosphate ions to form a 'journal Pap. J-8518 of the Iowa Agric. & Home Econ. Exp. Stn., Arnes, Iowa. Projects 1868 and 2112. Received 11 June 1976. Graduate Research Assistant and Associate Professor, respectively, Dep. of Agron., Iowa State Univ., Arnes, IA 50011. molybdophosphoric acid complex, which can be reduced to molybdenum blue in the aqueous phase (3, 7) or be reduced after extraction with an appropriate solution (4, 5, 8, 11, 14, 16). The most widely used procedure within the past decade, however, has been the one developed by Murphy and Riley (12). In this method, ascorbic acid is used as a reducing agent, and addition of antimony produces a molybdenum blue color in about 10 min that is stable for 24 hours. Several inorganic P(e.g.,Na tripolyphosphate, tetrasodium pyrophosphate, and Na hexaphosphate) and organic P compounds (e.g., adenosine triphosphate, fructose-6-phosphate, fructose-cliphosphate, and glucose-1-phosphate), however, interfere with this method. This interference may range from 2 to 10% for the condensed phosphates and from 0.1 to 10% for the organic P compounds present (6, 10), if the color measurement is made after 10 min. The percentage inference will increase with time of color development, because of hydrolysis of these P compounds in the acid medium. Pollution of water resources by phosphate derived from soils and fertilizers has generated interest in finding organic and inorganic P fertilizers that allow movement of P to the root zone and decrease phosphate fixation by soils, and thereby increase the fertilizer P use efficiency. Movement of such P compounds in soils allows their hydrolysis by soil and root enzymes in areas where the fertilizer is needed for plant uptake. One of the major difficulties in studying these P fertilizers is associated with the methods used for determination of Orthophosphate in presence of the acid-labile organic and inorganic P compounds. Also, the organic and condensed P compounds are very widely distributed in nature. They are present in water (5), soils (C. P. Ghonsikar. 1970. Naturally-occurring polyphosphates in soils—Reactions of these and other polyphosphate materials in soils. Unpublished Ph.D. Thesis. Dep. of Agron., Ohio State Univ., Columbus, Ohio), and microorganisms (9). Their presence in aqueous solutions may 82 J. Environ. Qua!., Vol. 6, no. 1, 1977 give misleading results of the amount of orthophosphate present in such samples. We required a simple, accurate, and specific method for determination of orthophosphate in the presence of various organic and inorganic P compounds. The method developed meets these requirements. It involves a rapid formation of molybdenum blue color from the reaction of orthophosphate with molybdate ions in the presence of ascorbic acid-trichloroacetic acid and citrate-arsenite reagents and complexation of the excess molybdate ions to prevent further formation of blue color from the phosphate derived from hydrolysis of the acid-labile P compounds. MATERIALS AND METHODS

Hydrocarbon gases produced during in vitro peroxidation of polyunsaturated fatty acids and decomposition of preformed hydroperoxides

Abstract: Hydrocarbon gases have been used previously as an index of lipid peroxidation in vivo and in vitro. In vitro experiments are reported on the formation of hydrocarbon gases from peroxidizing ω-3 and ω-6 fatty acids. Hydrocarbon gases were not related during a 20-hr peroxidation phase but were released following the decomposition of hydroperoxides by addition of excess ascorbic acid. The major hydrocarbon gas products in iron, copper, or hematin catalyzed peroxidation systems were ethane or ethylene from linolenic acid, and pentane from linoleic acid and arachidonic acid. Calculations of the ratios of hydrocarbon gases formed were based on fatty acid decrease and/or change in diene conjugation and peroxide values. Depending on the fatty acid, catalyst, and calculation basis used, pentane formation was a high as 1.3 mol %, ethanol 4.3 mol %, and ethylene 10.6 mol %.

Damage to ram spermatozoa by peroxidation of endogenous phospholipids

Abstract: We examined the damaging effects on spermatozoa of endogenous phospholipid peroxidation brought about by aerobic incubation at 37 degrees C in the presence of 0-5 mM-ascorbic acid and 0-5 mM-FeSO4. As well as becoming immotile, such peroxidized spermatozoa also lost, through leakage, certain intracellular enzymes into the surrounding medium, on a scale resembling that produced by cold shocking non-peroxidized spermatozoa. Morphological observations revealed that peroxidation damaged the plasma membrane, particularly in the region of the acrosome. Further experiments showed that lipid peroxidation irreversibly abolished the fructolytic and respiratory activity of spermatozoa. The susceptibility of spermatozoa to peroxidation was greater when the cells were damaged before incubation with ascorbic acid and FeSO4. To some extent, peroxidation could be prevented, but not reversed, by the addition to sperm suspensions of dialysed egg yolk or dialysed bull seminal plasma. However, dialysed seminal plasma from ram, stallion or man had no protective effect.

Protective effect of drugs on histamine-induced asthma.

Abstract: Controlled standardised histamine inhalation tests were carried out in 21 asthmatics to determine the degree of non-specific bronchial hyperreactivity with and without prior treatment with several anti-asthmatic drugs. A significant protective effect was produced by inhaled salbutamol, 200 microgram, ingested salbutamol, 4 mg, inhaled Sch1000, 40 microgram inhaled atropine sulphate, 290 microgram, and ingested choline theophylinate (200 or 400 mg) producing serum theophylline levels over 10 mg/l. Inhaled salbutamol was consistently the most effective and was significantly better than the other drugs. The protective effect between the other four was not significantly different. Drug side-effects occurred only with the ingested drugs. No significant protection was detected after ingested choline theophyllinate producing serum theophylline levels of less than 10 mg/l, inhaled sodium cromoglycate, 20 mg given once or six-hourly for one week, or ingested ascorbic acid, 1 gram.

The inhibition of lipid autoxidation by human caeruloplasmin.

Abstract: 1. Purified caeruloplasmin was shown to inhibit lipid autoxidation induced by ascorbic acid or inorganic iron in the following systems: (a) an emulsion of linolenic acid in water; (b) an untreated ox brain homogenate in phosphate buffer; (c) a similar homogenate whose susceptibility to autoxidation had been abolished by dialysis or by heating and then restored by the above pro-oxidants. 2. The optimum conditions for this antioxidant activity were studied. 3. Caeruloplasmin did not inhibit autoxidation by u.v. irradiation in dialysed or preheated homogenates. 4. The apoprotein (without copper) had no antioxidant activity, whereas CuSO4 alone was much less effective as an antioxidant. 5. Iron-free transferrin also had some antioxidant activity.

Enzymatische Bestimmung des Gesamtcholesterins mit dem Greiner Selective Analyzer (GSA-II)

Abstract: A fully enzymatic method to determine total cholesterol in serum is described. The method appears especially suitable for adaptation to discrete mechanical analyzers either of the single channel or the multi-channel type. The method uses the enzymes cholesterol esterase (EC 3.1.1.13), cholesterol oxidase (EC 1.1.3.6) and peroxidase (EC 1.11.1.7) with 4-aminophenazone and phenol as substrates in the indicator reaction. The method was adapted to the Greiner Selective Analyzer GSA-II. For this purpose the critical parameters of the reaction were intensively examined. The complete reagent is stable within the GSA II dispenser at 4 degrees C for at least 1 week. By omitting cholesterol oxidase in the blank reagent a sample bland and a partial reagent blank are obtained. Within a range up to 10.4 mmol/1 (4.0 g/l) the maximum colour is developed within 6 minutes. The calibration factor was stable for 4 months. The method allows absolute measurements. At concentrations between 2 and 4 mmol/1 within-batch precision ranged from 0.5 to 1.4%. Precision from day to day for the same control sera amounted to 2.8; 2.0; 2.7 and 2.0% for a period of 3 months. Examination of accuracy yielded satisfying results. Ascorbic acid in the physiological range did not alter results to a significant extent. Catalase or novaminesulfone added in vitro did not interfere. Optical interferences by bilirubin, hemoglobin or turbidity are compensated by a sample blank. A comparison of results with the enzymatic method of Roeschlau et al. (Z. Klin. Chem. Klin. Biochem. 12, 226 (1974)) yielded satisfactory agreement. The limits of detection of the present method can be lowered by a factor of 2.2 by replacing phenol by dihalogen phenols.

Catecholamine binding to the beta-adrenergic receptor

Abstract: The adenylate cyclase-coupled beta-adrenergic receptors of frog erythrocyte membranes have been identified by direct radioligand binding techniques using the potent catecholamine agonist (+/-)[3H]hydroxybenzylisproterenol (2-[3, 4-dihydroxyphenyl]-2-hydroxy-1', 1'-dimethyl-2'-[4-hydroxyphenyl]-diethylamine). The successful experimental conditions included the use of (i) high concentrations of catechol and ascorbic acid to suppress nonreceptor binding, (ii) a very potent radiolabeled catecholamine (10 times more potent than isoproterenol), and (iii) membranes rich in binding sites for beta-adrenergic receptors. Thus, previous problems in accomplishing successful catecholamine binding to the beta-receptors have been overcome. The binding sites identified with (+/-)[3H]hydroxybenzylisoproterenol in the erythrocyte membranes have all the characteristics expected of true beta-adrenergic receptors. These include rapidity of binding, saturability, specificity for beta-agonists and antagonists, and stereospecificity [(-)isomers more potent than (+)isomers]. Physiologically inactive compounds containing a catechol moiety do not compete for occupancy of these binding sites. Dissociation of the radiolabeled agonist from the receptors is slow and incomplete in the absence of guanine nucleotides. In the presence of nucleotide, however, dissociation is rapid and complete. beta-Adrenergic agonists and antagonists compete for the (+/-)[3H]hydroxybenzylisoproterenol binding sites in a fashion parallel to their competition for the receptors, as previously delineated with the beta-adrenergic antagonist (-)[3H]dihydroalprenolol.

Mechanism of L-ascorbic acid oxidation and dehydro-L-ascorbic acid reduction on a mercury electrode. I. Acid medium

Abstract: A polarographic study of the oxidation mechanism of L-ascorbic acid and of the reduction mechanism of dehydro-L-ascorbic acid was carried out in an acid medium.For L-ascorbic acid, the oxidation pr...

Oxidation of Ascorbate Anion by Electron Transfer to Phenoxyl Radicals

Abstract: Most phenoxyl radicals rapidly oxidize ascorbate anion (rate constants from 4 to 20 x 10/sup 8/ M/sup -1/ sec/sup -1/) by a simple electron transfer process. The product radical anion is relatively unreactive and has a well-characterized absorption at 360 nm where it has an extinction coefficient of 3300 M/sup -1/ cm/sup -1/. In the case of a phenoxyl radical produced by OH attack on phenol, oxidation appears to be quantitative. Ascorbate is oxidized only slowly or not at all by less reactive radicals, such as the alcohol radicals, para-semiquinones, or the phenyl radical. Ascorbate can, therefore, be used to selectively remove phenoxyl radicals from many mixed radical systems. Because ascorbate radical anion absorbs only weakly above 390 nm, where phenoxyl and para-semiquinone radicals absorb more strongly, ascorbate can be used to examine the oxidation of substrates in cases where phenoxyl and semiquinone radicals are produced simultaneously. This application is illustrated by a study of the attack of OH at the fluorine position of para-fluorophenol. A second illustrative example is provided by a study of the tertiary oxidation of ascorbate following reduction of the bromophenols by e/sub aq//sup -/. It is shown, in agreement with previous optical and ESR studies,more » that phenoxyl radicals are produced by rapid protonation of the hydroxyphenyl radical anion in the case of the ortho- and para-isomers but not in the case of the meta-isomer.« less

Method for the determination of substrates or enzyme activities

Abstract: In a process for the determination of substrates or enzyme activities in a test batch, utilizing a conventional redox reaction as a measurement reaction, the improvement comprising carrying out the process in the presence of ascorbate oxidase; the addition of ascorbate oxidase substantially eliminates the interfering effect of ascorbic acid frequently found in the test sample.

Assessment of carcinogenic volatile N-nitrosamines in tobacco and in mainstream and sidestream smoke from cigarettes.

Abstract: Summary Volatile N-nitrosamines were quantitatively determined in tobacco and fresh cigarette mainstream and sidestream smoke with a thermal energy analyzer. The smoke was trapped in ascorbic acid solution buffered at pH 4.5 and then extracted with dichloromethane; the organic phase was chromatographed on basic alumina and analyzed by gas-liquid chromatography with a thermal energy analyzer (sensitivity, 50 pg/injection). For positive identification the volatile nitrosamines were further enriched by distillation and chromatography and then identified by gas-liquid chromatography and mass spectrometry. In the un-aged mainstream smoke of 17 commercial and experimental cigarettes we found between 1.7 and 97 ng of dimethylnitrosamine, 0.1 and 9.1 ng of methylethylnitrosamine, up to 4.8 ng diethylnitrosamine, and between 2.6 and 52 ng nitrosopyrrolidine. The un-aged sidestream smoke of cigarettes contained these volatile nitrosamines in far greater concentrations with 680 to 1770 ng dimethylnitrosamine 9 to 75 ng methylethylnitrosamine, 8 to 73 ng diethylnitrosamine, and 204 to 612 ng nitrosopyrrolidine. The nitrate content of tobacco appears to be a determining factor for the concentration of volatile nitrosamines in the smoke. Selective removal of these nitrosamines does occur with cellulose acetate filter tips, but not with charcoal filter tips. Traces of volatile nitrosamines (7 to 190 ppb) were also found in processed tobacco.

PROOXIDANT AND ANTIOXIDANT EFFECTS OF ASCORBIC ACID AND METAL SALTS IN A β‐CAROTENE‐LINOLEATE MODEL SYSTEM

Abstract: The interacting effects of ascorbic acid and metal ions on carotene oxidation were studied in an aqueous carotene-linoleate solution at pH 7. Ascorbic acid at concentrations up to 10—3 M was a prooxidant. Fe3+ and, to a lesser extent Co2+, acted synergistically with ascorbic acid, the prooxidant effect increasing with metal concentration. Cu2+ formed a prooxidant system with ascorbic acid only at low metal concentration, but as the copper concentration was raised, inversion of activity occurred and the copper-ascorbic acid system exerted a stabilizing action on carotene. Prooxidant effects were enhanced and antioxidant effects weakened in the presence of added lmoleate hydroperoxides. The latter were unstable in the presence of ascorbic acid and especially ascorbic acid + Cu2+. Ascorbic acid itself became unstable in the presence of Cu2+. Oxygen depletion, brought about by the rapid oxidation of ascorbic acid, may be partly responsible for the carotene-stabilizing effect of the Cu*+-ascorbic acid couple. It is postulated that additional stabilization results from the radical-scavenging properties of copper or of a copper chelate formed by ascorbic and/or dehydro-ascorbic acid.

Effects of a prolonged vitamin E deficiency in the rat.

Abstract: Rats fed a vitamin E-deficient diet containing 10% "stripped" corn oil had reduced growth rate and elevated platelet count by 12 weeks of age, and a normocytic anemia with elevated reticulocytes by 16 weeks of age. After 5 months, rats became emaciated and developed kyphoscoliosis. Some rats developed skin ulcers and tremors, and mortality was high. Neuromuscular lesions included a chronic necrotizing myopathy and localized axonal dystrophy. There was also a selective activation of lysosomes in the central nervous system microcirculation. Liver ascorbic acid of deficient rats was the same as in those receiving vitamin E. Urinary excretion of p-hydroxyphenylpyruvate after a tyrosine load was also the same in deficient and control rats. It was concluded that neither vitamin C synthesis or utilization was affected the E-deficient rats.

Inhibition by L -ascorbate of bacterial mutagenesis induced by two N -nitroso compounds

Abstract: MANY chemicals are activated to carcinogens and mutagens by oxidative metabolism to alkylating agents1. Ascorbic acid has been reported to protect against tumour induction in mice by 3-hydroxyanthranilic acid, which induced bladder tumours2 and 7,12-dimethylbenzanthracene plus croton oil which induced skin tumours3. Ascorbic acid can also prevent the formation of carcinogenic N-nitroso compounds from nitrite and amines, in vivo4 and in vitro5. I report here that mutagenesis by two preformed N-nitroso compounds is effectively inhibited by ascorbic acid.

Dependence of the differentiated state on the cellular environment: modulation of collagen synthesis in tendon cells

Abstract: In an adequate environment, primary avian tendon cells are capable of retaining both the full expression of differentiated function and a correct morphological orientation for 1 week in culture. At high density and in the presence of ascorbate, they are fully stabilized in that they devote 25-30% of their total protein synthesis to collagen, a level comparable to that in tendon cells in ovo. However, either at low density or in medium without ascorbate, they synthesize collagen at only a third of this level. If plated on a collagen matrix, these cells will orient themselves in a manner similar to that of tendon cells in vivo. Furthermore, they are capable of fully modulating the percentage of collagen synthesis upon addition or removal of ascorbate and serum. The variation in the percentage of collagen produced is a result of alterations in collagen synthesis rather than of changes in total protein synthesis or hydroxylation of proline in collagen. Primary avian tendon cells, therefore, provide a suitable model for understanding the stability of the differentiated state, the mechanism of action of ascorbate, and the regulation of collagen biosynthesis.

Iron absorption from a cereal based meal containing cane sugar fortified with ascorbic acid

Abstract: 1. The feasibility of improving iron nutrition by fortifying cane sugar with ascorbic acid was studied. 2. The absorption of Fe added to maize-weal porridge was measured in 116 volunteer multiparous Indian women using the radio-Fe erythrocyte utilization method. The meals were fed with and without tea or coffee and with and without varying amounts of ascorbic acid. 3. The mean absorption of Fe from maize-meal porridge was very low (3.8 %), being even further reduced (2.1 %) when tea was drunk with the meal. 4. The addition of 50 or 100 mg ascorbic acid to maize-meal porridge caused approximately a 10-fold increase in Fe absorption. The increase was much less when tea was present, being 2-fold and 5-fold with 50 and 100 mg ascorbic acid respectively. The inhibitory effect of tea on Fe absorption could, however, be overcome by giving larger doses of ascorbic acid (250 and 500 mg). 5. When contaminating Fe (2.5 mg) in the form of labelled rust (Fe,O,) or ferric hydroxide was added to maize-meal porridge it was poorly absorbed (mean values were 0.01 % and 1.5 % respectively). The addition of 100 mg ascorbic acid increased the mean Fe absorption rates to 0.5 % and 6.7 %with Fep03 and Fe(OH), respectively. Fe(OH), was found to be absorbed about half as well as the intrinsic Fe present in maize-meal porridge. 6. It is concluded that ascorbic acid is capable of improving Fe absorption from a cereal source. It can partially overcome the inhibitory effect of tea and might be expected to facilitate the absorption of at least some forms of Fe that may contaminate food. Current methods aimed at promoting adequate iron nutrition in communities that are at risk of Fe deficiency have relied on the fortification of dietary staples with added Fe. How

A pulse-radiolysis study of the catalytic mechanism of the iron-containing superoxide dismutase from Photobacterium leiognathi.

Abstract: The mechanism of the enzymic reaction of an iron-containing superoxide dismutase purified from the marine bacterium Photobacterium leiognathi was studied by using pulse radiolysis. Measurements of activity were done with two different preparations of enzyme containing either 1.6 or 1.15 g-atom of iron/mol. In both cases, identical values of the second-order rate constant for reaction between superoxide dismutase and the superoxide ion in the pH range 6.2-9.0 (k=5.5 X 10(8) M-1-S-1 at pH 8.0) were found. As with the bovine erythrocuprein, there was no evidence for substrate saturation. The effects of reducing agents (H2O2, sodium ascorbate or CO2 radicals) on the visible and the electron-paramagnetic-resonance spectra of the superoxide dismutase containing 1.6 g-atom of ferric iron/mol indicate that this enzyme contains two different types of iron. Turnover experiments demonstrate that only that fraction of the ferric iron that is reduced by H2O2 is involved in the catalysis, being alternately oxidized and reduced by O2; both the oxidation and the reduction steps have a rate constant equal to that measured under turnover conditions. These results are interpreted by assuming that the superoxide dismutase isolated from the organism contains 1 g-atom of catalytic iron/mol and a variable amount of non-catalytic iron. This interpretation is discused in relation to the stoicheiometry reported for iron-containing superoxide dismutases prepared from several other organisms.

Analysis of water soluble vitamins by high pressure liquid chromatography.

Abstract: Resolution of the water-soluble vitamins--pyridoxin, riboflavin, niacinamide, vitamin B12, thiamin, ascorbic acid, niacin and folic acid--by high pressure liquid chromatography was examined on two bonded-phase columns, muBondapak C18 and muBondapak NH2. The effect on the retention times of individual vitamins and the separation of a multivitamin sample was determined using varying proportions of water/methanol as the eluting solvent and by addition of various salts, buffer solutions and PIC reagents to the water/methanol. Each vitamin was able to be eluted satisfactorily from muBondapak C18. It was found that seven vitamins could be resolved from a multivitamin mixture in a single analysis in several solvent systems with the total time for the analyses being always less than 40 min. With muBondapak NH2, all the vitamins except folic acid were eluted and six vitamins could be resolved from a mixture in a single analysis. The speed of analysis was greater with muBondapak NH2 with all compounds eluted in 15 min and the peaks were sharper. The order of elution was essentially the reverse of that obtained with muBondapak C18.