Selected methods for the determination of ascorbic acid in animal cells, tissues, and fluids
TL;DR: This chapter discusses selected methods for the determination of ascorbic acid in animal cells, tissues, and fluids and suggests that prompt stabilization is especially important in the case of plasma or serum.
Abstract: Publisher Summary This chapter discusses selected methods for the determination of ascorbic acid in animal cells, tissues, and fluids. Methods for determining ascorbic acid are numerous. In general, chemical analyses for the vitamin are divided into two groups; the determination of the reduced form and the determination of the oxidized form. The former group of analyses is usually based upon the oxidation–reduction properties of ascorbic acid. These are widely used as the fundamental reactions in the measurement of vitamin C. The latter group of analyses is usually based upon the oxidation of the ascorbic acid and the subsequent formation of a hydrazone or a fluorophore. Best results are obtained if samples, especially plasma, are quickly stabilized with either trichloroacetic acid or metaphosphoric acid and immediately analyzed. Prompt stabilization is especially important in the case of plasma or serum. The greater stability of ascorbic acid in acid solution is because of the decreased tendency for the hydrolysis of the lactone ring with decreasing pH.
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TL;DR: The data presented in this report strongly support the hypothesis that plant tissues also synthesize NO via the nonenzymatic reduction of apoplastic nitrite and may have possible significance for germinating grain and for plant roots.
Abstract: Nitric oxide (NO) is an important signaling molecule in animals and plants. In mammals, NO is produced from Arg by the enzyme NO synthase. In plants, NO synthesis from Arg using an NO synthase-type enzyme and from nitrite using nitrate reductase has been demonstrated previously. The data presented in this report strongly support the hypothesis that plant tissues also synthesize NO via the nonenzymatic reduction of apoplastic nitrite. As measured by mass spectrometry or an NO-reactive fluorescent probe, Hordeum vulgare (barley) aleurone layers produce NO rapidly when nitrite is added to the medium in which they are incubated. NO production requires an acid apoplast and is accompanied by a loss of nitrite from the medium. Phenolic compounds in the medium can increase the rate of NO production. The possible significance of apoplastic NO production for germinating grain and for plant roots is discussed.
535 citations
Cites methods from "Selected methods for the determinat..."
...The assay described by Omaye et al. (1979) measures the ability of a sample to reduce an iron-dipyridyl complex....
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...Reducing equivalents were measured using the dipyridyl reaction (Omaye et al., 1979)....
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TL;DR: The evidence for and the evidence against the presence of the enzyme dehydroascorbate reductase in animal cells is outlined in a balanced way in an attempt to make sense of this continuing controversy.
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TL;DR: Results show that rutin exhibits antihyperglycaemic and antioxidant activity in streptozotocin-induced diabetic rats.
Abstract: Flavonoids are non-nutritive dietary components that are widely distributed in plants. The present study investigated the antihyperglycaemic and antioxidant effect of rutin, a polyphenolic flavonoid in normal and streptozotocin-induced diabetic Wistar rats. Diabetes as induced in rats by an intraperitoneal injection of streptozotocin. Rutin was orally administered to normal and diabetic rats for a period of 45 days. Fasting plasma glucose, glycosylated haemoglobin, thiobarbituric acid reactive substances and lipid hydroperoxides were significantly (P<0.05) increased, whereas insulin, C-peptide, total haemoglobin, protein levels, non-enzymic antioxidants (glutathione, vitamin C, vitamin E and ceruloplasmin) were decreased significantly (P<0.05) in diabetic rats. Oral administration of rutin to diabetic rats significantly (P<0.05) decreased fasting plasma glucose, glycosylated haemoglobin and increased insulin, C-peptide, haemoglobin and protein levels. Administration of rutin also decreased thiobarbituric acid reactive substances and lipid hydroperoxides and increased the non-enzymic antioxidants significantly (P<0.05). Treatment of normal rats with rutin did not significantly (P<0.05) alter any of the parameters studied. These results show that rutin exhibits antihyperglycaemic and antioxidant activity in streptozotocin-induced diabetic rats.
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TL;DR: Either other compounds present in plasma are likely to exert antioxidant action, or a marked synergistic action between antioxidants should be postulated to exist, as the latter hypothesis is supported by the finding that the simultaneous inactivation of ascorbate and thiol groups produces a loss in antioxidant capacity of plasma greater than the sum of the decreases produced by the separate in activation of each of the two compounds.
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TL;DR: Measurements of the quantum efficiencies of photosynthetic electron transport through photosystem II (phiPSII) and CO2 assimilation (phiCO2) were made simultaneously on leaves of maize crops in the United Kingdom during the early growing season, when chilling conditions were experienced, supporting the hypothesis that the relative flux of photosynthesis reducing equivalents to O2 via the Mehler reaction is higher when leaves develop under chilling conditions.
Abstract: Measurements of the quantum efficiencies of photosynthetic electron transport through photosystem II (φPSII) and CO2 assimilation (φCO2) were made simultaneously on leaves of maize (Zea mays) crops in the United Kingdom during the early growing season, when chilling conditions were experienced. The activities of a range of enzymes involved with scavenging active O2 species and the levels of key antioxidants were also measured. When leaves were exposed to low temperatures during development, the ratio of φPSII/φCO2 was elevated, indicating the operation of an alternative sink to CO2 for photosynthetic reducing equivalents. The activities of ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase, and superoxide dismutase and the levels of ascorbate and α-tocopherol were also elevated during chilling periods. This supports the hypothesis that the relative flux of photosynthetic reducing equivalents to O2 via the Mehler reaction is higher when leaves develop under chilling conditions. Lipoxygenase activity and lipid peroxidation were also increased during low temperatures, suggesting that lipoxygenase-mediated peroxidation of membrane lipids contributes to the oxidative damage occurring in chill-stressed leaves.
423 citations
References
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TL;DR: The availability of labeled AA, metabolites, and analogues has made it possible to follow up the appearance of these compounds or mctabolites thereof in various tissues of animals by means of dissecting the animals with subsequent determination of the radioactive material accumulated by the tissues or by Means of whole-body autoradiography.
Abstract: One of the earliest attempts to gauge the involvement of ascorbic acid (AA) in the overall metabolism was thc determination of its distribution in thc tissues. A thorough knowledge of its occurrence was believed to be pertinent to the elucidation of the physiological role of the vitamin in the organism. The availability of labeled AA, metabolites, and analogues has made it possible to follow up the appearance of these compounds or mctabolites thereof in thc various tissues of animals by means of dissecting the animals with subsequent determination of the radioactive material accumulated by the tissues or by means of whole-body autoradiography, as described in detail by Kalberer.'
417 citations
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TL;DR: A rapid simple micromethod for the determination of l -ascorbic acid in plasma and other biological tissues using orthophosphoric acid and ferric iron is presented and can be used to accurately determine 0.1 μg of the vitamin in samples of plasma andOther biological tissues.
363 citations