Photometric Determination of Reduced and Total Ascorbic Acid

Hochberg, Melvin; Melnick, Daniel; Oser, Bernard L.

doi:10.1021/i560115a011

Cited by 44 publications

(11 citation statements)

References 18 publications

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“….Ascorbic acid: -AA was determined colorimetrically by means of 2-6-dicbIorophenol indo])Iienol (21, with modifications for the dye calibration (9). Semiquantitative determinations were also carried out by means of an UV spectropbotometer, where tbe cbanges in tbe absorption of ligbt by ascorbic acid at 265 nm (7) were measured.…”

Section: Methodsmentioning

confidence: 99%

Non‐Enzymatic Reduction of Nitrite by Means of Ascorbic Acid in Citrus and Other Higher Plant Tissues

Bar‐Akiva¹,

Sternbaum²

1966

Physiologia Plantarum

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It has been proved that the nitrite reduction in the leaves and other plant tissues of citrus and other green plants is partly or mainly a non‐enzymatic chemical process, and a heat‐stable factor present in these tissues is responsible for this reduction. It is suggested that ascorbic acid plays a major role in this chemical reaction since the reduction is inhibited by ascorbic acid oxidase. A significant association was also found between the ascorbic acid content and the nitrite reduction capacity of citrus leaves. Evidence has been presented that this non‐enzymatic chemical reduction of nitrite occurs also in vivo as undetached citrus leaves on branches placed in NaNO2 solution have shown diminution of their ascorbic acid content along with the absorption of nitrite. Stronger accumulation of nitrite in these leaf tissues was observed under dark conditions, apparently due to the inhibition of the biosynthesis of the ascorbic acid.

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Section: Methodsmentioning

confidence: 99%

Non‐Enzymatic Reduction of Nitrite by Means of Ascorbic Acid in Citrus and Other Higher Plant Tissues

Bar‐Akiva¹,

Sternbaum²

1966

Physiologia Plantarum

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“…Ascorbic Ac/d.--The method of Hochberg, Melnick, and Oser (20) was reduced in scale so that final volumes were 2 ml. and were read directly in Coleman microcuvettes.…”

Section: Methodsmentioning

confidence: 99%

The Position of the Cell Nucleus in Pathways of Hydrogen Transfer: Cytochrome C, Flavoproteins, Glutathione, and Ascorbic Acid

Stern

Timonen

1954

Journal of General Physiology

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The fact that isolated cell nuclei are capable of metabolizing carbohydrate at least to the stage of pyruvate or of ribose formation (1, 2) may be taken to mean that in the course of their intracellular metabolism nuclei will reduce either the glycolytic coenzyme DPN, or the hexosemonophosphate dehydrogenase coermyme TPN. The intensity of such metabolism being similar in nucleus and cytoplasm, the proportion of total cell coenzyme reduced by the nucleus will vary with its size---some 10 per cent in a liver cell, about 50 per cent in a thymus cell. Since the coenzymes in question are not terminal acceptors of hydrogen but serve only to mediate its transfer, it is a requirement of nuclear metabolism that mechanisms exist whereby reduced nuclear coenzylnes become reoxidized. Little, however, is known about the possibilities of hydrogen transfer in nuclei, and the present communication is therefore addressed to this problem.It is almost certain that nuclei cannot transfer hydrogen to molecular oxygen, a relation unequivocally demonstrated for cytochrome oxidase in rat liver by Hogeboom, Schneider, and Striebich (3). Thus, the ultimate problem of nuclear coenzyme reoxidation--at least for aerobic cells--resolves itself into a search for pathways of hydrogen transfer between nucleus and cytoplasm. No better situation illustrative of this point is to be found than in calf thymus where the nucleus accounts for 60 per cent of total cell mass. Although the nuclei of this tissue are capable of accounting for half the glucose-6-phosphate metabolized (2), it is clear from the data of Table II that the capacity to react with molecular oxygen is entirely restricted to the particles of the peripheral cytoplasm.The restriction of terminal oxidation to autonomous mitochondrial bodies means in effect that the reoxidation of coenzymes, reduced in the course of intermediary carbohydrate metabolism, is a problem common to cytoplasm and nucleus. It will be seen, however, that cytoplasm and nucleus do not share the same mechanisms in response to this common need, even though it is ira-* Present address:

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“…Two recent methods (25,38) have been proposed for the estimation of ascorbic acid through the observed extinction values of compounds produced by the interaction of the vitamin with certain reagents. In one of these (38), ferripyridyl is combined in excess with the vitamin, and is reduced by it to ferropyridyl, which is a stable red ion whose concentration, as observed spectrophotometrically a t its absorption maximum of 510 mp, is proportional to the amount of ascorbic acid.…”

Section: Vitamin C (Cascorbic Acid)mentioning

confidence: 99%

“…In one of these (38), ferripyridyl is combined in excess with the vitamin, and is reduced by it to ferropyridyl, which is a stable red ion whose concentration, as observed spectrophotometrically a t its absorption maximum of 510 mp, is proportional to the amount of ascorbic acid. The second method (25) is based on the rate of decoloration of the dye, 2,6-dichlorophenolindophenol, under controlled temperature and pH conditions, the color intensity being determined spectrophotometrically from the absorption values a t 520 mp.…”

Section: Vitamin C (Cascorbic Acid)mentioning

confidence: 99%

The Absorption Spectra of Vitamins, Hormones, and Enzymes

Brode¹

1944

Advances in Enzymology - And Related Areas of Molecular Biology

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Photometric Determination of Reduced and Total Ascorbic Acid

Cited by 44 publications

References 18 publications

Non‐Enzymatic Reduction of Nitrite by Means of Ascorbic Acid in Citrus and Other Higher Plant Tissues

Non‐Enzymatic Reduction of Nitrite by Means of Ascorbic Acid in Citrus and Other Higher Plant Tissues

The Position of the Cell Nucleus in Pathways of Hydrogen Transfer: Cytochrome C, Flavoproteins, Glutathione, and Ascorbic Acid

The Absorption Spectra of Vitamins, Hormones, and Enzymes

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