Pure Ascorbic Acid Research Articles

A D-Carnitine Dehydrogenase Electrode For The Assessment Of Enantiomeric Purity Of L-Carnitine Preparations

ABSTRACT The enantiomeric purity of pharmaceutical L-carnitine preparations can be assessed within 60 seconds using a highly selective bienzyme electrode. D-carnitine dehydrogenase from Agmbacterium is highly specific for the non-physiological D-enantiomer and was therefore used as the recognition element. NADH produced in the primary reaction was oxidized by salicylate hydroxylase (EC 1.14.13.1) in an oxygen and salicylate dependent reaction. The consumption of oxygen was monitored with a miniature Clark-electrode. A linear calibration graph from 0.01 mM through 0.6 mM D-carnitine was obtained in phosphate buffer pH 8 comprising 0.5 mM concentrations of the cosubstrates NAD and salicylate. The sensitivity for DL-carnitine was exactly 50% of the respective value for pure D-carnitine, while L-carnitine and ascorbic acid, a common interferent, gave no response at all. Mixtures of both enantiomers containing 1% and 3% D-carnitine, respectively, could be distinguished from each other and from pure (i.e. >98 %) L-carnitine preparations with the new sensor. The biosensor method is faster and less laborious than established HPLC and 1H-NMR methods since it requires no chemical derivatization. The lower detection limit was 10-fold reduced as compared with a recently published enzymatic assay.

Total antioxidant capacity of teas by the ferric reducing/antioxidant power assay.

This study aimed to compare in vitro antioxidant power of different types of tea (Camellia sinensis). The ferric reducing/antioxidant power (FRAP) assay was used to measure the total antioxidant power of freshly prepared infusions of 25 types of teas. Results showed that different teas had widely different in vitro antioxidant power and that the antioxidant capacity was strongly correlated (r = 0. 956) with the total phenolics content of the tea. Expressed as micromol of antioxidant power/g of dried tea leaves, values ranged as 132-654 micromol/g for black ("fermented") teas, 233-532 micromol/g for Oolong ("semifermented") teas, and 272-1144 micromol/g for green ("nonfermented") teas. One cup of tea of usual strength (1-2%), therefore, can provide the same potential for improving antioxidant status as around 150 mg of pure ascorbic acid (vitamin C).

Chemical Stability of Selenious Acid in Total Parenteral Nutrition Solutions Containing Ascorbic Acid

Reduction of selenious acid (H2SeO3) to elemental Se by ascorbic acid was investigated in regard to the stability of selenite in total parenteral nutrition (TPN) solutions. [75Se] H2SeO3 (100 micrograms Se/liter) was incubated at 25 degrees C with pure ascorbic acid (100 or 500 mg/liter) or added to complete TPN solutions containing similar levels of ascorbate. The mixtures were subjected to thin layer electrophoresis at pH 5.3 to separate HSeO3- from Se degree. In complete TPN formulas, little or no reduction of HSeO3- to Se degree occurred over a 24-hr period, whereas complete reduction occurred with pure ascorbic acid. Further experiments showed that the amino acid component of the TPN formula was preventing the reduction of selenite, and that reduction of selenite by ascorbate did not occur in buffered solutions having a pH of 5 or greater. These results show that reduction of selenite is strongly influenced by pH. At the concentrations of H2SeO3 and ascorbic acid commonly used, reduction to elemental Se is unlikely to be a practical problem in TPN solutions in the near-neutral pH range.

Improvement of iron nutrition in developing countries: comparison of adding meat, soy protein, ascorbic acid, citric acid, and ferrous sulphate on iron absorption from a simple Latin American-type of meal

A study in 49 subjects compared different methods for increasing the absorption of iron from a simple Latin American-type meal composed of maize, rice, and black beans. The addition of meat (75 g) increased the nonheme iron absorption from 0.17 to 0.45 mg; soy protein in an amount corresponding to the protein content of the meat increased the absorption to 0.51 mg (due to the high iron content of soy flour); cauliflower as a source of ascorbic acid (65 mg) increased the absorption to 0.58 mg, pure ascorbic acid (50 mg) to 0.41 mg, and ferrous sulphate mixed into the meal in an amount (6 mg) corresponding to the iron content of the soy flour increased the absorption to 0.64 mg. The addition of citric acid (1 g) reduced the absorption to 0.06 mg (to about one-third). We conclude that several methods are available for increasing iron absorption from a Latin American meal and that the choice of method depends on several factors, particularly cost.

Adventitious chemistry at reduced water activities: Free radicals and polyhydroxy agents

Free radicals have been associated with loss of viability of lyophilized bacteria exposed to oxygen. Free radical concentration was proportional to the log of the oxygen pressure in the sample. Sugars, such as lactose or sucrose, preserved viability and inhibited free radical production. Lyophilized tissue, particularly liver and spleen, also reacted with oxygen to produce free radicals, which appear to be associated with ascorbic acid in the tissues. Pure ascorbic acid in air does not produce free radicals, but when mixed with protein before lyophilization it reacts with oxygen in air. When a mixture of sodium ascorbate and phenylalanine or tryptophan is lyophilized, free radicals identical to those observed in tissue are obtained. Propyl gallate and di- or trihydroxybenzoates also react with oxygen when lyophilized with phenylalanine, but the g value of the free radical is significantly less than that obtained with ascorbate. A number of amino acids and similar nitrogenous compounds act as catalysts to form propyl gallate free radicals. As with the bacterial or tissue preparations, various sugars or similar carbohydrates inhibited free radical production by either ascorbate or gallate. In the absence of water the free radicals produced by the action of oxygen on lyophilized samples are stable for years. The rate of free radical production is increased by small amounts of moisture (exposure to moist air), but at humidities over 30% rh the radicals are unstable.

Activation and other properties of ascorbic acid oxidase

The properties of several different preparations of highly pure ascorbic acid oxidase (AAO) have been studied using both the Warburg and spectrophotometric methods. Activating agents were found to affect both the initial rate and maintenance of AAO activity. The enzymic catalysis is increased when oxygen replaces air as the gas phase. AAO activity, in the presence of activator, was found to be stable even when the enzyme was stored at 0° C in a diluted state, but was unstable at—15° C or 30° C. Estimated K m for ascorbate was 5·10 −3 M and 3·9·10 −5 M as determined by the Warburg and spectrophotometric technique respectively. Activators of AAO proved to be of two general types. The largest group comprises substances which activate AAO but never inhibit at any concentration. Most of these substances are powerful copper chelators and include representative proteins, amino acids, thyroxine analogs, and nucleic acid components. Activation was also observed with Al +++ and Ca ++. Activation at low concentrations but inhibition at high levels was obtained with cyanide, diethyldithiocarbamate, and 8-hydroxyquinoline. Irreversible inhibition was observed with Cu ++ and several other metal ions. A deinhibited enzyme, however, could not be prepared. The possible sulfhydryl nature of AAO was suggested by the above data and the observation of the reversal of the phenylmercuric chloride inhibition of AAO by sulfhydryl compounds. The interpretation of the data is complicated by the ability of non-sulfhydryl compounds also to reverse and prevent the phenylmercuric chloride inhibition of AAO. The implications of these observations is considered. Several schemes are presented to account for the properties and interactions of AAO involving the release of inhibitory Cu ++ from the enzyme and the production of a highly reactive intermediate in ascorbic acid oxidation.

The determination of ascorbic acid in canned foods containing ferrous iron

AbstractInterference by ferrous iron in the determination of ascorbic acid in canned foods can be eliminated by passing an oxalic acid extract through the cation‐exchange resin Zeo‐Karb 215.This method has given satisfactory results when tested on a number of canned food products. The average recovery of pure ascorbic acid added to extracts of iron‐contaminated canned foods was 97%, and the results showed less scatter than those obtained by another method. With citrus juices that were deliberately contaminated by iron, recovery of the natural ascorbic acid was not less than 95%.Results obtained by this method for the ascorbic acid contents of canned foods were generally in good agreement with those obtained on the same samples by another method based on a different principle.

Stability of Solutions of Pure Ascorbic Acid and of Dehydroascorbic Acid

Stability of Solutions of Pure Ascorbic Acid and of Dehydroascorbic Acid

Stability of Solutions of Pure Ascorbic Acid and of Dehydroascorbic Acid

Stability of Solutions of Pure Ascorbic Acid and of Dehydroascorbic Acid

Dietary Factors Concerned in Erythropoiesis—Continued

Dietary Factors Concerned in Erythropoiesis—Continued

Studies on Malarial Parasites. V. Effects of Ascorbic Acid on Malaria (Plasmodium knowlesi) in Monkeys.

Conclusions and Summary1. Plasma and whole blood ascorbic acid levels were significantly lower in parasitized monkeys than in normal animals.2. There was an abnormal course of parasitemia in 7 of our monkeys which showed spontaneous ascorbic acid deficiency and in 2 other animals which were made ascorbic acid deficient by removing the vitamin from their diet.3. Following the administration of the pure ascorbic acid, there was a normal course of parasitemia in one of the monkeys spontaneously ascorbic acid deficient and in those made ascorbic acid deficient by dietary means.Withholding ascorbic acid therapy for more than 7 days appeared to give the spontaneously deficient monkeys time to produce an immunity and to control the infections. If ascorbic acid treatment was withheld from the animals made vitamin C deficient there was a prolongation of the course of infection but eventually the parasitemia overwhelmed the animal.

Stability of Ascorbic Acid in Metaphosphoric Acid Extracts

IT is frequently impossible to perform an analysis of ascorbic acid in foods immediately after sampling. In some cases a delay of as long as 24 hours is unavoidable, and doubts have arisen as to the reliability of the results then obtained. Most analysts now employ metaphosphoric acid or a mixture of metaphosphoric and trichloroacetic acids as the extractant, when determining ascorbic acid by titration against 2,6-dichlorophenolindophenol. We have accordingly investigated the rate of oxidation of ascorbic acid in 5 per cent metaphosphoric acid solution and in a mixture containing 2 per cent metaphosphoric acid and 5 per cent trichloroacetic acids. The solutions were pure ascorbic acid and extracts of cabbage, potato and swede.

A 2,4-Dinitrophenylhydrazine Derivative of Dehydroascorbic Acid and the Estimation of Vitamin G

When dehydroascorbic acid is treated with a saturated solution of 2,4-dinitrophenylhydrazine in N HC1, a reddish crystalline derivative is formed. The reaction is catalyzed by acetic acid. Analysis of the product obtained showed it contains two 2,4-dinitrophenylhydrazine groups in its molecule. The derivative is apparently an osazone of dehydroascorbic acid with the hydrazine groups attached to carbon atoms 2 and 3. The compound melted at 257-259° (corrected) and microanalysis showed it has the following composition: C18 H14 O12 N8Calculated: C 40.43, H 2.64, N 20.98.Found: ″40.40, ″ 2.88, 21.11.The evidence indicates the reaction is as follows:This compound was prepared as follows: 0.2 gm. of pure ascorbic acid in 200 cc. of 10% acetic acid was shaken with norit and filtered. Two volumes of 2,4-dinitrophenylhydrazine in N HC1 were added. The mixture was allowed to stand at room temperature for 72 hours and then centrifuged. The precipitate was washed 6 times with distilled water.Advantage was taken of th...

Ascorbic Acid Content of Blood

While numerous papers have appeared dealing with the ascorbic acid content of various plant and animal tissues, and urine, only a few refer to the quantity present in the blood. Van Eekelen, Emmerie, Josephy and Wolff,1 and Emmerie and Van Eekelen2 deproteinize blood, blood plasma, or serum with trichloracetic acid, precipitate interfering substances, chiefly SH compounds, with mercuric acetate, then treat with H2S, which not only precipitates the mercury but also reduces that portion of ascorbic acid which in blood occurs in a reversibly oxidized state. The H2S is later removed by a stream of nitrogen, and the ascorbic acid estimated by titration with 2:6 dichlorobenzenoneindophenol.3 Gabbe4 claims that loss of ascorbic acid occurs if a solution of pure ascorbic acid is treated with H2S in the presence of mercuric acetate, and therefore, omits this step. Tauber and Kleiner5 describe a method generally applicable to plant and animal tissues (and to blood) in which the essential features of deproteinizatio...