Ascorbic Acid In Aqueous Solution Research Articles

Elevated Temperature Studies on Stability of Ascorbic Acid in Certain Fruit Juice and Aqueous Vehicles

The stability of ascorbic acid was investigated in certain fruit juice and aqueous vehicles between pH 2.5–6.5 at 37 and 55° in the presence of 0.2 per cent citric acid, 0.01 per cent EDTA, 0.01 per cent propyl gallate, 0.2 per cent ferrous gluconate, 0.2 per cent cysteine hydrochloride, and 0.2 per cent potassium m -bisulfite. Lime juice—sorbitol—glycerol (2:2:1) retained 70 per cent ascorbic acid at pH 6.5 after 120 days. Citric acid also protected ascorbic acid. EDTA gave little protection to ascorbic acid. The loss of ascorbic acid in aqueous solution at some pH values was counteracted by 0.9 per cent sodium chloride. Dihydrosteptomycin sulfate in the concentration of 0.33 mg./ml. gave protection to ascorbic acid at all pH levels, except at pH 6.5 (37°) and at pH 5.5 (55°), where a destructive effect was noticed. Stability of ascorbic acid was a function of pH, temperature, vehicle, and head space in the container.

Rate of Anaerobic Degradation of Ascorbic Acid in Aqueous Solution

The pH rate profile of the rate of disappearance of ascorbic acid from aqueous solution under anaerobic conditions has been determined at 96°. The dependency on pH is surprisingly low over pH range of 1-11. The profile shows a small but apparently real maximum at pH = pKa 1 , an effect which can be rationalized by assuming formation of a salt-acid complex in solutions. The anaerobic rate shows buffer dependency but relatively small ionic strength effect.

Radiolysis of Ascorbic Acid in Aqueous Solution by Gamma Radiation

Interest in the application of high-energy ionizing radiation for food sterilization has led a number workers to investigate the radiation sensitivity of vitamins (1-7). Ascorbic acid, which is known to be very sensitive to oxidation, has received special attention (3-7). Anderson and Harrison (3) studied the effect of X-rays on ascorbic acid in simple solution and in mixtures of naturally occurring compounds. Later, Proctor and co-workers (5, 6) reported in a series of papers the effect of X-rays on the destruction of ascorbic acid, riboflavin, and niacin in aqueous solutions. In the above studies, ascorbic acid was found to be highly sensitive to X-irradiation. Since the main interest in these investigations was to determine vitamin losses on irradiation, little attention was paid to evaluating quantitatively the interaction of radiation with ascorbic acid per se. Further, these workers used ascorbic acid solutions containing either oxalic acid (4-7) or metaphosphoric acid (3) in order to minimize the natural destruction of ascorbic acid. Since the interaction of radiation with ascorbic acid is likely to be modified by the presence of these other solutes, the reported results may not describe its true radiolysis. Moreover, no reports are available which describe in detail the sequence of chemical changes that take place in ascorbic acid solutions on irradiation.

Rubeanic acid as stabilizer of aqueous solutions of ascorbic acid.

ESPECIALLY noteworthy among the stabilizers of ascorbic acid solutions are sulphydric organic derivatives such as glutathione, thiourea, methylthiouracyl, cysteine1–3, 2-carbethoxy-mercapto-1-methylglyoxaline2,3, dithioglycerin, thioglycolic acid2, etc. On the other hand, acids have found application as agents reducing the rate of oxidation of ascorbic acid in solutions. Among these oxalic acid plays an important part. In 2 per cent and 1 per cent dilutions it is applied as a stabilizer of synthetic ascorbic acid in various solutions and of ascorbic acid in biological material.

ASSOCIATION BETWEEN ASCORBIC ACID CONCENTRATION AND COLD HARDENING IN YOUNG WINTER WHEAT SEEDLINGS

The ascorbic acid content of winter wheat varieties, germinated in the dark at various temperatures on the surface of moist vermiculite, was much higher at a hardening temperature of 1.5 °C than at higher temperatures of 5°, 10°, or 20 °C. There were no differences between the ascorbic acid contents of wheat grown at the three higher temperatures. Ascorbic acid content was dependent on the stage of development at all temperatures. At 1.5 °C, the ascorbic acid content increased during the first 6 weeks of growth (shoots about 15 mm) and then decreased rapidly. This variation in ascorbic acid content was closely associated with the increase and decrease in cold hardiness of wheat grown under similar conditions.Ascorbic acid content was highest in shoots, intermediate in roots, and lowest in the endosperm of wheat grown for 6 weeks at 1.5 °C.At hardening temperatures (1.5° and 3 °C) the more cold hardy winter wheat varieties had higher contents of ascorbic acid. At higher temperatures the differences between varieties were small. The ranking of varieties by ascorbic acid content could be influenced by relative stages of growth.Artificial cold hardiness was imparted to winter wheat seedlings by feeding them aqueous ascorbic acid solutions of adequate concentration. The ascorbic acid content of leaves required for artificial hardening appeared to be similar to that accumulated in sprouts hardened fully by growth at low temperature.

抗菌性物質の化学的定量法 第7報

Determination of Oleandomycin was attempted by the following process. A 0.5-cc portion of 1% hydrochloric acid solution of sulfanilic acid was diazotized with 1cc of 1% aqueous solution of sodium nitrite, for 2 minutes in ice water, the resultant solution was shaken with 1cc. of 0.40 N aqueous solution of sodium hydroxide and 0.5cc. of pyridine, 2cc. of aqueous solution of Oleandomycin phosphate (25-300γ/cc. sample solution) was added, and after warming at 30° for 30 minutes, this was shaken vigorously with 3cc. of ethanol and 1cc. of 0.5% aqueous solution of ascorbic acid. This solution colored pink and showed absorption at 532mμ, and the absorbancy was found to be proportional to the concentration, within a range of 25-300γ/cc. of sample concentration.Comparison of values of determination by the present process and by bioassay, using aqueous solution of Oleandomycin phosphate left to stand in a refigerator, at room temperature, and at 37°, for a long period to effect some degree of decomposition, gave well agreeing results. It was found that the aqueous solution of Oleandomycin, when stored at a low temperature, shows almost no decrease in potency even for a long period of time.

Amount of Ascorbic Acid in Normal Epidermis

In undertaking investigations of the function of ascorbic acid in the skin no reference could be found in the literature concerning the amount of ascorbic acid in epidermis. Jensen and Poulsen in 1942 made an extensive study of the concentration of ascorbic acid in 181 specimens of skin obtained by punch biopsy from 72 persons. They extracted the tissue with 8% metaphosphoric acid solution TABLE I Specimen Area Cause of Amputation Ascorbic Acid, mg. per 100 gm. wet weight Epidermis Corium Whole Skin 1 2 3 4 5 6 7 8 9* 10 Breast Breast Leg Leg Breast Leg Breast Breast Breast Breast Carcinoma Carcinoma Sarcoma of bone Arterial thrombosis Carcinoma Diabetic gangrene Carcinoma Carcinoma Carcinoma Carcinoma 8.35 8.26 4.94 6.64 6.63 6.89 12.80 5.41 11.31 13.40 3.48 1.00 0.18 3.37 4.98 3.08 6.40 3.23 4.25 7.00 7.30 9.90 Negro and titrated this extract with a solution of 2,6-dichlorophenol indophenol which had been standardized with an aqueous solution of ascorbic acid of known concentration. In 95% of the specimens of normal skin they found concentrations of ascorbic acid varying from 0 to 10 mg. per 100 grams of skin (wet weight). At that time no satisfactory method was available for separating epidermis from corium without some chemical alteration (1).

The stability of ascorbic acid in various liquid media

The stability of ascorbic acid at several concentrations in various liquid media including aqueous solutions of cellulose gums, pectin, sucrose, dextrose, corn syrup, and in glycerin and propylene glycol was studied. The effect of pH in aqueous solutions of ascorbic acid was also studied. Viscosity alone as produced by gums did not prevent decomposition of ascorbic acid. Sugar and sorbitol solutions exerted a marked stabilizing effect. Ascorbic acid was relatively stable in glycerin and propylene glycol and in sugar and sorbitol solutions. Data are presented on the rates of decomposition of ascorbic acid in these media after storage at room temperature and at 40°C. The stability of ascorbic acid in syrups containing conjointly vitamins of the B‐complex is not materially affected.

THE STABILITY OF ASCORBIC ACID IN SOLUTION

The stability of ascorbic acid in aqueous solution was increased under certain conditions by oxalic acid, metaphosphoric acid, glutathione, thiourea, and sodium diethyldithiocarbamate. A slight protective effect was exerted by creatinine; but formic, phthalic, and orthophosphoric acids, creatine, and caffeine had no demonstrable effect. In all these instances the pH, concentrations of reagents, etc., must be considered. In oxalate and thiourea maximum stability occurred at pH 2.5 to 3.0 and in glutathione at pH 3.6 to 4.2. The latter substance itself was also most stable at pH 3 to 4. At the optimum pH a concentration of 40 mM of oxalate gave maximal protection, this being independent of the initial concentration of ascorbic acid over the range 2 to 20 mM. Thus a stoichiometric relationship between the concentrations of the ascorbic acid and the oxalate required for protection was not found. A region of minimum solubility of oxalate in water occurred at pH 2.4 to 3.0, which coincides with the pH at which the maximum protective effect occurs and with the highest relative concentration of sodium hydrogen oxalate (or sodium hydrogen oxalate monohydrate). The absorption of ultraviolet light by ascorbic acid was altered by pH, the maximum shifting from 244 to 268 mμ from pH 2.8 to 4.5. The molecular extinction coefficient of ascorbic acid also changed with pH and was minimal at pH 4.0. This effect occurred in oxalate, which has a specific protective effect, and also in formate and orthophosphate, which have no specific protective effect. The possible mechanisms for the protection of ascorbic acid by oxalate are discussed.