Ascorbic acid vitamin estimation

Industrially the most important carbohydrate hydrogenation product is sorbitol (o-glucitol), which is obtained by reduction of the carbonyl group of o-glucose [4-7]. Worldwide production is estimated to be 650 000 tons p. a. Sorbitol is used in numerous cosmetic, food and drinks formulations, and as a starting material e. g. in the manufacture of ascorbic acid (vitamin C). 

Use of an Oral Contraceptive. An estimated 10 to 11 million American women use oral contraceptives. Some have used them for many years prior to discontinuing their use in order to have a child. Researchers have found that these agents change the nutritional needs of some women. The levels of several vitamins and minerals in the blood are known to be, or suspected to be, influenced by the pill. As a result, some oral contraceptive users need increased amounts of certain nutrients in their diets to maintain normal blood levels (a sign of adequate nutrition). Folacin, a B vitamin, is of particular concern since many oral contraceptive users may need a supplement of folacin. In addition, adequate amounts of vitamin C (ascorbic acid), vitamin B-2 (riboflavin), vitamin B-6 (pyridoxine), vitamin B-12, and zinc are needed. 

Mobilization and Metabolism. The total ascorbic acid body pool in healthy adults has been estimated to be approximately 1.5 g, which increases to 2.3—2.8 g with intakes of 200 mg/d (151—158). Depletion of the body pool to 600 mg initiates physiological changes, and signs of clinical scurvy are reported when the body pool falls below 300 mg (149). Approximately 3—4% of the body pool turns over daily, representing 40—60 mg/d of metabolized, or consumed, vitamin C. Smokers have a higher metaboHc turnover rate of vitamin C (approximately 100 mg/d) and a lower body pool than nonsmokers, unless compensated through increased daily intakes of vitamin C (159). The metaboHsm of ascorbic acid varies among different species. 

Ascorbic acid, H2C6H606, also known as vitamin C, is present in many citrus fruits. It is a diprotic acid with the following values = 7.9 X 105 K = 1-6 X 10 12. What is the pH of a 0.63 M solution of ascorbic acid Estimate [HC6H606-] and [C4H6062-]. 

The main value of ACU measurement is that it makes it possible to give a fast estimate of vitamin C deficiency because in healthy subjects ascorbic acid is about 90% of total ACU [33], A strong deficit of ACU, possibly due to vitamin C deficiency, was found in patients with breast tumors (Fig. 11). 

An extractive spectrophotometric procedure based on the complexation of reduced Iron(II) with 5-Chloro-7-iodo-8-hydroxyquinoline (CIHQ) for the estimation of micro amounts of vitamin C. The resulting brown colored complex was extracted into chloroform to give a reddish brown extract which shows an absorption band at 485 nm. This chelate was formed immediately and the apparent molar absorptivity and Sandell s sensitivity for vitamin C was found to be 8.5 x 105 dm3 mol"1 cm 1 and 2.072xl0 4g cm 2. Linear relationship between absorbance and concentration of ascorbic acid is observed up to 0.8 pg ml"1. Interference studies of different substances including sugars, vitamins and amino acids, metal ions and organic acids were carried out. The utility of the method was tested by analysing some of the marketed products of vitamin C... 

Many vegetables and fruits, other than citrus, contain ascorbic acid. It was estimated that citrus fruits and tomatoes provided only 18% of the total vitamin C intake in the American diet during the decade of 1910. These two fruits supplied 41% of vitamin C in 1956-58 (6j. Today orange juice alone provides nearly 60% of the U.S. Recommended Daily Allowance (U.S. RDA) of vitamin C in the American diet (7). 

Another important field of application concerns food and beverages, especially wine, juices, and tea (A2, A11, A17, B4, K12, V7, Yl). The antioxidant components of food include vitamin E (a-tocopherol), vitamin A (retinoids), vitamin C (ascorbic acid), and also fi-carotene (provitamin A), other carotenoids (of which more than 600 compounds have been identified), flavonoids, simple phenols, and glucobrasicins (H3). Unfortunately, the TAC value of a food is not informative on the bioavailability of its antioxidants. It has been estimated that polyphenols are normally present in blood plasma at concentrations of 0.2-2 //M (PI). However, it has been demonstrated that feeding rats a quercetin-augmented diet can increase their plasma levels of quercetin and its metabolites up to 10-100 //M (M27), and transient increases in the concentration of plant-derived phenolic compounds can take place after ingestion of food and beverages, which may affect blood plasma TAC (see later). 

Prieme, H Loft, S., Nyyssonen, K Salonen, J. T., and Poulsen, H. F. (1997). Mo effect of supplemental Inn with vitamin E, ascorbic acid, or coenzyme QIO on oxidative DNA damaj>e estimated by 8-oxy-7,8-dihydTQ-2-deoxyguanosinc excretion in smokers. Am. I. Clin. iVittr, 65, 503- 507,... 

The literature contains numerous references to the use of bromine for the estimation of olefinic unsaturation in fats, oils, and petroleum products. A method for the determination of ascorbic acid in vitamin C tablets is given in Section 371-3. 

One feature of ascorbic acid that attracted attention early in its history was that it appeared to be present in the body largely in the reduced state (AA), despite the fact that it is readily oxidized to dehydroascorbic acid (DHA) in vitro. Indeed it became, for a time, a convenient but unjustified assumption that the vitamin existed wholly in the reduced form in body tissues and fluids, and therefore could be estimated quite simply by methods employing the reduction of 2 6-dichlorphenolindo-phenol. Today it is clear that if the whole vitamin content is to be accurately measured, it is necessary to estimate both AA and DHA, e.g., by the method of Roe and Kuenther (1943). 

Poly(VPGVG) is a substrate for the natural enzyme prolyl hydroxylase, which uses molecular oxygen and the cofactor vitamin C (ascorbic acid) for the reaction. Figure 7.49 also contains the temperature profile for fiber formation that results from hydroxylation by prolyl hydroxylase. When 100% hydroxylated as in poly(Val-Hyp-Gly-Val-Gly), T, is about 65° C. An estimated 1 % hydroxylation by prolyl hydroxylase results in a value of T, of about 40°C. As shown in Figure 5.1C, T is just at the very onset of the aggregation, such that raising the value of T, from about 30° to about 40° C would prevent assembly into fibers at body temperature. Prolyl hydroxylation of the polypentapeptide model of elastin impairs fiber formation at physiological temperature. 

Ascorbic acid differs from the other vitamins in that most animal species continue to synthesize it despite its availability in natural foods. I think that the only reasonable explanation of this fact is that the foods available to most animals over the past several hundred million years have not provided a supply of ascorbic acid sufficient to justify the abandonment of the mechanism of its synthesis. We are accordingly able to make an estimate of the optimum daily intake of ascorbic acid, on the basis of this fact and the assumption that the foods listed in Table 1 represent approximately the foods available to the ancestors of existing animal species. 

The estimated total amount of ascorbic acid in the human body tissues is on average 1500 mg (maximum 5 g) when completely saturated. Any excess of vitamin... 

Since ascorbic acid is water-soluble and very easily oxidized, loss of this factor in the storage and preparation of food may be great. Destruction is more rapid in neutral and alkaline solutions than in acid solutions. In patients who have achlorhydria and in those who have received alkaline medication, ascorbic acid may be destroyed in the upper intestinal tract. The vitamin is absorbed readily, and the levels of ascorbic acid in plasma are related to recent dietary intake. Tissue saturation is achieved easily with large doses of ascorbic acid, and amounts in excess of this are excreted in the urine. It has been estimated that when the tissues of an adult human being are saturated the body contains about 5 g. of ascorbic acid. 

Different investigators have employed a variety of tests for estimating the vitamin C nutrition of man and animals. The simplest of these is measurement of the L-ascorbic acid content of serum or plasma. Approximate values of L-ascorbic acid of man which may be used for guide purposes follow ... 

Vitamin C (L-ascorbic acid, l-AA), is an essential nutrient for humans and some animal species [9] (Figure 10.1). l-AA is a cofactor of at least eight enzymatic reactions, which are crucial for collagen synthesis. Deficiency in L-AA could cause the most severe symptoms of scurvy in humans [10]. L-AA can also act as an antioxidant [11], and is required for a range of essential metabolic reactions in all animals and plants [9,12]. It is produced internally by almost all organisms with the exception of some species of birds and fish [12, 13]. All species that do not synthesize ascorbate require it in their diet. L-AA is also widely used as a food additive to prevent the oxidation of other nutrients or some food dyes [14]. The global vitamin C production is currently estimated at about 11000 tons annually. The main producers include DSM (Scotland) and other four producers in China (Northeast Pharmaceutical Co. Ltd., North China Pharmaceutical Co. Ltd.,... 

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