INDEX ascorbate

S / V CONTENTS Preface, Robert W. Hay. Structure and Function of Manganese-Containing Biomolecules, David C. Weather-bum. Repertories of Metal Ions as Lewis Acid Catalysts in Organic Reactions, Junghan Suh. The Multicopper-Enzyme Ascorbate Oxidase, Albrecht Messerschmidt. The Bioinorganic Chemistry of Aluminum, Tomas Kiss and Etelka Farkas. The Role of Nitric Oxide in Animal Physiology, Anthony R. Butler, Frederick Flitney and Peter Rhodes. Index. 

FIG. 10 Vitamin C loss (percentage of apricot content before drying) and browning index (BI) of apricot cubes air dried (NT) or air dried following 60-min osmotic dehydration at 25 °C at atmospheric pressure in 60% (w/w) sucrose (SU) or maltose (MA) or 13% (w/w) sucrose (ISO) solution added with 1% ascorbic acid and 0.5% NaCl (Camacho et al., 1998). All samples were dried at 60 °C up to aw = 0.80. 

A simple method for assessing lipid oxidation is measuring the headspace concentration of hexanal by capillary GLC. Also, the total volatiles appearing in the chromatogram up to hexanal can be taken as oxidation index. The method was applied to determine the amounts of lipid peroxides present in rat liver cells. Enhancement of the hexanal concentration can be achieved on adding ascorbic acid (22), that reduces Fe(ni) present in the matrix to Fe(II), which catalyzes decomposition of hydroperoxides to aldehydes. Significant correlations are found between hexanal concentrations and various oxidation indices, such as TBARS (Section IV.D.2)" . ... 

The long-standing interest in the properties of L-ascorbic acid is manifested by the fact that 1146 references related to vitamin C are listed for year 2000 in the PUB MED index in the Internet. The most popular use of L-ascorbic acid is for prevention and treatment of the common cold, but this role remains controversial. In a recent review, the authors conclude that the long-term daily supplementation with large doses of vitamin C does not appear to prevent colds, but there is a modest therapeutic effect on the duration of cold symptoms.369... 

Blood plasma of children with cystic fibrosis was found to have decreased TAC (by 16%) in spite of increased concentrations of ascorbic acid, uric acid, and thiol groups (L4). In another study TAC of children with cystic fibrosis was normal, but these children received vitamin supplementation in doses prescribed in international guidelines (a-tocopherol <10 years, 100 mg daily, and >10 years, 200 mg daily retinol 2.5 mg daily ascorbic acid 100-200 mg daily) (M2). Other authors found TAC values for nonhospitalized patients (1.40 0.20 mM) not different from laboratory control values (1.35 0.11 mM), but greater than values for hospitalized patients (1.09 0.17 mM). TAC in CF children correlated positively with anthropometric values (height, weight, body mass index) and pulmonary function (forced expiratory volume in 1 sec), but not with age (L3). 

Fumed silica A-200 (Pilot plant at the Institute of Surface Chemistry, Kalush, Ukraine specific surface area Ascorbic acid (vitamin C) and all-rac-a-Tocopheryl acetate (vitamin E acetate) were used as adsorbates. Folin-Ciocalteu s phenol reagent (Merck) was used to measure the total polyphenolic index. Silica samples with different degree of surface silylation were obtained using gas-phase chemical modification of highly disperse silica (A-200) surface by trimethylchlorosilane.6... 

Antioxidant activity of silica nanocomposites with immobilized vitamin C was tested using the polyphenolic activity index.8 After adsorption of ascorbic acid on the silica surface and centrifugation, the excess solution was removed to obtain the suspension of a fixed volume (2 ml). Distilled water, sodium carbonate solution, and Folin-Ciocalteu s phenol reagent were subsequently added to suspensions and to the reference Vitamin C solution. The suspensions were then stored for 30 min, and the optical density of supernatant was measured at X = 750 nm. The reference solution of ascorbic acid was used to compare antioxidant activity of vitamin-containing nanocomposites with the activity of dissolved vitamin C. 

However, while some reports (Schwartz and Parks, 1974) indicate a correlation between the oxidation of ascorbic acid and the development of an oxidized lipid flavor, Smith and Dunkley (1962c) concluded that the oxidation of ascorbic acid alone cannot be used as an index of lipid oxidation. They reported that although ascorbic acid oxidation curves for homogenized and pasteurized milk were similar, the homogenized samples had a significantly lower tendency to develop oxidized flavor. 

About 70% of blood ascorbate is in plasma and erythrocytes (which do not concentrate the vitamin from plasma). The remainder is in white cells, which have a marked ability to concentrate ascorbate mononuclear leukocytes achieve 80-fold, platelets 40-fold, and granulocytes 25-fold concentration, compared with plasma concentration. In adequately nourished subjects, and those receiving supplements, the ascorbate concentration in erythrocytes, platelets, and granulocytes, but not in mononuclear leukocytes, is correlated with plasma concentration. Mononuclear leukocytes concentrate ascorbate independendy of plasma concentration (Evans et al., 1982). In deficiency, as plasma concentrations of ascorbate fall, mononuclear leukocyte, granulocyte, and platelet concentrations of ascorbate are protected to a considerable extent. As discussed in Section 13.5.2, the leukocyte content of ascorbate is used as an index ofvitamin C nutritional status, but in view of the differing capacity of different cell types to accumulate the vitamin, differential white cell counts are essential to interpret the results. 

As shown in Table I, iron intakes of both groups was approximately the same with mean values being only about one-half the NRC RDA allowances for this age/sex group. However, ascorbic acid intake levels were high which might have helped in the utilization of the iron provided. Hemoglobin and hematocrit levels which are sometimes used as indexes of adequate iron... 

The results of enzymatic determinations of ceruloplasmin are often expressed in arbitrary units, and the values judged in the light of a series of results obtained in normal subjects by the same method. Expression of the enzyme activity in milligrams of ceruloplasmin per unit volume of serum is also possible. The relation between oxidase activity and the amount of ceruloplasmin in serum can be determined by measuring in parallel samples of sera both the oxidase activity and the change of optical density at 610 mix before and after the addition of ascorbic acid or cyanide. On the basis of the known absorbancy index, the ceruloplasmin concentration can be calculated (see Section 2.2.1) and the relation between it and the enzyme activity determined. Alternatively, purified human ceruloplasmin can be used for standardization of the enzymatic method. The ceruloplasmin content of the purified preparation can be determined colorimetrically or, in the case of a highly purified preparation, by nitrogen analysis. Predetermined increments of ceruloplasmin can then be added to aliquots of a selected serum. It is convenient to select a serum with relatively low ceruloplasmin level to start with. Serum of a patient with Wilson s disease, some of whom have no measurable amount of enzyme activity, would be ideal for the purpose however, Walshe (W5) has recently found an inhibitor in these sera. 

Effect on liver function liver somatic index, level of ascorbic add, together with enzyme levels, e.g., EROD noted above ... 

Indoles, ascorbic acid 0.1 mol I. 1 phosphate buffer, pH 7.4 4.61-6.75 Differential refractive index detection Dm little affected by the analyte concentration [78]... 

A6. Anisova, A. A., Changes in the ascorbic acid content of the white blood as an index of the vitamin C content of the body. Bull. Exptl. Biol. Med. (U.S.S.R.) (English translation) 47, 708-710 (1959). 

The reader will also find in the Index certain broad classifications of components, like oxidases and free radicals. These and similar examples in the Index are not there to confuse the reader, as many of the individual components in the broad classifications have specific CAS numbers. Generally, the references associated with these classes of components (found within the chapters noted in the Index) will provide the reader with information of a common nature. In nearly all cases, individual components such as ascorbate oxidase, choline oxidase, cytochrome oxidase, and glycolate oxidase follow after the broadly classified component, oxidase. Likewise, specific free radicals such as methyl-acyl radical, ethyl-acyl radical, and propyl-acyl radical 2 isomers may be found in the Index. For some components in the Index, several partially identified isomers exist, their number noted, and included in the total number of components identified in tobacco and/or smoke. 

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