W Ascorbic acid

Kojima, J., and Hess, J. W. Ascorbic acid interference with estimation of beta-glucosamlnidase activity. Annals Biochem., 23 474-483,1968. Krasner, N., and Dymock, I. W. Ascorbic acid deficiency in malignant diseases a clinical and biochemical study. Br. J. Cancer, 30 142-145, 1974. 

Microemulsions are known to enhance the efficiency of antioxidants (Hanagan and Singh, 2006). Moberger and co-workers (1987) studied triglyceride oxidation in microemulsions consisting of soybean oil, sunflower oil monoglycerides and water. Soybean oil was stable against oxidation for an additional 50 days upon incorporation of 5% (w/w) ascorbic acid into the water phase compared to similar microemulsions without added ascorbic acid. 

Udenfriend et al. observed that aromatic compounds are hydroxyl-ated by a system consisting of ferrous ion, EDTA, ascorbic acid, and oxygend Aromatic and heteroaroinatic compounds are hydroxylated at the positions which are normally most reactive in electrophilic substitutions. For example, acetanilide gives rise exclusively to the o-and p-hydroxy isomers whereas quinoline gives the 3-hydroxy prod-uct. - The products of the reaction of this system w ith heterocyclic compounds are shown in Table XIII. 

XU D p and wells w w (1996) Alpha-hpoic acid dependent regeneration of ascorbic acid from dehydroascorbic acid in rat liver mitochondria , J Bioenergetics Biomembranes, 28, 77-85. 

This method requires about 40 g of tobacco which are extracted with ethyl acetate in the presence of ascorbic acid. A trace amount of C-NDELA is added as an internal standard for quantitative analytical work. The filtered extract is concentrated and NDELA is enriched by column chromatography of the concentrate on silica gel. The residues of fractions with p-activity are pooled and redissolved in acetonitrile. Initially, we attempted to separate NDELA on a 3% OV-225 Chromosorb W HP column at 210 C using a GC-TEA system with direct interface similar to the technique developed by Edwards a. for the analysis of NDELA in urine (18). We found this method satisfactory for reference compounds however, it was not useful for an optimal separation of NDELA from the crude concentrate of the tobacco extract (Figure 4). Therefore, we silylated the crude concentrate with BSTFA and an aliquot was analyzed by GC-TEA with direct interface. The chromatographic conditions were 6 ft glass column filled with 3% OV-... 

Apples (Red Belle de Boskoop, Jonagold or Mutzu) were cut and milled (1.5 mm) and 5% (w/w) of a 2% ascorbic acid solution was added immediately. Enzyme preparations (25 mg enzyme protein / kg mash) were added and the mash was incubated for 2 hours at 20°C whereafter it was pressed. The resulting apple juice was pasteurised at 85°C to discontinue further enzyme degradation. The cloud was measured as turbidity in EF/F units [15]. The cloud stability was determined by a centrifugation test as the amount of turbidity remaining after centrifugation at 4,200 x g for 15 minutes [15]. 

Haworth, W.N. Hirst, E.L. (1933) Synthesis of Ascorbic Acid. Chemistry Industry (London), 645-646. 

Cort, W.M. (1982). Antioxidant properties of ascorbic acid in foods. In Ascorbic Acid Chemisty, Metabolism and Uses (eds. P.A. Seib and B.M. Tolbert) Advanced Chemical Series No. 200, p. 531. American Chemical Society, Washington, DC. 

Fessenden, R.W. and Verma, N.C. (1978). A time-resolved electron spin resonance study of the oxidation of ascorbic acid by the hydroxyl radical. Biophys. J. 24, 93. 

Figure 2 Selective electrochemical detection of a mixture on multielectrode amper-ometry. AA = Ascorbic acid, NE = norepinephrine, DOPAC = 3-4-dihydroxy-phenylacetic acid, E = epinephrine bitartrate, 5-HIAA = 5-hydroxyindole-3-acetic acid, HVA = homovanillic acid, TRP = tryptophan, 5-HT = 5-hydroxytryptamine, and 3-MT = 3-methoxytyramine (separated by RPLC). Detection was with a 4-electrode glassy carbon array, with electrode 1 at 500 m V) electrode 2 at 700 mV, electrode 3 at 900 mV, and electrode 4 at 1100 mV. Note that at electrode 1, HVA, TRP, and 3-MT are not seen. At electrode 2, only TRP is not seen. A standard calomel electrode was used as reference. (Reprinted with permission from Hoogvliet, J. C., Reijn, J. M., and van Bennekom, W. P., Anal. Chem., 63, 2418, 1991. 1991 Analytical Chemistry.)...

P. Zhang, F.H. Wu, G.C. Zhao, and X.W. Wei, Selective response of dopamine in the presence of ascorbic acid at multi-walled carbon nanotube modified gold electrode. Bioelectrochem. 67, 109—114... 

Figure 2.5. Analytical manifolds for the determination of phosphate by flow injection analysis (a) and reverse flow injection (b). The symbols S, M, and A are the seawater, mixed reagent, and the ascorbic acid solutions. The pump injection valve and detector are represented by P, I, and D, respectively. W = waste. From [177]... 

Tominaga et al. [682,683] studied the effect of ascorbic acid on the response of these metals in seawater obtained by graphite-furnace atomic absorption spectrometry from standpoint of variation of peak times and the sensitivity. Matrix interferences from seawater in the determination of lead, magnesium, vanadium, and molybdenum were suppressed by addition of 10% (w/v) ascorbic acid solution to the sample in the furnace. Matrix effects on the determination of cobalt and copper could not be removed in this way. These workers propose a direct method for the determination of lead, manganese, vanadium, and molybdenum in seawater. 

Sublethal effects in birds are similar to those in other species and include growth retardation, anemia, renal effects, and testicular damage (Hammons et al. 1978 Di Giulio et al. 1984 Blus et al. 1993). However, harmful damage effects were observed at higher concentrations when compared to aquatic biota. For example, Japanese quail (Coturnix japonica) fed 75 mg Cd/kg diet developed bone marrow hypoplasia, anemia, and hypertrophy of both heart ventricles at 6 weeks (Richardson et al. 1974). In zinc-deficient diets, effects were especially pronounced and included all of the signs mentioned plus testicular hypoplasia. A similar pattern was evident in cadmium-stressed quail on an iron-deficient diet. In all tests, 1% ascorbic acid in the diet prevented cadmium-induced effects in Japanese quail (Richardson et al. 1974). In studies with Japanese quail at environmentally relevant concentrations of 10 pg Cd/kg B W daily (for 4 days, administered per os), absorbed cadmium was transported in blood in a form that enhanced deposition in the kidney less than 0.7% of the total administered dose was recovered from liver plus kidneys plus duodenum (Scheuhammer 1988). 

Hodson, P.V., J.W. Hilton, B.R. Blunt, and S J. Slinger. 1980. Effects of dietary ascorbic acid on chronic lead toxicity to young rainbow trout (Salmo gairdneri). Canad. Jour. Fish. Aquat. Sci. 37 170-176. 

Pb Food Extract Pb w/diethyl-ammonium diethyl-dithiocarbamate into xylene in presence of ascorbic acid 273)... 

Fig. 6. Dynamical phase diagram of the ascorbic acid/copper(II)/oxygen system in a CSTR in the kf — [Cu2+]0 plane. Fixed reactor concentrations [H2Asc]0 = 5.0x10 4M [H2SO4]0 = 6.0 x 10-5 M [Na2SO4]0 = 0.04M. Symbols O, steady state , oscillations , bistability. The asterisk ( ) marks the Takens-Bogdanov point. Strizhak, P. E. Basylchuk, A. B. Demjanchyk, I. Fecher, F. Shcneider, F. W. Munster, A. F. Phys. Chem. Chem. Phys. 2000, 2, 4721. Reproduced by permission of The Royal Society of Chemistry on behalf of the PCCP Owner Societies.

FIG. 8 Effect of 60-min osmotic dehydration at 25 °C at atmospheric pressure in 60% (w/w) sucrose (SU) or sorbitol (SO) solution or 14% (w/w) sucrose (ISO) solution added with 1% ascorbic acid and 0.5% citric acid on drying rates at 70 °C of apricot cubes (NT, not pretreated) (Campolongo, 2002). 

Slade, R., Highfill, J.W., and Hatch, G.E. 1989. Effects of depletion of ascorbic acid or nonprotein sulfhydryls on the acute inhalation toxicity of nitrogen dioxide, ozone, and phosgene. Inhalation Toxicol. 1 261-271. 

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