D-Ascorbic acid

XVII XVIII XIX XX D-Xyloascorbic acid (D-Ascorbic acid) ... 

The RQ flex test kit (Merck) which uses specific test strips is useful for the semi-quantitative determination of several analytes. D(+) ascorbic acid can be determined in fortified food products with an accuracy of 85-115% (unpublished data), however the procedure cannot be applied to coloured food products. Added iron salts may be extracted from food products with dilute sulphuric acid and adjusted to pH2 with NaOH solution. Fe3+ is reduced to Fe2+ with ascorbic acid. Fe2+ reacts with Ferrospectral to form a red-violet complex. An internal calibration is provided on a barcode which is read by the RQ-flex reflectometer prior to any measurements. This avoids the need to calibrate the instrument with standard solutions. 

HPLC on a Cosmosil 5 Cis column, using a perchloric acid-acetonitrile eluent (pH 7.6), followed by CLD in the presence of hydrogen peroxide and bis(2,4,6-trichlorophenyl) oxalate (42), was applied to the determination of 1-aminopyrene (43a) and various diaminopyrenes (43b-d). Ascorbic acid was added to avoid oxidative degradation of the aminopyrenes in the presence of metals LOD in the sub-fmol range (SNR 3)147. A fast (less than 10 min) HPLC-ELCD method was proposed for determination of dopamine (19b) and its metabolites in microdialysates, using packed fused silica capillary columns LOD 0.05 Xg/L of dopamine in a 2 XL sample, RSD 3% (n = 10)148. 

The nitriles can also be employed as intermediates in the condensation of ethyl glyoxylate with aJdehydo sugars under the influence of sodium methoxide, leading to the preparation of L-ascorbic acid and similar compounds. Helferich and Peters described the synthesis of D-ascorbic acid (XXVIII) from tetraacetyl-n-xylononitrile (XXVI) presumably the nitrile underwent a type of ZempMn degradation and the n-threose (XXVII) thus formed condensed with the glyoxylic ester. The method... 

D-Ascorbic acid (lAA) is not present in natural products, but it is present in vitamin C-enriched foods or as an antioxidant. Therefore, it is important to distinguish between AA and lAA [417]. 

S. Margolis and R. Schapira,/ Chromatogr. 690, 25-33 (1996). The Measurement of L-Ascorbic Acid and D-Ascorbic Acid in Biological Samples. ... 

D-Ascorbic acid was prepared by Gatzi and Reichstein28 by oxidation of diacetone-D-sorbose to 2-keto-D-gulonic acid, and a desoxy derivative, 6-desoxy-L-a8corbic acid, with some vitamin activity, was synthesized from L-sorbomethylose.116... 

Luteic acid, II, 165, 191, 224 Luteolin, IV, 63 Luteose, II, 191, 224 Lysine, in blood group substances, IV, 49 D-Lyxoascorbio acid. See D-Ascorbic acid. 

Pure, crystalline dehydro-D( — >ascorbic acid (2) is obtained in pure form as prisms, m.p, 191 193° dec., in 25% yield by oxidation of d( - )-ascorbic acid (1) with iodine in acetic acid methanol. ... 

Erythorbic acid (or D-ascorbic acid) (Figure 5) is a white or slightly yellow crystalline powder that is often used in fruits and cured meats to enhance curing action and to stabilize the color of food products (34). Unlike its isomer L-ascorbic acid, erythorbic acid is not a natural constituent of foods and has minimal Vitamin C activity (11). 

Fig. 23 Pellets prepared by spherical agglomeration. Overview about ascorbic acid pellets prepared from powder of a mean particle diameter of 8.8 pm. The bar is 1 mm (A). SEM picture from left (B). Ascorbic acid pellet prepared from powder of a mean diameter of 8.8 pm without the addition of povidone (C). Pellet from left prepared with the addition of 2% PVP (D). Ascorbic acid pellet prepared from powder of a mean particle diameter of 3.0 pm without the addition of povidone (E). Pellet from left with the addition of 2.0% povidone (F).

In geranium, the C2-C3 cleavage of L-ascorbic acid is enantiomeri-cally specific (ii). When L-[6- C]ascorbic acid was replaced by d-[6- C] ascorbic acid, labeled tartaric acid was not found in the acid extractable fraction (Table V). There was considerable decomposition of D-ascorbic acid. Only 17% of the D-ascorbic acid remained in the tissues at the end of the metabolic period. Some metabolism of these... 

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