L-ascorbic add

In ketones existing largely as the enol, palladium may prove effective in minimizing hydrogenolysis, Hydrogen was added slereoselectively to the least hindered side of L-ascorbic add (3) to give L-gulono-1,4-lactone (4)... 

G. C. Andrews, 5,6-Anhydro-L-ascorbic add. A reactive intermediate for the formation of 6-substituted derivatives of L-ascorbic acid, Carboydr. Res., 134 (1984) 321-326. 

Fig. 19 Randomly scattered low internal standard (IS) responses observed for incurred samples only, whose IS responses were within normal range during repeat analyses. Analyte olanzapine IS olanzapine-d3 sample pretreatment at clinic 25 % (w/v) L-ascorbic add added to plasma in a ratio of 1.25 100 (v/v) extraction MCX (mixed-mode strong cation exchange)-based solid-phase extraction. An incurred sample was coded for reassay when its IS response was outside 50 % of the mean IS response of the accepted calibration standards and quality controls. Reproduced from ref. [36] with permission from Elsevier...

Chandy. T and Sharma C.P, Changes in protein adsorption on polycartxtnate-due to L-ascorbic add, Biomatenals, 6,416-420 (1985). 

In the rat, the synthesis of D-glyceric add seems to be connected with that of L-ascorbic acid administration of chloretone increases the urinary elimination of both acids (cf. Article by W. E. Knox and M. N. D. Goswami, Section 3.4, this volume). o-Glyceric acid is not, however, a direct precursor of L-ascorbic add, and Isherwood et al. (13) state that the connection between these two acids may lie only in that both require some common enzyme or coenzyme system. 

The method established has been applied in particular to the assessment of the effects of L-ascorbic add, vitamin A, triparanol, and dimethyl sulfoxide on human skin (B9), on account of uses of these compounds in therapy. The effect of triparanol on incorporation of [ S]sulfate into proteoglycans and adenosine 3 -phosphate 5 -sulfatophosphate of the epidermis was reduction in each case, but an increase into those of the dermis, thus demonstrating a serious disruptive effect of the drug on tissue processes. 

Monosaccharides. - 1.1.1 Acyclic Compounds. A new route to 2-deoxypentose dialkyl dithioacetals 2 involved opening of the L-ascorbic add-derived epoxide 1 with lithiated formaldehyde dialkyl dithioacetals. Standard protecting group manipulations converted 2 (R = Bu ) to the 4-mesylate 3. ... 

Good linearity was achieved in both ranges of concentrations tested, with correlation coefficients higher than 0.999 in all cases. The proposed method showed a good sensitivity, with limit of detection (LOD) and limit of quantification (LOQ) of 22 and 67 ng/mL, respectively. The method also showed satisfactory precision. All relative standard deviation (RSD) values achieved for peak areas were lower than 4%. The results obtained showed that the applied method has a good reproducibility and that is stable and reliable. The recovery rate of L-ascorbic acid and total vitamin C was evaluated to assess the extraction efficiency of the proposed method and matrix effects. Satisfactory results were obtained for L-ascorbic add (96.6 4.4%) and total vitamin C (103.1 4.8%) [75]. 

The reductive decomposition of S-nitrosogluta-thione by L-ascorbic acid yields NO which was monitored both electrochemically and spectropho-tometrically (Smith and Dasgupta 2000). The rate of reaction and NO release was found to be pH dependent in a manner which dramatically increases with pH demonstrating that the L-ascorbic acid dianion is by far the most reactive species of l-ascorbic add. S-Nitrosoglutathione is relatively stable in the dark, aqueous medium and even in the presence of trace quantities of Cu. Induced catalytic decomposition of S-nitrosoglutathione only becomes significant above ca. 10 [xM Cu % but beyond this it shows linear dependency. 

The intricacies of the metabolic pathway that leads from ascorbic acid to oxalate are not clear. Ascorbic acid is oxidized to yield dehydro-L-ascorbic add this compound is further hydrated to yield 2,3-diketo-L-gulonic acid. The intermediates between 2,3-diketo-L-gulonic acid and oxalate are not known. L-Xylulose, L-xylose, and L-xylosone have been eliminated. An enzyme was partially purified from rat kidney it catalyzes the decarboxylation of 2,3-diketo-L-gulonic acid to yield L-xylonic and L-lyxonic acids [105]. 

Ascorbic acid was identified in 1932 as the antiscorbutic vitamin. Chemically L-ascorbic add is related to the hexose sugars from which it can be synthesized by most animal species. The chief exceptions are primates and guinea-pigs. L-Ascorbic add is very soluble in water and, although when dry it is stable in light and air, it is readily oxidized in solution, particularly in the presence of metals such as copper. On oxidation it is converted first to dehydroascorbic acid but although the ascorbic acid-dehydroascorbic add conversion is reversible, subsequent stages of oxidation are irreversible and the oxidation products have no vitamin activity. 

Vitamin C, also named as L-ascorbic add, is a kind of essential vitamin and antioxidant for human beings and some primates (Zhang et al. 2011). Vitamin C is widely used in pharmaceutical, foods, beverages, cosmetics and feeds industries (Table 12.1). Along with the expansion of vitamin C in different field, the market is still growing. The world market for vitamin C and its direct derivatives (such as calcium salt, potassium salt, sodium salt, and glycosylation derivatives) is beyond 0.5 billion US dollars. 

Sauer M, Branduardi P, VaUi M, Porro D (2004) Production of L-ascorbic add by metaboUcally engineered Saccharomyces cerevisiae and Zygosaccharomyces bailii. Appl Environ Microbiol... 

Saito K, Kasai Z 1984 Synthesis of L-(+)-tartaric acid from L-ascorbic add via 5-keto-gluconic acid in grapes. Plant Physiol 76 170-174... 

L-Ascorbate 2-triphosphate has been obtained in 86% yield 1 phosphorylation of L-ascorbic add with sodium trimetaphosphate. The phosphorylated product appears to be much more stable towards oxidation by oxygen than is the parent compound. ... 

L Sorbose------------ L-Sorbosone-------------- 2 keto-L-gulonic acid --------- L Ascorbic add... 

The compounds of interest in the chemical determination of vitamin C are L-ascorbic acid, dehydro-L-ascorbic add, and diketo-n-gulonic add. The structure and interrelationships of these compounds are indicated below. In further discussion these compounds will be referred to without the use of the letter l, designating configuration. 

The reaction of S,6-0-isopropylidene-L-ascorbic add with superoxide followed by methylation of carboxyl groups has afforded oxidation products 46 and 47. In contrast, 5,6-0-isopropylidene-3-0-methyl-L-ascorbic add under the same conditions gave only 47 in 82% yield. ... 

Some 6-deoxy-6-7V -trimethylammonium salt analogues of L-ascorbic add have been synthesized, and carbocyclic analogues of L-ascorbic add are mentioned in Chapter 18. 

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