Uronic acids characterization

Dermatan sulfate, also termed chondroitin sulfate B, a related glycosaminoglycan constituent of connective tissue, was known to be composed of galactosamine and a uronic acid, originally believed to be glucuronic acid but then claimed to be iduronic acid based largely on color reactions and paper chromatography. However, the d or L-enantiomer status of the latter monosaccharide was not clear. Jeanloz and Stoffyn unequivocally characterized the monosaccharide as L-iduronic acid by consecutive desulfation, reduction, and hydrolysis of the polysaccharide, followed by isolation of the crystalline 2,3,4-tri-0-acetyl-l,6-anhydro-/ -L-idopyranose, which was shown to be identical to an authentic specimen synthesized from 1,2-0-isopropylidene-/ -L-idofuranose.34... 

The quantitative determination of uronic acids in polysaccharides is complicated by lactonization, and these problems have been carefully examined by Blake and Richards.26,98 In the course of these studies, D-glucuronic acid was reduced to D-glucitol, which was characterized as the hexaacetate.98 As uronic acid residues in a polysaccharide may be reduced relatively easily,465,466 determination as the alditol provides an alternative method of analysis.461,468 This procedure is most valuable when different uronic acids are present in... 

With the aldaric acids, condensation occurs on both ends of the molecule, yielding products having two benzimidazole rings separated by a polyhydroxyalkylidene group, as in 97. These products are well adapted for the characterization of uronic acids and their polymers114-116 and of the hydrolysis products of nucleic acids.117... 

Wagner et al. 33) have shown that two distinct polysaccharide fractions from Echinacea purpurea exhibited pronounced activities characterized by a high rate of phagocytosis stimulation. One polysaccharide was shown to be a heteroxylan of molecular weight 35000 and an arabinorhamnogalactan of molecular weight 450000. The main characteristics of these polysaccharides from Echinacea were the optimal solubility in water, the high content of uronic acids, and the very complex structure. 

The characterization and quantitative determination of uronic acid components in polysaccharides faces the problem of complete release of the uronic acids without accompanying decomposition. This is a difficult task because of the acid resistance of the glycosiduronic bond. From a comparison of several methods, it was shown that methanolysis combined with trifluoroacetic acid hydrolysis is the best for the liberation of uronic acids.204 The identification can be performed by gas chromatography of the trimethylsilyl derivatives.205... 

The following Tables (II, III, and IV) record appropriate data and references relating to the methyl ethers of some hexuronic acids and their derivatives. In the case of methyl ethers of aldobiouronic acids (Table V), data have been recorded only for crystalline derivatives. Where uronic acids have been characterized by reduction to the corresponding hexose, reference should be made to the previous articles in this series dealing with the methyl ethers of D-glucose,71 D-galactose,72 and D-mannose.73... 

The literature on /3-D-glucosiduronic acids is particularly voluminous, and the subject has been extensively reviewed from several aspects. Section III, dealing with this class of compounds, is devoted more to a general overview of their preparation, characterization, and reactions than to individual members. On the other hand, the categories of 1-esters of glycuronic acids and of (glycosylamine)uronic acids, which appear not to have been treated previously as separate topics, receive relatively more attention. 

Despite extensive studies, the enzymic formation of (D-glucosyl-amine)uronic acids as a result of the transformation of amino compounds in vivo, and the susceptibility of this type of conjugate towards hydrolysis by /3-D-glucosiduronase, are still the subject of controversial results. It should be emphasized that the high lability of (D-glucosyl-amine)uronic acids in general, and the lack of adequately characterized, synthetic model-compounds, create problems in obtaining reliable results. 

Pellerin, P, Vidal, S., Williams, R, Brillouet, J. M. (1995). Characterization of five type II arabinogalactan-protein fractions from red wine of increasing uronic acid content. Carbohydr. Res., 277, 135-143. 

Dog A, female, 13 kg, gastric fistula and esophagotomy, operated March 1945. Sections A and B represent an experiment of November 22, 1948, and section C an experiment of January 4, 1949. In the latter 2 mg atropine sulfate were injected 42 minutes before the injection of histamine phosphate. Rate of secretion and concentration of total acid and pepsin are shown by line graphs in order to more completely characterize the samples. The spontaneous mucus specimens represent 30-minute samples. UA = uronic acid HN = total hexosamine HN = excess hexosamine mmoles/liter. From Grossberg et al. (G70). 

Humic acids of marine and estuarine sediments are characterized by major amounts of paraffinic structures that previous studies have shown to be highly branched and to contain significant quantities of carboxyl/amide and alcohol/ether carbon. Some humic acids, namely those from well preserved sapropelic marine sediments show significant quantities of carbohydrate-like structures incorporated. This, no doubt, is a reflection of the solubility characteristics of polysaccharides which may have some carboxyl functionalities (uronic acid groups). 

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