Uronic acids analysis

The floss silk from Chorisia speciosa furnished a polysaccharide with a main chain of (1 -> 4) linked P-Xylp substituted at 0-2 by 5 % of uronic acid. The xylan structure also was interposed with a-Rhap units in small amounts. The defatted seeds furnished on aqueous extraction a major fraction, ((9-acetyl, 10 % and protein, 45 %) wich was hydrolysed and analysed by p.c. and GLC, showing Rha (20 %), Ara (16 %), Gal (64 %) and also uronic acids (45 %). Partial hydrolysis gave rise to a polysaccharide free of arabinose, with 46 % of uronic acids. Methylation analysis (GLC -MS) indicated a chain of (1 4) - linked Gal/ (42 % of 2,3,6-Me3-Gal). 

Neutral sugar, uronic acid and methylation analysis (mol%) of fractionated pectins from ripe red beets... 

De Ruiter, G. A., Schols, H. A., Voragen, A. G. J., and Rombouts, F. M., Carbohydrate analysis of water-soluble uronic acid-containing polysaccharides with high-performance anion-exchange chromatography using methanolysis combined with TFA hydrolysis is superior to four other methods, Anal. Biochem., 207, 176, 1992. 

Both positional linkages (uronic acid to hexosamine and hexosamine to uronic acid) were established as being (1 — 4) by structural analysis of the previously mentioned (see Section IV), crystalline disaccharides containing D-glucuronic acid, isolated from an acid hydrolyzate of carboxyl-reduced heparin.128-129 Further evidence was obtained from the structure of the D-glucuronic acid-containing counterpart of disaccharides 6 and 8, obtained as minor products from pig-mucosal heparin following nitrous acid deamination,1110 136-138 and acid hydrolysis followed by N-acetylation,130 respectively. 

The purification of a pneumococcal polysaccharide may be difficult, and the polysaccharide material is sometimes contaminated by a cell-wall component known as the C-substance. The methods for structural analysis of polysaccharides (which, like several of the pneumococcal polysaccharides, contain amino sugar and uronic acid... 

Chaplin used methanolysis for the analysis of carbohydrates in glycoproteins. His method was a variation of the foregoing procedures, with an improvement of using tert-hvAyX alcohol to remove hydrogen chloride by coevaporation, instead of prolonged trituration with silver carbonate. His method is useful for samples containing uronic acids and lipids. Mononen studied methanolysis, followed by deamination and reduction with borohydride, for determination of the monosaccharide constituents of glycoconjugates. This method was applied to a lipid-free, protein fraction of rat brain. 

Many authors have commented upon the problems associated with the hydrolytic step, which has been considered to be the main source of loss in carbohydrate analysis.19 The fact that, in determining uronic acids, differing results were obtained, depending on whether hydrolysis or methanolysis was employed, led others20 to conclude that... 

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... 

The sulfone degradation has been applied to other polysaccharides, in particular to the product obtained from the Pneumococcus type 2 polysaccharide after methylation and uronic acid elimination (see Section IV,2, p. 218).127 Only about one third of the terminal D-glucose residues was eliminated, and an analysis of... 

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