Uronic acid composition determination

Rha, Ara and Gal are the neutral sugar components from all the fractions. Xyl is not present in Fla and is significantly present in the hemicellulose fractions, indicating that this monosaccharide is component of hemicellulosic polymers. Chemical composition of the water fractions were determined (Table V). High protein contents and the presence of O-acetyl-groups were observed in four aqueous fractions. Neutral sugar and uronic acid composition points to inclusion of these polymers in the class of pectic polysaccharides. 

A. Haug and B. Larsen, Quantitative determination of the uronic acid composition of alginates, Acta. Chem. Scand., 16 (1962) 1908-1918. 

Sanchez-Machado, D. I., Lopez-Cervantes, I, Lopez-Hernandez, J., Paseiro-Losada, P., and Simal-Lozano, J. (2004), Determination of the uronic acid composition of seaweed dietary fibre by HPLC, Biomed. Chromatogr., 18(2), 90-97. 

Uronic Acid Composition and Block Length. A sample containing 75 mg alginic acid was first suspended in a small volume of D2O, then fully neutralized by titration with 1.0 M NaOD. D2O was added to achieve a final concentration of 25 mg alginic acid/mL D2O. Equilibration of at least one hour was allowed prior to NMR acquisition. The uronic acid composition was determined by NN spectroscopy, with a 2 s pulse repetition time and 16,000 scans. The reported composition and block lengths were the average of two determinations. 

Uronic acid compositions is determined colorimetrically using the m-hydroxydiphenyl assay described by Bramenkrantz and Asboe-Hansen (1973). 

Table II. Carbohydrate compositions (weight percentage) of individual oligomer peaks purified (QAE-Sephadex or HPLC ion-exchange separation, respectively) from mixtures of citrus pectin oligomers or B fruit extracts Compositions shown are for peaks whose biological activity is described in Figure 4. Uronic acid values are based on colorimetric assay. Proportions of neutral sugars were determined by GC and adjusted so that totals equal 100%. In fact, some oligomers (G7 peaks 8, 9 and 10. B extract peak 10) produced small (less than 1 % of the total integrated area), unknown peaks in the GC chromatograms.

The determination of the sugar composition was performed with and without prehydrolysis to determine the cellulose content. Cellulose was present in soy meal and in WUS, the content was respectively 17.2 and 17.9 mol%. Both soy meal and WUS contained mainly galactose, glucose (cellulose), arabinose and uronic acids and their sugar compositions were very similar. This indicates that no sugar residues were specifically removed during the isolation procedure. 

When 1.5 volumes acetone is added to the trichloroacetic acid filtrate of the gastric juice, an abundant flocculent precipitate forms, which contains all the components of dissolved mucin with the exception of soluble mucus. If this precipitate is taken up in dilute alkali and then acidified with dilute HCl down to pH 3.5, a fine flocculent precipitate forms, which we named dissolved mucoprotein (G27, G36). It was later renamed glandular mucoprotein (G9, G38) because of its close relationship to the fundic glands of the stomach. This material contained much protein its nitrogen content was 12.61 0.44% and its tyrosine content 7.50 0.65% by the Folin-Giocalteu reaction. The reducing substance content was 6.38 1.48% before and 12.5% after hydrolysis (G9, G27, G36) (see Table 4). Werner (W9) determined the composition of this mucoprotein fraction and found that it contained 11.2% N by Kjeldahl, 8.8% hexosamine, 4.8% uronic acid, and 2.0% sialic acid. 

Other workers determined the entire carbohydrate spectrum of human gastric juice in an attempt to evaluate the composition of gastric mucosubstances. Richmond et al. (R4) and Hoskins and Zamcheck (H50) studied a large number of individual gastric juices in our laboratory (G55) a large pool of normal gastric juices was studied for hexoses, hexosamine, fucose, sialic acid, uronic acid, and total carbohydrate content. Results obtained in normals and patients with various gastric diseases are summarized in Tables 8 and 9. 

The carbohydrate composition (neutral carbohydrates and uronic acid residues) of the isolated xylan was determined by enzymatic hydrolysis and subsequent capillary zone electrophoresis analysis (ENZ/CZE) according to a method described elsewhere... 

Polysaccharides which contain uronosyl residues, such as the acidic pectic polysaccharides and the glucuronoarabinoxylans, pose a particular problem in quantitative determinations of glycosyl compositions. Urono-sidic bonds are resistant to acid hydrolysis. Conditions sufficiently harsh to hydrolyze the uronosidic bonds often result in significant degradation of the uronic acids as well as degradation of some of the neutral sugars. Uronic acids, even when converted into their monomeric form, do not form stable alditol acetates as the reduced form of an uronic acid is an aldonic acid which cannot be acetylated by the standard procedures. 

The proximate composition of the dialyzed EPS of Lactobacillus sp. CFR-2180 was determined. It had a moisture content of 2% with negligible amount of protein (0.7%), as an impurity, which was also confirmed with the presence of a peak at 289 nm in UV spectrum (data not shown). The total carbohydrate and uronic acid contents of the sample were found to be 65 and 10%, respectively and the remaining might be the minerals or other impurities. Similarly, presence of glucuronic acid in the EPS produced b by Lact. acidophilus LMG 9433 was reported (Robjin et al, 1996). The sugar composition of the dialyzed EPS was found to... 

The sequence and composition of uronate residues in intact alginate samples have been determined by high resolution H n.m.r. spectroscopy. Problems encountered owing to the viscosity of the samples were overcome by controlled and slight depolymerization before n.m.r. at 90 °C. The D-mannuronic acid L-guluronic acid molar ratio was obtained from the intensities of the signals from... 

---