Containing No Uronic Acid

The mucilage consists mainly of D-galactose, the content of which is about 70% on an ash-free basis. L-Galactose is considered to be absent because the benzimidazole procedure of Link and coworkers48 failed to detect it. While carrageenin is believed to contain no uronic acid, Dilsea mucilage contains 9.6-11.0% of it. The nature of the uronic acid is... 

Keratan sulfate constitutes approximately half the total mucopolysaccharide fraction of bovine cornea, where it was isolated originally by Meyer et al. (M16). It occurs fairly widely in animal connective tissues, and its presence has been reported in nucleus pulposus (G2), aorta (B17), and costal cartilage (M20). Unlike the acid mucopolysaccharides described previously, keratan sulfate contains no uronic acid residue but is comprised of V-acetyl-n-glucosamine, D-galactose, and sulfate, in equimolar ratio. The small amount of L-fucose detected in acidic... 

Keratan sulfate is very much the odd one out in the polysaccharides embraced by the term glycosaminoglycan since it contains no uronic acid. In place of the uronic acid residue in other glycosaminoglycans, there is a neutral hexose unit— n-galactose. The second component monosaccharide is normal being a 2-acetamido-2-deoxyhexose. The repeating disaccharide unit of keratan sulfate is -0-jS-D-galactopyranosyl-(l- 4)-O- (2-acetamido-2-deoxy- 3-D-glucopyranosyl 6-sulfate) - (1 3) - ( VIII)... 

In 1933, Fischer and Schmitz first claimed to have isolated a pure heparin preparation. Their lengthy extraction and isolation procedure culminated in the isolation of a microcrystalline brucine salt 32 times as active as the starting material. No evidence other than that of appearance was quoted in support of the claimed crystallinity of the product. It was concluded that heparin was a carbohydrate (Molisch test) and contained a uronic acid. 

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. 

Three uronic acids occur in nature, D-galacturonic, D-glucuronic and D-mannuronic acids. No polyuronide is known that contains two different uronic acids. D-Glucuronic acid containing an ether-linked methyl group occurs in mesquite gum. It probably is the monomethyluronic acid that occurs in many hemicelluloses. - ... 

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). 

---