Uronic acids isolation

A -Androsten-3/3-yl-17-one p-( Dehydroepisterone n-glucoside ) 0 Pt/C 54 70 49% of crude product glycosid-uronic acid isolated chromatographically 39... 

The heteroxylans (CHX) present in cereals, seeds, gum exudates, and mucilages are structurally more complex [6]. They have a (1 4)-)0-d-xylopyranose backbone decorated, except of the single uronic acid and arabinosyl residues with various mono- and oligoglycosyl side chains. Reinvestigations of CHX isolated from corn bran [52] have confirmed that the xylan backbone is heavily substituted (at both positions 2 and 3) with y0-D-Xylp, y0-L-Ara/, of-D-GlcpA residues and oligosaccharide side chains (1), (3) and (4). 

The first paper on the bioactive polysaccharides from Glycyrrhiza uralensis roots was published in 1996 by Kiyohara et al. [57]. They isolated a pectic type polymer with anti-complementary and mitogenic activity that was an acidic pectin, possibly containing rhamnogalacturonan type I as part of the total structure. Degradation of the uronic acid part of the molecule decreased both types of bio activities. The neutral oligosaccharide chains were shown to retain some of the activities of the native polymer, but it was suggested that they should be attached to the acidic core to retain maximum activity. 

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. 

Examination of early -n.m.r. spectra of heparin and of chemically modified heparins121 prompted a reinvestigation of N,0-desulfated, carboxyl-reduced heparin, leading to the isolation of substantial amounts of L-iditol pentaacetate.121,122 In addition, improved conditions for the acid hydrolysis of heparin and carboxyl-reduced heparin gave increased recoveries of L-iduronic acid and 1,6-anhydro-L-idose, respectively.123 These findings confirmed the L-enantiomeric designation of the iduronic acid, and established that it is the main uronic acid in heparin. 

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. 

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... 

D-Glucofuranosylamine)uronic acids attained biological significance after nucleoside antibiotics containing hexuronic acid residues were isolated from natural sources examples are gougerotin and blasticidin S. 

All of the possibilities mentioned are credible perhaps each participates to some extent in the reaction. No studies similar to those with aldoses have been made of substituted uronic acids, and no intermediates have been isolated. Aso,96 who first suggested 72 as a precursor for 2-furaldehyde and reductic acid,92 has prepared 72, but its significance in the decarboxylation reactions has not been fully examined.123... 

Uronic acid derivatives are also known among the guanosine 5 -pyrophosphate esters. A mixture of the a-D-mannopyranosyluronic acid ester (20) and, presumably, the /J-L-gulopyranosyluronic acid ester (21) was isolated from the brown alga Fucus gardneri,88 The conversion of the uronic acid in the ester 20 into D-mannitol, and that... 

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