Aldobiouronic Acid Research Articles

Molecular structures of gum exudates from Hakea species

Partial acid-hydrolysis of the gum exudates from Hakea sericea and H. gibbosa yields l-arabinose, d-galactose, d-xylose, d-mann

Structure of 3- O-(α- d-glucopyranosyluronic acid)- l-galactopyranose, an aldobiouronic acid isolated from the polysaccharides of various unicellular red algae

Structure of 3- O-(α- d-glucopyranosyluronic acid)- l-galactopyranose, an aldobiouronic acid isolated from the polysaccharides of various unicellular red algae

Acid hydrolysis and high-performance liquid chromatography of xanthan

A method for the routine determination of the hexose and organic acid content of xanthan preparations based on acid hydrolysis of the exopolysaccharide followed by high-performance liquid chromatography (HPLC) of the hydrolysate on two cation-exchange columns was investigated. A kinetic model was fitted to the recoveries of these components over a range of hydrolysis conditions using non-linear regression, affording values for the rate constants and the initial concentration of each compotent in the unhydrolysed polysaccharide. The ratio of glucose to mannose was greater than the assumed 1:1 ratio in unhydrolysed xanthan, suggesting that the polysaccharide may contain fewer terminal mannosyl residues than previously proposed. Quantification of glucuronic acid was complicated by its lactonisation and consequent elution as two peaks and by interference from its degradation products. The possibility of determining this component as its aldobiouronic acid [β- d-GlcA p-(1→2)- d-Man p] precursor was investigated. Acetic acid recovery was not significantly affected by the hydrolysis conditions over the range studied. The difference between the maximum recoveries and the fitted initial concentrations of each component indicate that compositional analyses of xanthan samples based on single time and acid strength conditions should be treated with caution as they are unlikely to yield quantitatively accurate values.

Preparation of glucuronoxylooligosaccharides from an acid hydrolysate of corn-hulls.

The preparation of four kinds of aldobiouronic acids and two kinds of aldotriouronic acids from an acid hydrolysate of corn-hulls is report on

The glycoproteins of Acacia erioloba exudates

The gum exudate from Acacia erioloba (syn. giraffae) contains protein (53–56%) and carbohydrate as a mixture of glycoproteins that are relatively resistant to proteases and not readily separable. The protein components have high contents of hydroxyproline and serine, and the carbohydrate is composed mainly of l-arabinose, d-galactose, and 4- O-methyl- d-glucuronic acid residues. Methylation, partial acid hydrolysis, and alkaline hydrolysis studies revealed units of the aldobiouronic acids α-4MeGlc pA-(1→4)-Gal and β-4MeGl cpA-(1→6)-Gal, and that the carbohydrate, mainly in the form of short, linear oligosaccharides, is attached to Hyp residues in the peptide chains. This gum exudate differs markedly from others derived from the same taxonomic series (Bentham's Series 4) of Acacia.

Structural analysis of papaya polysaccharide II

The structure of papaya polysaccharide II (PP II) isolated by Chandrasekaran et al. [ Carbohydr. Res., 60 (1978) 105–115] has been investigated by methylation analysis of the carboxyl-reduced polymer and by partial hydrolysis of both the intact (arabinose, 31.0; rhamnose, 13.3; galactose, 42.6; glucuronic acid, 10.3; and 4- O-methylglucuronic acid, 2.8%), and carboxyl-reduced polymers. Methylation analysis of carboxyl-reduced PP II indicated a very highly branched structure in which approximately 39% of the galactopyranose units are disubstituted, 24% are monosubstituted, 20% are trisubstituted, and 17% are nonreducing end units. Methylation analysis of products of partial hydrolysis of both intact and carboxyl-reduced polymers indicated that the backbone of the polysaccharide is made up of galactosyl residues substituted at either O-3 or -6, that the principal aldobiouronic acid fragment is 6- O-(glucopyranosyluronic acid)galactose, that the rhamnosyl units are substituted at O-3 with either terminal arabinofuranosyl or galactopyranosyl groups, and that the rhamnosyl residues are themselves linked to glucuronic acid residues through O-4. From this information, a possible statistical fragment with six arabinofuranose and two galactopyranose nonreducing end-groups per 19 sugar units [five units in the main chain of (1→3)-linked galactopyranose units] is proposed.

Structure of the Klebsiella type 10 capsular polysaccharide

The capsular polysaccharide from Klebsiella Type 10 was found to contain d-galactose, d-glucose, d-mannose, and d-glucuronic acid in the ratios 3:1:1:1. Acid hydrolysis of the polysaccharide gave one aldobiouronic acid, one aldotriouronic acid, one aldotetraouronic acid, and two neutral disaccharides the structures of which were established. The native and carboxyl-reduced polysaccharide have been subjected as appropriate to methylation analysis and Smith degradation. Degradation of the methylated polysaccharide with base established the identity of the sugar unit preceding the glucosyluronic acid residue. The anomeric configurations of the sugar residues were determined by oxidation of the acetylated native and carboxyl-reduced polysaccharides with chromium trioxide. Based on these studies, the hexasaccharide structure 1 has been assigned to the repeating unit of the K-10 polysaccharide. ▪

A highly substituted glucuronoarabinoxylan from developing maize coleoptiles

A glucuronoarabinoxylan in which about six of every seven xylosyl residues were substituted with terminal arabinofuranosyl and glucosyluronic groups was extracted from developing maize coleoptiles with dilute alkali and purified by gel-permeation chromatography. Terminal arabinofuranosyl groups attached mostly to O-3 of the xylan backbone constituted most of the substitution. Indirect double-methylation analysis of mild acid-hydrolyzed xylan, direct methylation analyses of carbodiimide-activated, NaBH 4-reduced uronic acid groups, and isolation of the glucosyluronic-xylose aldobiouronic acids followed by 2-D COSY 1H-n.m.r. spectroscopy indicated that most, if not all, of the d-glucosyluronic groups were α-(1→2)-linked to the xylan. Smith degradation indicated that at least a portion of this highly substituted xylan may have a repeating-unit structure.

An acidic xylan from the capsular polysaccharide-complex of Ocimum gratissimum seeds

An acidic xylan composed of d-xylose (48%), l-arabinose (16%), d-galactose (16%), and d-galacturonic acid (∼20%) has been isolated from the capsular, mucilaginous polysaccharide-complex of the seeds of Ocimum gratissimum. Graded, acid hydrolysis afforded O-β- d-galactopyranosyl-(1→3)- l-arabinose, an aldobiouronic acid, and an aldotriouronic acid composed of d-xylose and d-galacturonic acid. Methylation analysis, together with the isolation of a xylan core from the acid-degraded polysaccharide, indicated that the polysaccharide contains a (1→4)-linked xylan backbone with 60% of the xylosyl residues substituted either on O-2 or O-3 with O-β- d-galactopyranosyl-(1→3)- l-arabinofuranosyl, l-arabinofuranosyl, or d-galactopyranosyluronic acid side-chains. These structural features for the polysaccharide accord with periodate-oxidation studies.

Investigations on the structure of a hemicellulose fraction isolated from the trunk of a young bael ( Aegle marmelos) tree

Purified hemicellulose isolated from a young bael ( Aegle marmelos) tree with 2.5 m sodium hydroxide contained d-xylose and 4- O-methyl- d-glucoronic acid in the molar ratio of 7.43:1; traces of glucose, galactose, rhamnose, and arabinose were also present. The linkages between the monosaccharide units were determined by methylation analysis of a hemicellulose fraction (II A) and carboxyl-reduced, hemicellulose II A, and the results were corroborated by those from periodate oxidation and Smith degradation. The anomeric configurations of the d-xylopyranosyl residues were determined by chromium(VI) trioxide oxidation of the acetylated, carboxyl-reduced hemicellulose, and the aldobiouronic acid obtained from graded hydrolysis was characterized. These experiments clearly revealed the structure of this hemicellulose.

Acylated oligosaccharides from Klebsiella K63 capsular polysaccharide: Depolymerization by partial hydrolysis and by bacteriophage-borne enzymes

The extracellular polysaccharide from Klebsiella K63 is unique in having acetic and formic ester groups attached to the d-galactopyranosyluronic residues in the trisaccharide repeating-sequence. These O-acyl substituents are shown to be some what resistant to mild hydrolysis by both acid and alkali. Bacteriophage-induced depolymerization of the polysaccharide generated a series of acylated oligosaccharides comprising one, or more, repeating unit(s). By mild hydrolysis with acid, the same series of oligomers was released from the polysaccharide, together with the corresponding non-acylated compounds and the expected acylated and non-acylated aldobiouronic acids. A study of these oligosaccharides, as well as of a number of their related compounds, is described, with particular emphasis on the methods used to locate the formic and acetic ester groups. The location of the O-acyl substituents on the galactosyluronic residues was further supported by the results obtained from the high-resolution, 400-MHz, p.m.r. spectra and 13C-n.m.r. spectra of a number of the oligosaccharides.

Chemical ionization-mass spectra of aldobiouronic acids and dialdose dianhydrides

Chemical ionization (c.i.) mass spectra with isobutane as the reagent gas are reported for the peracetates of aldobiouronic acids and related compounds, and for peracetates and permethylated derivatives of dialdose dianhydrides. Ions (M + + 43) having relatively high intensities were detected in the spectra of disaccharides lacking the dianhydride structure. Peracetylated dialdose dianhydrides showed very weak (M + + 43) ions, and permethylated dianhydrides did not show them. The (M + + 43) ion consisted of molecular ion and acetoxyl radical (but not of the reagent gas). In the c.i. mass spectra of the usual disaccharide peracetates, (M + − 31) and (M + − 60) ions had large intensities. In contrast, c.i. mass spectra extremely similar to the corresponding e.i. mass spectra were obtained for dialdose dianhydrides.

Chemical structure of the water-soluble polysaccharide of Phellodendron amurense Ruprecht

Purified, water-soluble polysaccharide (P-WSPS) of Phellodendron amurense Ruprecht consists of residues of l-rhamnose, l-arabinose, d-galactose, and d-galacturonic acid in the ratios of 29.26:22.45:31.17:17.10 (% by weight). G.l.c.m.s. analysis of methylated-reduced P-WSPS showed that it has a very complicated and highly branched structure, and consists mainly of (1→2)-linked l-rhamnose, (1→4)-linked l-arabinose, (1→4)-linked d-galactose, and (1→3)- and (1→4)-linked d-galacturonic acid. The presence of 2- O-(α- d-galactopyranosyluronic acid)- l-rhamnopyranose, 2- O-(β- d-galactopyranosyluronic acid)- l-arabinose, 4- O-(α- d-galactopyranosyluronic acid)- l-rhamnopyranose, and 4- O-(α- d-galactopyranosyluronic acid)- d-galactopyranose in the aldobiouronic acid fraction of the hydrolyzate of P-WSPS was also shown.

Investigations on the fibers of pineapple [ Ananas comosus (L). Merr.] leaves

Hemicelluloses were isolated from pineapple-leaf fibers under different conditions. Study of the properties of these hemicelluloses gave direct evidence of some ester linkages between the hemicellulose and the lignin in this fiber. An aldobiouronic acid was isolated from this fiber hemicellulose, and characterized as 2- O-(4- O-methyl-α- d-glucopyranosyluronic acid)- d-xylose. This indicates that the general nature of the hemicellulose is similar to those of jute and other fiber hemicelluloses.

Investigation on the structure of the hemicellulose obtained from the fiber of sanseviera trifasciata leaves

On purification, the hemicellulose released from the extractive-free, delignified fiber of Sansevieria trifasciata leaves by 4% alkali yielded a product containing d-xylose and 4- O-methyl- d-glucuronic acid in the molar ratio of ∼5:1. An aldobiouronic acid from this hemicellulose was characterized. The investigation revealed that the hemicellulose consists of a polymer of (1→4)-linked d-xylopyranosyl residues having branches of d-xylopyranosyl and 4- O-methyl-α- d-glucopyranosyluronic acid groups on the O-2 atoms of the main chain.

β-elimination of aldobiouronic acids during methylation by the Hakomori method

On methanolysis and subsequent saponification, the aldobiouronic acids 2- O-(4- O-methyl-α- d-glucopyranosyluronic acid)- d-xylose ( 1) and 4- O-(α- d-galactopyranosyluronic acid)- d-xylose ( 2) gave four ( 3–6) and two ( 7 and 8) methyl glycosides, respectively. These glycosides were well separated by ion-exchange chromatography and their structures were established by methylation analysis, mass spectrometry of their permethylated derivatives, and 13C-n.m.r. spectroscopy. On methylation by the method of Hakomori, compounds 3–6, having 4- O-substituted uronic acid residues, afforded β-elimination products ( 15–18) in addition to the permethylated derivatives ( 9–12). On the other hand, compounds 7 and 8, having HO-4′ unsubstituted, gave the products of direct methylation ( 13 and 14), which gave, on re-methylation, permethylated, unsaturated aldobiouronic acids ( 19 and 20).

Mass spectra of peracetates of some (1→2)-linked disaccharides

The mass spectra of two peracetylated disaccharides and the pentaacetate ( 1) of an aldobiouronic acid methyl ester, all having a (1→2)-linkage, were analyzed. The fragmentation pathway common to these compounds could be classified into four groups: ( 1) the aA type, which was the main pathway, ( 2) the abJ type, ( 3) the baA type, and ( 4) the baC type. The manner of fragmentation of peracetate 1 was similar to those of the disaccharides.

Structural data for the carbohydrate of ispaghula husk ex Plantago ovata forsk

The husk from the seeds of Plantago ovata Forsk yielded two fractions when exposed to mild aikali, namely, the mucilage polysaccharide (85%, apparently a single species) and the non-polysaccharide component (15%). Methylation analysis and partial hydrolysis with acid showed the mucilage polysaccharide to be a highly branched, acidic arabinoxylan, the xylan backbone having both (1→4) and (1→3) linkages. The majority of the residues in the xylan backbone are variously substituted at O-2 and O-3 with arabinose, xylose, and an aldobiouronic acid identified as 2- O-(galactopyranosyluronic acid)-rhamnose. A structure incorporating these features for the husk polysaccharide is proposed.

Binding of calcium ions on acid polysaccharides of peach gum and distribution pattern of carboxyl groups in the macromolecule

The acid polysaccharide of peach gum and its macromolecular products of a gradual degradation by acid hydrolysis were characterized by molecular weight (Mw) and molar ratios of both uronic acids and neutral saccharide units. The single-ion activity coefficient of calcium ions (γCa2+) bound to these acid polysaccharides and to the corresponding aldobiouronic acids was measured and CD spectra of potassium and calcium salts of these compounds were recorded. It was ascertained that Ca2+ ions are bound to carboxyl groups of polysaccharides under study by an electrostatic bond in molecular disperse solutions. The mean distance of the neighboring carboxyl groups b = 0.83 to 1.00 nm, calculated from the measured values γCa2+ indicates a very close arrangement of uronic acid units, which does not undergo alteration with the stepwise degradation of the macromolecule. The obtained results let us conclude that the main chain of the polysaccharide is substituted in longer segments by D-glucuronic acid units and its 4-O-methyl derivative (monomeric side chains), at least at each second D-galactose unit.

Structural studies on Klebsiella type 61 capsular polysaccharide

The capsular polysaccharide from klebsiella type 61 was found to contain d-galactose, d-glucose, d-mannose, and d-glucuronic acid in the ratios 1:2:1:1. Acid hydrolysis of the polysaccharide gave one aldobiouronic acid, whose structure was established. Methylation analysis of the polysaccharide provided information about the linkages in the polysaccharide. The polysaccharide is composed of a pentasaccharide repeating unit for which structures are proposed.