Applications of Gas-Liquid Chromatography to Carbohydrates :Part I

Cereal Non-Cellulosic Polysaccharides: Structure and Function Relationship—An Overview

The non-cellulosic polysaccharides present in cereals (2-8%) are mostly arabinoxylans, (1 --> 3),(1 --> 4)-beta -glucans, pectins and arabinogalactans. Of these, the arabinoxylans are known to absorb large amounts of water and influence significantly the water balance, rheological properties of dough, and the retrogradation of starch and bread quality. (1 --> 3),(1 --> 4)-beta -glucans are known as biological response modifiers (BMS) as they are believed to modulate the immune response. Cereal Pectins and arabinogalactans form a very small amount and do not contribute substantially to the functionality of noncellulosic polysaccharides. Detailed structural investigations on cereal hetero xylans using modern techniques were initiated in the 1990s and still pose a challenge to carbohydrate chemists because of their structural complexity. Nutritionally, they are classified under "unavailable carbohydrates" (dietary fiber) along with lignin and cellulose and are known to have beneficial effects in alleviating disease symptoms such as diabetes, atherosclerosis, and colon cancer. In this review isolation, purification, characterization, structural elucidation, functional, and nutritional attributes of cereal heteroxylans are covered with particular emphasis on recently characterized finger millet arabinoxylans.

In vitrofermentation by human faecal bacteria of total and purified dietary fibres from brown seaweeds

The in vitro degradation of dietary fibre from three brown seaweeds (Himanthalia elongata, Laminaria digitata and Undaria pinnatiJda) was studied, using human faecal flora. Two sets of fibre were tested: (1) total algal fibres extracted from the whole algae, mainly composed of alginates, and (2) purified fibres (sulphated fucans, Na-alginates and laminarans) representative of those contained in the whole brown algae. Mannuronate, one algal component, was also investigated. Substrate disappearance and short- chain fatty acid (SCFA) production were monitored after 6, 12 and 24 h fermentation. Gas production was followed hourly during the first 9 h and then at 12 and 24 h. Sugarbeet fibre was used as a fermentation reference substrate. According to the fermentative indices used, most of each of the total algal fibres disappeared after 24 h (range 60–76 %) hut, unlike the reference substrate, they were not completely metabolized to SCFA (range 47–62 %). Among the purified algal fibres, disappearance of laminarans was approximately 90% and metabolism to SCFA was approximately 85% in close agreement with the fermentation pattern of reference fibres. Sulphated fucans were not degraded. Na- alginates exhibited a fermentation pattern quite similar to those of the whole algal fibres with a more pronounced discrepancy between disappearance and production of SCFA: disappearance was approximately 83 % but metabolism was only approximately 57 YO. Mannuronate was slowly fermented hut its metabolism corresponded to its disappearance from the fermentative medium. Thus, the characteristic fermentation pattern of the total fibres from the three brown algae investigated was attributed to the peculiar fermentation of alginates, and mannuronate was shown not to be directly involved.

Sourdough bread made from wheat and nontoxic flours and started with selected lactobacilli is tolerated in celiac sprue patients

This work was aimed at producing a sourdough bread that is tolerated by celiac sprue (CS) patients. Selected sourdough lactobacilli had specialized peptidases capable of hydrolyzing Pro-rich peptides, including the 33-mer peptide, the most potent inducer of gut-derived human T-cell lines in CS patients. This epitope, the most important in CS, was hydrolyzed completely after treatment with cells and their cytoplasmic extracts (CE). A sourdough made from a mixture of wheat (30%) and nontoxic oat, millet, and buckwheat flours was started with lactobacilli. After 24 h of fermentation, wheat gliadins and low-molecular-mass, alcohol-soluble polypeptides were hydrolyzed almost totally. Proteins were extracted from sourdough and used to produce a peptic-tryptic digest for in vitro agglutination tests on K 562(S) subclone cells of human origin. The minimal agglutinating activity was ca. 250 times higher than that of doughs chemically acidified or started with baker's yeast. Two types of bread, containing ca. 2 g of gluten, were produced with baker's yeast or lactobacilli and CE and used for an in vivo double-blind acute challenge of CS patients. Thirteen of the 17 patients showed a marked alteration of intestinal permeability after ingestion of baker's yeast bread. When fed the sourdough bread, the same 13 patients had values for excreted rhamnose and lactulose that did not differ significantly from the baseline values. The other 4 of the 17 CS patients did not respond to gluten after ingesting the baker's yeast or sourdough bread. These results showed that a bread biotechnology that uses selected lactobacilli, nontoxic flours, and a long fermentation time is a novel tool for decreasing the level of gluten intolerance in humans.

Simultaneous gas-chromatographic measurement of rhamnose, lactulose and sucrose and their application in the testing gastrointestinal permeability

BACKGROUND

As it is important to test gastric and intestinal permeability simultaneously in gastrointestinal disorders such as Celiac disease, we developed a gas-chromatographic (GC) method to estimate rhamnose (L-rh), lactulose (Lacl) and sucrose (Suc) in urine.

METHODS

The method is based on the use of alditol acetate derivatives giving a lower number of GC peaks than reducing sugars do. Acetate derivatives are more stable and less expensive than GC silylates and keep the flame-detector cleaner. We checked the chemical stability of alditol acetates by verifying the reproducibility of the standard curve of a sugar derivative sample which had been stored for 2 months at -20 degrees C.

RESULTS

The calibration proved linear over the range 0.1-1 microg of sugar injected. Analytical sugar recovery was 88%+/-19.4% (mean+/-S.D.) for rhamnose, 105%+/-7.4% for sucrose and 102%+/-2.4% for lactulose. Mean within-day precision (CV) was 7.7% for rhamnose, 5.7% for sucrose and 1.9% for lactulose, and between-day (CV) was 6.7% for rhamnose, 3.9% for sucrose and 1.6% for lactulose. The rhamnose, lactulose and sucrose as the lactulose/rhamnose ratio clearly differentiated 25 healthy controls from 36 patients with active gluten-sensitive enteropathy.

CONCLUSIONS

A fast, reliable and cheap gas-chromatographic method is presented here to evaluate gastric and intestinal permeability.

A water-soluble galactomannan from the seeds of Phoenix dactylifera L

A water-soluble polysaccharide, isolated from the seeds of dates, has been investigated using methylation, periodate and CrO(3) oxidation, NMR spectroscopy, and reaction with Bandeiraea simplicifolia lectin and alpha-D-galactosidase. The polysaccharide consists of a backbone composed of (1-->4)-beta-D-mannopyranosyl residues and carries a single (1-->6)-alpha-linked D-galactopyranosyl residue.

Analysis of sialo-N-glycans in glycoproteins as 1-phenyl-3-methyl-5-pyrazolone derivatives by capillary electrophoresis

A method for the analysis of the sialo-N-glycans in glycoproteins was established by the electrokinetic chromatography mode of capillary electrophoresis (CE) in sodium dodecyl sulfate (SDS) micelles as 1-phenyl-3-methyl-5-pyrazolone (PMP) derivatives, using sialo-N-glycans in fetuin as a model. Six major and some minor peaks were observed for the N-glycans in fetuin, which were well separated from each other using 50 mM phosphate buffer, pH 6.0, containing SDS to a concentration of 30 mM in an uncoated fused-silica capillary, and these peaks were assigned to sialo-N-glycans having either of the biantennary or beta1-3/beta1-4 linked galactose-containing complex type triantennary N-glycans as the basic structures, by an indirect method based on the assignment of the peaks in high-performance liquid chromatography separated in parallel with CE and peak collation between these two separation methods. The attaching position of the sialic acid residue was determined using the linkage preference of neuraminidase isozymes. The established system is considered to be useful for routine analysis of microheterogeneity of the carbohydrate moiety of this model glycoprotein from the following reasons: (1) the derivatization with PMP proceeds quantitatively under mild conditions without causing release of the sialic acid residue, (2) the derivatives can be sensitively detected by UV absorption, (3) the procedure is simple, rapid and reproducible. Preliminary results of N-glycan analysis for several other glycoproteins under these conditions are also presented.

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

Sulfuric acid hydrolysis according to the Saeman procedure, TFA hydrolysis, and methanolysis combined with TFA hydrolysis were compared for the hydrolysis of water-soluble uronic acid-containing polysaccharides originating from fungi, plants, and animals. The constituent sugar residues released were subsequently analyzed by either conventional GLC analysis of alditol acetates or high-performance anion-exchange chromatography with pulsed-amperometric detection. It was shown that TFA hydrolysis alone is not sufficient for complete hydrolysis. Sulfuric acid hydrolysis of these polysaccharides resulted in low recoveries of 6-deoxy-sugar residues. Best results were obtained by methanolysis combined with TFA hydrolysis. Methanolysis with 2 M HCl prior to TFA hydrolysis resulted in complete liberation of monosaccharides from pectic material and from most fungal and animal polysaccharides tested. Any incomplete hydrolysis could be assessed easily by HPAEC, by the detection of characteristic oligomeric products, which is difficult using alternative methods currently in use. Methanolysis followed by TFA hydrolysis of 20 micrograms water-soluble uronic acid containing polysaccharides and subsequent analysis of the liberated sugar residues by HPAEC allowed us to determine the carbohydrate composition of these polysaccharides rapidly and accurately in one assay without the need for derivatization.

Chlorination of cellulose with N-chlorosuccinimide-triphenylphosphine under homogeneous conditions in lithium chloride-N,N-dimethylacetamide

Microcrystalline cellulose was chlorinated with N-chlorosuccinimide-triphenylphosphine under homogeneous conditions in LiCl-N,N-dimethylacetamide. At the early stage of the reaction only replacement of the 6-hydroxyl groups with chlorine was observed, and 3-hydroxyl groups were replaced at a lower rate with Walden inversion. The effects of reaction conditions on the extent of chlorination were studied in detail. More than two equivalents of chlorination reagents per glucose residue were necessary to attain a high degree of substitution (ds) by chlorine, and the maximum ds attained was 1.86. Chlorinated disaccharides were found in the hydrolyzates of chlorodeoxycelluloses hydrolyzed under mild conditions, and their structures were studied by mass spectrometry.

Analysis of the amino acid and sugar composition of streptococcal cell walls by gas chromatography-mass spectrometry

A procedure for determining the amino acid and sugar composition of streptococcal peptidoglycan-polysaccharide complexes by capillary gas chromatography-mass spectrometry (GC-MS) was established. Amino acids are analysed as butyl heptafluorobutyl derivatives and sugars as alditol acetates. These two different groups of compounds are derivatized independently but chromatography in both cases utilizes the same OV-1701 fused-silica capillary column which simplifies GC-MS analysis. The butyl heptafluorobutyl procedure incorporates new pre- and post-derivatization clean-up steps. Additionally, selected-ion monitoring MS allows amino acids to be readily analysed without interference from background noise.

Modifications in the alditol acetate method for analysis of muramic acid and other neutral and amino sugars by capillary gas chromatography-mass spectrometry with selected ion monitoring

Two alditol acetate methods for the gas chromatographic (GC) analysis of neutral and amino sugars were compared. Following sodium borohydride reduction, one method uses methylimidazole as an acetylation catalyst without prior removal of water or borate salts and the other method uses sodium acetate after removal of borate and water. Depending on the acetylation conditions, muramic acid produced different derivatives. With methylimidazole, reliable derivatization of muramic acid was not possible, although other sugars derivatized reliably. With sodium acetate, all sugars tested were reproducibly derivatized. The utility of the sodium acetate method is shown by the trace GC-mass spectrometric analysis of muramic acid and rhamnose derived from bacterial peptidoglycan-polysaccharide complexes in mammalian tissue.

Capillary gas chromatographic analysis of alditol acetates of neutral and amino sugars in bacterial cell walls

Several improvements in the preparation of alditol acetates of neutral and amino sugars and in the preparation of glass capillary columns for their separation are described. Modifications in sample preparation permitted the simultaneous processing of multiple samples and eliminated extraneous background peaks. Efficient and inert columns were tailor-made for the separation of alditol acetates of neutral and amino sugars by leaching glass capillaries with aqueous hydrochloric acid and dynamically coating with SP-2330.

Detection of neutral and aminosugars from glycoproteins and polysaccharides as their alditol acetates

A new method for the preparation and separation of alditol acetates from neutral sugars has been applied to aminosugars. Reduced aminosugars were rapidly acetylated using 1-methylimidazole as the catalyst without removal of borate formed during reduction. The alditol acetates were separated by glass capillary gas chromatography on Silar 10C. The alditol acetates of aminosugars had retention times much longer than those of neutral sugars. However, the alditol acetates of the deamination products of aminosugars had shorter retention times and were resolved from those of neutral sugars. This method was used for the simultaneous detection of neutral and aminosugars in acid hydrolysates of chitin and the glycoproteins, ovalbumin and peroxidase.

A simple procedure for combined gas chromatographic analysis of neutral sugars, hexosamines and alditols. Determination of degree of polymerization of oligo- and polysaccharides and chain weights of glycosaminoglycans

A reliable and reproducible method that allows the combined, simultaneous gas chromatographic (GC) determination of neutral sugars, hexosamines, alditols, identification and quantitation of the reducing aldose end-group in oligo and polysaccharides and glycosaminoglycans has been described. It involves the following steps: release of the reducing end-group from its protein linkage in glycosaminoglycans and reduction of this reducing end-group into alditol, release of the components of the reduced polymer by resin-catalysed hydrolysis, nitrous acid deamination of the resin-bound hexosamines in this hydrolysate into anhydroaldoses and a combined derivatization and GC determination of the neutral sugars as aldononitrile acetates, anhydroaldoses as peracetylated oximes and alditols as alditol acetates. Application of the method to determination of degree of polymerization of oligo-and polysaccharides and chain weights of proteoglycans has been described. This method has several advantages over the previous methods.

Simultaneous determination of neutral sugars and hexosamines in glycoproteins and acid mucopolysaccharides (glycosaminoglycans) by gas-liquid chromatography

A reliable and reproducible method for the simultaneous determination of neutral sugars and hexosamines in glycoproteins and acid mucopolysaccharides has been described. It involves the following steps: the release of neutral sugars and hexosamines from biopolymers by resin-catalysed hydrolysis, the nitrous acid deamination of resin-bound hexosamines in this hydrolysate to aldoses, and the determination of these newly formed anhydroaldoses together with the pre-existing neutral sugars as aldononitrile acetates by gas chromatography. Applications of this method to analyses of glycoprotein from urine of schizophrenic patients, bovine thyroglobulin, human brain glycoprotein, chondroitin sulfates from bovine vitreous humor, and veal brain, and human umbilical cord hyaluronic acid are given.