Analysis of Low Molecular Weight Carbohydrates in Food and Beverages: A Review

This review presents a study of new advances in chromatographic methods and capillary electrophoresis for the analysis and quantification of carbohydrates in food and drink that have been made in essentially the last seven years (1995–2002). All the main groups of sugars have been considered: monosaccharides, disaccharides, trisaccharides, oligosaccharides, related compounds such as alditols, alditol glycosides, polyols, amino sugars, deoxy sugars, uronic acids and aldonic acids. The chromatographic methods referred to are High Performance Liquid Chromatography (HPLC), Gas Chromatography (GC) and related techniques (AMD-HPTLC: High Performance Thin-Layer Chromatography with Automated Multiple Development). Capillary Electrophoresis (CE) was also discussed.     

First protection-free protocol for synthesis of 1-deoxy sugars through glycosyl dithiocarbamate intermediates

A practical two-step synthetic process for 1-deoxy sugars has been established. The process consists of the direct introduction of a dimethyldithiocarbamate group into the anomeric center of unprotected sugars and subsequent hydrogenation in the AIBN-H₃PO₂-NaHCO₃ system. No protecting groups are needed to synthesize 1-deoxy monosaccharides and 1-deoxy disaccharides.     

Optimization of the capillary gas chromatographic analysis of mono- and oligosaccharides in honeys

Summary A capillary gas chromatographic method has been developed for simultaneous determination of at least 18 sugars (2 monosaccharides, 11 disaccharides and 5 trisaccharides) in honey, as their oxime-trimethylsilyl ethers. The chromatographic conditions have been systematically and thoroughly optimized, to eliminate the peak overlap commonly reported for this and other methods, especially for disaccharides. Complete analytical details are reported.     

单糖/双糖对近中性pH下共轭亚油酸囊泡影响的比较

比较了乳糖等3种双糖或核糖等3种单糖及其复配物对近中性范围共轭亚油酸(CLA)形成脂肪酸囊泡(FAV)的影响. 用激光丁达尔效应确定FAV的pH窗口及各相区, 用透射电子显微镜及动态光散射表征其形貌和尺寸, 用浊度法研究了其稳定性, 用等温滴定量热证明各种糖及其复配物与FAV表面的弱非共价键合作用, 并经理论计算获得结合能. 实验和计算结果表明, 各种糖及其复配物均可以双向拓宽CLA形成FAV的pH窗口, 且拓宽其近中性pH窗口的能力按照双糖<单糖≈双糖/单糖≤单糖/单糖的顺序依次增强. 主要归结为单糖在FAV表面的强竞争吸附, 以及双糖可能因多结合位点吸附而减少其自由羟基与环境水分子的缔合作用, 从而影响多羟基小分子依靠自由羟基增强囊泡表面亲水性的效果.     

Syntheses of spherical silica and titania from alkoxides on a laboratory scale

Summary A process to synthesize silica and titania as spherical packing materials has been investigated on the laboratory scale by the sol-gel method. The silica and titania obtained were tested under normal-phase separation conditions for comparison of their retention characteristics silica witha a commercial. The silica was found to be similar in its retention behaviour to the commercial silica. The titania showed basic properties and strongly retained acidic compounds.     

Effects of chemical functional groups on the polymer adsorption behavior onto titania pigment particles

The effects of functional groups on polymer adsorption onto titania pigment particles have been investigated as a function of pH and ionic strength using polyacrylic acid and modified polyacrylamides. The polyacrylamides include the homopolymer, an anionic copolymer with hydroxyl and carboxylate group substitution, and a nonionic copolymer with hydroxyl group substitution. Adsorption isotherms and infrared spectroscopy were used to examine the polymer-pigment interactions. The adsorption of the polyacrylic acid and anionic polyacrylamide on titania pigment is greatest when electrostatic repulsion is absent or reduced. At low pH values, below the pigment isoelectric point (IEP), or at high ionic strength, the adsorption density of the anionic polymers on titania pigment is high, while at higher pH values above the pigment IEP, the adsorption density decreases. But the adsorption of nonionic polymers on titania pigment is not influenced by either ionic strength or pH. Acrylamide groups were found to hydrogen bond with the titania pigment surface, independent of pH. With the inclusion of hydroxyl functional groups into the polyacrylamide chain, the polymer adsorption density increased without increased adsorption affinity. Carboxylate functional groups in the anionic polymers strongly interact with the pigment surface, producing the highest adsorption density at low pH values. All polymers exhibit Langmuir adsorption behavior with hydrogen bonding found as the dominant mechanism of adsorption in addition to electrostatic interaction occurring for the anionic polymers.     

超高效合相色谱-蒸发光散射检测法测定蜂蜜中4种单、双糖的含量

采用超高效合相色谱-蒸发光散射检测( UPC2-ELSD)技术,建立了测定蜂蜜中4种单、双糖含量的方法。其中单糖为果糖和葡萄糖,双糖为蔗糖和麦芽糖。以ACQUITY UPC2BEH(100 mm×3.0 mm,1.7μm)为色谱柱,超临界CO2和甲醇(含0.2%氨水, V/V)作为流动相,流速为1.0 mL/min,柱温为50℃,ELS为检测器,漂移管温度为50℃,N2压力为260.7 kPa(30 psi)。研究表明,4种单、双糖化合物在线性范围内线性关系良好,线性相关系数(R)均大于0.9983;目标物的检出限(S/N≥3)为2.0~4.7 mg/L;3个加标水平下的回收率为86.6%~103.8%,相对标准偏差为1.8%~4.3%。此方法简单、快速、分离效果好、分析成本低,是一种测定蜂蜜样品中单、双糖的优良方法,且检测结果与国家标准方法保持一致。     

Interaction of the sugars trehalose, maltose and glucose with a phospholipid bilayer: a comparative molecular dynamics study

Molecular dynamics simulations are used to investigate the interaction of the sugars trehalose, maltose, and glucose with a phospholipid bilayer at atomic resolution. Simulations of the bilayer in the absence or in the presence of sugar (2 molal concentration for the disaccharides, 4 molal for the monosaccharide) are carried out at 325 and 475 K. At 325 K, the three sugars are found to interact directly with the lipid headgroups through hydrogen bonds, replacing water at about one-fifth to one-quarter of the hydrogen-bonding sites provided by the membrane. Because of its small size and of the reduced topological constraints imposed on the hydroxyl group locations and orientations, glucose interacts more tightly (at identical effective hydroxyl group concentration) with the lipid headgroups when compared to the disaccharides. At high temperature, the three sugars are able to prevent the thermal disruption of the bilayer. This protective effect is correlated with a significant increase in the number of sugar-headgroups hydrogen bonds. For the disaccharides, this change is predominantly due to an increase in the number of sugar molecules bridging three or more lipid molecules. For glucose, it is primarily due to an increase in the number of sugar molecules bound to one or bridging two lipid molecules.     

The hydration of monosaccharides—an NMR study

At temperatures close to 0°C proton exchange between sugar hydroxyl groups and water is slow, and separate proton resonance peaks can be detected for the hydroxyl protons. All are shifted downfield of the water resonance, the anomeric hydroxyl proton shift being the greatest. Axial anomeric hydroxyl protons are shifted less than corresponding equatorial protons. Proton exchange with water is strongly acid and base catalyzed, but, at least in some cases, there seems to be an additional pH-independent mechanism involved. From the temperature effect on the shifts, and the effect of added dimethyl sulfoxide, we conclude that each hydroxyl group is bonded on average to two water molecules. This estimate of the hydration number for monosaccharides is far greater than those previously deduced from relaxation studies. It is suggested that the source of this difference lies in the residence times of the bound water molecules. Shifts of the hydroxyl proton resonances for sugars in methanol are compared with those for aqueous solutions and are found to be very similar. Hence it is concluded that these shifts do not reveal any special effects due to water structure. There are quite marked differences in the shifts for different sugars, and, in particular, the anomeric hydroxyl proton shifts for ketoses are smaller than those for aldoses.Taken as solvation spectra, Part 56.     

高效阴离子交换色谱-脉冲安培检测法分析啤酒和麦汁中的糖

建立了高效阴离子交换色谱-脉冲安培检测(HPAEC-PAD)同时测定单糖、二糖和多种低聚糖的方法。采用水、0.25 mmol/L NaOH溶液和1 mol/L NaAc溶液三元梯度淋洗,在CarboPac PA-100色谱柱上,11种糖在40 min内达到良好分离;采用积分脉冲安培检测方法,无需对样品进行复杂的前处理或衍生反应便可直接检测。11种糖的检出限(S/N=3)在13～88 pg范围内。将该方法用于啤酒和麦汁样品中单糖、二糖及低聚糖的分析取得了很好的结果,样品中的加标回收率为81%～107%。     

The stereochemical dependence of unimolecular dissociation of monosaccharide-glycolaldehyde anions in the gas phase: a basis for assignment of the stereochemistry and anomeric configuration of monosaccharides in oligosaccharides by mass spectrometry via a key discriminatory product ion of disaccharide fragmentation, m/z 221

Mass spectrometry of hexose-containing disaccharides often yields product ions of m/z 221 in the negative ion mode. Using a Paul trap, isolation and collision-induced dissociation of the m/z 221 anions yielded mass spectra that easily differentiated their stereochemistry and anomeric configuration, for all 16 stereochemical variants. The ions were shown to be glycopyranosyl-glycolaldehydes through chemical synthesis of their standards. The stereochemistry dramatically affected fragmentation which was dependent on four relative stereochemical arrangements: (1) the relationship between the hydroxyl group at position 2 and the anomeric configuration, (2) a cis relationship of the anomeric position and positions 2 and 3 (1,2,3-cis), (3) a 1,2 trans-2,3 cis relationship, and (4) the relationship between the hydroxyl group at position 4 and the anomeric configuration. After labeling the reducing carbonyl oxygen of a series of disaccharides with 18O to mass-discriminate between their monosaccharide components, it was demonstrated that m/z 221 anions are comprised of an intact nonreducing sugar glycosidically linked to a 2-carbon aglycon derived from the reducing sugar, irrespective of the linkage position between monosaccharides. This enabled the location of the intact sugar to be assigned to the nonreducing side of a glycosidic linkage. Detailed studies of experimental factors necessary for reproducibility demonstrated that the unique mass spectrum for each m/z 221 anion could be obtained from month-to-month through the use of an internal energy-input calibrant ion that ensured reproducible energy deposition into the ions. The counterparts to these ions for the 2-acetamido-2-deoxyhexoses were m/z 262 anions, and the anomeric configuration and stereochemistry of these anions could also be reproducibly discriminated for N-acetylglucosamine and N-acetylgalactosamine. The fragmentation patterns of m/z 221 anions provide a firm reproducible basis for assignment of sugar stereochemistries in the gas phase.     

A Facile,One‐Step Conversion of 6‐O‐Trityl and 6‐O‐TBDMS Monosaccharides into the Corresponding Formate Esters

A convenient method has been developed for a facile and high‐yield conversion of 6‐O‐tert‐butyldimethylsilyl and 6‐O‐trityl protected monosaccharides to their formate esters, which may serve as useful intermediates for the replacement of the primary hydroxyl group of sugars by other functional groups.     

Chromatographic behavior of xanthines in aqueous normal phase chromatography using titania stationary phase

The chromatographic behavior of native titania was investigated in aqueous normal phase chromatography using a set of N-methylated xanthines as polar test solutes. In agreement with a hydrophilic interaction on a polar bed, the retention of xanthine models increased mainly along their molecular polarity. Adsorption of these molecules on the hydrated surface of titania prevailed as a retention mechanism for low water contents in the mobile phase. Several N-methylated xanthines could be easily discriminated along the number and position of their methyl groups while the nitrogen atom at position 3 was found deeply involved in the retention on titania. To get further insights on the interactions occurring on the surface of titania, the retention of xanthine derivatives based on ligand-exchange was evaluated as a function of the buffer concentration and type. The separation efficiency of native titania for the set of N-methylated xanthines was comparable to that observed on zirconia but lower than that obtained on native silica due to mixed-mode interactions. However, titania exhibited a superior ability to recognize several isomeric positions of xanthine derivatives in comparison to zirconia and silica.     

Stereo‐ and Regioselective Direct Multi‐Deuterium‐Labeling Methods for Sugars

Deuterium‐labeled sugars can be utilized as powerful tools for the architectural analyses of high‐sugar‐containing molecules represented by the nucleic acids and glycoproteins, and chiral building blocks for the syntheses of new drug candidates (heavy drugs) due to their potential characteristics, such as simplifying the ¹H NMR spectra and the stability of C? D bonds compared with C? H bonds. We have established a direct and efficient synthetic method of deuterated sugars from non‐labeled sugars by using the heterogeneous Ru/C‐catalyzed H–D exchange reaction in D₂O under a hydrogen atmosphere with perfect chemo‐ and stereoselectivities. The direct H–D exchange reaction can selectively proceed on carbons adjacent to the free hydroxyl groups, and the deuterium labeling of various pyranosides (such as glucose and disaccharides), as well as furanosides, represented by ribose and deoxyribose was realized. Furthermore, the desired number of deuterium atoms can be freely incorporated into selected positions by the site‐selective protection of the hydroxyl groups using acetal‐type protective groups because the deuterium exchange reaction never proceeds on positions adjacent to the protected hydroxyl groups.     

Long-range influence of carbohydrates on the solvation dynamics of water--answers from terahertz absorption measurements and molecular modeling simulations

We present new terahertz (THz) spectroscopic measurements of solvated sugars and compare the effect of two disaccharides (trehalose and lactose) and one monosaccharide (glucose) with respect to the solute-induced changes in the sub-picosecond network dynamics of the hydration water. We found that the solute affects the fast collective network motions of the solvent, even beyond the first solvation layer. For all three carbohydrates, we find an increase of 2-4% in the THz absorption coefficient of the hydration water in comparison to bulk water. Concentration-dependent changes in the THz absorption between 2.1 and 2.8 THz of the solute-water mixture were measured with a precision better than 1% and were used to deduce a dynamical hydration shell, which extends from the surface up to 5.7 +/- 0.4 and 6.5 +/- 0.9 A for the disaccharides lactose and trehalose, respectively, and 3.7 +/- 0.9 A for the glucose. This exceeds the values for the static hydration shell as determined, for example, by scattering, where the long-range structure was found to be not significantly affected by the solute beyond the first hydration shell. When comparing all three carbohydrates, we found that the solute-induced change in the THz absorption depends on the product of molar concentration of the solute and the number of hydrogen bonds between the carbohydrate and water molecules. We can conclude that the long-range influence on the sub-picosecond collective water network motions of the hydration water is directly correlated with the average number of hydrogen bonds between the molecule and adjacent water molecules for carbohydrates. This implies that monosaccharides have a smaller influence on the surrounding water molecules than disaccharides. This could explain the bioprotection mechanism of sugar-water mixtures, which has been found to be more effective for disaccharides than for monosaccharides.     

Gold-catalyzed glycosidations: synthesis of 1,6-anhydro saccharides

Various 1,6-anhydro sugars are synthesized utilizing salient features of gold-catalyzed glycosidations. All the reactions occurred under mild conditions in the presence of 7 mol % of AuBr₃ enabling easy synthesis of 1,6-anhydro sugars from corresponding 6-hydroxy propargyl/methyl monosaccharides, disaccharides, and trisaccharides in good yields.     

Ion Chromatographic Analysis of Monosaccharides and Disaccharides in Raw Sugar

A simple and effective method using ion chromatography was developed for the simultaneous determination of five monosaccharides (arabinose, glucose, fructose, xylose, and ribose) and two disaccharides (sucrose and lactose) in raw sugar samples. The separation was performed on a CarboPac PA 10 column using the gradient elution of sodium hydroxide and water as the mobile phase. Monosaccharides and disaccharides were detected by an integrated pulsed amperometric detection (IPAD) using gold working electrode. Acid hydrolysis was used for sample preparation before the analysis of glucose and fructose. All the studied sugars showed good linear ranges within 0.5–100 µg mL⁻¹ with the correlation coefficients higher than 0.997. The limits of detection were all less than 0.5 µg mL⁻¹. The RSDs of the method were less than 10 %. The recoveries of the sugars that spiked in raw sugar samples ranged from 96.1 to 102.4 %. The method was successfully applied for the analysis of sugars in raw sugar samples. Sucrose is the major constituent found in the samples at 97 %.

     

A colorimetric sensor array for detection and identification of sugars

Molecular recognition of sugars and a practical method to detect and discriminate among a large number of such similar analytes remain substantial scientific challenges. We report here a low-cost, simple colorimetric sensor array capable of identification and quantification of sugars and related compounds. Fifteen different monosaccharides, disaccharides, and artificial sweeteners were differentiated without error in 80 trials. Limits of detection at pH 7.4 for glucose were <1 mM, which is below physiologically important levels.     

Silicate complexes of sugars in aqueous solution

Certain sugars react readily with basic silicic acid to form soluble 2/1 (sugar/silicic acid) silicate complexes. Failure of monohydroxy compounds to give soluble products under these conditions indicates that the sugar silicates are chelates: five-membered diolato rings. Only furanose forms react. Pyranose sugars are stable under these conditions. Because all glycosides fail to react with silicic acid under these conditions, reaction appears to involve the anomeric position (C1 in aldoses, C2 in ketoses), which has a more acidic hydroxy group. Reaction is completed only when the anomeric hydroxy group is cis to an adjacent hydroxy group. The appropriate furanose form must have sufficient natural abundance and solubility to provide an observable product, as measured by (29)Si and (13)C NMR spectroscopy. These structural and practical constraints rationalize the successful reaction of the monosaccharides ribose, xylose, lyxose, talose, psicose, fructose, sorbose, and tagatose and the disaccharides lactulose, maltulose, and palatinose. Glucose, mannose, galactose, and sucrose, among others, failed to form complexes. This high selectivity for formation of sugar silicates may have ramifications in prebiotic chemistry.     

Oligosaccharide sequencing by means of mass spectrometry—I: N-phenylosotriazole acetates

Fragmentation of the acetates of the N-phenylosotriazoles of some mono-, di, tri-, tetra- and pentasaccharides under electron-impact (EI) has been studied. The mass spectra of these derivatives can be used for determination of the sequence of monosaccharide units in oligosaccharides (oligosaccharide sequencing), of molecular weight, of the location of the position of the interglycosidic bond in disaccharides and of the position of the methyl group in partially methylated monosaccharides.