Structural characterization of mesquite (Prosopis velutina) gum and its fractions

Structural and physicochemical characteristics of mesquite gum (from Prosopis velutina) were investigated using FT-IR spectroscopic, mass spectrometric and chromatographic methods. Four fractions (F-I, F-IIa, F-IIb and F-III) were isolated by hydrophobic interaction chromatography. The samples were characterized and analyzed for their monosaccharide and oligomers composition by high performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD). L-Arabinose (L-Ara) and D-galactose (D-Gal) were found as the main carbohydrate constituent residues in the polysaccharides from mesquite gum and their ratio (L-Ara/D-Gal) varied within the range 2.54 to 3.06 among the various fractions. Small amounts of D-glucose (D-Glc), D-mannose (D-Man) and D-xylose (D-Xyl) were also detected, particularly in Fractions IIa, IIb and III. Infrared spectroscopy identified polysaccharides and protein in all the samples. Data from mass spectrometry (MALDI-TOF MS) was consistent with the idea that the structure corresponding to the periphereal chains of Fraction I is predominantly a chain of pentoses attached to uronic acid.     

阿拉伯树胶修饰的纳米Ru-Zn催化剂上苯选择加氢制环己烯

用共沉淀法制备了纳米Ru-Zn催化剂,考察了阿拉伯树胶修饰对苯选择加氢制环己烯催化剂性能的影响,并用X射线衍射(XRD)、透射电镜(TEM)、N₂-物理吸附、X射线光电能谱(XPS)和X射线荧光光谱(XRF)等手段对催化剂进行了表征。结果表明,阿拉伯树胶的用量可以调变Ru-Zn催化剂的粒径。最高环己烯收率随粒径的增大呈火山型变化趋势。当阿拉伯树胶与RuCl₃·xH₂O的质量比为0.033时,Ru-Zn催化剂的最佳粒径为4.0 nm,最高环己烯收率达59.6%。且该催化剂具有良好的重复使用性能。     

RHEOLOGICAL PROPERTIES AND APPLICATIONS OF MESQUITE TREE (PROSOPIS JULIFLORA) GUM. 5. THE RHEOLOGICAL PROPERTIES AND STABILITY OF CORN OIL -IN-WATER EMULSIONS STABILISED BY BLENDS OF MESQUITE GUM AND TWEEN 60.

Corn oil-in-water emulsions were prepared using mesquite gum and Tween 60 in conjunction as emulsifier-stabilisers. The mesquite gum/ Tween 60 ratio influenced the viscoelasticity and stability of the emulsions. The viscoelasticity parameters decreased in magnitude, and the rate of drop coalescence increased, as the mesquite gum/Tween 60 ratio decreased. In addition, this ratio influenced the pattern of change in the viscoelasticity parameters when the emulsions were aged. Mixed films of mesquite gum and Tween 60 adsorbed at a flat corn oil-water interface exhibited viscoelasticity, the parameter magnitudes decreasing as the mesquite gum/ Tween 60 ratio decreased. The influence of the mesquite gum/Tween 60 ratio on both the emulsions and model interfacial films is attributed to the relative proportions of the two emulsifier-stabilisers adsorbed at the oil-water interface, their configuration in the adsorbed state and their ability to interlink to form a network.     

阿拉伯树胶修饰的纳米Ru-Zn催化剂上苯选择加氢制环己烯

用共沉淀法制备了纳米Ru-Zn催化剂,考察了阿拉伯树胶修饰对苯选择加氢制环己烯催化剂性能的影响,并用X射线衍射(XRD)、透射电镜(TEM)、N_2-物理吸附、X射线光电能谱(XPS)和X射线荧光光谱(XRF)等手段对催化剂进行了表征。结果表明,阿拉伯树胶的用量可以调变Ru-Zn催化剂的粒径。最高环己烯收率随粒径的增大呈火山型变化趋势。当阿拉伯树胶与RuCl_3·x H_2O的质量比为0.033时,Ru-Zn催化剂的最佳粒径为4.0 nm,最高环己烯收率达59.6%。且该催化剂具有良好的重复使用性能。     

Spectrophotometric determination of paraquat with BiI(-)(4) in the presence of gum arabic

A spectrophotometric method for determination of Paraquat, based on its reaction with BiI(-)(4) ion in the presence of gum arabic, is described. The apparent molar absorptivity of the product is 1.64 x 10(4) 1.mole(-1).cm(-1) at 515 nm. Results for the analysis of commercial herbicides are in good agreement with those obtained by the dithionite method.     

RHEOLOGICAL PROPERTIES AND APPLICATIONS OF MESQUITE TREE (PROSOPIS JULIFLORA) GUM. 3. THE INFLUENCE OF MESQUITE GUM OH THE INTERFACIAL TENSION BETWEEN OIL AND WATER

The influence of mesquite gum on the interfacial tension between liquid paraffin and distilled water has been studied as a function of gum concentration, pH, and added NaCl or CaCl₂. The time dependence of the reduction in interfacial tension was influenced by all three variables. Diffusion to the oil-water interface was the dominant factor in the initial decrease of interfacial tension when low mesquite gum concentrations were used. Reconformation of molecules adsorbed at the oil-water interface controlled the reduction in interfacial tension at longer times when using more concentrated gum solutions.     

Impact of Adding Polysaccharides on the Stability of Egg Yolk/Fish Oil Emulsions under Accelerated Shelf-Life Conditions

Polysaccharides can form interfacial complexes with proteins to form emulsions with enhanced stability. We assessed the effect of adding gum guar or gum arabic to egg yolk/fish oil emulsions. The emulsions were produced using simple or high-pressure homogenization, stored for up to 10 days at 45 °C, and characterized for their particle size and distribution, viscosity, encapsulation efficiency, oxidative stability, and cytotoxicity. Emulsions containing gum guar and/or triglycerides had the highest viscosity. There was no significant difference in the encapsulation efficiency of emulsions regardless of the polysaccharide used. However, emulsions containing gum arabic displayed a bridging flocculation effect, resulting in less stability over time compared to those using gum guar. Emulsions produced using high-pressure homogenization displayed a narrower size distribution and higher stability. The formation of peroxides and propanal was lower in emulsions containing gum guar and was attributed to the surface oil. No significant toxicity toward Caco-2 cells was found from the emulsions over time. On the other hand, after 10 days of storage, nonencapsulated fish oil reduced the cell viability to about 80%. The results showed that gum guar can increase the particle stability of egg yolk/fish oil emulsions and decrease the oxidation rate of omega-3 fatty acids.     

Characterisation of natural polysaccharides (plant gums) used as binding media for artistic and historic works by capillary zone electrophoresis

The monosaccharide constituents of plant gums were separated by capillary electrophoresis at pH 12.1 and detected with indirect UV absorbance. The plant gums investigated were gum arabic, gum acacia, gum tragacanth, cherry gum and locust bean gum (carob gum). The monosaccharides obtained after hydrolysis with 2M trifluoroacetic acid and lyophilisation of the hydrolysate were arabinose, galactose, mannose, rhamnose, xylose, fucose, and glucose, and the two sugar acids galacturonic and glucuronic acid, in accordance with the literature. They were separated in a background electrolyte consisting of NaOH to adjust the pH, 20 mM 2,6-pyridinedicarboxylic acid as chromophore for detection and 0.5 mM cetyltrimethylammonium bromide as additive to reverse the electroosmotic flow. Based on their electropherograms, the plant gums could be identified by their typical composition (depicted in a decision scheme) as follows: a peak of glucuronic acid, together with that of rhamnose, is indicative for gum arabic. Peaks of galacturonic acid and fucose point to gum tragacanth. Locust bean gum shows a major peak for mannose (with the concomitant galactose peak in ratio 4-1), whereas a glucuronic acid and a mannose peak together with a prominent arabinose peak indicates cherry gum. The method was applied to identify the plant gums in samples like watercolours and in several paint layers like gum tempera or those with egg white or drying oils as additives. Artificial aging experiments of thin layers of gum arabic on paper or glass carried out with UV-A radiation (366 nm) did not result in changes of the saccharide patterns, in contrast to the simultaneously conducted aging of a drying oil layer.     

In situ stabilization of Pd(0) nanoparticles into a mixture of natural carbohydrate beads: A novel and highly efficient heterogeneous catalyst system for Heck coupling reactions

A convenient, mild and cost‐effective synthesis of palladium nanoparticles stabilized by a mixture of natural carbohydrate beads (gum arabic and pectin) as a new bio‐organometallic catalyst is reported. Powder X‐ray diffraction, transmission and scanning electron microscopies and energy‐dispersive X‐ray and UV–visible spectroscopies were employed to characterize this supported Pd nanoparticles/gum arabic/pectin catalyst. The nanocatalyst exhibited efficient activity in Mizoroki–Heck cross‐coupling reactions between various aryl halides and n ‐butyl acrylate under solvent‐free conditions. The catalyst can easily be recovered from the reaction system and reused several times with high yields. The products were obtained in short reaction times with excellent yields.     

Influence of Storage Conditions on the Stability of Gum Arabic and Tragacanth

Storage conditions should be chosen so that they do not affect the action and stability of the active pharmaceutical substance (API), and excipients used in pharmacy. UV irradiation, increased temperature, and relative humidity can decompose storage substances by photolysis, thermolysis, and hydrolysis process, respectively. The effect of physical factors may be the decomposition of pharmaceutical substances or their inappropriate action, including pharmacological effects. Polymers of natural origin are increasingly used in the pharmaceutical industry. With this in mind, we evaluated the effect of storage conditions on the stability of gum arabic (GA) and tragacanth (GT). The influence of higher temperature, UV irradiation, and relative humidity on GA and GT was tested. Thermogravimetry (TG, c-DTA), colorimetric analysis, UV-Vis spectrophotometry, and optical microscopy were used as research methods. The TGA and c-DTA examination indicated that decomposition of GA starts at a higher temperature compared to GT. This indicate that gum arabic is more resistant to higher temperatures compared to tragacanth. However, the conducted analysis showed that gum arabic is more sensitive to the tested storage conditions. Among the tested physical conditions, both polymers were most sensitive to conditions of increased relative humidity in the environment.     

Kinetic flow-injection determination of hydrogen peroxide by use of iron(III)-catalyzed coloration and its application to the determination of biological substances.

A kinetic flow-injection (FI) method is described for the determination of hydrogen peroxide. This method is based on an iron(III)-catalyzed oxidative coupling of 4-aminoantipyrine with N,N-dimethylaniline by hydrogen peroxide. By measuring the change in the absorbance of the dye formed at 560 nm, 1 x 10(-6) - 6 x 10(-4) M hydrogen peroxide could be determined with a sampling rate of 15 h(-1). The relative standard deviation (n = 30) was 0.8% for 5 x 10(-5) M hydrogen peroxide. There was little interference of the co-existing ions and compounds. After introducing some immobilized enzyme reactors to the FI system, the proposed method allowed the determination of glucose and uric acid ranging from 1 x 10(-6) to 6 x 10(-4) M with relative standard deviations of below 2%. The applicability of the method was demonstrated by determining these substances in serum samples.     

混合增溶剂对离子缔合物作用的研究

慈云祥等在研究铂、钯、金-碘化钾-丁基罗丹明B显色体系时发现,使用明胶或阿拉伯胶与TritonX-100的混合液,有良好的增溶作用和极好的增敏效应。我们的研究表明:在不少离子缔合物显色体系中,聚乙烯醇-TritonX-100或阿拉伯胶-β-环糊精等混合液,也有很好的增溶(或分散)、增敏和增稳作用。     

Use of specific polysaccharide‐immobilized monodisperse poly(glycidyl methacrylate) core–silica shell microspheres for affinity purification of lectins

Immobilization of polysaccharides (yeast mannan and gum arabic) on the macroporous poly(glycidyl methacrylate) monodisperse microspheres coated with silica (SiO₂)‐containing amino groups on the surface was used to prepare affinity sorbents for lectin purification. The efficiency of isolating mannose specific Pisum sativum lectin was demonstrated on sorbent with immobilized yeast mannan and that of galactose specific Glycine hispida lectin on sorbent with immobilized gum arabic. The microspheres with immobilized polysaccharides can be used for selecting an affinity sorbent for purification of other mannose‐ and galactose‐specific lectins. In contrast to yeast mannan, the gum arabic immobilized on the microspheres possesses much narrower specificity and is suitable for purification of only those galactose specific lectins which interact well with l ‐rhamnose or l ‐arabinose. The synthesized macroporous particles are capable of immobilizing 50 mg of polysaccharide per 1 g of the matrix, which is 10 times higher than the capacity of epoxy‐activated Sepharose 6B. That makes it possible to obtain the same lectin quantity using a column of 10 times smaller volume. Another advantage of novel affinity sorbents comparing corresponding Sepharose gels is the possibility of sorbent drying after use. Copyright © 2014 John Wiley & Sons, Ltd.     

Molecular organization in two-dimensional films of liquid I. Langmuir films of binary mixtures of liquid crystals with a crystalline mixtures terminal cyano group

The Langmuir films of two liquid crystal materials, 4-octyl-4'-cyanobiphenyl (8CB) and 4-pentyl-4"-cyano-p-terphenyl (5CT), and of their mixtures have been studied by recording surface pressure-area isotherms and Brewster angle microscopy (BAM) images. The pure liquid crystals revealed very different characters of the surface pressure-area isotherms indicating different organization of the molecules and different molecular interactions in the monolayer at the water-air interface. The surface pressure-area isotherms of Langmuir films formed from 8CB/5CT mixtures give evidence for phase separation of the components over the whole range of molar fractions. Similar conclusions have been drawn on the basis of BAM image analysis.     

Found in the Folds: A Rediscovery of Ancient Egyptian Pleated Textiles and the Analysis of Carbohydrate Coatings

Charles T. Currelly, first director of the Royal Ontario Museum, participated in excavations of the tomb of King Nebhepetre, now known as Mentuhotep II, (Dynasty XI) in Deir el-Bahri, Egypt in 1906. He brought to Canada many objects from the excavations, and objects that he purchased while in Egypt; these formed the initial collection of the museum. Among the objects were seven fragments of fine linen cloth with intricate pleat patterns. Recently, the cloths became the subject of a study to learn how they had retained their pleats for 4000 years. Samples were examined and analysed using polarised light microscopy, scanning electron microscopy-electron dispersive X-ray spectrometry, gas chromatography-mass spectrometry, and pyrolysis-gas chromatography-mass spectrometry. Three of the cloths were likely fragments of clothing re-purposed as bandages and were found to be saturated in mummification balms composed of Pinaceae resin, Pistacia resin, and an essential oil characterised by a high abundance of cedrol, possibly originating from a juniper species. All seven of the cloths were found to have traces of polysaccharides from two probable sources: an arabinogalactan gum such as gum arabic or a fruit gum, and a polyglucoside, possibly starch.     

Molecular organization in two-dimensional films of liquid I. Langmuir films of binary mixtures of liquid crystals with a crystalline mixtures terminal cyano group

The Langmuir films of two liquid crystal materials, 4-octyl-4'-cyanobiphenyl (8CB) and 4-pentyl-4"-cyano-p-terphenyl (5CT), and of their mixtures have been studied by recording surface pressure-area isotherms and Brewster angle microscopy (BAM) images. The pure liquid crystals revealed very different characters of the surface pressure-area isotherms indicating different organization of the molecules and different molecular interactions in the monolayer at the water-air interface. The surface pressure-area isotherms of Langmuir films formed from 8CB/5CT mixtures give evidence for phase separation of the components over the whole range of molar fractions. Similar conclusions have been drawn on the basis of BAM image analysis.     

The effects of gum arabic oral treatment on the metabolic profile of chronic renal failure patients under regular haemodialysis in Central Sudan

This study aimed at assessing the effect of gum arabic (Acacia senegal) oral treatment on the metabolic profile of chronic renal failure (CRF) patients. A total of 36 CRF patients (under regular haemodialysis) and 10 normal subjects participated in this study. The patients were randomly allocated into three groups-group A: 12 CRF patients under low-protein diet (LPD) (<40 g day(-1)) and gum arabic (50 g day(-1)) treatment; group B: 14 CRF patients under LPD and gum arabic, iron (ferrous sulphate, 200 mg day(-1)) and folic acid (5 mg day(-1)) treatment; group C (control group): 10 CRF patients under LPD and iron and folic acid treatment and group D: 10 normal volunteers (on normal diet) under daily dose of 50 g gum arabic. Each of the above treatments was continued for three consecutive months. Blood samples were collected from each subject before treatment and twice per month "pre-dialysis" for 3 months. Biochemical parameters measured were: serum urea, serum creatinine, serum uric acid, serum calcium and serum phosphorus. By the end of the 3 months of treatment, serum urea levels significantly decreased by 31.2 and 44.18% for group A and B, respectively, compared with the baseline (0.01 < p < 0.001) and control group (p < 0.05). Serum creatinine levels significantly decreased in the groups of gum users (A, B and D) by 9.94, 12.65 and 11.7%, respectively, compared with the control group (p < 0.001). There was a significant decrease (p < 0.05) in serum uric acid levels by 14 and 19.9% for group A and B, respectively, compared with the baseline. Serum calcium levels increased by 12.64, 15.75 and 8.75% for group A, B and D, respectively, and these increases were significantly different (0.05 < p < 0.001) from baseline and control group for groups A and B. Serum phosphorus levels significantly decreased by 22.54% for group A, 17.69% for group B and 7.71% for group D, compared with the baseline (0.05 < p < 0.001). From this study, we conclude that oral administration of gum arabic could conceivably alleviate adverse effects of CRF.     

Pingba RP-3喷气燃料中有色组分的鉴定及其特性研究

用中性氧化铝吸附、无水乙酸脱附的方法，对储存中变色的Pingba RP-3喷气燃料中的有色组分进行分离制备。应用有机元素分析、红外光谱、色质联用和裂解色质联用等分析法对富集有色组分的吸附胶质进行了分析鉴定，对燃料的储存特性和有色组分的化学特性进行了考察。结果表明，Pingba RP-3喷气燃料中的有色组分全部集中在吸附胶质中，吸附胶质以含氧化合物为主，其主要成分为烷基苯酚类（及其多聚体）化合物，含氮化合物质量分数极少，未检出含硫化合物。Pingba RP-3在储存中颜色变深的主要原因是胶质中的烷基苯酚类化合物氧化和缩聚。储存过程中喷气燃料的吸附胶质和颜色增加显著，与燃料在一定条件下的氧化反应有关。     

Nanostructure of polysaccharide complexes

The interaction of gum arabic (GA) with chitosan (Ch) of different degree of deacetylation was studied by turbidity measurements, dynamic light scattering and atomic force microscopy. The structure of the complexes was found to be directly related to the charge density of chitosan molecules. Gum arabic and chitosan with a degree of deacetylation of 75% form soluble complexes with a loosely globular structure of about 250 nm, at weight ratios up to 1.2, if the concentrations are kept low (total biopolymer concentration up to 0.06%). If chitosan has a higher charge density (degree of deacetylation of 93%), colloidal particles are formed, independently of the polymer concentration or ratio. At low concentrations and GA/Ch ratios of 1 or 1.2, the particles have diameters of 200-250 nm. The formation of soluble complexes is attributed to a chitosan lower charge density and the presence of non-charged monomers, which prevent the efficient self-assembly of the macromolecules.     

Molecular Weight and Aggregation of Erwinia Gum in Aqueous Solutions

Erwinia(E) gum is composed of glucose, fucose, galactose and glucuronic acid. The weight-average molecular weights Mw, number-average molecular weights Mn and intrinsic viscosities[η] of the four fractions and the unfractionated E gum in aqueous solutions at desired temperatures were studied by light scattering, membrane osmometry, size exclusion chromatography(SEC) and viscometry. The experimental results prove that E gum formed aggregates in the aqueous solution at 25 ℃ and the aggregates were broken gradually with increasing temperature. The dissociation of the aggregates of E gum in the aqueous solution started at 36 ℃, and was completed at around 90 ℃. The [η] values of E gum and its fractions are much higher than those of the conventional polymers with the similar molecular weights, and decrease with increasing NaCl concentration.