Aqueous Ammonium Oxalate Solutions Research Articles

Polysaccharides of Salsola passerina: Extraction, Structural Characterization and Antioxidant Activity.

The above-ground part of the Salsola passerine was found to contain ~13% (w/w) of polysaccharides extractable with water and aqueous solutions of ammonium oxalate and sodium carbonate. The fractions extracted with aqueous sodium carbonate solutions had the highest yield. The polysaccharides of majority fractions are characterized by similar monosaccharide composition; namely, galacturonic acid and arabinose residues are the principal components of their carbohydrate chains. The present study focused on the determination of antioxidant activity of the extracted polysaccharide fractions and elucidation of the structure of polysaccharides using nuclear magnetic resonance (NMR) spectroscopy. Homogalacturonan (HG), consisting of 1,4-linked residues of α-D-galactopyranosyluronic acid (GalpA), rhamnogalacturonan-I (RG-I), which contains a diglycosyl repeating unit with a strictly alternating sequence of 1,4-linked D-GalpA and 1,2-linked L-rhamnopyranose (Rhap) residues in the backbone, and arabinan, were identified as the structural units of the obtained polysaccharides. HMBC spectra showed that arabinan consisted of alternating regions formed by 3,5-substituted and 1,5-linked arabinofuranose residues, but there was no alternation of these residues in the arabinan structure. Polysaccharide fractions scavenged the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical at 0.2-1.8 mg/mL. The correlation analysis showed that the DPPH scavenging activity of polysaccharide fractions was associated with the content of phenolic compounds (PCs).

Influence of different solvents on the growth, thermal and dielectric properties of Phthalic acid single crystals

ABSTRACT Good quality Phthalic acid single crystals were grown in aqueous solutions of ammonium oxalate and ammonium bromide by slow evaporation solution growth method. Single crystal X-ray diffraction of PA1 and PA2 was analysed in this article. The functional groups of crystals were identified and confirmed by FT-IR analysis. UV-Vis absorption spectrum was analysed, which shows that least absorbance in the entire visible region and the value of an optical band gap was determined. The second harmonic generation efficiency of the crystals was determined by Kurtz’s powder method, which confirms non-linear optical property of the title material. The thermal stability and melting point of PA1 and PA2 crystals were found by the TGA and DTA thermal analysis. The kinetic parameters were calculated using Coats and Redfern method. The dielectric study was carried out by determining dielectric constant, dielectric loss and ac conductivity using LCR metre and the variation of these parameters with frequency and temperature was analysed.

Preliminary Structural Characteristic of Polysaccharides Extracted From the Callus Tissue of Sosnowskyi’s Hogweed (Heracleum Sosnowskyi Manden) Stem by Aqueous Ammonium Oxalate

Pectic polysaccharides have been isolated from callus tissue of the stem of Sosnowskyi’s hogweed (Heracleum sosnowskyi Manden) by extraction with a 0.7% aqueous solution of ammonium oxalate and characterized. It was shown that they differ from pectic polysaccharides of a native plant by a lower content of D‑galacturonic acid residues and a higher content of arabinose and galactose residues. The results obtained by a combination of ion exchange chromatography, enzymatic hydrolysis, periodate oxidation, methylation and NMR spectroscopy indicated the presence of low-methyl esterified 1,4-α-D-galacturonan, rhamogalacturonan-I, arabinan and galactan or arabinogalactan. The terminal 1,2- and 1,5-linked arabinofuranose residues, terminal, 1,3-, 1,6-linked and 3,6-substituted galactopyranose residues and 1,4-linked hexopyranose (galactopyranose or glucopyranose) residues were identified in the composition of neutral carbohydrate chains. The presence in the NMR spectra of trans-glycosyl correlation peaks of the methyl groups of 2,4-di-O-substituted rhamnose residues indirectly confirm the attachment arabinan, galactan or arabinogalactan carbohydrate chains to rhamnopyranose residues of the backbone at C-4 position.

Characterization of tissue specific differences in cell wall polysaccharides of ripe and overripe pear fruit

Cell walls from flesh, parenchyma cells, stone cells and skin were isolated from ripe and overripe Pyrus communis L. cv “De Cloche” using the phenol-buffer method. Pear polysaccharides were solubilized from cell walls by sequential extractions with aqueous solutions of ammonium oxalate, Na2CO3, and increasing concentration of NaOH, to explore overripening impact. Cell walls were also differentiated using MIR spectral data. Stone cells contained high levels of xylose and lignin while parenchyma cells had high levels of glucose, uronic acids and arabinose. Sequential extractions revealed that pear pectins had highly branched rhamnogalacturonans and were extremely methylated. Xylans were the main hemicelluloseespecially for stone cells. Cellulose represented about half of all cell walls. This heterogeneous composition of pear affected differently cell wall evolutions and properties. Thus, overripening involved a decrease in arabinose and a loss of pectic side chains mostly from parenchyma cells. Changes in hemicellulose and cellulose were minor.

Composition and properties of pectin polysaccharides of St. John’s wort Hypericum Perforatum L.

Three fractions of acidic water-soluble polysaccharides (concentration of glucuronic acid 10–65%) were obtained from the above-ground part of St. Johns wort Hypericum perforatum L. by serial extraction with water and 0.7% aqueous solution of ammonium oxalate. Enzymatic hydrolysis of these polysaccharides using endo-polygalacturonase indicates that their carbohydrate chains contain the units of galacturone formed by 1,4-α-linked residues of non-substituted D-galacturonic acid. The extracted polysaccharides have been purified by means of gel filtration. It has been shown that water-soluble polysaccharides obtained by extraction with water manly contain the residues of galactose, mannose, glucose, and arabinose (the concentration of glucuronic acid being 10–27%) while the polysaccharide fraction extracted using 0.7% aqueous solution of ammonium oxalate is presented by pectin polysaccharides. Only the residues of galacturonic acid (55–72%) have been identified among glucuronic acids in its composition using chromatography/mass spectrometry of trimethylsilyl derivatives. In addition, this fraction contains the residues of the neutral monosaccharides which are typical for pectins: arabinoses, galactoses, rhamnoses, and glucose; there are also minor concentrations of residues of xylose and mannose. IR spectra of pectin polysaccharides of St. John’s wort have absorption bands in the ranges 1740, 1640–1620, 1236–1200, and 1200–1000 cm−1 which are typical for pectins. It has been demonstrated that aqueous solutions of pectin polysaccharides of St. John’s wort (2 mg/mL) have pronounced antioxidant activity (44% of the activity of trolox taken for 100%).

Study of the nature of Cu(II) complexes in aqueous ammonium oxalate solutions by ultraviolet-visible spectroscopy

Experimental results of an investigation of aqueous ammonium oxalate solutions containing Cu(II) impurity by ultraviolet–visible spectroscopy are described and discussed from the standpoint of speciation of complexes. The results show that absorption of light by aqueous ammonium oxalate solutions containing Cu(II) impurity in the range −5 < ln(ci/c) < 2.5 of the ratio of concentrations ci and c of impurity and solute, respectively, leads to decrease or increase in the intensity of bands of the ultraviolet–visible spectral regions, and these changes may be expressed by full width at half maximum, molar extinction coefficient, peak wavelength and oscillator strength. The changes are caused by the coordination of C2O42− ligand with Cu(H2O)62+ aquocomplex, and are related with the impurity–solute concentration ratio ci/c. The coordination of C2O42− ligand with Cu(H2O)62+ aquocomplex in the range 0 < ln(ci/c) < 2.5 leads to the formation of Cu(C2O4) complex, but the coordination of the C2O42− ligand with Cu(C2O4) complex in the concentration ratio range −5 < ln(ci/c) < 0 results in the formation of predominantly Cu(C2O4)22− complex. The effect of successive coordination of the C2O42− ligand is well-defined in the ultraviolet spectral region but poor in the visible region.

The nature of Mn(II) complexes in concentrated aqueous ammonium oxalate solutions

AbstractThe paper presents an analysis of the results of spectroscopic studies obtained in the ultraviolet range UV for unsaturated ammonium oxalate solutions containing Mn(II) impurity ci. The aim is to follow manganese oxalate formation processes at different ammonium oxalate concentrations c and Mn(II) impurity ci and also to establish how concentrations of particular species change with a change of ratio (ci /c). Spectroscopic analysis is discussed from the standpoint of speciation of these complexes in the abovementioned solutions. The coordination of C2O42– ligand with Mn(H2O)62+ aquacomplex in the range ‐2 &lt; ln(ci/c) &lt; 1.5 leads to the formation of Mn(C2O4) and Mn(C2O4)22– complexes, but the coordination of the C2O42– ligand with Mn(C2O4)22– complex in the concentration ratio range ‐5 &lt; ln(ci/c) &lt; ‐2 results in the formation of predominantly Mn(C2O4)34– complex. The effect of successive coordination of the C2O42– ligand is well‐defined in the ultraviolet spectral region. (© 2010 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Study of copper complexes in saturated and unsaturated aqueous ammonium oxalate solutions containing Cu(II) impurity

The influence of Cu(II) impurity on chemical equilibria in unsaturated and saturated ammonium oxalate (AO) aqueous solutions was investigated as a function of concentration c i of impurity. Using the computer programme “Hyss” the species present in the solutions were analysed. It was found that in the aqueous solutions of ammonium oxalate containing Cu(II) ions the following species are formed: Cu 2+, Cu(OH) +, Cu(OH) 2, CuC 2O 4 0 and Cu(C 2O 4) 2 2− in addition to C 2O 4 2−, HC 2O 4 −, H 2C 2O 4 and (NH 4) 2C 2O 4 0 species, and their concentration depends on concentrations c i of Cu(II) impurity and c of ammonium oxalate. The dependences of solution pH and of absorbance A and the corresponding wavelength λ for unsaturated aqueous solutions on ammonium oxalate concentration c containing different concentrations c i of Cu(II) ions showed three well-defined regions characterised by transition values of solution pH or solute concentration c. Speciation analysis revealed that Cu 2+ and CuC 2O 4 0, CuC 2O 4 0 and Cu(C 2O 4 )2 2−, and Cu(C 2O 4) 2 2− complexes are predominantly present in the solute concentration intervals c ≤ 0.01 mol/dm 3, 0.01 mol/dm 3 < c < 0.03 mol/dm 3 and c ≥ 0.03 mol/dm 3, respectively. The concentration interval range 0.01 mol/dm 3 < c < 0.03 mol/dm 3 corresponds to the pH interval where Cu(OH) 2 is precipitated. It was found that the solubility of ammonium oxalate at 30 ° C increases practically linearly with an increase in the concentration of Cu(II) impurity. Speciation analysis of saturated aqueous solutions of ammonium oxalate revealed that Cu(II) ions contained in AO saturated solutions exist mainly as Cu(C 2O 4) 2 2−-type complexes, and the increase in the solubility of AO in the presence of Cu(II) impurity is essentially due to an increase in the ratio of the concentrations of CuC 2O 4 0 and Cu(C 2O 4) 2 2− species.

Structural study of bergenan, a pectin from Bergenia crassifolia

A pectin polysaccharide named bergenan was isolated from the freshly collected leaves of the leather bergenia Bergenia crassifolia by extraction with an aqueous solution of ammonium oxalate. The main component of its carbohydrate chain was shown to be the residues of D-galacturonic acid (about 80%). In addition, the polysaccharide contains residues of galactose, arabinose, and rhamnose; their total content is less than 15%. It was shown that the bergenan samples from bergenia leaves collected at different vegetation periods (from July to September) do not substantially differ either in monosaccharide composition or in the viscosity of aqueous solutions they form. The results of enzymatic hydrolysis by alpha-1,4-galacturonase (pectinase), partial acidic hydrolysis, NMR spectroscopy, and methylation with subsequent analysis of the results by GC-MS indicate that the bergenan macromolecule contains the regions of a linear alpha--1,4-D-galactopyranosyluronan and rhamnogalacturonan-I (RG-1). Galacturonan responds for a greater part of the macromolecule. A considerable amount of its constituent galacturonic acid residues are present as methyl esters. The side chains in RG-I are attached to the rhamnopyranose residues of the main carbohydrate chain by 1,4-link and are composed of the residues of terminal arabinofuranose and galactopyranose, 1,5-linked (-arabinofuranose, and 1,4-and 1,6-linked beta-galactopyranose. The branching points of the side chains of the RG-I molecule are 3,4- and 3,6-di-O-substituted galactose residues.

On the dimensions of species participating in the growth of ammonium oxalate monohydrate crystals from viscosity data of concentrated aqueous solutions

AbstractThe experimental data of the temperature and concentration dependence of viscosity of concentrated aqueous ammonium oxalate solutions are analysed using the hole theory of liquids and Einstein's model of viscosity. Analysis of the data revealed that the dimensions of the species participating in the growth of ammonium oxalate monohydrate crystals are 3‐5 times larger than the dimensions of individual NH4+ and C2O42‐ ions composing them. (© 2004 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Isolation of Polysaccharides from the Callus Culture of Lemna minor L.

Two fractions that included acid arabinogalactan and pectin were extracted from the callus culture of duckweed plants (Lemna minor L.) with water and ammonium oxalate. Residues of galactose and arabinose in the 2.0-2.5:1 ratio were the major constituents of acid arabinogalactan. The pectin fraction contained primarily residues of glucuronic acids, galactose, and arabinose. The percentage of arabinogalactan and pectin was similar. The yield of polysaccharide fractions did not depend on the method for their isolation. Extraction with water, treatment of the biomass with an aqueous solution of formalin and diluted hydrochloric acid, and extraction with an aqueous solution of ammonium oxalate allowed us to obtain the highest-purity pectin polysaccharide.

Simplified chemical route for the synthesis of barium titanyl oxalate (BTO)

A simple chemical route is developed to obtain an important molecular precursor (leading to barium titanate powders), namely barium titanyl oxalate (BTO) with nearly theoretical yield. In this route, 0.1 M alcoholic solution of titanium tetrabutoxide is reacted with 0.1 M alcoholic solution of oxalic acid to form titanyl oxalate (TiOC2O4). This was further converted to soluble ammonium titanyl oxalate (ATO); (NH4)2TiO(C2O4)2.H2O by reacting with an equimolar aqueous solution of ammonium oxalate (pH 4.25). Instead of using available barium salts (halide/nitrate/acetate) solution, a modified barium precursor solution with controlled pH (=4.2) is prepared for carrying out cation-exchange reaction with ATO. For this purpose the modified Ba-precursor solution is freshly prepared by partial neutralization of a 0.1 M aqueous solution of barium hydroxide with controlled addition of dilute HNO3 (1.1 M) solution. The pH of this solution is the same as that of the ATO solution. The exchange reaction between equimolar ATO and modified Ba-precursor solution precipitated barium titanyl oxalate (BTO) with a quantitative yield at room temperature. Submicron-sized, stoichiometric, pure BaTiO3 powders were obtained by the controlled pyrolysis of BTO in air. The present communication deals with the detailed analysis of this simplified method in producing BTO/BT powders and their characterization employing various physicochemical techniques.

Density and Viscosity of Undersaturated, Saturated, and Supersaturated Aqueous Ammonium Oxalate Solutions from 287 K to 325 K

Experimental data on the density, d, and viscosity, η, of ammonium oxalate aqueous solutions in the range of undersaturation and supersaturation are reported for solutions of saturation concentrations, cs, between 0.36 M and 0.75 M. It was found that the temperature dependence of d for solutions of different saturation concentrations may be described by a first-order equation while that of η may be described by an Arrhenius-type relation. Moreover, for solutions of particular saturation concentrations, cs, both d and η linearly increase with supersaturation.

The isolation, preliminary structural studies, and physiological activity of water-soluble polysaccharides from the squeezed berries of the snowball treeViburnum opulus

Water-soluble polysaccharide fractions VO1–VO4 were isolated from the squeezed berries of the snowball tree (Viburnum opulus) by successive extraction with water at various temperatures and pH and with aqueous solutions of ammonium oxalate. These fractions were purified by ion-exchange chromatography on DEAE cellulose, and the homogeneity of the purified polysaccharides was determined by gel filtration on Sephacryl S-500. Acidic polysaccharides close to pectins in their sugar composition were found in all the extracts (fractions VO1-1, VO2-1, VO3-2, and VO4-2). Residues of galacturonic acid, galactose, arabinose, and (to a lesser extent) rhamnose are their main constituents. Neutral polysaccharides composed mainly of galactose and mannose residues were additionally found in fractions extracted with acidified water (pH 4.0) and with aqueous ammonium oxalate solutions. Partial acidic hydrolysis and digestion with pectinase of acidic polysaccharides indicated that their carbohydrate backbone consists of α-1,4-linked residues ofD-galacturonic acid. NMR spectra of acidic polysaccharides (fractions VO3-2 and VO3-3) confirmed this and demonstrated that their side oligosaccharide chains are composed of β-1,4-linked galactopyranose residues and of terminal and 2,5- and 3,5-substituted residues of α-arabinofuranose at a Gal : Ara ratio of 3 : 1. Some polysaccharides fromV. opulus were found to possess an immunostimulating activity: they enhance phagocytosis, in particular, the phagocytic index and the secretion of lysosomal enzymes with peritoneal macrophages. Calcium ions were found to be necessary for the appearance of the stimulating effect of acidic polysaccharides fromV. opulus.

Density, Surface Tension, and Refractive Index of Aqueous Ammonium Oxalate Solutions from 293 K to 333 K

Density d, surface tension γ, and refractive index n of ammonium oxalate aqueous solutions of concentrations up to saturation have been measured in the temperature range between 293 K and 333 K. The results of d, γ, and n are fitted as functions of solution concentration. It was found that the first- and second-order equations relating these quantities with solution concentration can satisfactorily be used to describe the data.

Polysaccharides of soy-beans. II. Fractionation of hull cell-wall polysaccharides and the ructure of a xylan.

Successive extractions of water-extracted soy-bean hulls with aqueous solutions of ammonium oxalate, ethylenediaminetetra-acetic acid disodium salt, potassium hydroxide, and sodium hydroxide–sodium borate afford a series of acidic polysaccharide fractions of the pectic acid type, a xylan, and a mannan containing a small proportion of galactose residues, and leave a cellulosic residue. Structural studies have shown that the xylan contains essentially linear chains of 1,4-linked β-D-xylopyranose residues which carry 3–4% of D-glucopyranosyluronic acid residues as single-unit side-chains joined by 1,2-linkages.