Aqueous Ammonium Oxalate Research Articles

Characteristics and rheological properties of ammonium oxalate extracted rosehip pectin

Rosehip fruits are an abundant source of bioactive compounds with enormous application in food technology, because of its nutritional and healthy properties. However, isolation and characterization of rosehip pectin remained challenges, because its properties depend on extraction procedure. Therefore, this study aims to evaluate the characteristics of ammonium oxalate-extracted rosehip pectin and its rheological behavior. Dried rosehip fruits (cultivar Plovdiv 1) were used for alcohol-insoluble solids (AIS) preparation. Rosehip pectin was extracted from AIS using 0.5% aqueous ammonium oxalate. The obtained polysaccharide was characterized with a degree of esterification 68%, degree of acetylation 1.0%, anhydrouronic acid content 87% and yield 13%. FTIR spectrum confirmed the pectin structure with typical bands, especially in finger print region showing the presence of α-(1→4)-bond between the galacturonic acid units. To the best of our knowledge, some physicochemical properties of rosehip pectin were evaluated for the first time. The rheological studies showed the non-Newtonian, shear-thinning and weak thixotropic behavior. The rosehip pectin demonstrated good swelling properties (22 ml/g), higher water holding capacity (6.04 g water/g sample), than oil-holding capacity (2.44 g oil/g sample). The obtained results highlighted that rosehips are rich in pectin with valuable rheological properties, revealing their potential use in food technology.

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.

Isolation and Characterization of Pectic Polysaccharide Fraction fromIn VitroSuspension Culture ofFumaria officinalisL.

In the current study, an acidic polysaccharide from thein vitrosuspension culture ofFumaria officinalisL. was obtained by extraction with 0.8% (w/v) aqueous ammonium oxalate. The polysaccharide fraction mainly consisted of galacturonic acid (41.0%), followed by galactose (7.3%) and arabinose (5.6%). This suggests the presence of arabinogalactan side chains in the rhamnogalacturonan-I segment of the studied pectin, which was mainly built up by homogalacturonan segments. The pectin was evaluated as low-methyl-esterified (45.0%) with degree of acetylation 3.4%. The polymer fraction was consisted of different molecular weight populations in the range of 6–600 kDa. The high amount of 4-L-hydroxyproline (11.7% of total protein) and the specific positive reaction to Yariv’s phenylglycoside reagent indicated the presence of an arabinogalactan protein in the cell walls. The functional properties of the polysaccharide fraction were evaluated, as it possessed better water-holding capacity than oil-holding capacity. The studied pectin demonstrated significant foaming ability and promising emulsifying properties in a concentration 1%. Therefore, the isolated polysaccharide fraction could be successfully used as emulsifier and foaming agent in food products and pharmaceutical supplements.

Extraction of Soluble Polysaccharides from Grape Skins

Obtaining polysaccharides from grape cell walls is an interesting topic for the wine industry given its implications with regards to wine treatments and potential sensory attributes. In the present work, several conditions (i.e., a chelating agent, pH, titratable acidity, extraction time, number of successive extractions, solid to liquid ratio and alcoholic fermentation) were tested to assess their effects on the yield of soluble polysaccharides obtained from grape skins. Among the four tested solvents (i.e., water, tartaric acid, ammonium oxalate, and ethylenediaminetetraacetic acid), aqueous ammonium oxalate was the most effective for polysaccharide extraction but also produced the highest amount of protein impurities. Increasing the number of successive extractions or modifying the extraction time does not increase the amount of total extracted polysaccharides but produces more polysaccharides with a low molecular mass. The extraction yield of polysaccharides does not increase by increasing the tartaric acid concentration; however, the extraction yield increases by increasing the pH of the solvent or decreasing the solid to liquid ratio during the extraction. During the fermentative maceration of the skins, the extraction of soluble polysaccharides is significantly higher than that obtained with aqueous solvents. Thus, it seems that grape skins contain some pectic polysaccharides that are tightly bound to the cell wall matrix that are not immediately solubilized by aqueous buffers and are released under alcoholic fermentation conditions.

Physicochemical and rheological properties of gelling pectin from Sosnowskyi's hogweed (Heracleum sosnowskyi) obtained using different pretreatment conditions

Using extraction with 0.7% aqueous ammonium oxalate, Sosnowskyi's hogweed pectins (yield 5–10%) with high molecular weight (200–700 kDa) and galacturonic acid content (70–85%), low degree of methylation (17–28%) and neutral sugar content (7–15%) were isolated from fresh, previously air-dried and frozen plant materials. All plant raw materials were pretreated with aqueous formaldehyde at 25 °C and dilute hydrochloric acid (pH 1.0 or 4.0, 50 °C). The different pretreatments of plant raw material slightly affected yield, chemical composition and molecular weight (average value and distribution) of hogweed pectin. The 13C-NMR spectroscopy indicated the similar structure of the pectins isolated from fresh and air-dried hogweed raw materials. The pectins were differed slightly in thermal degradation depending on the type of hogweed raw material. The aqueous solutions of hogweed pectins had a pseudoplastic flow behavior. Dynamic oscillatory shear tests showed that the pectin hydrogels in the presence Ca2+ (R∼0.6) represent true gels. The pectins from fresh plant material (pH 4.0) formed stronger gel networks (G' ∼2400 Pa) then compared to pectins from air-dried (G' ∼1400 Pa) and frozen (G' ∼900 Pa) plant raw materials. The pectin gelispheres of different size, particle shape, density and textural parameters were prepared by ionotropic gelation. The gelispheres derived from hogweed pectins (fresh and air-dried raw materials) were more stiffness compared to the gelispheres from the commercial low methoxyl apple pectin.

Chemical studies on the polysaccharides of Salicornia brachiata

A group of 12 polysaccharide extracts were prepared from the tips, stem and roots of an Indian halophyte Salicornia brachiata Roxb. obtained by sequential extractions with cold water (CW), hot water (HW), aqueous ammonium oxalate (OX) and aqueous sodium hydroxide (ALK) solutions. Monosaccharide composition analysis revealed that all the polysaccharide extract samples consisted primarily of rhamnose, arabinose, mannose, galactose, glucose, whereas ribose and xylose were present only in some of the extracts. All the extracts exhibited low apparent viscosity (1.47–2.02cP) and sulphate and contained no prominent toxic metal ions. Fucose was detected only in OX extract of the roots. These polysaccharides were found to be heterogeneous and highly branched (glycoside linkage analysis, size-exclusion chromatography, 13C-NMR, FT-IR, circular dichroism and optical rotation data). Physico-chemical analyses of these polysaccharides including uronic acid, sulphate and protein contents were also carried out. This constitutes the first report on the profiling of Salicornia polysaccharides.

Structural characterisation of the polysaccharides from endemic Mongolian desert plants and their effect on the intestinal absorption of ovalbumin

Using successive extractions with water and 0.7% aqueous ammonium oxalate, pectic polysaccharides were isolated from the following plants growing in the arid climate of Mongolia (Gobi): saxaul Haloxylon ammodendron Maxim., rhubarb Rheum nanum Sievers, Nitraria sibirica Pall., Peganum harmala L. and almond Amygdalus mongolica Maxim. The data obtained exhibited the primary synthesis of the cell wall pectic polysaccharides but not the middle lamellae water-soluble pectins in plants growing in the dry climatic zone.Both α-(1→4)-d-galacturonan and α-(1→4)-d-galacturonan, which was substituted with methyl groups, were found to be backbone of pectins. The l-arabinofuranose residues were identified as the main components of ramified regions. The pectins from almond differed from other pectins due to a high arabinose content. The data from NMR spectroscopy and methylation analyses demonstrated that pectic polysaccharides from almond included terminal, (1→5)-, (1→3)-linked and 3,5-substituted l-arabinofuranose residues and a small terminal d-galactopyranose and 2,5- and 2,3,5-substituted l-arabinofuranose residue content.The pectic polysaccharides were found to decrease the absorption of ovalbumin (OVA) in the blood from the gut lumen. The serum OVA level was lower in mice fed with OVA mixed with the pectins compared with the control group, which was administered OVA alone.

Electrochemical preparation and characterization of nickel and zinc-modified poly-2-aminothiazole films on mild steel surface and their corrosion inhibition performance

Poly-2-aminothiazole (pAT) was electrochemically synthesized on a mild steel (MS) specimen from 0.3 M aqueous ammonium oxalate solution containing 0.01 M 2-aminothiazole (2-AT) using cyclic voltammetry technique. The synthesized polymer film was then modified by electrodeposition of 100 μg cm −2 Ni (MS/pAT–Ni) and Zn (MS/pAT–Zn) on top of the polymer surface. The surface morphologies of the polymer films were examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The elemental analysis of the surface films was performed by energy dispersive X-ray spectroscopy (EDX). The effectiveness of the coatings in preventing corrosion of MS in 3.5% NaCl solution was assessed using electrochemical techniques. It was found that the obtained coatings were adherent to the steel surface. The pAT film provided a good corrosion protection against the attack of corrosive environment. Moreover, the modification of pAT film by deposition of Ni and Zn on top of the polymer surface significantly enhances the corrosion protection performance of the polymer film by exhibiting an improved barrier effect against the attack of corrosive environment. The surface morphologies and protection ability of the layers were found to be dependent on the type of deposited metal.

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.

Chemical composition and immunomodulatory activity of a pectic polysaccharide from the ground thistle Cirsium esculentum Siev.

The pectic polysaccharide cirsiuman CE was extracted from the stems of the ground thistle Cirsium esculentum Siev. using 0.7% aqueous ammonium oxalate, yielding 10.4% of the air-dried material. The backbone of cirsiuman was proved to consist of 1,4-α-d-galactopyranosyluronan blocks interconnected by 1,2-linked l-rhamnose residues. The side chains were attached to the 4-position of the l-rhamnopyranose residues. The side chains include 1,4-β-galactopyranan, which contains 3,4- and 4,6-substituted d-galactopyranose residues as branched points, and 1,5-α-arabinofuranan bearing 3,5-substituted α-l-arabinofuranose residues as the branching points. Oral administration of cirsiuman was found to prevent induction of oral tolerance to ovalbumin (OVA), increased the levels of serum IgG2a, and downregulated serum IgE responses, therefore it was tested for anti-allergic properties. The score of systemic anaphylactic reaction and the levels of both serum IgE and IL-4 were found to decrease; however, IFN-γ response was upregulated by cirsiuman feeding.

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)

Copper modified poly-6-amino-m-cresol (poly-AmC/Cu) coating for mild steel protection

Poly-6-amino-m-cresol (poly-AmC) was electrochemically synthesized on mild steel (MS) surface from 0.3 M aqueous ammonium oxalate solution containing 0.005 M 6-amino-m-cresol (AmC) using cyclic voltammetry technique. The synthesized film was modified by electrodeposition of a small amount of copper on top of the polymer surface from a copper deposition bath. Corrosion behaviors of both modified and nonmodified polymer films were investigated in 3.5% NaCl solution using anodic polarization curves, change of open circuit potential with immersion time ( E ocp–t) and electrochemical impedance spectroscopy (EIS) techniques over 120 h. It was shown that, the electrodeposition of copper on top of the polymer surface improves the corrosion performance of the polymer film and gives a better corrosion protection by exhibiting a better barrier effect against the attack of corrosive environment.

Chemical composition and anti-inflammatory activity of pectic polysaccharide isolated from celery stalks

A pectic polysaccharide called apiuman was isolated from fresh celery stalks by extraction with an aqueous ammonium oxalate followed by ultrafiltration, and was shown to consist of d-galacturonic acid (GalA, 81.0%), l-rhamnose (Rha, 2.6%), l-arabinose (Ara, 2.5%), and d-galactose (Gal, 3.6%) residues. Apiuman was found to be digestible with α-1,4- d-galacturonase to yield d-GalA, thus confirming that apiuman represents a pectic polysaccharide. The purified apiuman (AG) obtained was subjected to ion exchange chromatography on DEAE-cellulose to produce two polysaccharide fractions, AG-1 and AG-2, which had similar sugar compositions. Partial acid hydrolysis of apiuman, AG, revealed galacturonan to be at the core of the macromolecule. Nuclear magnetic resonance (NMR) spectra indicated that the backbone of apiuman appeared to represent α-1,4- d-galacturonan, with considerable amounts of l-Rha residues involved by α-1,2-linkages in the linear chain of the macromolecule core. The side chains were found to consist of Ara and Gal attached at the 4-position of the Rha residues. Furthermore, apiuman, AG, was found to improve the survival of mice subjected to a lethal dose of lipopolysaccharide (LPS), and the anti-endotoxemic effect of apiuman, AG, was shown to be mediated by decreased interleukin-1β (IL-1β and increased interleukin-10 (IL-10) production. Apiuman was also shown to diminish the amount of neutrophils migrating to the peritoneal cavity after LPS injection.

Hydrometallurgical route to recover molybdenum, nickel, cobalt and aluminum from spent hydrotreating catalysts in sulphuric acid medium

This work describes a hydrometallurgical route for processing spent commercial catalysts (CoMo and NiMo/Al 2O 3), for recovering the active phase and support components. They were initially pre-oxidized (500 °C, 5 h) in order to eliminate coke and other volatile species present. Pre-oxidized catalysts were dissolved in H 2SO 4 (9 mol L −1) at ∼90 °C, and the remaining residues separated from the solution. Molybdenum was recovered by solvent extraction using tertiary amines. Alamine 304 presented the best performance at pH around 1.8. After this step, cobalt (or nickel) was separated by adding aqueous ammonium oxalate in the above pH. Before aluminum recovery, by adding NaOH to the acid solution, phosphorus (H 2PO 4 −) was removed by passing the liquid through a strong anion exchange column. Final wastes occur as neutral and colorless sodium sulphate solutions and the insoluble solid in the acid leachant. The hydrometallurgical route presented in this work generates less final aqueous wastes, as it is not necessary to use alkaline medium during the metal recovery steps. The metals were isolated in very high yields (>98 wt.%).

Chemical characterization and anti-inflammatory effect of rauvolfian, a pectic polysaccharide of Rauvolfia callus

The pectic polysaccharide named rauvolfian RS was obtained from the dried callus of Rauvolfia serpentina L. by extraction with 0.7% aqueous ammonium oxalate. Crude rauvolfian RS was purified using membrane ultrafiltration to yield the purified rauvolfian RSP in addition to glucan as admixture from the callus, with molecular weights 300 and 100-300 kD, respectively. A peroral pretreatment of mice with the crude and purified samples of rauvolfian (RS and RSP) was found to decrease colonic macroscopic scores, the total area of damage, and tissue myeloperoxidase activity in colons as compared with a colitis group. RS and RSP were shown to stimulate production of mucus by colons of the colitis mice. RSP appeared to be an active constituent of the parent RS. The glucan failed to possess anti-inflammatory activity.

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.

Preventative antiinflammatory effect of potamogetonan, a pectin from the common pondweed Potamogeton natans L.

The pectic polysaccharide named potamogetonan (PN) was obtained using extraction of the leaves and stems of the common pondweed Potamogeton natans L. by an aqueous ammonium oxalate. The purified potamogetonan PN-300 was obtained using membrane ultrafiltration of PN and proved to be pectin with a molecular weight of 300 kDa. The capacity of potamogetonan PN-300 to prevent inflammation was assessed using a carrageenan paw edema test in mice. Oral administration of PN-300 24 h prior to induction of inflammation was found to reduce edema formation in a dose-related manner. The maximal effect of PN-300 was observed at 1 h after carrageenan injection (60% reduction of footpad swelling) and was comparable to that of indomethacin. The delayed edema (5 h) was less affected by pre-administration of PN-300 (33% reduction). PN-300 was found to improve the survival of mice subjected to a lethal dose of LPS. The anti-endotoxemic effect of PN-300 was shown to be mediated by decreased TNF-alpha and IL-1beta and increased IL-10 production.Thus, a pectin named potamogetonan PN-300 was isolated from P. natans and was shown to possess a preventive antiinflammatory effect following oral administration.

Isolation, characterization and anti-inflammatory activity of pectin from common pondweed Potamogeton natans L

The pectic polysaccharide named potamogetonan PN was obtained using extraction of the floating leaf of the aquatic plant P. natans L. (Potamogetanaceae) by 0.7% aqueous ammonium oxalate and subsequent precipitation with ethanol. The polysaccharide obtained (yield 4%) proved to compose mainly of D-galacturonic acid (82%) mainly altogether with the minor residues of galactose (1.7%), rhamnose (0.8%), arabinose (1.4%) and glucose (1.1%). Potamogetonan PN was shown to contain sugar chains of molecular weights more than 300 kDa (78%) as proved by membrane ultrafiltration.

Antiinflammatory activity of the pectic polysaccharide from Comarum palustre

A pectic polysaccharide named comaruman (CP) was extracted from the aerial part of Comarum palustre with 0.7% aqueous ammonium oxalate and subsequent precipitation with ethanol. Oral administration of comaruman (5–100 mg/kg) was found to reduce a paw edema observed 24 h after injection of 2% formalin in mice. A fraction of comaruman (CP-H9) exhibited a similar antiinflammatory activity. Comaruman, CP deprived of lipid, CP purified by proteins and CP fractions obtained with acidic hydrolysis inhibit spontaneous and phorbol-12-myristate-13-acetate-activated adhesion of peritoneal leukocytes in vitro.

Immunostimulating activity of pectic polysaccharide fromBergenia crassifolia (l.) Fritsch

The pectic polysaccharide named bergenan BC was obtained using extraction of the green leaves of Siberian tea Bergenia crassifolia (L.) Fritsch. by an aqueous ammonium oxalate. The polysaccharide obtained was proved to comprise mainly d-galacturonic acid, galactose, rhamnose, arabinose and glucose residues and appeared to be pectin. Delayed type hypersensitivity (DTH) reaction to aggregated ovalbumin (agOVA) was found to increase in mice that received bergenan solution (2 mg/mL) for 3 weeks. Bergenan BC was observed to enhance the uptake capacity of human neutrophils at a concentration 100 microg/mL and to stimulate the generation of oxygen radicals by mouse peritoneal macrophages in vitro. Bergenan BC was found to increase the spontaneous adhesion of peritoneal leukocytes and failed to influence adhesion stimulated by PMA or adhesion of peritoneal leukocytes incubated in the presence of 5 mm EDTA. Bergenan failed to show cytotoxic action. The viability of peritoneal leukocytes was estimated to be equal to 91% +/- 8% and 90% +/- 7%% in the control and in the pectin solution at a concentration of 1 mg/mL.Thus, bergenan was shown to possess immunostimulating activity in relation to DTH response in vivo and phagocytic activity in vitro.