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At least 379 records · Page 21Linked to original sources
PubMed2006

Sigmoidal release of indomethacin from pectin matrix tablets: effect of in situ crosslinking by calcium cations.

Sigmoidal release pattern is therapeutically beneficial for timed release and colonic drug delivery, and is always observed in coated systems. In this study, sigmoidal release from pectin matrix tablets with indomethacin as a model drug was investigated. The underlying mechanisms are calcium cation-induced in situ crosslinking that retard the initial drug release to a limited percentage. Power law equation n values were estimated for sigmoidal release profiles. Results indicated that calcium chloride incorporated in pectin matrix functioned as retarding mechanisms on drug release. Larger amount of calcium chloride led to slower drug release and matrix erosion. Even at extremely high levels, retarding on drug release and matrix erosion rate was obvious, which highlighted the effect of calcium-induced in situ crosslinking as calcium chloride was a freely water-soluble salt. The sigmoidal release profiles were characterized by power law equation with high correlation coefficients of about 0.99 or over. Power law n values increased up to as high as 1.20 when calcium chloride content kept increasing. Erosion correlated well with release in almost all pectin matrix tablets indicating erosion-controlled mechanisms. It is concluded that large amount of calcium induces in situ crosslinking of pectin matrix and leads to sigmoidal release of indomethacin, and power law n values, sometimes larger than 1.0, are suitable to be used to describe sigmoidal release profiles.

Algorithms↗
PubMed2000

Analysis of different de-esterification mechanisms for pectin by enzymatic fingerprinting using endopectin lyase and endopolygalacturonase II from A. niger.

A series of pectins with different distribution patterns of methyl ester groups was produced by treatment with either plant (p-PME) or fungal pectin methyl esterases (f-PME) and compared with those obtained by base catalysed de-esterification. The products generated by digestion of these pectins with either endopectin lyase (PL) or endopolygalacturonase II (PG II) from Aspergillus niger were analysed using matrix assisted laser desorption ionisation mass spectrometry (MALDIMS) and high-performance anion-exchange chromatography with pulsed amperometric or UV detection (HPAEC-PAD/UV). Time course analysis using MALDIMS was used to identify the most preferred substrate for each enzyme. For PL, this was shown to be fully methyl esterified HG whereas for PG II, long regions of HG without any methyl esterification, as produced by p-PME was the optimal substrate. The blockwise de-esterification caused by p-PME treatment gave a decrease of partly methylated oligomers in PL fingerprints, which did not effect the relative composition of partly methylated oligomers. PG II fingerprints showed a constant increase of monomers and oligomers without any methyl ester groups with decreasing degree of esterification (DE), but almost no change in the concentration of partly methylated compounds. PL fingerprints of f-PME and chemically treated pectins showed decreasing amounts of partly methyl esterified oligomers with decreasing DE, together with a relative shift towards longer oligomers. PG II fingerprints were characterised by an increase of partly methylated and not methylated oligomers with decreasing DE. But differences were also seen between these two forms of homogenous de-esterification. Introduction of a certain pattern of methyl ester distribution caused by selective removal of certain methyl ester groups by f-PME is the most reasonable explanation for the detected differences.

Aspergillus niger↗
PubMed2002

Application of mass spectrometry to determine the activity and specificity of pectin lyase A.

Electrospray ionization (ESI) with quadrupole ion-trap mass spectrometry was used to assess the activity and specificity of the enzyme pectin lyase A (PLA) (EC 4.2.2.10) on model pectins with varying degrees and patterns of methyl esterification. PLA is a pectinase which cleaves alpha-(1-->4)-glycosidic linkages in pectin by a trans-elimination process. Using pectins with different degrees and patterns of methyl esterification, there was a significant variation in the activity rate of PLA. The enzymatic products generated at various time intervals were structurally analyzed by mass spectrometry to determine the specificity of PLA. Although the preferred substrate for PLA is fully methyl esterified polygalacturonate, cleavage was also observed with a non-methyl esterified galacturonic acid residue on either the non-reducing end or the reducing end. The current study shows that although PLA prefers fully methyl esterified substrates it can also accept partially esterified ones. It also demonstrates the suitability of ESI ion-trap mass spectrometry in determining enzyme specificities.

Carbohydrate Sequence↗
PubMed2003

New polygalacturonases from Trichoderma reesei: characterization and their specificities to partially methylated and acetylated pectins.

Two extracellular isoenzymes of polygalacturonases PG1 and PG2 were isolated from 3-day-old culture filtrates of Trichoderma reesei. The two enzymes were purified to homogeneity by ion-exchange, gel filtration and hydrophobic interaction chromatographies. PG1 and PG2 exhibit similar molecular weights from gel filtration and SDS-PAGE. Their properties, including optimal pH and temperature, thermal stability and Km were compared. Characterization of substrate specificity showed that the two enzymes had higher affinity toward PGA (B0100) derived from sugar beet pectin (SBP) than PGA from lime pectin. A series of SBPs with different distribution patterns of methyl and acetyl groups, produced by treatment with either plant pectin methylesterase (P-series) or fungal pectin methylesterase (F-series) or base catalysis (B-series), was used as substrates for PG1 and PG2. Substrates with a low degree of esterification were preferred substrates. The activities of PG1 and PG2 were strongly correlated to the degree of methylation and very little effect from acetylation. The products generated by digestion of selected lime and SBPs were analysed using matrix assisted laser desorption ionisation time of flight (MALDI TOF) MS. A mode of action revealed a random cleavage pattern for PG1 and PG2, confirming that these enzymes are endopolygalacturonases.

Acetylation↗
PubMed2003

Rapid quantification of O-acetyl and O-methyl residues in pectin extracts.

A rapid method for the determination of the degrees of methylation (DM) and acetylation (DA) of pectins was developed. The polymer substitution degree as determined after saponification at 80 degrees C with NaOD during 1H NMR analysis. Under alkaline conditions, the cleavage of O-acetyl and O-methyl linkages allows the detection and the integration of the H-4 signal from galacturonic acid residues in the newly unesterified pectins. So, after a 10-min NMR recording, sodium acetate and sodium methanolate can be easily quantified relative to the clearly identified H-4 signal in galacturonic acid residues. Protons signals from pectin neutral sugars do not interfere with H-4. During the analysis, a limited (<3%) methanol evaporation leading to a weak reduced signal from the methanolate protons was observed. The proposed method allows in few minutes an accurate simultaneous quantification of DM and DA from few mg of pectin extracts, without the need of external standards.

Acetylation↗
PubMed1998

Unsaturated oligogalacturonic acids are generated by in vitro treatment of pectin with human faecal flora.

Pectins with a degree of esterification (DE) of 95, 66, 34 and 0%, respectively, were incubated in vitro with human faecal flora (pH 7.8). The concentration and composition of oligogalacturonic acids (oligoGalA) generated were determined using high-performance thin-layer chromatography (HPTLC) with UV and colorimetric detection. In the first period of the anaerobic degradation, the pectin macromolecules were fragmented into unsaturated oligoGalA as intermediate products by the action of bacterial pectate lyases. Depending on the incubation time and the DE of pectin, the amount of unsaturated oligoGalA having different degrees of polymerization changed continuously. These oligoGalA were present in the cultures for some hours. Mixtures of unsaturated di-, tri- and tetraGalA were the end products of a pectate lyase action. Later, the oligoGalA disappear as a result of their further fermentation by the gastrointestinal microflora under formation of short-chain fatty acids (SCFA). Low-esterified pectins were depolymerized and fermented faster than the highly esterified by the human faecal flora in vitro. Furthermore, a mixture of unsaturated oligoGalA prepared from pectic acid by the action of pectate lyase from Erwinia carotovora was completely fermented by human faecal flora.

Chromatography, Thin Layer↗
PubMed2000

An investigation into the efficacy of the pectin based anti-reflux formulation-Aflurax.

The properties of the new pectin-based anti-reflux agent Aflurax (Ferrosan) were studied in vitro and in vivo. Aflurax had a significantly higher in vitro raft strength than the placebo which was matched to the active except for the pectin (4.66+/-2.10 and 0. 22+/-0.04 g, respectively). In the modified Rossett and Rice test, the pectin raft remained above pH 3 for 130 min, whereas the pH in the acid phase remained unchanged. A modification to the stirring speed of the Rossett and Rice test was required to obtain a neutralisation profile for the placebo. The neutralisation profiles for the Aflurax and placebo were the same since both contained 5 mEq of base per tablet. In the in vivo study, subjects were randomly assigned to two groups, which either received radiolabelled food and unlabelled formulation, or unlabelled food and radiolabelled formulations. A pH probe was passed naso-gastrically and placed 5 cm from the cardia, and a small gamma detector was placed on the chest wall, coincident with the pH probe. The subjects received the test meal after an overnight fast. The pectin formulation or placebo was administered 30 min later. Each part of the study was performed as a single-blind two-way cross over with the active versus placebo. The reflux of radiolabel and acid was monitored for three hours postprandially. Aflurax reduced the H(+) concentration (total refluxed hydrogen ion index for Aflurax=3.5 x 10(3)+/-2.1 x 10(3), placebo=29 x 10(3)+/-16 x 10(3)) and amount of radiolabelled food reaching the oesophagus (total refluxed count index of food in counts x 1000 min(-1) Aflurax=19.2+/-2.3, placebo=525+/-423). The mean time for which the oesophageal pH fell below pH 4 was 2.58+/-1. 0 and 0.86+/-0.4 minutes for the placebo and Aflurax groups, respectively. The total amount of radiolabelled formulation which reached the oesophagus was 1000+/-660 for the placebo and 621+/-580 for the Aflurax.

Adolescent↗
PubMed2002

Quantum chemical descriptors in the formulation of pectin pellets produced by extrusion/spheronisation.

The objective of this study was to employ quantitative structure-activity relationships (QSAR) to relate calculated molecular descriptors of granulation liquid additives to improvements in the size of pectin pellets produced by extrusion/spheronisation. Quantum chemical descriptors were calculated for a large number of candidate additives. Based on a principal component analysis (PCA) of descriptors of the candidates, a few substances were selected. The most suitable concentration for each additive was found, and pellets were prepared by an extrusion/spheronisation process. Three pectin grades of different methoxy and amide substitution were tested and the quality of the pellets was evaluated based on size. PLS models were constructed to identify the molecular properties that were most important in producing short, nearly spherical pellets. The results show that quantum chemical descriptors can be a useful tool in the formulation of pectin pellets. Acceptable models relating additive properties and pellet size were achieved. Independent of the pectin grade, the two most important factors favouring formation of small spherical pellets were a small molecular size and a strong hydrogen bond forming ability of the additive molecules.

Chemistry, Pharmaceutical↗
PubMed1999

Effect of calcium concentration, hardening agent and drying condition on release characteristics of oral proteins from calcium pectinate gel beads.

Pectin has been investigated for its ability to produce solid calcium pectinate gel (CPG) beads containing bovine serum albumin (BSA). Several factors can influence the properties and release characteristics of the CPG beads. In this study, the effect of calcium concentration, hardening agent and drying condition on the encapsulation and release characteristics of BSA from the matrix gel beads made of calcium pectinate were studied. BSA release studies under conditions mimicking mouth to colon transit have shown that calcium pectinate protects the drug from being released completely in the physiological environment of the upper gastrointestinal tract, and is susceptible to the enzymatic action with consequent drug release. In addition, the release of BSA from CPG beads was strongly affected by calcium concentration and drying condition. However, the release was not particularly affected by the presence of hardening agent at the concentration of 1% or lower. Since the release of BSA as a model protein drug could be controlled by the regulation of the preparation conditions of CPG beads, the CPG beads may be used for a potential oral controlled release system for protein drugs.

Calcium↗
PubMedDate not supplied

Flash extraction of pectin from orange albedo by steam injection.

Pectin was acid extracted from orange albedo by steam injection heating under pressure. Extraction times ranged from 2 to 6 min at a pressure of about 15 psi. Solubilized pectin was characterized by HPSEC with online light scattering and viscosity detection. Molar mass (M), radius of gyration (R(g)), and intrinsic viscosity ([eta]) all decreased with increasing extraction time when heating temperature was 120 degrees C. At heating times of 3 min, M(w) ranged from 4.9 to 4.5 x 10(5), R(gz) was about 44 nm, and [eta](w) ranged from 8.4 to 7.9 dL/g. Chromatography revealed that solubilized pectin distributions were bimodal in nature at 3 min extraction time and trimodal when the extraction time was 6 min. Scaling law exponents obtained for the highest molar mass fractions were consistent with a very compact spherical structure. For the intermediate fraction, scaling law exponents were consistent with a less compact spherical structure comparable to a random coil. In the case of the low molar mass fractions, scaling law exponents were consistent with a structure more asymmetric in shape. These results are consistent with earlier results which indicated that pectin distributions were mixtures of two or more of the following due to disaggregation during extraction: spherical aggregates, hydrogen bonded network structures, and partially or fully disaggregated components of network structures which could include branched structures, rods, segmented rods, and kinked rods.

Chromatography↗
PubMedDate not supplied

New insights into the mechanism of gelation of alginate and pectin: charge annihilation and reversal mechanism.

Studies have been undertaken on the binding of Mn2+ ions to two alginate samples of different mannuronate:guluronate ratios (M:G), a sample of low-ester amidated pectin and poly(acrylic acid) (PAA). The binding of Ca2+ ions has also been included for the latter for comparison. The binding curves showed an initial steep rise at low additions of Mn2+ or Ca2+ indicating that all of the ions were bound to the polymer chains with none remaining in solution. At higher additions, the binding curves showed a plateau region and the maximum amount bound, theta, was found to be 0.2, 0.2, 0.25, and 0.33 mol M(2+)/mol COO- for high M:G alginate, low M:G alginate, pectin, and PAA, respectively. The binding curves for Mn2+ and Ca2+ with PAA were superimposable. In all cases, theta was less than the stoichiometric equivalent and also less than predicted by Manning counterion condensation theory. The linear charge density, xi, for the polymers is 1.49, 1.55, 1.62, and 2.85, and it was found that at maximum binding the effective linear charge density, xi(effective), decreased to a value close to 1 in each case and not 0.5 as predicted from Manning's two-variable theory. The mobility of the PAA chains has been followed by electron spin resonance spectroscopy using nitroxide spin labels covalently attached to the polymer, and the gelation of the pectin and alginate samples has been monitored using small deformation oscillatory experiments. For PAA at maximum binding, it was noted that there was a loss of chain mobility and precipitation. For pectin and alginate, gelation occurred and the stoichiometric ratio for maximum binding corresponded to the stoichiometric ratio for the maximum in G'. Precipitation and gelation are attributed to the formation of polymer-metal complexes involving one or two carboxylate groups resulting in charge reversal or charge annihilation.

Alginates↗
PubMedDate not supplied

Influence of chain length and polymer concentration on the gelation of (amidated) low-methoxyl pectin induced by calcium.

The gelation of low-methoxyl pectin (LMP) induced by addition of Ca2+ was studied by measuring the storage modulus as a function of temperature during cooling. Samples with different molar masses were prepared by mechanical degradation. The effect of the molar mass and the pectin concentration on the gelation properties was investigated. The effect of partial amidation was studied by comparing LMP and partially amidated LMP with the same molar mass and degree of methylation. The results are compared to those from a model developed for Ca2+-induced pectin gelation, and good agreement is found except at low concentrations and low molar masses where the gels are weaker than predicted. At low concentrations intrachain bonding weakens the gel, while the presence of small pectin chains weakens the gel because it neutralizes binding sites on larger chains.

Amides↗
PubMed2002

Physicochemical properties and bacterial resistance of biodegradable milk protein films containing agar and pectin.

Free-standing sterilized edible films based on milk proteins, namely calcium caseinate and whey protein isolate, and polysaccharides, namely pectin and agar, were developed. Cross-linking of the proteins was achieved by the combination of thermal and radiative treatments. Autoclaving pectin and agar prior to their addition to the protein solutions generated films with an improved (P < or = 0.05) puncture strength. The presence of proteins and pectin-agar in the film formulation enhanced (P < or = 0.05) the moisture barrier of the films by 18%. A strain of Streptococcus thermophilus was used to assess the biodegradability behavior of the cross-linked films. Microbiological counts and soluble nitrogen analysis confirmed the biodegradability property of the milk protein films containing autoclaved pectin and agar.

Agar↗
PubMed2003

Transacylation and de-esterification reactions of pectin as catalyzed by pectinesterases from tomato and citrus.

The optimal conditions for the de-esterification reaction of tomato pectinesterase (PE) and citrus PE was 0.1-0.2 M NaCl and at pH 7.5-8.5, 65 degrees C, almost identical to those for the transacylation reaction as observed by turbidity (absorbance at 400 nm) change. Among the PEs tested, pea pod PE presented the most remarkable catalysis on the transacylation reaction, and 1.5% pectin solution was determined to be suitable for this reaction. Low methoxy pectin with a DE (degree of esterification) of 31% displayed a slow turbidity increase, revealing that the extent of DE was influential on the transacylation. Besides citrus pectin, apple pectin was also proved to progress transacylation reaction by PEs from tomato and citrus sources as apparently observed by turbidity method.

Acylation↗
PubMed2003

Quantification of the interactions between beta-lactoglobulin and pectin through capillary electrophoresis analysis.

Biopolymer interactions have many potential applications in pharmaceutical, cosmetic, nutraceutical, and functional food industries. Attractive interactions between proteins and polysaccharides can lead to the formation of complexes. Binding parameters of beta-lactoglobulin (beta-lg)/pectin complexes were determined using frontal analysis continuous capillary electrophoresis and the overlapping binding site model. At pH 4, approximately 23 beta-lg molecules were cooperatively complexed on low-methoxyl pectin, where each beta-lg molecule covered an average of 12 galacturonic acid residues. The calculated binding constant was 1431 M(-1). The interactions between pectin and four selected peptides located on the outer surface of the beta-lg were investigated in order to identify which part of the protein was likely to interact with the pectin. The peptide beta-lg 132-148, which corresponds to the alpha-helix zone, and the peptides beta-lg 76-83, 41-60, and 1-14 would be involved in the interaction with the pectin.

Binding Sites↗
PubMed2003

Inhibitory activities of semicarbazide-sensitive amine oxidase and angiotensin converting enzyme of pectin hydroxamic acid.

Solutions of 100 mL of 1% commercial pectin each with a different degree of esterification (DE), DE94, DE65, and DE25, were reacted with 100 mL of 2 M alkaline hydroxylamine (pH 12.0) at room temperature for 4 or 18 h. These pectin hydroxamic acids (PHAs; DE94T4, DE94T18, DE65T4, and DE25T4) were used to test the inhibitory activities against semicarbazide-sensitive amine oxidase (SSAO) and angiotensin-converting enzyme (ACE). Compared to different DE pectins (DE94, DE65, and DE25), the PHAs of DE94T4, DE94T18, DE65T4, and DE25T4 showed different inhibition activities against SSAO or ACE. Commercial pectins with different DE values showed negligible SSAO or ACE inhibitions. The order of SSAO inhibition was DE65T4 > DE94T18 approximately DE25T4 >> DE94T4. However, the order of ACE inhibition was DE94T4 > DE94T18 >> DE65T4 > DE25T4. The SSAO activity staining or ACE-hydrolyzed products on TLC chromatogram also confirmed the inhibitory activities of PHAs against SSAO or ACE.

Amine Oxidase (Copper-Containing)↗
PubMed2006

Mode of de-esterification of alkaline and acidic pectin methyl esterases at different pH conditions.

Highly esterified citrus pectin was de-esterified at pH 4.5 and 8.0 by a fungal pectin methyl esterase (PME) that was shown to have an acidic isoelectric pH (pI) and an acidic pH optimum and by a plant PME that was characterized by an alkaline pI and an alkaline pH optimum. Interchain and intrachain de-esterification patterns were studied by digestion of the pectin products with endo-polygalacturonase and subsequent analysis using size exclusion and anion-exchange chromatography. No effect of pH was observed on the de-esterification mode of either of the two enzymes. Acidic, fungal PME converted pectin according to a multiple-chain mechanism, with a limited degree of multiple attack at the intrachain level, both at pH 4.5 and at pH 8.0. A multiple-attack mechanism, with a high degree of multiple attack, was more appropriate to describe the action mode of alkaline, plant PME, both at pH 4.5 and at pH 8.0.

Aspergillus↗
PubMed2002

Immunohistochemical localization of hemicelluloses and pectins varies during tissue development in the bamboo culm.

The distribution of hemicelluloses and pectins in bamboo internodes was studied immunocytochemistrically at various stages of development. The ultra-structures of bamboo cell walls have been reported previously at various stages. The internodes were identically classified into three developmental phases: primary wall stage (phase I), unlignified secondary wall stage (phase II) and lignified wall stage (phase III), using the same bamboo culm. (1-->3, 1-->4)-Beta-glucans were distributed in nearly all tissues in an actively elongating stage. Limited amounts of beta-glucans were deposited in primary walls and the middle lamellae, but were limited to the phloem in secondary walls. This suggests that the function of beta-glucans might be different in phloem vis-à-vis other tissues. Highly-substituted xylans were located in nearly all tissues of early phase I, but had disappeared in all tissues immediately prior to lignification. In contrast, low-branched xylan epitopes were present only in the protoxylem in phase I, but were present in all tissues immediately prior to lignification in phase II. In phase III, the epitopes were densely localized in lignified walls, suggesting that the substitution of xylans is closely related to maturation. Methyl-esterified (but not unesterified) pectins were present in all tissues of early phase I. Just before and after lignification, both types of pectins were concentrated in the phloem and protoxylem. Xyloglucans were largely distributed in the phloem and in lignified tissues, suggesting that they might be closely correlated with maturation. This represents the first account of the distribution of hemicelluloses and pectins at the tissue and ultrastructural level in bamboo internodes at various stages of development.

Bambusa↗