Gel permeation chromatography and the Mark-Houwink relation for pectins with different degrees of esterification

Optimization of extraction with salicylic acid, rheological behavior and antiproliferative activity of pectin from Citrus sinensis peels

A Box-Behnken design was used to optimize extraction temperature, extraction time and concentration of the salicylic acid to obtain a maximum polysaccharide yield from Citrus sinensis peels. The optimal settings were: extraction time 3 h, extraction temperature 80 °C and concentration of the salicylic acid 1.5%. Under these conditions, the experimental yield and uronic acid content were 11.74% and 66.9% respectively. Preliminary characterization was performed via FT-IR, SEC/MALS/VD/DRI and GC-MS after hydrolysis. SEC analysis showed that the extracted polysaccharide had a weight average molar mass of 350 kDa and an intrinsic viscosity of 640 mL/g. The GC-MS results revealed that the extracted polysaccharide was composed of arabinose 56.7%, galactose 17.8%, xylose 13.8%, rhamnose 5.1%, mannose 2.5% and glucose 1.5% suggested a rhamnogalacturonan pectin type I with a degree of esterification of 50.9% (IRTF). The flow curve and the dynamic frequency sweep were obtained at 10, 20, 30 and 40 g/L in water and at 30 g/L in presence of CaCl₂ or NaCl at 1 mol/L. The solutions showed shear-thinning behavior fitted with Ostwald-De Waele model, except 10 g/L with a Newtonian behavior. The apparent viscosity and, the G' and G" moduli increase with PACO concentration in agreement with a slow-down of the dynamic chain. In the presence of CaCl₂ or NaCl the reduction of electrostatic repulsions between pectin chains decreases the rheological parameters. The effect is less sensitive with CaCl₂ due to intermolecular interactions. The antiproliferative activity of the extracted pectin on human Caco-2 and Hep-2 cells was very interesting with an IC₅₀ 1.4 and 1.8 μg/mL respectively.

Multivalent Ions as Reactive Crosslinkers for Biopolymers-A Review

Many biopolymers exhibit a strong complexing ability for multivalent ions. Often such ions form ionic bridges between the polymer chains. This leads to the formation of ionic cross linked networks and supermolecular structures, thus promoting the modification of the behavior of solid and gel polymer networks. Sorption of biopolymers on fiber surfaces and interfaces increases substantially in the case of multivalent ions, e.g., calcium being available for ionic crosslinking. Through controlled adsorption and ionic crosslinking surface modification of textile fibers with biopolymers can be achieved, thus altering the characteristics at the interface between fiber and surrounding matrices. A brief introduction on the differences deriving from the biopolymers, as their interaction with other compounds, is given. Functional models are presented and specified by several examples from previous and recent studies. The relevance of ionic crosslinks in biopolymers is discussed by means of selected examples of wider use.

Box-Behnken design based statistical modeling for the extraction and physicochemical properties of pectin from sunflower heads and the comparison with commercial low-methoxyl pectin

A natural low-methoxyl pectin (LAHP), was extracted with oxalic acid solution from dried heads of sunflower (Helianthus annuus L.). The single-factor experiments and response surface methodology (RSM) were used to optimize LAHP extraction conditions. The extraction yield of LAHP was 18.83 ± 0.21%, and the uronic acid content was 85.43 ± 2.9% obtained under the optimized conditions (temperature of 96 °C, time of 1.64 h, oxalic acid concentration of 0.21%). Experimentally obtained values were in agreement with those predicted by RSM model, indicating suitability of the employed model and the success of RSM in optimizing the extraction conditions. LAHP has been characterized by ash content, degree of esterification (DE), galacturonic acid (GalA) content, molecular weight and intrinsic viscosity meanwhile commercial low-methoxyl pectin (CLMP) as comparison. This study finds out a potential source of natural LMP which expands the application scope of sunflower heads. It is an efficient reuse of waste resources and provides a novel thought to explore the natural resources for food and pharmaceutical applications.

Changes of flooding reagents' properties under simulated high temperature/pressure conditions in oil reservoirs and their impact on emulsion stability

It is of great significance to know the fate of the polymers and surfactants used for enhanced oil recovery (EOR) in oil reservoirs at a relatively high temperature/pressure. In this paper, the changes of the properties of a polymer (partially hydrolyzed polyacrylamide, HPAM) and a surfactant (petroleum sulfonate, PS) were investigated under simulated oil reservoir conditions (a temperature of 45, 60 or 75 °C and a pressure of 10, 15 or 20 MPa). The impacts of the property changes to emulsion stability were also highlighted. The results showed that the hydrolysis degree of HPAM increased from 24.3% to 28.9%, 29.7% and 35.4%, whereas the molecular weight (M_w) decreased from 7.60 × 10⁶ g mol⁻¹ to 5.43 × 10⁶ g mol⁻¹, 4.49 × 10⁶ g mol⁻¹ and 2.87 × 10⁶ g mol⁻¹ as a function of raising the temperature to 45, 60 and 75 °C with 20 MPa, respectively, for a duration of one week. However, the increased pressure showed obvious prevention effects on the degradation of HPAM M_w in the investigated pressure range of 10–20 MPa. There were no changes in the oil–water interfacial tension for PS solutions after high temperature/pressure treatment. The stabilization ability of HPAM to the emulsion decreased markedly after treatment because of the decreased viscosity attributed to the reduction of molecular weight, while that of PS did not change. It is reasonable to speculate that the influence of back produced HPAM to the stability of EOR produced water will be quite different in different oil reservoirs because of the differences in reservoir temperature, pressure and retention time, and therefore different strategies should be considered in treating the produced water from EOR.

It is of great significance to know the fate of the polymers and surfactants used for enhanced oil recovery (EOR) in oil reservoirs at a relatively high temperature/pressure.

Biocompatible chitosan-pectin polyelectrolyte complex for simultaneous electrochemical determination of metronidazole and metribuzin

Development of novel biocompatible sensor material suitable for modest, cost-effective, and rapid practical application is a demanding research interest in the field of electroanalytical chemistry. In this context, for the first time, we utilized biocompatible chitosan-pectin biopolyelectrolyte (CS-PC BPE) complex for the simultaneous electroreduction of an important antibiotic drug (metronidazole-MNZ) and herbicide (metribuzin-MTZ). This sensor reveals an attractive welfares such as simplicity, biocompatibility, and low production cost. Under optimized experimental conditions, the electroanalytical investigation confirmed that CS-PC BPE modified glassy carbon electrode (CS-PC BPE/GCE) was found to sense MNZ and MTZ in the nanomolar range. Moreover, as-prepared CS-PC BPE/GCE exhibited prominent selectivity, stability, and reproducibility. Additionally, the possible MNZ and MTZ sensing mechanism of CS-PC BPE/GCE have been discussed in detail. Lastly, real sample analysis was also carried out and revealed from several investigations that the CS-PC BPE/GCE is a good electrochemical sensor system for the detection of targeted analytes.

Electrostatic Self-Assembled Chitosan-Pectin Nano- and Microparticles for Insulin Delivery

A polyelectrolyte complex system of chitosan-pectin nano- and microparticles was developed to encapsulate the hormone insulin. The aim of this work was to obtain small particles for oral insulin delivery without chemical crosslinkers based on natural and biodegradable polysaccharides. The nano- and microparticles were developed using chitosans (with different degrees of acetylation: 15.0% and 28.8%) and pectin solutions at various charge ratios (n⁺/n^- given by the chitosan/pectin mass ratio) and total charge. Nano- and microparticles were characterized regarding particle size, zeta potential, production yield, encapsulation efficiency, stability in different media, transmission electron microscopy and cytotoxicity assays using Caco-2 cells. The insulin release was evaluated in vitro in simulated gastric and intestinal media. Small-sized particles (~240-~1900 nm) with a maximum production yield of ~34.0% were obtained. The highest encapsulation efficiency (~62.0%) of the system was observed at a charge ratio (n⁺/n^-) 5.00. The system was stable in various media, particularly in simulated gastric fluid (pH 1.2). Transmission electron microscopy (TEM) analysis showed spherical shape particles when insulin was added to the system. In simulated intestinal fluid (pH 6.8), controlled insulin release occurred over 2 h. In vitro tests indicated that the proposed system presents potential as a drug delivery for oral administration of bioactive peptides.

Extraction optimization and physicochemical properties of pectin from melon peel

In this study, acidic extraction (citric acid) was used for the extraction of pectin from melon peel. A central composite design (CCD) was applied to study the effect of temperature (35-95°C), time (40-200min), pH (1-3) and solvent to sample ratio (10-50v/w) on the yield and degree of esterification (DE). The results showed that the yield and DE ranged from 2.87 to 28.98% and 1.33-29.33%, respectively. Also, the highest extraction yield (29.48±1.7%) was obtained under optimal conditions (pH of 1, temperature of 95°C and ratio of 10v/w after 200min). The protein, ash, carbohydrate and galacturonic acid content of pectin obtained under optimal conditions were about 1.5, 3.5, 10 and 48%, respectively. Rheological experiments determined that melon peel pectin dispersions behaved as a weak gel at concentrations of 1%w/v. The emulsifying activity was 35% and also, the emulsion stability was higher at 4°C than at 23°C.

Opuntia dillenii (Ker-Gawl) Haw cladode mucilage: Physico-chemical, rheological and functional behavior

The yield of mucilage extracted from cladodes of Opuntia dillenii (Ker-Gawl) Haw in aqueous medium was 6.2%. The neutral sugar comprised of arabinose (38.80%), galactose (33.00%), rhamnose (15.70%), xylose (5.10%), and glucose (5.10%). The mucilage showed pseudo plastic behavior with good swelling index (20%), water holding capacity (g water/g dry sample; 4±0.10) and micrometric properties. In addition, mucilage presented intrinsic viscosity of 3.7 dL/g with average molecular weight of 1.9×10³kDa. The FTIR and NMR spectra of extracted mucilage showed characteristic polysaccharide nature. Further, the mucilage exhibited anti-obesity property through lipase inhibition. These findings could highlight that isolated mucilage could be exploited as an additive in food and pharmaceutical sector.

Nature of pectin–protein–catechin interactions in model systems: Pectin–protein–catechin interactions

Apple pectins, proteins and catechins were combined in model systems, and the resulting hazes were measured by spectrophotometric method, a zeta potential and particle size analyzer and Ostwald viscosimeter. The amount of hazes formed depends on the concentrations of both protein and pectin. The cooperative hydrogen bonding between the numerous hydroxyl groups of pectins and hydrone and the gel-like structure developed by pectin induced the solvation or solubilization of polymers, and the protein molecule has a fixed number of polyphenol binding sites. The influence of pectin relative molecular mass and degree of esterification on the formation of suspended particles is prominent, and this makes the number of hydroxyl groups and charge of pectin which is concerned with combining protein and catechin to change a lot. More haze was observed when model systems were heated, suggesting that hydrophobic groups of protein are beneficial to their binding with phenols and pectins. The pH value affects the charged state of the protein and pectin, which influences the combination of pectin–gliadin–catechin.

Aegle marmelos fruit pectin for food and pharmaceuticals: Physico-chemical, rheological and functional performance

Pectin is used in a number of foods as a gelling agent, thickener, texturizer, emulsifier and stabilizer. Bael fruit, obtained from Aegle marmelos, is a rich source of pectin. Bael fruit pectin (BFP) was extracted from ripe Bael fruits. The process yielded 15% (w/w) pure BFP. The swelling index decreased in the following order: water>pH 7.4>pH 6.8>pH 1.2>HCl (0.1N). Galacturonic acid content of 87.8%, degree of esterification of 47.2%, 17.3% methoxy groups, 0.29% acetyl groups and equivalent weight of 1209.5, indicate it to be a good gelling agent and easily amenable to derivatization. BFP exhibited a significant concentration-dependent prolongation of prothrombin time. The absence of hemagglutinating activity and antinutritional factors coupled with the activity to confer better emulsion capacity, stability and antimicrobial activity gives BFP a clear edge over commercial citrus pectin (CP) for exploitation as an additive in food and pharmaceuticals.

Cerium binding activity of pectins isolated from the seagrasses Zostera marina and Phyllospadix iwatensis

Cerium binding activity of three different water soluble pectin compounds of different origin was studied in a batch sorption system. The Langmuir, Freundlich and BET sorption models were adopted to describe the binding reactions between metal ions and pectin molecules. The Langmuir model provided the best fit. Within the pH range from 4.0 to 6.0, the largest amount of the cerium ions was bound by pectin isolated from the seagrass Phylospadix iwatensis in comparison to pectin extracted from the seagrass Zostera marina and pectin obtained from citrus peel (commercial grade). The Langmuir constants were also highest for the pectin samples isolated from the seagrass P. iwatensis. The results obtained from this study suggest that pectin is a prospective source for the development of radioisotope-removing pharmaceuticals.

Permeation modulating properties of natural polymers--effect of molecular weight and mucus

The permeation modulating effects of 5 natural polymers; low-ester, amidated and high-ester pectin, as well as hyaluronic acid and chitosan were tested at two different molecular weights each. The model membrane was methotrexate treated HT29 cells grown for 2 or 3 weeks, respectively, thereby differing in the amount of goblet cells and hence mucus. The pectins decreased the permeation of the paracellular marker carboxyfluorescein. Free acid groups and a high molecular weight increased this membrane protective effect. Chitosan displayed pronounced and hyaluronic acid modest permeation enhancing properties. In this case, a low molecular weight accentuated the effect. In all cases, the permeation modulating properties were reduced by mucus.

Viscometric study of pectin. Effect of temperature on the hydrodynamic properties

Hydrodynamic properties are important parameters affecting the performance of pectin. This polysaccharide is used as a thickening and gelling agent in food and pharmaceutical industries. The most common and economical of the hydrodynamic properties is the determination of viscosity, in which are determined the intrinsic viscosity and the diffusion coefficient. They indirectly measure the molecular weight (M(w)); hydrodynamic radius (R(H)); number of Simha, (ν(a/b)); Perrin parameter (P); Scheraga-Mandelkern parameter (β); and Flory parameters (ϕ(0) and P(0)). All the hydrodynamic parameters are dependent on temperature. Normally these parameters are reported at a temperature of 25°C, which limits their application to different temperatures. This work studies pectin dependence on temperature, finding that this biopolymer in aqueous solution presents a conformation of rod-like with ν(a/b)=10.5, and a value from 0.8232 to 0.8129. Pectin behavior in this system indicates that it behaves like a colloidal particle that tends to compact with increasing temperature (R(H) decrease). The molecular weight calculated for pectin is 180,000 g/mol. Mark-Houwink-Sakurada (M-H-S) equation constants, a and k, for pectin in water solvent-temperature systems have been already reported.

Putrescine-polysaccharide conjugates as transglutaminase substrates and their possible use in producing crosslinked films

Putrescine (1,4-diaminobutane) was covalently linked to alginate and low-methoxyl pectin to synthesize new aminated polysaccharides. Both putrescine-pectin and -alginate conjugates, although the latter at higher concentrations, were found to be able to act as effective acyl acceptor transglutaminase substrates in vitro using both dimethylated casein and soy flour proteins as acyl donors. Monodansylcadaverine, a well known acyl acceptor transglutaminase substrate, dose-dependently counteracted the covalent binding of the aminated polysaccharides to the proteins. Putrescine-pectin conjugate was also tested to prepare, in combination with soy flour proteins, edible films in the presence of purified microbial transglutaminase. Characterization of the enzymatically crosslinked films showed a significant decreased water vapor permeability, with respect to the ones obtained with non-aminated pectin in the presence of transglutaminase, as well as improved mechanical properties, such as high extensibility. Possible biotechnological applications of hydrocolloid films containing putrescine-polysaccharide derivatives enzymatically crosslinked to proteins were suggested.

In vitro measurements of mucoadhesive properties of six types of pectin

The objective of this study was to measure and compare the specific- and general mucin interaction of six pectin types from three manufacturers, differing mainly in the degree of methoxylation and degree of amidation. Mucoadhesive properties were measured using a texture analyzer. It was found that an intermediate degree of methoxylation (35 and 36%) improved the specific mucin interaction. Amidation did not increase mucin interaction. Samples from different manufacturers did not alter these conclusions. This study indicates that the general classification of pectin as a poor mucoadhesive, without differentiating between the amount and type of substituents, probably is an oversimplification.

Extraction and characterization of Foeniculum vulgare pectins and their use for preparing biopolymer films in the presence of phaseolin protein

Pectins from Foeniculum vulgare were extracted under acidic conditions. The obtained pectins were mainly composed of uronic acid but also contained traces of rhamnose, galactose, and arabinose. Extracted pectins were used as a carbohydrate source to prepare biopolymer films in the absence and in the presence of phaseolin protein. The swelling characteristics of the films were examined as a function of ionic strength, pH, and the applied osmotic stress. The swelling behavior was dominated by a Donnan-type effect, which decreases with increasing ionic strength and counterion valency. In all cases the swelling of films containing phaseolin was reduced, suggesting a network formation between protein and pectins. Mechanical property studies have also estimated the validity of the obtained novel biopolymer films in terms of mechanical resistance.

Yellow passion fruit rind--a potential source of low-methoxyl pectin

Yellow passion fruit (Passiflora edulis f. flavicarpa Degener) rind pectic substances were fractionated with water, ammonium oxalate, and dilute acid solutions. The extracted pectins were rich in anhydrogalacturonic acid and had a low degree of methyl esterification. Moreover, their acetyl groups and neutral sugar contents were relatively low. Furthermore, a low amount of proteinaceous material was also found within them. Their gelling ability and viscoelastic properties as evaluated by the SAG and small amplitude oscillatory shear tests, respectively, were comparable to those of a commercial citrus low-methoxyl pectin. Hence, yellow passion fruit rind occurs as a potentially good source of naturally low-methoxyl pectin.

Polyelectrolyte complex formation mediated immobilization of chitosan-invertase neoglycoconjugate on pectin-coated chitin

Saccharomyces cerevisiae invertase, chemically modified with chitosan, was immobilized on pectin-coated chitin support via polyelectrolyte complex formation. The yield of immobilized enzyme protein was determined as 85% and the immobilized biocatalyst retained 97% of the initial chitosan-invertase activity. The optimum temperature for invertase was increased by 10 degrees C and its thermostability was enhanced by about 10 degrees C after immobilization. The immobilized enzyme was stable against incubation in high ionic strength solutions and was 4-fold more resistant to thermal treatment at 65 degrees C than the native counterpart. The biocatalyst prepared retained 96 and 95% of the original catalytic activity after ten cycles of reuse and 74 h of continuous operational regime in a packed bed reactor, respectively.

Cell wall polysaccharides from chalkumra (Benincasa hispida) fruit. Part I. Isolation and characterization of pectins

Pectic polysaccharides were obtained from chalkumra (Benincasa hispida) fruit by sequential extraction with ammonium oxalate (fraction BOX), dilute acid (fraction BHCl), and cold dilute alkali (fraction BOH). The highest yield of polysaccharides was obtained with oxalate and HCl. BOX was enriched in partly methyl-esterified galacturonic acid, whereas BHCl and BOH contained mostly galactose. All of the extracts showed similar elution patterns in size exclusion chromatography although the intrinsic viscosities (eta) were different (132 +/- 6, 100 +/- 5, and 285 + 10 mL/g for BOX, BHCl, and BOH, respectively). From fractionation by anion exchange chromatography, homogalacturonan (as seen from sugar analysis and Fourier transform infrared spectrum) accounted for more than half of BOX and 11% of BHCl. Methylation analyses and hydrolysis of BHCl with endo-beta-(1-->4)-d-galactanase showed the presence of beta-(1-->4)-d-galactan. The neutral galactan represented more than 76% of BHCl and approximately 40% of BOH. The other polysaccharides were complex galactans in BOH and an acidic arabinan (<1%) in BOX and BHCl.