The mercury binding activity of pectin isolated from the seagrass Zostera marina

The kinetics of mercury binding by pectin isolated from the seagrass Zostera marina was described, and its maximum mercury binding activity at pH from 2.0 up to 6.0 was determined. It was shown that mercury binding by pectin in in vitro conditions did not depend on concentration of hydrogen ions in the environment. The maximum mercury binding activity estimated from the Langmuir equation was 2.64 mmol/g of dry mass of the pectin.     

Modeling the kinetics of the pectin methylesterase catalyzed de-esterfication of pectin in frozen systems

The applicability of the William, Landel, and Ferry (WLF) equation with a modification to take into account the effect of melt-dilution and an empirical log-logistic equation were evaluated to model the kinetics of diffusion-controlled reactions in frozen systems. Kinetic data for the pectin methylesterase catalyzed hydrolysis of pectin in four model systems with different glass transition temperatures: sucrose, maltodextrin (DE = 16.5-19.5), carboxymethylcellulose (CMC) and fructose in a temperature range of -24 to 0 degrees C were used. The modified WLF equation was evaluated with a concentration-dependent glass transition temperature (T(g)) as well as the glass transition temperature of the maximally freeze-concentrated matrix (T(g)') as reference temperatures. The equation with temperature-dependent T(g) described the reaction kinetics reasonably well in all the model systems studied. However the kinetics was better described by a linear relationship between log(V(0)/V(0ref)) and (T - T(ref)) in all cases except CMC. The log-logistic equation also described the kinetics reasonably well. The effect of melt-dilution on reactant concentration was found to be minimal in all cases.     

Study of pectin esterase and changes in pectin methylation during normal and abnormal peach ripening

Peach fruit ( Prunus persica cv. Hermosa) were allowed to ripen immediately after harvest or after 30 days of 0°C storage. The fruits lost 75–80% of their firmness after 5 days at 20°C. During ripening after harvest there was a loss of both uronic acid and methyl groups from the cell wall. Cell wall labelling with JIM 7, a monoclonal antibody which recognized pectins with a high degree of methylation, was lower in ripe fruits than in freshly harvested fruits. However, ripe fruit cell walls did not cross-react with JIM 5, which recognizes pectins with low methylation. During storage, de-methylation occurred and in fruit ripened after storage there was little further change in pectin methylation or pectin content in the cell walls. The labelling of stored or stored plus ripened cell walls with JIM 7 was similar, but the cell walls of fruit ripened after storage showed some low cross-reactivity with JIM 5. The in vitro activity and mRNA abundance of pectin esterase (EC 3.1.1.11) was not correlated with the amount of de-esterification as measured chemically or by immuno-labelling in the cell walls. Eighty percent of the fruits which ripened after storage developed a woolly texture. It is suggested that woolliness is due to de-esterification of pectins, not accompanied by depolymerization, which leads to the formation of a gel-like structure in the cell wall.     

Consumption of sugars, hemicellulose, starch, pectin and cellulose by the grasshopper Arcris flavolineata

Adults (0.61 g, fresh-weight) of Abracris flavolineata De Geer (Orthoptera: Acrididae) feeding on Brassica oleracea acephala leaves ingest 21 mg dry-weight/day with an approximate digestibility of 42%. Chemical determinations performed on the leaves ingested and on the feces expelled led to the determination of the approximate digestibilities (%) of the major carbohydrates of leaves as follows: soluble carbohydrates, 91; pectin, 32.1; hemicellulose, 0; starch, 66; cellulose, 15. The results are not sufficient to disregard the possibility that digestible hemicellulose polymers contaminate the pectin and the cellulose fraction. Thus, it is possible that the digestibility of hemicellulose is different from zero, and that the digestibility of pectin and cellulose are somewhat lower than reported. The data are used to propose physiological roles of the enzyme activities previously found in the A. flavolineata midgut.     

Comparative effect of amidated pectin and psyllium on cholesterol homeostasis in rats

The effects of amidated pectin and psyllium on serum, hepatic and faecal cholesterol concentration were compared in female rats fed diets supplemented with palm fat and cholesterol at 50 and 10 g/kg, respectively. Control rats were fed a diet supplemented with cellulose at 60 g/kg. In treated rats, cellulose was replaced with either amidated pectin or psyllium. Amidated pectin and psyllium intake significantly decreased serum cholesterol from 3.41 μmol/ml (control) to 1.68 and 2.04 μmol/ml, respectively, and hepatic cholesterol from 31.9 μmol/g (control) to 7.2 and 9.0 μmol/g, respectively. Histology with lipid-staining Sudan Black B revealed that liver tissue from control rats was infiltrated with lipids, but staining was absent in livers of treated rats. No hepatic pathophysiology was apparent in treated rats. Amidated pectin and psyllium intake significantly increased faecal fat content. Faecal cholesterol content was significantly increased in rats that were fed amidated pectin, and non-significantly increased in rats that were fed psyllium. Body weight and food intake did not differ among treatment groups. In conclusion, amidated pectin, a novel sequestrant of sterols, demonstrated a similar effect on rat serum and hepatic cholesterol concentration to psyllium, which is a well-established hypocholesterolaemic agent.     

Rapeseed hull pectin

A pectin isolated from rapeseed, hulls by extraction with aqueous ammonium oxalate, had a degree of esterification of 83% and contained residues of hexuronic (mainly D-galacturonic) acid (76%), D-galactose (2–3%), L-arabinose (8–9%), D-xylose (2%), L-rhamnose (2–3%), and L-fucose (1%). Partial acid hydrolysis of the derived pectic acid furnished 2-O-(α-D-galactopyranosyluronic acid)-L-rhamnose, 4-O-(α-D-galactopyranosyluronic acid)-D-galacturonic acid and the polymer-homologous tri- and tetrasaccharides, and 4-O-(glucopyranosyluronic acid)-L-fucose. The cleavage products from the methylated pectin were examined by g.l.c. and the partially methylated alditol acetates from the methylated carboxyl-reduced polysaccharide by g.l.c.-mass spectrometry. Parallel methylation studies on lemon-peel pectin have established a close similarity between the two pectins.     

Effect of pectin and amidated pectin on cholesterol homeostasis and cecal metabolism in rats fed a high-cholesterol diet

Two experiments were performed to compare the effect of pectin and its hydrophobic derivatives on homeostasis of cholesterol and cecal metabolism in male young rats. Control rats were fed a diet supplemented with palm fat and cholesterol (50 and 10 g/kg, respectively). Rats of other groups were fed the same diet containing citrus pectin or octadecylpectinamide (60 g/kg). Diets were fed for 4 weeks. In experiment I, pectinamide of lower degree of amidation (30 %) increased serum HDL cholesterol from 1.20 to 1.43 micromol/ml (p>0.05) at the expense of other cholesterol fractions. In experiment II, pectinamide of a higher degree of amidation (53 %) significantly decreased total serum cholesterol from 2.08 to 1.67 micromol/ml. Amidated pectins at both levels of substitution significantly decreased hepatic concentrations of cholesterol and fat. In both experiments the relative weight of cecum in the pectinamide group was significantly lower than in pectin group. The highest cecal concentrations of short-chain fatty acids (SCFA) were found in rats fed a diet with pectin (133.2 and 129.3 micromol/g in experiment I and II, respectively). In other groups, cecal SCFA was significantly (pectinamide groups) or non-significantly (controls) lower. In wet feces, SCFA concentrations were higher and butyrate molar proportions lower than in corresponding cecal contents. Pectinamide of a lower or higher degree of substitution significantly increased fecal content of cholesterol from 18.5 and 17.3 micromol/g in controls to 31.8 and 28.0 micromol/g, respectively. Corresponding concentrations of coprostanol were decreased. Effects of pectin on cholesterol homeostasis were absent or marginal. Histological examination revealed that hepatic tissue of control and pectin-fed rats was infiltrated with lipids. The Sudan black-positive material was absent in the liver of rats fed pectinamides. No pathological changes of liver tissue were apparent. In summary, hydrophobic amidated pectins significantly altered cholesterol homeostasis in rats and might be considered as a clinically effective hypocholesterolemic agent. Low cecal SCFA concentrations in rats fed pectinamides suggest that amidation of pectin had decreased its fermentability.     

Physicochemical studies of pectin/poly-L-lysine gelation

The effect of poly-L-lysine concentration and degree of polymerisation on the gelation of pectins differing in charge density and distribution was examined, through the determination of gel stiffness, swelling behaviour and the binding of poly-L-lysine to the gel network. Poly-L-lysine acts as a crosslinker of concentrated pectin solutions, with its effectiveness showing dependencies on pH and charge distribution on the pectin. Neutralisation of the anionic charge on the pectin with the polycationic peptide leads to gel opacity and eventually network collapse.     

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.     

Measurement of pectin methylation in plant cell walls

A procedure was developed to measure the degree of pectin methylation in small samples of isolated cell walls from nonlignified plant tissues or pectin solutions. Galacturonic acid was determined colorimetrically with the 3,5-dimethylphenol reagent. Methylation was measured by base hydrolysis of galacturonic acid methyl esters, followed by gas chromatographic determination of released methanol. Estimates of the precision of analysis of pectin and cell wall samples were made. The coefficient of variation for estimates of the pectin esterification in cell walls isolated from 10-g samples of cucumber tissue ranged from 7.7 to 13.2%.     

Immunolocalization of homogalacturonans in the apex of the long-day plant Sinapis alba at floral transition. The pectin content drops dramatically in the first hours of this transition

The pectin content in the meristem of Sinapis alba at flowering transition was assessed in electron microscopy using immunocytochemistry and the monoclonal antibody 2F4 that recognizes a Ca²⁺-induced supramolecular conformation of homogalacturonans (Liners et al. Plant Physiol 91: 1419–1424, 1989; Liners et al. Plant Physiol 99: 1099–1104, 1992). The meristem's pectins were not recognized at all by the 2F4 monoclonal antibody unless they were enzymatically (PME: pectin methylesterase) or chemically (NaOH) de-esterified, indicating that native pectin must be largely esterified in the apical meristem. A striking but transient decrease of the homopolygalacturonic content of the meristem's cell walls occurred between 20 and 24 h after start of the inductive long day. These changes suggest a role for pectin in floral transition.     

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 (?(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.     

Unstirred water layers in rabbit intestine: effects of pectin

Pectins have been shown to affect the absorption of several different nutrients in clinical studies; however, the mechanisms for decreased absorption have not been defined. A possibility not studied with regards to pectin, but previously demonstrated to be important in absorption, is the effect of change in the unstirred water layer. As the unstirred water layer increases in thickness, the rate of absorption decreases for certain nutrients. The effect of pectin on the unstirred water layer in the lumen of rabbit jejunum was examined by previously described techniques. It was observed that: (1) increases in pectin concentration resulted in an increased thickness of the unstirred water layer; (2) for any stir rate, the addition of pectin increased the thickness of the unstirred water layer; and (3) stir rate is inversely related to the thickness of the unstirred water layer. It was concluded from these results that pectin increases the thickness of the unstirred water layer in rabbit jejunum. This mechanism may explain, in part, the reduction of the rate of absorption of certain nutrients seen following pectin ingestion.     

Pectinolytic enzymes of anaerobic fungi

Pectinolytic enzymes of four rumen fungi have been described. Three fungal species were monocentric Neocallimastix spp. H15, JL3 and OC2, and one isolate was a polycentric strain of Orpinomyces joyonii , A4. They differed in degree of pectin degradation and utilization. Only the strain Neocallimastix sp. H15 and partially Orpinomyces joyonii A4 were able to utilize pectin to a higher extent. The most important pectinolytic activity in all these isolates represented pectin lyase (EC 4.2.2.10) and polygalacturonase (EC 3.2.1.15). Their specific activities were in the range of 100–900 and 10–450 μg galacturonic acid h^-1 mg protein^-1 for pectin lyase and polygalacturonase, respectively. Polygalacturonase, located mainly in the endocellular fraction, was inhibited by calcium ions and had the main pH optimum at pH 6.0. All strains produced pectate lyase (EC 4.2.2.2). None of the strains tested produced pectinesterase (EC 3.1.1.11).     

Studies on the growth of Candida utilis on d-galacturonic acid and the products of pectin hydrolysis

Candida utilis was found to utilize d-galacturonic acid for cell growth, the incubation conditions being similar to those reported for growth on other substrates. At concentrations of d-galacturonic acid below 3 g l⁻¹cell yields were similar to those obtained using glucose, although at higher concentrations cell yields were reduced. Small, regular increases in the concentration of d-galacturonic acid substantially increased cell yields under the incubation conditions employed. Poly-d-galacturonic acid, hydrolysed by a fungal polygalacturonase [poly(1,4-α-d-galacturonide) glycanohydrolase, EC 3.2.1.15] prior to cell growth, yielded 27 g C. utilis cells/100 g substrate. Acid-hydrolysed pectin yielded 23 g cells/100 g substrate but no cell growth was found using pectin which had been degraded by alkali. The possibility of using pectin materials for the production of singlecell protein in a modified Symba process is discussed.     

Impact of pectin esterification on the antimicrobial activity of nisin‐loaded pectin particles

The relationship between pectin structure and the antimicrobial activity of nisin‐loaded pectin particles was examined. The antimicrobial activity of five different nisin‐loaded pectin particles, i.e., nisin‐loaded high methoxyl pectin, low methoxyl pectin, pectic acid, dodecyl pectin with 5.4 and 25% degree of substitution were tested in the pH range of 4.0–7.0 by agar‐diffusion assay and agar plate count methods. It was found that the degree of esterification of carboxyl group of galacturonic acid in pectin molecule is important for the antimicrobial activity of nisin‐loaded pectin particles. Nisin‐loaded particles prepared using pectic acid or the pectin with low degree of esterification exhibit higher antimicrobial activity than nisin‐loaded high methoxyl pectin particles. Pectins with free carboxyl groups or of low degree of esterification are the most suitable for particles preparation. Moreover, nisin‐loaded pectin particles were active at close to neutral or neutral pH values. Therefore, they could be effectively applied for food preservation. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:245–251, 2017     

Eudragit-coated pectin microspheres of 5-fluorouracil for colon targeting

An objective of the present investigation was to prepare and evaluate Eudragit-coated pectin microspheres for colon targeting of 5-fluorouracil (FU). Pectin microspheres were prepared by emulsion dehydration method using different ratios of FU and pectin (1:3 to 1:6), stirring speeds (500–2000 rpm) and emulsifier concentrations (0.75%–1.5% wt/vol). The yield of preparation and the encapsulation efficiencies were high for all pectin microspheres. Microspheres prepared by using drug:polymer ratio 1:4, stirring speed 1000 rpm, and 1.25% wt/vol concentration of emulsifying agent were selected as an optimized formulation. Eudragit-coating of pectin microspheres was performed by oil-in-oil solvent evaporation method using coat: core ratio (5:1). Pectin microspheres and Eudragit-coated pectin microspheres were evaluated for surface morphology, particle size and size distribution, swellability, percentage drug entrapment, and in vitro drug release in simulated gastrointestinal fluids (SGF). The in vitro drug release study of optimized formulation was also performed in simulated colonic fluid in the presence of 2% rat cecal content. Organ distribution study in albino rats was performed to establish the targeting potential of optimized formulation in the colon. The release profile of FU from Eudragit-coated pectin microspheres was pH dependent. In acidic medium, the release rate was much slower; however, the drug was released quickly at pH 7.4. It is concluded from the present investigation that Eudragit-coated pectin microspheres are promising controlled release carriers for colon-targeted delivery of FU. Published: February 16, 2007     

Pollen-specific pectin methylesterase involved in pollen tube growth

Pollen tube elongation in the pistil is a crucial step in the sexual reproduction of plants. Because the wall of the pollen tube tip is composed of a single layer of pectin and, unlike most other plant cell walls, does not contain cellulose or callose, pectin methylesterases (PMEs) likely play a central role in the pollen tube growth and determination of pollen tube morphology. Thus, the functional studies of pollen-specific PMEs, which are still in their infancy, are important for understanding the pollen development. We identified a new Arabidopsis pollen-specific PME, AtPPME1, characterized its native expression pattern, and used reverse genetics to demonstrate its involvement in determination of the shape of the pollen tube and the rate of its elongation.     

High-performance liquid chromatographic determination of hydrocortisone and methylprednisolone and their hemisuccinate esters in human serum

A high-performance liquid chromatographic method is described for the simultaneous determination of methylprednisolone (MP) and methylprednisolone hemisuccinate (MPHS), or hydrocortisone (HC) and hydrocortisone hemisuccinate (HCHS) in human serum. Reversed-phase liquid chromatography was performed on a microparticulate C₁₈ column (Spherisorb, 5 μm) using a mobile phase of 2% glacial acetic acid, 30–35% acetonitrile, 70–65% water with ultraviolet detection (254 nm). The method uses 17α-hydroxyprogesterone as the internal standard for the determination of methylprednisolone and its hemisuccinate ester, or 11-deoxy-17-hydroxycorticosterone as the internal standard for the determination of hydrocortisone and its hemisuccinate ester. The sensitivity is 0.03 μg/ml for HC, 0.07 μg/ml for MP, 0.04 μg/ml for MPHS, and 0.10 μg/ml for HCHS, with a detection limit of 0.02 μg/ml for all four steroids. Calibration curves are linear up to 3 μg/ml for MP or MPHS (as equivalent MP) and up to 4 μg/ml for HC and 7 μg/ml (as equivalent HC) for HCHS. The pooled relative standard deviation for replicate samples for each steroid is < 7%. Plasma concentration—time curves are reported for MP and MPHS or HC and HCHS of two human subjects following intramuscular administration of 125 mg of methylprednisolone sodium succinate for injection, U.S.P., or 250 mg of hydrocortisone sodium succinate for injection, U.S.P.     

Biosynthesis of pectin

Pectin consists of a group of acidic polysaccharides that constitute a large part of the cell wall of plants. The pectic polysaccharides have a complex structure but can generally be divided into homogalacturonan, rhamnogalacturonan I, rhamnogalacturonan II (RGII) and xylogalacturonan (XGA). These polysaccharides appear to be present in all cells but their relative abundance and structural details differ between cell types and species. Pectin is synthesized in the Golgi vesicles and its complexity dictates that a large number of enzymes must be involved in the process. The biosynthetic enzymes required are glycosyltransferases and decorating enzymes including methyltransferases, acetyltransferases and feruloyltransferases. Biochemical methods successfully led to the recent identification of a pectin biosynthetic galacturonosyltransferase (GAUT1), and recent functional genomics and mutant studies have allowed the identification of several biosynthetic enzymes involved in making different parts of pectin. Strong evidence has been obtained for two xylosyltransferases (RGXT1 and RGXT2) with documented in vitro activity and apparently involved in making a side chain of RGII. Strong circumstantial evidence has been obtained for a putative glucuronosyltransferase (GUT1) involved in making RGII, a putative arabinosyltransferase (ARAD1) involved in making arabinan, and a putative xylosyltransferase (XGD1) involved in making XGA. In several other cases, enzymes have been identified as involved in making pectin but because of ambiguity in the cell wall compositions of mutants and lack of direct biochemical evidence their specific activities are more uncertain.