Determination of methanol and its application to measurement of pectin ester content and pectin methyl esterase activity

Preparation, physicochemical characterization and swelling properties of composite hydrogel microparticles based on gelatin and pectins with different structure

Composite hydrogel microparticles based on pectins with different structures (callus culture pectin (SVC) and apple pectin (AU)) and gelatin were developed. Hydrogel microparticles were formed by the ionotropic gelation and electrostatic interaction of COO- groups of pectin and NH3+ groups of gelatin, which was confirmed by FTIR spectroscopy. The addition of gelatin to pectin-based gel formulations resulted in a decrease in gel strength, whereas increasing gelatin concentration enhanced this effect. The microparticle gel strength increased in proportion to the increase in the pectin concentration. The DSC and TGA analyzes showed that pectin-gelatin gels had the higher thermal stability than individual pectins. The gel strength, Ca2+ content and thermal stability of the microparticles based on gelatin and SVC pectin with a lower degree of methylesterification (DM) (14.8 %) were higher compared to that of microparticles based on gelatin and AU pectin with a higher DM (40 %). An increase in the SVC concentration, Ca2+ content and gel strength of SVC-gelatin microparticles led to a decrease in the swelling degree in simulated gastrointestinal fluids. The addition of 0.5 % gelatin to gels based on AU pectin resulted in increased stability of the microparticles in gastrointestinal fluids, while the microparticles from AU without gelatin were destroyed.

ZmBELL10 interacts with other ZmBELLs and recognizes specific motifs for transcriptional activation to modulate internode patterning in maize

Plant height is an important agronomic trait that affects crop yield. Elucidating the molecular mechanism underlying plant height regulation is also an important question in developmental biology. Here, we report that a BELL transcription factor, ZmBELL10, positively regulates plant height in maize (Zea mays). Loss of ZmBELL10 function resulted in shorter internodes, fewer nodes, and smaller kernels, while ZmBELL10 overexpression increased plant height and hundred-kernel weight. Transcriptome analysis and chromatin immunoprecipitation followed by sequencing showed that ZmBELL10 recognizes specific sequences in the promoter of its target genes and activates cell division- and cell elongation-related gene expression, thereby influencing node number and internode length in maize. ZmBELL10 interacted with several other ZmBELL proteins via a spatial structure in its POX domain to form protein complexes involving ZmBELL10. All interacting proteins recognized the same DNA sequences, and their interaction with ZmBELL10 increased target gene expression. We identified the key residues in the POX domain of ZmBELL10 responsible for its protein-protein interactions, but these residues did not affect its transactivation activity. Collectively, our findings shed light on the functions of ZmBELL10 protein complexes and provide potential targets for improving plant architecture and yield in maize.

Properties of cell wall polysaccharides of raw nectarine fruits after treatment under conditions that modulate gastric digestion

The results of the study of the physicochemical properties of the high-molecular-weight soluble and insoluble components of nectarine cell walls obtained by fruit treatment under conditions that modulate of gastric digestion are presented. Homogenized nectarine fruits were sequentially treated by natural saliva and simulated gastric fluid (SGF) at pH 1.8 and 3.0. The isolated polysaccharides were compared with polysaccharides obtained by sequential extraction of nectarine fruit with cold, hot, and acidified water, solutions of ammonium oxalate and sodium carbonate. As a result, high-molecular-weight water-soluble pectic polysaccharides, weakly bound in the cell wall, were dissolved in the simulated gastric fluid, regardless of pH. Homogalacturonan (HG) and rhamnogalacturonan-I (RG-I) were identified in all pectins. It was shown that their quantity and ability to form highly viscous solutions determine high values of the rheological characteristics of the nectarine mixture formed under simulated gastric conditions. The modifications occurring with the insoluble components under the influence of acidity of SGF were importance. They determined difference in the physicochemical properties of both the insoluble fibres and the nectarine mixtures.

Plant Polysaccharide Array for Studying Carbohydrate-Binding Proteins

The specificity of the most plant carbohydrate-binding proteins (CBP), many of which are known only through bioinformatic analysis of the genome, has either not been studied at all or characterized to a limited extent. The task of deciphering the carbohydrate specificity of the proteins can be solved using glycoarrays composed of many tens or even hundreds of glycans immobilized on a glass surface. Plant carbohydrates are the most significant natural ligands for plant proteins; this work shows that plant polysaccharides without additional modification can be immobilized on the surface, bearing N-hydroxysuccinimide activated carboxyl groups. As a result, an array of 113 well-characterized polysaccharides isolated from various plant cell walls, 23 mono- and oligosaccharides - components of polysaccharides, and glycans - ligands for widely known plant lectins was designed. Upon chemical immobilization of polysaccharides, their functional activity was preserved, which was confirmed by the results of interaction with antibodies and the plant lectin ricin. Using the constructed array, a previously unknown ability of ricin to bind polysaccharides was found, which significantly expands the knowledge of its specificity, and it was also found that a large variety of antibodies to plant polysaccharides are present in human peripheral blood.

Short-chain aldehydes increase aluminum retention and sensitivity by enhancing cell wall polysaccharide contents and pectin demethylation in wheat seedlings

Upon environmental stimuli, aldehydes are generated downstream of reactive oxygen species and thereby contribute to severe cell damage. In this study, using two wheat genotypes differing in aluminum (Al) tolerance, we investigated the effects of lipid peroxidation-derived aldehydes on cell wall composition and subsequent Al-binding capacities. The spatial accumulation of Al along wheat roots was found to the generation of reactive aldehydes, which are highly localized to the apical regions of roots. Elimination of aldehydes by carnosine significantly reduced Al contents in root tips, with a concomitant alleviation of root growth inhibition. In contrast, root growth and Al accumulation were exacerbated by application of the short-chain aldehyde (E)-2-hexenal. We further confirmed that cell wall binding capacity, rather than malate efflux or pH alteration strategies, is associated with the aldehyde-induced accumulation of Al. Scavenging of lipid-derived aldehydes reduced Al accumulation in the pectin and hemicellulose 1 (HC1) fractions of root cell walls, whereas exposure to (E)-2-hexenal promoted a further accumulation of Al, particularly in the cell wall HC1 fraction of the Al-sensitive genotype. Different strategies were introduced by pectin and HC1 to accumulate Al in response to aldehydes in wheat roots. Accumulation in pectin is based on a reduction of methylation levels in response to elevated pectin methylesterase activity and gene expression, whereas that in HC1 is associated with an increase in polysaccharide contents. These findings indicate that aldehydes exacerbate Al phytotoxicity by enhancing Al retention in cell wall polysaccharides.

Swelling, Protein Adsorption, and Biocompatibility In Vitro of Gel Beads Prepared from Pectin of Hogweed Heracleum sosnówskyi Manden in Comparison with Gel Beads from Apple Pectin

The study aims to develop gel beads with improved functional properties and biocompatibility from hogweed (HS) pectin. HS4 and AP4 gel beads were prepared from the HS pectin and apple pectin (AP) using gelling with calcium ions. HS4 and AP4 gel beads swelled in PBS in dependence on pH. The swelling degree of HS4 and AP4 gel beads was 191 and 136%, respectively, in PBS at pH 7.4. The hardness of HS4 and AP4 gel beads reduced 8.2 and 60 times, respectively, compared with the initial value after 24 h incubation. Both pectin gel beads swelled less in Hanks’ solution than in PBS and swelled less in Hanks’ solution containing peritoneal macrophages than in cell-free Hanks’ solution. Serum protein adsorption by HS4 and AP4 gel beads was 118 ± 44 and 196 ± 68 μg/cm² after 24 h of incubation. Both pectin gel beads demonstrated low rates of hemolysis and complement activation. However, HS4 gel beads inhibited the LPS-stimulated secretion of TNF-α and the expression of TLR4 and NF-κB by macrophages, whereas AP4 gel beads stimulated the inflammatory response of macrophages. HS4 gel beads adsorbed 1.3 times more LPS and adhered to 1.6 times more macrophages than AP4 gel beads. Thus, HS pectin gel has advantages over AP gel concerning swelling behavior, protein adsorption, and biocompatibility.

Sodium bicarbonate reduces the cooked hardness of lotus rhizome via side chain rearrangement and pectin degradation

In this study, 0.1% (W/V) sodium bicarbonate (SB) solution was used to soften lotus rhizome, and the mechanism was characterized by monoclonal antibodies labeling (mAbs) and atomic force microscopy (AFM). The results showed that the cell wall of lotus rhizome was disintegrated under SB treatment. In addition, the mAbs results revealed that low-esterified homogalacturonan (HG) at the tricellular junction was degraded, the rearrangement of Ara and the interaction between Gal and cellulose may be related to the texture changes. Compared with distilled water treatment, SB treatment reduced the relative content of pectin from 34.1% to 19.1% while increased that of cellulose from 65.9% to 80.9%. AFM results revealed that the height of CSF skeleton decreased from about 32 nm to 1.5 nm. These results clearly demonstrate that cooking with 0.1% SB can soften lotus rhizome through degradation of pectin and arrangement of side chains of rhamnogalacturonan-Ⅰ (RG-Ⅰ).

Isolation, Chemical Characterization and Antioxidant Activity of Pectic Polysaccharides of Fireweed (Epilobium angustifolium L.)

The aim of this study was to isolate pectins with antioxidant activity from the leaves of Epilobium angustifolium L. Two pectins, EA-4.0 and EA-0.8, with galacturonic acid contents of 88 and 91% were isolated from the leaves of E. angustifolium L. by the treatment of plant raw materials with aqueous hydrochloric acid at pH 4.0 and 0.8, respectively. EA-4.0 and EA-0.8 were found to scavenge the DPPH radical in a concentration-dependent manner at 17–133 μg/mL, whereas commercial apple pectin scavenged at 0.5–2 mg/mL. The antioxidant activity of EA-4.0 was the highest and exceeded the activity of EA-0.8 and a commercial apple pectin by 2 and 39 times (IC₅₀—0.050, 0.109 and 1.961 mg/mL), respectively. Pectins EA-4.0 and EA-0.8 were found to possess superoxide radical scavenging activity, with IC₅₀s equal to 0.27 and 0.97 mg/mL, respectively. Correlation analysis of the composition and activity of 32 polysaccharide fractions obtained by enzyme hydrolysis and anionic exchange chromatography revealed that the antioxidant capacity of fireweed pectins is mainly due to phenolics and is partially associated with xylogalacturonan chains. The data obtained demonstrate that pectic polysaccharides appeared to be bioactive components of fireweed leaves with high antioxidant activity, which depend on pH at their extraction.

The Emission Mechanism of Gold Nanoclusters Capped with 11-Mercaptoundecanoic Acid, and the Detection of Methanol in Adulterated Wine Model

The absorption and emission mechanisms of gold nanoclusters (AuNCs) have yet to be understood. In this article, 11-Mercaptoundecanoic acid (MUA) capped AuNCs (AuNC@MUA) were synthesized using the chemical etching method. Compared with MUA, AuNC@MUA had three obvious absorption peaks at 280 nm, 360 nm, and 390 nm; its photoluminescence excitation (PLE) peak and photoluminescence (PL) peak were located at 285 nm and 600 nm, respectively. The AuNC@MUA was hardly emissive when 360 nm and 390 nm were chosen as excitation wavelengths. The extremely large stokes-shift (>300 nm), and the mismatch between the excitation peaks and absorption peaks of AuNC@MUA, make it a particularly suitable model for studying the emission mechanism. When the ligands were partially removed by a small amount of sodium hypochlorite (NaClO) solution, the absorption peak showed a remarkable rise at 288 nm and declines at 360 nm and 390 nm. These experimental results illustrated that the absorption peak at 288 nm was mainly from metal-to-metal charge transfer (MMCT), while the absorption peaks at 360 nm and 390 nm were mainly from ligand-to-metal charge transfer (LMCT). The PLE peak coincided with the former absorption peak, which implied that the emission of the AuNC@MUA was originally from MMCT. It was also interesting that the emission mechanism could be switched to LMCT from MMCT by decreasing the size of the nanoclusters using 16-mercaptohexadecanoic acid (MHA), which possesses a stronger etching ability. Moreover, due to the different PL intensities of AuNC@MUA in methanol, ethanol, and water, it has been successfully applied in detecting methanol in adulterated wine models (methanol-ethanol-water mixtures).

Physicochemical and swelling properties of composite gel microparticles based on alginate and callus cultures pectins with low and high degrees of methylesterification

Composite gel microparticles based on alginate and callus culture pectins with low and high degrees of methylesterification or apple pectin were produced. By varying the chemical composition of the pectic samples and the ratio of alginate to pectin, the gel strength, morphology, and swelling properties of composite microparticles can be altered. The inclusion of increasing concentrations of alginate in gel formulations promoted an increase in the microparticle gel strength and the formation of a smoother surface microrelief independently of the pectin chemical composition. Microparticles based on the pectin with a low degree of methylesterification (DM) and a higher concentration of alginate exhibited an increased swelling degree in the simulated digestive fluids. Microparticles based on the pectin with high DM and low alginate concentration were destroyed in the simulated intestinal fluid within 1 h due to the low Ca²⁺ content, gel strength, and grooved and rough surface of these microparticles. An increase in alginate concentration of gel formulations based on pectin with high DM led to increased stability of the microparticles in the simulated intestinal and colonic fluids due to increased Ca²⁺ content, microparticle gel strength and degree of crosslinking.

Acetic acid reducing the softening of lotus rhizome during heating by regulating the chelate-soluble polysaccharides

Lotus rhizomes were used to study on the relationship between the cell wall polysaccharides and cooked texture by adding acetic acid. Hardness and scanning electron microscopy results showed that acetic acid treatment can maintain higher hardness and the integrity of the cell wall. Then, the cell walls were sequentially extracted and divided into water-soluble fraction, chelate-soluble fraction (CSF), sodium carbonate-soluble fraction and hemicellulose fraction. The pectin fraction contents, monosaccharides composition, esterification degree and sugar ratios in different groups were evaluated, the results showed that acetic acid increased the total amount of CSF, decreased the esterification degree and less side chain compared that in the solely thermal treatment group. The nanostructures showed that acetic acid treatment maintained longer chain and destroy helical structure of CSF backbone. This work helps us to demonstrate the relationship between polysaccharides structure and cooked texture, and further control the plant-based vegetables processing texture in food industry.

Structural characteristics of oxalate-soluble polysaccharides from Norway spruce (Picea abies) foliage

Structurally different polymers were derived from Picea abies foliage by successive extraction with water (PA_W), HCl solution (PA_A) and (NH₄)₂C₂O₄ solution (PA_O). The P. abies foliage was found to contain basically low-methoxyl pectin extractable with an (NH₄)₂C₂O₄ solution. PA_W was shown to comprise primarily arabinogalactan-proteins (AGPs); PA_A was composed of mixed AGPs and pectic polysaccharides, with the latter prevailing; and polysaccharide PA_O isolated in the highest yield included chiefly pectic polysaccharides. The major constituents of PA_O were low-methoxyl and low-acetylated 1,4-α-d-galacturonan and partially acetylated RG-I. The sugar side chains of RG-I contained chiefly highly branched 1,5-α-l-arabinan and arabinogalactan type I as a minor constituent. RG-I whose side chains had 1,5-α-l-arabinan represented short regions alternating with non-acetylated and unmethylesterified galacturonan regions. In addition to pectins, polysaccharide PA_O contained AGPs, xylanes and glucomannans, indicating that these polysaccharides are in an intimate interaction.

Rhamnogalacturonan-I is a determinant of cell-cell adhesion in poplar wood

The molecular basis of cell-cell adhesion in woody tissues is not known. Xylem cells in wood particles of hybrid poplar (Populus tremula × P. alba cv. INRA 717-1B4) were separated by oxidation of lignin with acidic sodium chlorite when combined with extraction of xylan and rhamnogalacturonan-I (RG-I) using either dilute alkali or a combination of xylanase and RG-lyase. Acidic chlorite followed by dilute alkali treatment enables cell-cell separation by removing material from the compound middle lamellae between the primary walls. Although lignin is known to contribute to adhesion between wood cells, we found that removing lignin is a necessary but not sufficient condition to effect complete cell-cell separation in poplar lines with various ratios of syringyl:guaiacyl lignin. Transgenic poplar lines expressing an Arabidopsis thaliana gene encoding an RG-lyase (AtRGIL6) showed enhanced cell-cell separation, increased accessibility of cellulose and xylan to hydrolytic enzyme activities, and increased fragmentation of intact wood particles into small cell clusters and single cells under mechanical stress. Our results indicate a novel function for RG-I, and also for xylan, as determinants of cell-cell adhesion in poplar wood cell walls. Genetic control of RG-I content provides a new strategy to increase catalyst accessibility and saccharification yields from woody biomass for biofuels and industrial chemicals.

Rice Putative Methyltransferase Gene OsPMT16 Is Required for Pistil Development Involving Pectin Modification

Pectin synthesis and modification are vital for plant development, although the underlying mechanisms are still not well understood. Furthermore, reports on the function of pectin in the pistil are limited. Herein, we report the functional characterization of the OsPMT16 gene, which encodes a putative pectin methyltransferase (PMT) in rice. The cell walls of rice leaves contain less pectin, and chemical analysis of pectin in the flower organ had not been previously performed. Therefore, in the present study, the amount of pectin in the reproductive tissues of rice was investigated. Of the reproductive tissues, the pistil was especially rich in pectin; thus, we focused on the pistil. OsPMT16 expression was confirmed in the pistil, and effects of pectin methylesterification regulation on the reproductive stage were investigated by studying the phenotype of the T-DNA insertion mutant. The ospmt16 mutant showed significantly reduced fertility. When the flowers were observed, tissue morphogenesis was abnormal in the pistil. Immunofluorescence staining by pectin-specific monoclonal antibodies of the pistil revealed that total pectin and esterified pectin were decreased among ospmt16 mutants. These results indicate that OsPMT16 contributes significantly to pistil development during reproductive growth.

Structural, rheological and antioxidant properties of pectins from Equisetum arvense L. and Equisetum sylvaticum L

The pectins were isolated from sterile stems of E. arvense (EA, yield 5.9%) and E. sylvaticum (ES, yield 4.8%) (Equisetaceae) using ammonium oxalate extraction after preliminary treatment with dilute HCl (рH 4.0). The pectins possessed high molecular weight (Mw, 340-360 kDa), high GalA content (ca. 85%), low degrees of methyl-esterification (14-16%) and acetylation (3-8%). NMR analysis indicated extensive regions of partially methyl-etherified and 3-O-acetylated HG and minor regions of low branched RG in the fragment isolated after hydrolysis of pectin EA by pectinase. Pectin EA produced a higher viscosity solution, formed a stronger and more rigid ionotropic hydrogel than pectin ES. The pectins scavenged DPPH and hydroxyl radicals, but not the superoxide radical and hydrogen peroxide. Phenolic compounds (0.11 and 0.23%) associated with polysaccharide moieties were apparently responsible for the differences in the anti-DPPH scavenging activity of pectins EA and ES (63 and 49%). The findings suggested that pectin from E. arvense should be more perspective than pectin from E. sylvaticum on their use as components of wound healing remedies.

Isolation a Homogalacturonan from the Outer Seed Coat of Shaddock (Citrus grandis Osbeck)

An acidic mucilage was isolated from the outer-layer seed coat of shaddock (Citrus grandis Osbeck) by water extraction at room temperature, and purified by DE-52 anion-exchange chromatography using 0.26 – 0.37 M NaCl. This purified mucilage was almost entirely composed of galacturonic acid residues. Glycosyl-linkage analysis showed that the backbone was 1→4 linked. Fourier Transform Infrared Spectroscopic analysis and determination of the degree of methylation further revealed that the mucilage was a low-degree (11.94%) esterified homogalacturonan. Size exclusion chromatography showed that the major molecular weight distribution of 610.9 kDa.

Transcriptomic insights into citrus segment membrane's cell wall components relating to fruit sensory texture

Background

During fresh fruit consumption, sensory texture is one factor that affects the organoleptic qualities. Chemical components of plant cell walls, including pectin, cellulose, hemicellulose and lignin, play central roles in determining the textural qualities. To explore the genes and regulatory pathways involved in fresh citrus’ perceived sensory texture, we performed mRNA-seq analyses of the segment membranes of two citrus cultivars, Shiranui and Kiyomi, with different organoleptic textures.

Results

Segment membranes were sampled at two developmental stages of citrus fruit, the beginning and end of the expansion period. More than 3000 differentially expressed genes were identified. The gene ontology analysis revealed that more categories were significantly enriched in ‘Shiranui’ than in ‘Kiyomi’ at both developmental stages. In total, 108 significantly enriched pathways were obtained, with most belonging to metabolism. A detailed transcriptomic analysis revealed potential critical genes involved in the metabolism of cell wall structures, for example, GAUT4 in pectin synthesis, CESA1, 3 and 6, and SUS4 in cellulose synthesis, CSLC5, XXT1 and XXT2 in hemicellulose synthesis, and CSE in lignin synthesis. Low levels, or no expression, of genes involved in cellulose and hemicellulose, such as CESA4, CESA7, CESA8, IRX9 and IRX14, confirmed that secondary cell walls were negligible or absent in citrus segment membranes. A chemical component analysis of the segment membranes from mature fruit revealed that the pectin, cellulose and lignin contents, and the segment membrane’s weight (% of segment) were greater in ‘Kiyomi’.

Conclusion

Organoleptic quality of citrus is easily overlooked. It is mainly determined by sensory texture perceived in citrus segment membrane properties. We performed mRNA-seq analyses of citrus segment membranes to explore the genes and regulatory pathways involved in fresh citrus’ perceived sensory texture. Transcriptomic data showed high repeatability between two independent biological replicates. The expression levels of genes involved in cell wall structure metabolism, including pectin, cellulose, hemicellulose and lignin, were investigated. Meanwhile, chemical component contents of the segment membranes from mature fruit were analyzed. This study provided detailed transcriptional regulatory profiles of different organoleptic citrus qualities and integrated insights into the mechanisms affecting citrus’ sensory texture.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4669-y) contains supplementary material, which is available to authorized users.

Pectinolytic enzymes-solid state fermentation, assay methods and applications in fruit juice industries: a review

A plethora of solid substrates, cultivation conditions and enzyme assay methods have been used for efficient production and estimation of polygalacturonase and pectin methylesterase enzymes. Recent developments in industrial biotechnology offer several opportunities for the utilization of low cost agro-industrial waste in Solid State Fermentation (SSF) for the pectinolytic enzyme production using fungi. Fruit waste mainly citrus fruit waste alone and along with other agro-industrial waste has been explored in SSF for enzyme production. Agro-industrial waste, due to the economic advantage of low procuring cost has been employed in SSF bioreactors for pectinolytic enzyme production. Acidic pectinases produced by fungi are utilized especially in food industries for clarification of fruit juices. This review focuses on the recent developments in SSF processes utilizing agro-industrial residues for polygalacturonase and pectin methylesterase production, their various assay methods and applications in fruit juice industries.

Prevention of postoperative adhesions by biodegradable cryogels from pectin and chitosan polysaccharides

The main complication that may arise after surgery is the formation of adhesions. The current trend in the prevention of postoperative adhesions is the application of anti-adhesive barrier materials for the separation of wound tissue during the critical period of mesothelial repair and healing. In this work, cryogels based on pectin and chitosan were obtained by the ionic cryotropic gelation method. It was found that the Heracleum L. pectin cryogels are more elastic (73 ± 6 kPa) than the apple pectin cryogels (29 ± 11 kPa). The addition of chitosan with different physical and chemical characteristics did not significantly affect the elasticity of pectin–chitosan cryogels. The greatest swelling ability was achieved during in vivo incubation of Heracleum L. pectin cryogels and Heracleum L. pectin with reacetylated chitosan cryogels (17.1 ± 1.6 and 14.2 ± 2.0 g/g, respectively). It was found that the complete biodegradation of apple pectin cryogels occurred within 24 h of incubation in the rat abdominal cavity. Heracleum L. pectin cryogels were encapsulated in a fibrous capsule and detected in the abdominal cavity after 168 h. Maximum anti-adhesion effect was observed through the use of apple pectin cryogels (0 ± 0.5 score). Significant anti-adhesive effect was also observed through the use of apple pectin–reacetylated chitosan cryogels (1 ± 0.5 score). Due to the high anti-adhesive activity, such cryogels can be recommended for the development of a new barrier material for use in surgery. The potential anti-adhesive mechanism of apple pectin cryogels which may be attributed to a combination of barrier function and bioactivity of cryogels components was discussed.

The Antioxidant Properties of Pectin Fractions Isolated from Vegetables Using a Simulated Gastric Fluid

The antioxidant properties of vegetable pectin fractions against intraluminal reactive oxygen species were elucidated in vitro in conjunction with their structural features. The pectin fractions were isolated using a simulated gastric fluid (pH 1.5, pepsin 0.5 g/L, 37°C, 4 h) from fresh white cabbage, carrot, onion, and sweet pepper. The fraction from onion was found to inhibit the production of superoxide radicals by inhibiting the xanthine oxidase. The high molecular weight of onion pectin and a large number of galactose residues in its side chains appeared to participate in interaction with xanthine oxidase. All the isolated pectic polysaccharides were found to be associated with protein (2–9%) and phenolics (0.5–0.7%) as contaminants; these contaminants were shown to be responsible for the antioxidant effect of vegetable pectin fractions against the hydroxyl and 1,1-diphenyl-2-picrylhydrazyl radicals.

Characterisation of Fiber Obtained from Pumpkin (cucumis moschata duch.) Mesocarp Through Enzymatic Treatment

Cell wall-enriched pumpkin ( Cucumis moschata Duch.) powder was submitted to enzymatic hydrolysis by cellulase or hemicellulase in order to evaluate the performance of these cell wall-degrading enzymes on that substrate. Different enzyme-substrate ratios were evaluated and the effect exerted by the buffer on cell wall polysaccharides. Cellulase produced the release of pectin macromolecules which include homogalacturonans side chains, the rhamnogalacturonan I core and rhamnogalacturonan II, in conjunction with xylogalacturonans. The content of galacturonic acid in product obtained ranged from 545 to 781 g/kg of fiber. Hemicellulases produced intense pectin hydrolysis leading to fiber-fractions with galacturonic acid contents ranging from 390 to 444 g/kg of fiber and enriched in glucose polymers as the enzyme proportion increased. Few rhamnogalacturonan-I was present.The acidic citrate buffer (pH 5.2) used for allowing enzyme activity could per se remove noncovalent cross-links like ionic bonds. As a consequence, pectin-in-extensin entanglements, pectins joined by Ca2+-bridges through the homogalacturonan side chains, and some pectins that are originally soluble in cold water due to little or no binding to the cell wall, could be removed by this citrate buffer. Enzymatic hydrolysis as well as buffer extraction produced fiber-products with an important thickening effect of aqueous systems. This effect was smaller as the ratio enzyme-substrate was increased and, in general, the fiber fractions isolated produced an in vitro glucose diffusion retardation.

Calcium pectinate gel beads obtained from callus cultures pectins as promising systems for colon-targeted drug delivery

Low methyl-esterified pectins obtained from the cell walls of the campion (SV, SV>300), tansy (TV, TV>300) and duckweed (LM, LM>300) callus cultures and apple pectin (AP, Classic AU 701) were used as the carriers for colon delivery of prednisolone. The pectins with molecular weight more than 300kDa (SV>300, TV>300, LM>300) formed gels which exhibited the higher gel strength. The higher gel strength of these gels appeared to be related to the higher Mw and the lower degree of methylesterification (DE) of these pectins. Release aspects of prednisolone in the simulated gastric (pH 1.25), intestinal (pH 7.0) and colonic (pH 7.0+pectinase) media were investigated. The LM-5%, AP-3% and AP-5% beads destroyed in simulated intestinal medium probably due to the higher DE of the LM and AP pectins. The SV>300-3% and TV>300-3% prednisolone loaded bead systems showed a high stability at pH 1.25 and pH 7.0. Prednisolone release occurred in a larger extent in colonic medium due to the enzymatic erosion of the beads. The SV>300-3% and TV>300-3% particles showed a more controlled release that appeared to be related to the lower DE, rhamnogalacturonan content, rhamnogalacturonan I branching and the higher linearity and Mw of the TV>300 and SV>300 pectins, as well as to the higher gel strength. This in vitro study suggests that calcium pectinate gel beads obtained from callus cultures pectins can be proposed as potential systems for colon-targeted drug delivery.