Structural study of bergenan, a pectin from Bergenia crassifolia

A pectin polysaccharide named bergenan was isolated from the freshly collected leaves of the leather bergenia Bergenia crassifolia by extraction with an aqueous solution of ammonium oxalate. The main component of its carbohydrate chain was shown to be the residues of D-galacturonic acid (about 80%). In addition, the polysaccharide contains residues of galactose, arabinose, and rhamnose; their total content is less than 15%. It was shown that the bergenan samples from bergenia leaves collected at different vegetation periods (from July to September) do not substantially differ either in monosaccharide composition or in the viscosity of aqueous solutions they form. The results of enzymatic hydrolysis by alpha-1,4-galacturonase (pectinase), partial acidic hydrolysis, NMR spectroscopy, and methylation with subsequent analysis of the results by GC-MS indicate that the bergenan macromolecule contains the regions of a linear alpha--1,4-D-galactopyranosyluronan and rhamnogalacturonan-I (RG-1). Galacturonan responds for a greater part of the macromolecule. A considerable amount of its constituent galacturonic acid residues are present as methyl esters. The side chains in RG-I are attached to the rhamnopyranose residues of the main carbohydrate chain by 1,4-link and are composed of the residues of terminal arabinofuranose and galactopyranose, 1,5-linked (-arabinofuranose, and 1,4-and 1,6-linked beta-galactopyranose. The branching points of the side chains of the RG-I molecule are 3,4- and 3,6-di-O-substituted galactose residues.     

Structural study of bergenan,a pectin from <Emphasis Type="Italic">Bergenia crassifolia</Emphasis>

A pectin polysaccharide named bergenan was isolated from the freshly collected leaves of the leather bergenia Bergenia crassifolia by extraction with an aqueous solution of ammonium oxalate. The main component of its carbohydrate chain was shown to be the residues of D-galacturonic acid (about 80%). In addition, the polysaccharide contains the residues of galactose, arabinose, and rhamnose; their total content is less than 15%. It was shown that the bergenan samples from bergenia leaves collected at different vegetation periods (from July to September) do not substantially differ either in monosaccharide composition or in the viscosity of their aqueous solutions. The results of enzymatic hydrolysis by α-1,4-galacturonase (pectinase), partial acidic hydrolysis, NMR spectroscopy, and methylation with subsequent analysis of the results by GC-MS indicate that the bergenan macromolecule contains the regions of a linear α-1,4-D-galactopyranosyluronan and rhamnogalacturonan-I (RG-I). Galacturonan responds for a greater part of the macromolecule. A considerable amount of its constitutent galacturonic acid residues are present as methyl esters. The side chains in RG-I are attached to the rhamnopyranose residues of the backbone by a 1,4-linkages and are composed of the residues of terminal arabinofuranose and galactopyranose, 1,5-linked α-arabinofuranose, and 1,4- and 1,6-linked β-galactopyranose. The branching points of the side chains of the RG-I molecule are 3,4- and 3,6-di-O-substituted galactose residues.     

Composition of cell walls from cotyledons of Pisum sativum,Vicia faba and Glycine max

Cell walls from cotyledons of smooth field pea, broad bean and soya bean contain ca 55% pectic polysaccharides associated with 9% cellulose. Arabinose is the major pectic sugar of pea and broad bean walls whereas soya bean pectic polymers are constituted of galactose and arabinose in the ratio (2:1). Galacturonic acid represents ca 20% of the walls. In addition, pea and broad bean cell walls contain, respectively, 12% and 6% of non-starchy and non-cellulosic glucans bearing 4,6-linked and 3-linked glycosyl units. EDTA-soluble acidic pectic substances are distinct rhamnogalacturonans bearing decreasing proportions of interrupting rhamnose from highly interrupted moieties to nearly homogenous homogalacturonans. Pea and broad bean rhamnogalacturonans are associated with arabinose-containing polymers of average DP ca 30–35 whereas soya bean ones have side chains of arabinose and galactose of DP ca 40.     

Polysaccharides of cell cultures of Silene vulgaris

Callus and suspension cultures of campion (Silene vulgaris) produced pectin polysaccharides, similar in structure to the polysaccharides of intact plants. The major components of the pectins were D-galacturonic acid, galactose, arabinose, and rhamnose residues. The maximum content of pectins was found in callus. The monosaccharide composition of arabinogalactans isolated from cells and a culture medium of callus cultures were similar, with the ratio between arabinose and galactose of 1: (2.3-6.5) being retained. The arabinogalactans from the cells and culture medium of the suspension cultures also had a similar structure, and the arabinose to galactose ratio was 1: (1.5-1.8). In contrast to the callus cultures, the suspension cultures produced arabinogalactans with an increased content of arabinose residues and a decreased content of galactose residues. The greatest content of arabinogalactan was detected in the culture medium of the suspension cultures.     

Cell Wall Metabolism in Ripening Fruit: IV. Characterization of the Pectic Polysaccharides Solubilized during Softening of ;Bartlett' Pear Fruit

Fractionation of pectic polysaccharides from the juice of ripening `Bartlett' pears (Pyrus communis) gave two general types of polyuronides. The major type was a homogalacturonan (HGA) whose molecular weight decreased upon ripening. The other type comprised heteropolymers composed of various amounts of arabinose, rhamnose, and galactose. Treatment of the major arabinose-containing heteropolymeric fraction of high molecular weight (400,000) with a pear exo-polygalacturonase to degrade contaminating HGA gave a polyuronide which was inert to tomato endopolygalacturonase. Glycosyl-linkage analysis of this arabinosyl-polyuronide gave results expected from a rhamnogalacturonan I-like polysaccharide with large, highly branched araban side chains (RG-I). A linkage between HGA and RG-I was not found. RG-I, in ripening pears, appeared to be degraded with the initial loss of much of its arabinose.     

Polysaccharides of cell cultures of <Emphasis Type="Italic">Silene vulgaris</Emphasis>

Callus and suspension cultures of campion (Silene vulgaris) produced pectin polysaccharides, similar in structure to the polysaccharides of intact plants. The major components of the pectins were D-galacturonic acid, galactose, arabinose, and rhamnose residues. The maximum content of pectins was found in callus. The monosaccharide composition of arabinogalactans isolated from cells and a culture medium of callus cultures were similar, with the ratio between arabinose and galactose of 1: (2.3–6.5) being retained. The arabinogalactans from the cells and culture medium of the suspension cultures also had a similar structure, and the arabinose to galactose ratio was 1: (1.5–1.8). In contrast to the callus cultures, the suspension cultures produced arabinogalactans with an increased content of arabinose residues and a decreased content of galactose residues. The greatest content of arabinogalactan was detected in the culture medium of the suspension cultures.     

Degradation of forage chicory by ruminal fibrolytic bacteria

Aims: Determine the susceptibility of forage chicory (Cichorium intybus L.) to degradation by ruminal fibrolytic bacteria and measure the effects on cell-wall pectic polysaccharides. Methods and Results: Large segments of fresh forage chicory were degraded in vitro by Lachnospira multiparus and Fibrobacter succinogenes, but not by Ruminococcus flavefaciens or Butyrivibrio hungatei. Cell-wall pectins were degraded extensively (95%) and rapidly by L. multiparus with a simultaneous release of uronic acids and the pectin-derived neutral monosaccharides arabinose, galactose and rhamnose. Fibrobacter succinogenes also degraded cell-wall pectins extensively, but at a slower rate than L. multiparus. Immunofluorescence microscopy using monoclonal antibodies revealed that, after incubation, homogalacturonans with both low and high degrees of methyl esterification were almost completely lost from walls of all cell types and from the middle lamella between cells. Conclusions: Only two of the four ruminal bacteria with pectinolytic activity degraded fresh chicory leaves, and each showed a different pattern of pectin breakdown. Degradation was greatest for F. succinogenes which also had cellulolytic activity. Significance and Impact of the Study: The finding of extensive removal of pectic polysaccharides from the middle lamella and the consequent decrease in particle size may explain the decreased rumination and the increased intake observed in ruminants grazing forage chicory.     

Comparison between maize root cells and their respective regenerating protoplasts: wall polysaccharides

The cell-wall polysaccharides from different parts of maize roots have been analysed. The arabinose, galactose and mannose contents are influenced by cell differentiation, whereas xylose, rhamnose and uronic-acid contents are not. In cap cells, the pectin content is low but rhamnose and fucose are present in larger quantities. The cell-wall polysaccharides from cells of the elongation zone and their respective regenerating protoplasts were also analysed. The walls of the protoplasts contained higher xylose and mannose levels and a much lower level of cellulose than the cells from which they were derived.     

Studies of the polysaccharides from sunflower heads

Extraction of sunflower heads with ammonium oxalate afforded water-soluble pectin material and water-insoluble glycoprotein material, the carbohydrate portion of which consisted of galacturonic acid and xylose residues; the pectin material defied fractionation with cetylpyridinium chloride. Extraction with hydrochloric acid (pH 1.5) afforded water-soluble and water-insoluble polysaccharide materials. The former, when fractionated with cetylpyridinium chloride, gave a glycoprotein, the carbohydrate moiety of which was composed of galacturonic acid, galactose (major), glucose, arabinose, and xylose, and also a rhamnan. The latter was a glycoprotein, the carbohydrate portion of which consisted of galactose (major), glucose, xylose, and rhamnose residues. Extraction of the sunflower heads with water also gave glycoprotein material, which was fractionated by paper electrophoresis into a glyco-protein, the carbohydrate moiety ofwhich was composed of galacturonic acid (minor), galactose, glucose, xylose, arabinose, and rhamnose (major) residues, and a heteropolysaccharide composed of galactose (major), glucose, xylose, and arabinose residues.     

Pectin substances of the callus culture of Silene vulgaris (M.) G

Pectin-protein fraction SVC was isolated from the callus culture of the bladder campion (Silene vulgaris). The main components in it were residues of D-galacturonic acid, galactose, arabinose, rhamnose, and protein. Using ion-exchange chromatography, ultrafiltration, and acid and enzymatic hydrolysis, it was shown that SVC contained a mixture of molecules of linear pectin, branched pectin polysaccharide, and pectin-protein polymer. A fragment of the linear chain of galacturonan amounted to more than half of the entire carbohydrate silenan chain. The branched area of the macromolecule is represented by rhamnogalacturonan I. The pectin-protein polymer consisted mainly of protein and weakly branched pectin fragments with molecular mass of more than 300 kDa.     

Sugars in hydrolysates of fungal melanins and soil humic acids

Humic acids from four Brazilian topsoils of different origin and four fungal melanins, synthesized under two cultural conditions were subjected to a two step hydrolysis procedure and the released monosaccharides qualitatively and quantitatively determined by gas-liquid chromatography. The neutral sugars, glucose, galactose, mannose, arabinose, xylose, fucose, rhamnose and the alcohol sugar inositol, were detected in most of the soil humic acid samples. The fungal melanins showed the presence of glucose, galactose, mannose and arabinose. Ribose was present in two out of the eight samples tested. Some quantitative differences in the two types of humic polymers were noted and expected considering their origins. However, similarities were more apparent than differences and give further indication that melanic fungi may play a significant role in the formation of soil humic acids.     

Bioactive polysaccharides from the stems of the Thai medicinal plant Acanthus ebracteatus: their chemical and physical features

Crude water-soluble polysaccharides were isolated from Acanthus ebracteatus by hot water extraction followed by ethanol precipitation after pre-treatment with 80% ethanol. The crude polysaccharides were separated into neutral and acidic polysaccharides by anion-exchange chromatography. The neutral polysaccharide (A1001) was rich in galactose, 3-O-methylgalactose and arabinose, whereas the acidic polysaccharide (A1002) consisted mainly of galacturonic acid along with rhamnose, arabinose and galactose as minor components indicating a pectin-type polysaccharide with rhamnogalacturonan type I (RG-1) backbone. 3-O-Methylgalactose is also present in the acidic fraction. Both neutral and acidic fractions showed potent effects on the complement system using pectic polysaccharide PM II from Plantago major as a positive control. A small amount of 3-O-methylgalactose present in the pectin seemed to be of importance for activity enhancement in addition to the amount of neutral sugar side chains attached to RG-1. The relationship between chemical structure and effect on the complement system of the isolated polysaccharides is considered in the light of these data. The presence of the rare monosaccharide 3-O-methylgalactose may indicate that this can be used as a chemotaxonomic marker. The traditional way of using this plant as a medical remedy appears to have a scientific basis.     

Pectin substances of the callus culture of <Emphasis Type="Italic">Silene vulgaris</Emphasis> (M.) G.

Pectin-protein fraction SVC was isolated from the callus culture of the bladder campion (Silene vulgaris). The main components in it were residues of D-galacturonic acid, galactose, arabinose, rhamnose, and protein. Using ion-exchange chromatography, ultrafiltration, and acid and enzymatic hydrolysis, it was shown that SVC contained a mixture of molecules of linear pectin, branched pectin polysaccharide, and pectin-protein polymer. A fragment of the linear chain of galacturonan amounted to more than half of the entire carbohydrate silenan chain. The branched area of the macromolecule is represented by rhamnogalacturonan I. The pectin-protein polymer consisted mainly of protein and weakly branched pectin fragments with molecular mass of more than 300 kDa.     

Cell wall formation in zoospores of Allomyces arbuscula

Carbohydrate composition was determined in isolated cell walls of meiospores of Allomyces arbuscula after incubation for 15 min (encysted meiospores: cysts), 150 min (germlings: cysts + rhizoids) and 24 h (cysts + rhizoids + hyphae). The principal constituent in all cell wall samples is chitin, accounting for about 75% of the recovered carbohydrates. In addition, cell walls of all stages examined contain polysaccharides which release galactose, glucose, mannose, arabinose, xylose, fucose, and rhamnose on acid hydrolysis. While different developmental stages show minor quantitative changes in chitin, the ratio of galactose to glucose decreases sharply during differentiation of ungerminated cysts into germlings with rhizoids and hyphae. The increase in glucose is accompanied by a decrease in the amount of xylose and/or fucose and of galactose.List of Abbreviation TFA trifluoroacetic acid     

The pectic components of plum fruits

Pectic substances were extracted from plum fruit tissue and the whole pectin, crude pectinic acid, purified pectinic acid and neutral fractions were prepared. Each of the fractions contained galacturonic acid, arabinose, galactose, xylose and rhamnose. High voltage electrophoresis indicated the presence of neutral and negatively charged material, and treatment with pectinesterase showed that the neutral component was completely esterified. The three cultivars of fruits studied showed close similarities. The results are consistent with proposed models of pectin structure and indicate the probable existence of a continuous gradation with respect to degree of esterification and molecular size.     

Pectin-modifying enzymes and pectin-derived materials: applications and impacts

Pectins are complex branched polysaccharides present in primary cell walls. As a distinctive feature, they contain high amount of partly methyl-esterified galacturonic acid and low amount of rhamnose and carry arabinose and galactose as major neutral sugars. Due to their structural complexity, they are modifiable by many different enzymes, including hydrolases, lyases, and esterases. Their peculiar structure is the origin of their physicochemical properties. Among others, their remarkable gelling properties make them a key additive for food industries. Pectin-degrading enzymes and -modifying enzymes may be used in a wide variety of applications to modulate pectin properties or produce pectin derivatives and oligosaccharides with functional as well as nutritional interests. This paper reviews the scientific information available on pectin structure, pectin-modifying enzymes, and the use of enzymes to produce pectin with controlled structure or pectin-derived oligosaccharides, with functional or nutritional interesting properties.     

Structural aspects of the exudate from the fruit of Chorisia speciosa St. Hil

Mature fruit of Chorisia speciosa yield an exudate (E-I) following mechanical injury. The polysaccharide contains rhamnose, arabinose, xylose, mannose, glucose, galactose and glucuronic acid in molar ratios of 20:11:1:3:2:40:23. The main chain of the structure is composed by beta-galactopyranosyl units linked (1 --> 3) and (1 --> 6) as indicated by NMR spectra and methylation data. Arabinosef and rhamnose are terminal residues. In order to compare E-I with the polysaccharides from the fruit mesocarp, the latter was submitted to different extractions. The water fraction contains rhamnose, arabinose, xylose, mannose, glucose, galactose and uronic acid in molar ratios of 18:4:1:2:3:44:28. It was treated with CTAB yielding a precipitate which was decomplexed with NaCl, giving four fractions. The fraction obtained using 0.15 M NaCl had a quantitative composition similar that of E-I.     

Water-soluble polysaccharides from Ginkgo biloba leaves.

The water-soluble polysaccharides from dried Ginkgo biloba leaves were isolated after exhaustive extraction with organic solvents. The polysaccharide mixture could be separated into a neutral (GF1) and two acidic (GF2 and GF3) polysaccharide fractions by ion exchange chromatography. According to the Mr distribution GF1 and GF3 seemed to be homogenous, whereas GF2 could be further fractionated into two subfractions (GF2a and GF2b) by gel permeation chromatography. GF1 (Mr 23,000) showed the structural features of a branched arabinan. The main chain was composed of 1,5-linked arabinose residues and three in 12 arabinose molecules were branched via C-2 or C-3. GF2a (Mr 500,000) consisted mainly of 1,2,4-branched mannose (29%), 1,4-linked glucuronic (32%) and galacturonic (8%) acid as well as terminal rhamnose (25%). After removal of ca 70% of the terminal rhamnose the remaining polysaccharide showed a decrease in 1,2,4-branched mannose and an increase in 1,2-linked mannose indicating that at least half of the rhamnose residues were linked to mannose via C-4. GF3 (Mr 40,000) consisted of 1,4-linked galacturonic (30%) and glucuronic (16) acid, 1,3,6-branched galactose (15%), 1,2-linked (5%) and 1,2,4-branched (3.5%) rhamnose as well as 1,5-linked arabinose (11%). Rhamnose (5%) and arabinose (10%) were present as terminal groups. Mild acid hydrolysis selectively cleaved arabinose and the remaining polysaccharide showed an increased amount of 1,6-linked and terminal galactose and a decreased quantity of 1,3,6-branched galactose. These results indicated that the terminal as well as the 1,5-linked arabinose were mainly connected to galactose via C-3. The GF3 polysaccharide appeared to be a rhamnogalacturonan with arabinogalactan side chains.     

Fractional purification and bioconversion of hemicelluloses

Hemicelluloses are types of plant cell wall polysaccharides, and the world's second most abundant renewable polymers after cellulose in lignocellulosic materials. They represent a type of hetero-polysaccharide with complex structure containing glucose, xylose, mannose, galactose, arabinose, rhamnose, glucuronic acid, and galacturonic acid in various amounts, depending on the source. Hemicelluloses are usually bonded to other cell-wall components such as cellulose, cell-wall proteins, lignin, and phenolic compounds by covalent and hydrogen bonds, and by ionic and hydrophobic interactions. This paper provides a review on hemicelluloses from lignocellulosic materials, especially in regard to their isolation and purification methods, and bioconversion. Current isolation and purification strategies are summarized, including: alkali peroxide extraction, organic solvent extraction, steam explosion, ultrasound-assisted extraction, microwave-assisted extraction, column chromatography, and membrane separation. In addition, the bioconversion of hemicelluloses including pretreatment, enzymatic hydrolysis, and fermentation are discussed.     

An arabinogalactan protein isolated from medium of cell suspension cultures of Silybum marianum (L.)Gaernt

Cell suspension cultures of Silybum marianum secreted polymers extracellularly containing 97% carbohydrates and 3% proteins. Fractionation of polysaccharides by anion-exchange chromatography yielded an unbound neutral fraction composed of glucose, xylose, galactose, arabinose and rhamnose and a bound fraction in which galactose and arabinose were predominantly found. The bound fraction specifically bind to Yariv phenylglycoside suggesting the presence of an arabinogalactan protein (AGP). Further purification of the AGP was done by precipitation of the culture medium with the Yariv reagent. The precipitated AGP eluated as single peak by gel permeation with an average molecular weight of 100. Eighteen aminoacids were detected, Ser, Gly, Glu, Asp, Thr and Hyp being the major ones. Linkage analysis showed terminal and 1,3-linked arabinose and almost all galactose was present in the 1,3-galactopyranoside form. The NMR spectral data revealed residues of galactopyranose and arabinofuranose as constituents of AGP. This study is the first examination of an AGP secreted by S. marianum cells in suspension culture.