Isolation and structural study of polysaccharides from campion Silene vulgaris

Silenan SV, a pectic polysaccharide, was isolated from the aerial part of Silene vulgaris (Moench) Garke (Oberna behen (L.) Ikonn.), widespread through the European North of Russia. The polysaccharide was found to contain residues of galacturonic acid (63%), arabinose, galactose, and rhamnose as the main constituents. The results of a partial acidic hydrolysis, pectinase digestion, and NMR studies of silenan SV indicated that its molecule contains a linear alpha-1,4-D-galacturonan backbone and ramified regions. The core of the ramified regions is composed of residues of alpha-1,4-D-galacturonic acid along with 2-substituted alpha-rhamnopyranose residues. The NMR data showed that the silenan SV side chains are composed of the blocks built from the terminal alpha-1,5-linked arabinofuranose and beta-1,4-linked galactopyranose residues; these most likely are the side chains of rhamnogalacturonan, characteristic of other pectic polysaccharides. The nonreducing ends of these side chains contain alpha-arabinofuranose residues.     

Structural studies of the pectic polysaccharide from duckweed Lemna minor L

The pectic polysaccharide of duckweed Lemna minor L. termed lemnan (LM) was shown to contain the ramified, "hairy" region. Using partial acid hydrolysis and Smith degradation followed by NMR spectroscopy of the fragments obtained, some structural features of the hairy region of LM were elucidated. Partial acid hydrolysis of LM afforded the crude polysaccharide fraction LMH that was separated into two polysaccharide fractions: LMH-1 and LMH-2. In addition, the oligosaccharide fraction LMH-3 contained 97% D-apiose was obtained from the supernatant. A further more rigorous acidic hydrolysis of LMH led to the crude polysaccharide fraction LMHR which was separated in to two fractions: LMHR-1 and LMHR-2. Smith degradation of LMH afforded the polysaccharide fragment LMHS differed in low contents of apiose residues. Unfortunately, NMR-spectroscopy failed to provide significant evidence concerning the structure of LMH-1 due to the complexity of the macromolecule. The structure of the 1H/13C-NMR spectroscopy including the correlation 2D NMR spectroscopy. As a result, alpha-1,4-D-galactopyranosyluronan was confirmed to be the main constituent of the LM backbone. In addition, the ramified, "hairy" region of the macromolecule appeared to contain segments consisting of residues of terminal and beta-1,5-linked apiofuranose, terminal and alpha-1,5-linked arabinofuranose, terminal and beta-1,3- and beta-1,4- linked galactopyranose, the terminal and beta-1,4-linked xylopyranose, and beta-1,4-linked 2-mono-O-methyl xylopyranose. Analytical and NMR-spectral data of LMHS confirmed the presence of considerable amounts of the non-oxidized of 1,4-linked D-galactopyranosyl uronic acid residues. Thus, some side chains of the ramified region of lemnan appeared to attach to D-galactopyranosyl uronic acid residues of the backbone.     

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.     

Structural Studies on Pectin from Marsh Cinquefoil <Emphasis Type="Italic">Comarum palustre</Emphasis> L.

Pectin with [alpha]D(20) +192 degrees (c 0.1; water), named comaruman, was isolated from marsh cinquefoil Comarum palustre L., which is widespread in the European North. The sugar chain of comaruman contains residues of D-galacturonic acid (64%), D-galactose (13%), L-rhamnose (12%), L-arabinose (6%), and trace amounts of xylose and glucose. Partial acid hydrolysis and digestion with pectinase demonstrated that comaruman composed of the backbone comprised regions of linear alpha-1,4-D-galactopyranosyl uronan interconnected by numerous residues of alpha-1,2-L-rhamnopyranose. In addition to the backbone (core of the macromolecule), ramified regions are involved in comaruman and comprise alpha-2,4-L-rhamno-alpha-4-D-galacturonan with side chains consisting mainly of beta-1,4-linked residues of D-galactopyranose. The ramified region contains additionally residues of 5-O-substituted arabinofuranose and 3- and 6-O-substituted galactopyranose. The present 3,4- and 4,6-di-O-substituted residues of galactopyranose appear to be branching points of the side chains. Some galactopyranose residues were found to occupy the terminal positions of the side chains or appeared to be single sugar residues attached to the side chains. Methylation analysis data indicated that comaruman contains residues of terminal, 3- and 3,4-di-O-substituted galactopyranosyl uronic acid, which appeared to be constituents of the side chains, and the latter represented additionally branching points of the backbone.     

Structure of Silenan, a Pectic Polysaccharide from Campion Silene vulgaris (Moench) Garcke

A pectic polysaccharide named silenan, [alpha]D20 +148.6 degrees (c 0.1; H2O), was isolated earlier from the aerial part of campion, Silene vulgaris (Moench) Garcke. Silenan has been shown to contain homogalacturonan segments as "smooth regions" and rhamnogalacturonan fragments as "hairy regions". The present study reveals a generalization of structural features of silenan. Silenan was subjected to enzymic digestion with pectinase, to Smith degradation, and to lithium-degradation to determine the conforming poly- and oligosaccharide fragments of "hairy regions" of silenan. The NMR-spectral data and mass-spectrometry confirmed that the core of the ramified region of silenan consisted of residues of alpha-rhamnopyranose 2-O-glycosylated with the residues of alpha-1,4-D-galactopyranosyl uronic acid. The part of the alpha-rhamnopyranose residues of the backbone are branched at O-4. On the basis of the data, the hairy regions of silenan proved to contain mainly linear chains of beta-1,3-, beta-1,4-, and beta-1,6-galactopyranan and alpha-1,5-arabinofuranan. The side chains of the ramified region were shown to have branching points represented 2,3-, 3,6-, 4,6-di-O-substituted beta-galactopyranose residues.     

Polysaccharides from the callus tissue of the rowan tree Sorbus aucuparia L. stem

Polysaccharide fractions SAcI and SAcII were isolated from callus tissues of rowan tree stems. The SAcI fraction was shown to contain compounds belonging to the arabinogalactan II group. The SAcII fraction, called sorban, comprised pectic polysaccharides composing the protopectin complex of the cell wall callus. The SAcII fraction was found to contain a large amount of galacturonic acid residues and a set of neutral sugars characteristic of rhamnogalacturonan I. The composition and properties allowed a suggestion that the sorban backbone is mainly formed by 1,4-α-D-galactopyranosyluronic acid residues, while the neutral sugars are represented by 1,4-linked glucopyranose and xylopyranose residues, 1,5-linked arabinofuranose, 1,6-linked galactopyranose and mannofuranose residues as well as terminal glucopyranose and xylopyranose residues. The callus growth was shown to be associated with nearly a constant content of galacturonic acid and neutral sugar residues in sorban (fraction SAcII).     

Structural features of the hemicellulose a from the stem of Mimosa bracatinga

The hemicellulose A from the stem of Mimosa bracatinga contains residues of d-xylose and 4-O-methyl-d-glucuronic acid. Smith-degradation and methylation data indicate it to consist of a backbone of (1 → 4)-linked β-d-xylopyranosyl residues with side chains consisting of single units of 4-O-methyl--d-glucosyluronic acid attached to position 3. The branched structure was also indicated by Smith-degradation and methylation analysis of the oligosaccharides obtained by enzymic hydrolysis of the hemicellulose.     

Structural studies of arabinogalactan and pectin from Silene vulgaris (M.) G. callus

Arabinogalactan and pectin (named silenan) were isolated from Silene vulgaris (M.) G. callus. Fractionation by ion-exchange chromatography on DEAE-cellulose and digestion with pectinase demonstrated that silenan from S. vulgaris callus (80% of D-galacturonic acid) and silenan from the aerial part of the campion S. vulgaris are similar: both pectins contain a high quantity of homogalacturonan segments. The NMR spectral data and mass spectrometry of the purified polysaccharide and its fragment obtained by Smith degradation confirmed that the core of the arabinogalactan consisted of the different segments of β-1,3-D-galactopyranan. Some of the β-galactopyranose residues of the backbone are branched at O-6. The side chains of the arabinogalactan were shown to contain residues of terminal and 3-O-substituted β-galactopyranose, terminal α-arabinofuranose and α-rhamnopyranose, and 2-O-substituted α-rhamnopyranose. The α-rhamnopyranose residues in the sugar chain appeared to be 2-O-glycosylated by the β-1,4-D-galactopyranosyl uronic acid residues. Published in Russian in Biokhimiya, 2006, Vol. 71, No. 6, pp. 798–807.     

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.     

Streptococcus pneumoniae type XIV polysaccharide: synthesis of a repeating branched tetrasaccharide with dioxa-type spacer-arms

β-Glycosides of 2-acetamido-2-deoxy- -glucopyranose were synthesized, using either 7-methoxycarbonyl-3,6-dioxa-1-heptanol or 8-azido-3,6-dioxa-1-octanol. Selective β-lactosylation of 7-methoxycarbonyl-3,6-dioxaheptyl 2-acetamido-3-O-benzyl-2-deoxy-β- -glucopyranoside with hepta-O-acetyl-lactosyl-trichloroacetimidate, followed by β-galactosylation of the secondary hydroxyl group with O-(2,3,4,6-tetra-O-acetyl-- -galactopyranosyl)trichloroacetimidate, catalytic hydrogenolysis, and O-deacetylation, gave 7-methoxycarbonyl-3,6-dioxaheptyl 2-acetamido-2-deoxy-4-O-β- -galactopyranosyl-6-O-(4-O-β- -galactopyranosyl-β- -glucopyranosyl)β- -glucopyranoside. Selective β-lactosylation of 8-azido-3,6-dioxaocytl 2-acetamido-3-O-benzyl-2-deoxy-β- -glucopyranoside with hepta-O-acetyl-lactosyl bromide in the presence of silver triflate, followed by condensation with 2,3,4,6-tetra-O-acetyl-- -galactopyranosyl bromide in the presence of silver triflate, catalytic hdyrogenolysis, and O-deacetylation, gave 8-azido-3,6-dioxaoctyl 2-acetamido-2-deoxy-4-O-β- -galactopyranosyl-6-O-(4-O-β- -galactopyranosyl-β- -glucopyranosyl)-β- glucopyranoside.     

The isolation, preliminary structural studies, and physiological activity of water-soluble polysaccharides from the squeezed berries of the snowball treeViburnum opulus

Water-soluble polysaccharide fractions VO1–VO4 were isolated from the squeezed berries of the snowball tree (Viburnum opulus) by successive extraction with water at various temperatures and pH and with aqueous solutions of ammonium oxalate. These fractions were purified by ion-exchange chromatography on DEAE cellulose, and the homogeneity of the purified polysaccharides was determined by gel filtration on Sephacryl S-500. Acidic polysaccharides close to pectins in their sugar composition were found in all the extracts (fractions VO1-1, VO2-1, VO3-2, and VO4-2). Residues of galacturonic acid, galactose, arabinose, and (to a lesser extent) rhamnose are their main constituents. Neutral polysaccharides composed mainly of galactose and mannose residues were additionally found in fractions extracted with acidified water (pH 4.0) and with aqueous ammonium oxalate solutions. Partial acidic hydrolysis and digestion with pectinase of acidic polysaccharides indicated that their carbohydrate backbone consists of α-1,4-linked residues ofD-galacturonic acid. NMR spectra of acidic polysaccharides (fractions VO3-2 and VO3-3) confirmed this and demonstrated that their side oligosaccharide chains are composed of β-1,4-linked galactopyranose residues and of terminal and 2,5- and 3,5-substituted residues of α-arabinofuranose at a Gal : Ara ratio of 3 : 1. Some polysaccharides fromV. opulus were found to possess an immunostimulating activity: they enhance phagocytosis, in particular, the phagocytic index and the secretion of lysosomal enzymes with peritoneal macrophages. Calcium ions were found to be necessary for the appearance of the stimulating effect of acidic polysaccharides fromV. opulus.     

Mango ripening--chemical and structural characterization of pectic and hemicellulosic polysaccharides

Ripening of mango is characterized by a gradual, but natural softening of the fruit, which is due to progressive depolymerization of pectic and hemicellulosic polysaccharides with significant loss of galactose, arabinose and mannose residues at the ripe stage. Structural characterization employing permethylation followed by GC-MS analysis, IR and ¹³C NMR measurements revealed the major CWS fractions of both unripe and ripe mangoes to be of variable molecular weights and having a 1,4-linked galactan/galacturonan backbone, which is occasionally involved in side chain branches consisting of single residues of galactose and arabinose or oligomeric 1,5-linked arabinofuranose residues linked through 1,3-linkages; whereas the major hemicellulosic fractions of unripe mango to be of xyloglucan-type having 1,4-linked glucan backbone with branching by non-reducing terminal arabinose and xylose residues.     

Pectin polysaccharides of rowan Sorbus aucuparia L.

Water-soluble polysaccharide fractions were extracted from the fruit of rowan Sorbus aucuparia L. by water and 0.7% ammonium oxalate water solution. The total yield was 4.2%. It is demonstrated that these fractions are pectin polysaccharides, and their carbon chains are primarily composed of galactunoric acid residue (up to 68%), arabinose and galactose. Sephacryl S-500 gelfiltration of rowan fruit pectin polysaccharides proved their relative homogeneity pertaining to their molecular weights, whereas endo-polygalacturonase enzymatic hydrolysis gives evidence of the presence of extended galacturonan (rhamnogalacturonan) ranges in their carbohydrate chains. Methylation of rowan pectin polysaccharides shows that their carbohydrate pendants are formed by 1,5-linked arabinofuranose residue, 1,4-linked glucopyranose residue, 1,6-linked galactopyranose residue, 1,3,6-linked mannopyranose residue and 1,3,6-linked galactopyranose residue. Glucopyranose residue is identified at non reducible ends of these pendants. It was demonstrated that antioxidant activity of water solutions of pectin polysaccharides extracted from rowan S. aucuparia L. (0.5 mg/mL) is 37?C53% of trolox activity, which is 100%.     

Polysaccharide component in the stigmatic exudate from Lilium longiflorum

The polysaccharide component of the stigmatic exudate from Lilium longiflorum has the composition, arabinose (26%), rhamnose (6%), galactose (57%) and glucuronic acid (11%). The highly branched polysaccharide bears a striking resemblance to the acidic polysaccharide exudate from Araucaria bidwillii in belonging to the galactan group and in carrying outer chains terminated by arabinofuranose, rhamnopyranose, galactopyranose and glucuronic acid residues. Both polysaccharides contain the sequence O-rhamnopyranosyl-(1→4)-glucopyranosyluronic acid-(1→6)-galactopyranose in some of the outer chains.     

Pectin Biosynthesis: GALS1 in Arabidopsis thaliana Is a β-1,4-Galactan β-1,4-Galactosyltransferase

β-1,4-Galactans are abundant polysaccharides in plant cell walls, which are generally found as side chains of rhamnogalacturonan I. Rhamnogalacturonan I is a major component of pectin with a backbone of alternating rhamnose and galacturonic acid residues and side chains that include α-1,5-arabinans, β-1,4-galactans, and arabinogalactans. Many enzymes are required to synthesize pectin, but few have been identified. Pectin is most abundant in primary walls of expanding cells, but β-1,4-galactan is relatively abundant in secondary walls, especially in tension wood that forms in response to mechanical stress. We investigated enzymes in glycosyltransferase family GT92, which has three members in Arabidopsis thaliana, which we designated GALACTAN SYNTHASE1, (GALS1), GALS2 and GALS3. Loss-of-function mutants in the corresponding genes had a decreased β-1,4-galactan content, and overexpression of GALS1 resulted in plants with 50% higher β-1,4-galactan content. The plants did not have an obvious growth phenotype. Heterologously expressed and affinity-purified GALS1 could transfer Gal residues from UDP-Gal onto β-1,4-galactopentaose. GALS1 specifically formed β-1,4-galactosyl linkages and could add successive β-1,4-galactosyl residues to the acceptor. These observations confirm the identity of the GT92 enzyme as β-1,4-galactan synthase. The identification of this enzyme could provide an important tool for engineering plants with improved bioenergy properties.     

Structure of tanacetan,a pectic polysaccharide from tansy Tanacetum vulgare L

Tanacetan TVF was found to have a branched structure with a backbone of linear -1,4-D-galacturonan. The ramified regions consist of linear -1,2-L-rhamno--1,4-D-galacturonan as the core. The side chains appear to attach to the 4-position of the L-rhamnopyranose residues. They are present as single -galactopyranose residues or a branching -1,4-galactopyranan bearing 4,6-substituted -D-galactopyranose residues as branched points. In addition, the ramified regions contain side chains of a branched -1,5-arabinofuranan possessing 2,5- and 3,5-substituted -L-arabinofuranose residues as branching points. Some side chains of rhamnogalacturonan appear to be arabinogalactan which contains branched sugar chains of -1,5-arabinofuranan attached to the linear chains of -1,4-galactopyranan by 1,3- and 1,6-linkages. The residues of -L-arabinofuranose seem to occupy the terminal positions of the arabinogalactan side chains.     

An Antioxidant Acidic Polysaccharide from Cuscuta chinensis

An acidic polysaccharide, H2, was isolated from the alkali-extract CHC of seeds of Cuscuta chinensis Lam. with the molecular weight more than 1.0×106. Chemical and spectroscopic studies led to the structure determination as follows: the backbone chain consists of 1,6-linked-β- D Galp, 1,4-linked-β- D Galp, 1,4-linked-β- D GalA and 1,2- or 1,4-linked-β- L Rhap having branching points at position O-3 of some 1,6-linked-β- D Galp residues (one among eight) and O-4 or O-2 of 1,2- or 1,4-linked-β- L Rhap residues to terminal β-D-galactopyranose. The side chains composed of terminal Galp, 1,6-linked-β- D Galp, 1,4-linked β- D Galp and 1,3,6-linked-β- D Galp also linked at position O-3 of 1,6-linked-β- D Galp residues in the backbone chain. β- L -arabinofuranosyl and terminal β- L -rhamnopyranosyl residues existed in the periphery of this polysaccharide linked to O-3 of 1,6-linked-β- D Galp residues in the backbone chain and the side chains. The polysaccharide H2 increased significantly the survival rate of PC12 cells indicating that it had protective effects against H2O2 insult.     

Chemical structure of kenaf xylan

Methylation and partial acid hydrolysis of xylans from the bast and core of kenaf (Hibiscus cannabinus) showed that the main chain of these xylans consists of (1 → 4)-linked β-d-xylopyranosyl (Xylp) residues, some of which carry a -1,2-linked 4-O-methyl-glucopyranosyluronic acid (Me-GlcAp) and glucopyranosyluronic acid (GlcAp) residues as side chains. Partial hydrolysis of kenaf xylans afforded two series of aldouronic acids from aldobio- to aldotetraouronic acids. The acids of the first series composed of 4-O-Me-d-GlcAp and d-Xylp residues: 4-O-Me-GlcA-Xyl₃, 4-O-Me-GlcA-Xyl₂ and 4-O-Me-GlcA-Xyl. The second series composed of d-GlcAp and d-Xylp: GlcA-Xyl₃, GlcA-Xyl₂ and GlcA-Xyl.

In addition to these acids, another aldobiouronic acid, 4-O-(-d-GalAp)-d-Xyl was found to be present in the partial hydrolysate.

The molar ratio of GalA, GlcA, 4-O-Me-GlcA, and Xyl residues was calculated to be 1.0:2.0:9.4:119 for the bast xylan and 1.0:1.3:7.9:99.4 for the core xylan.     

Structure of Plant Cell Walls : XII. Identification of Seven Differently Linked Glycosyl Residues Attached to O-4 of the 2,4-Linked l-Rhamnosyl Residues of Rhamnogalacturonan I

Seven differently linked glycosyl residues have been found to be glycosidically linked to O-4 of the branched 2,4-linked l-rhamnosyl residues contained in the rhamnosyl and galacturonosyl backbone of the cell wall pectic polysaccharide rhamnogalacturonan I. These seven glycosyl residues are, therefore, the first residues of at least seven different side chains attached to the rhamnogalacturonan backbone. These first side chain glycosyl residues are 5-linked l-arabinofuranosyl and terminal 3-, 4-, 6-, 2,6-, and 3,6-linked d-galactopyranosyl residues. The existence of at least seven different side chains in rhamnogalacturonan I indicates that rhamnogalacturonan I is either an exceedingly complex polysaccharide or that rhamnogalacturonan I is a family of polysaccharides with similar or identical rhamnogalacturonan backbones substituted with different side chains.     

Cordiachromes from Auxemma oncocalyx

Further cordiachromes, rel-10,11β-epoxy-11-ethoxy-8-hydroxy-2-methoxy-8aβ-methyl-5,6,7,8,8a,9,10aβ-octahydro-1,4-anthracendione, 6-formyl-2-methoxy-9-methyl-7,8-dihydro-1,4-phenanthrendione, rel-8,11;9,11-diepoxy-1,4-dihydroxy-2-methoxy-8aβ-methyl-5,6,7,8,8a,9,10,10aβ-octahydro-10-anthracenone, rel-9,11-epoxy-1,4,8-trihydroxy-2-methoxy-8aβ-methyl-5,6,7,8,8a,9,10,10aβ-octahydro-10-anthracenone, rel-2″-methoxy-7″-methyl-1″,4″-naphtalendione-(6″→5)-tetrahydropyran-(2-eq→O→2ax)-tetrahydropyran-(5′→6)- 2-methoxy-7-methyl-1,4-naphthalendione, together with the known, allantoin, sitosterol and 3β-O-d-glucopyranosylsitosterol, have been isolated from Auxemma oncocalyx. Their structures were determined from spectral data, including 2D NMR experiments.