Polypotency of the immunomodulatory effect of pectins.

Pectins are the major component of plant cell walls, and they display diverse biological activities including immunomodulation. The pectin macromolecule contains fragments of linear and branched regions of polysaccharides such as homogalacturonan, rhamnogalacturonan-I, xylogalacturonan, and apiogalacturonan. These structural features determine the effect of pectins on the immune system. The backbones of pectic macromolecules have immunosuppressive activity. Pectins containing greater than 80% galacturonic acid residues were found to decrease macrophage activity and inhibit the delayed-type hypersensitivity reaction. Branched galacturonan fragments result in a biphasic immunomodulatory action. The branched region of pectins mediates both increased phagocytosis and antibody production. The fine structure of the galactan, arabinan, and apiogalacturonan side chains determines the stimulating interaction between pectin and immune cells. This review summarizes data regarding the relationship between the structure and immunomodulatory activity of pectins isolated from the plants of the European north of Russia and elucidates the concept of polypotency of pectins in native plant cell walls to both stimulate and suppress the immune response. The possible mechanisms of the immunostimulatory and anti-inflammatory effects of pectins are also discussed.

Influence of the fungus Trichoderma harzianum on the enzyme and polysaccharide composition of Silene vulgaris Callus.

Activities of polygalacturonase and 1,3-ß-glucanase increased in campion (Silene vulgaris) callus cells during co-cultivation with the fungus Trichoderma harzianum. This was associated with a decrease in galacturonic acid residues in the pectic polysaccharide of campion silenan and also in the production of pectin by the callus. Co-cultivation of the callus and the fungus resulted in an increase in contents of arabinose residues in the intracellular arabinogalactan and in contents of galactose residues in the extracellular arabinogalactan.

Synthesis of sulfated pectins and their anticoagulant activity.

The following pectins were sulfated: bergenan BC (the pectin of Bergenia crassifolia L), lemnan LM (the pectin of Lemna minor L), and galacturonan as a backbone of pectins. Pyridine monomethyl sulfate, pyridine sulfotrioxide, and chlorosulfonic acid were used as reagents for sulfation. Chlorosulfonic acid proved to be the optimal reagent for sulfation of galacturonan and other pectins. Galacturonan and pectin derivatives with different degrees of sulfation were synthesized and their anticoagulant activities were shown to depend on the quantity of sulfate groups in the pectin macromolecules.

Modification of polysaccharides from callus culture of Silene vulgaris (M.) G. using carbohydrases in vitro.

Polysaccharides (pectin and intracellular and extracellular arabinogalactans) were isolated from campion callus culture cultivated on medium with varied concentrations of pectinase and beta-galactosidase. A decrease in contents of arabinose residues in pectin and arabinogalactans and of galactose residues in arabinogalactans was associated with an increase in the activities of alpha-L-arabinofuranosidase and beta-galactosidase upon addition of pectinase into the medium. Pectinase destroyed the high-molecular-weight (more than 300 kD) fraction of pectin and decreased the content of galacturonic acid residues. alpha-L-Arabinofuranosidase transformed arabinogalactan into galactan, and galactan was destroyed under the influence of galactosidase. The contents of arabinogalactan and/or galactan in the cells were decreased, and it was released into the culture medium. Pectin samples with low contents of arabinose and galactose in the side chains and galactan samples were obtained from the callus grown on the medium with beta-galactosidase. Cultivation of the plant cells on medium containing carbohydrases resulted in modification of pectin and arabinogalactan of the cell walls.

Chemical characterization and anti-inflammatory effect of rauvolfian, a pectic polysaccharide of Rauvolfia callus.

The pectic polysaccharide named rauvolfian RS was obtained from the dried callus of Rauvolfia serpentina L. by extraction with 0.7% aqueous ammonium oxalate. Crude rauvolfian RS was purified using membrane ultrafiltration to yield the purified rauvolfian RSP in addition to glucan as admixture from the callus, with molecular weights 300 and 100-300 kD, respectively. A peroral pretreatment of mice with the crude and purified samples of rauvolfian (RS and RSP) was found to decrease colonic macroscopic scores, the total area of damage, and tissue myeloperoxidase activity in colons as compared with a colitis group. RS and RSP were shown to stimulate production of mucus by colons of the colitis mice. RSP appeared to be an active constituent of the parent RS. The glucan failed to possess anti-inflammatory activity.

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 beta-1,3-D-galactopyranan. Some of the beta-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 beta-galactopyranose, terminal alpha-arabinofuranose and alpha-rhamnopyranose, and 2-O-substituted alpha-rhamnopyranose. The alpha-rhamnopyranose residues in the sugar chain appeared to be 2-O-glycosylated by the beta-1,4-D-galactopyranosyl uronic acid residues.

Branching of the galacturonan backbone of comaruman, a pectin from the marsh cinquefoil Comarum palustre L.

Galacturonan, the main constituent of the backbone (core) of the comaruman macromolecule, a pectin from the marsh cinquefoil Comarum palustre L., was obtained on partial acid hydrolysis of the pectin. Using atomic force microscopy and methylation analysis of the galacturonan, the backbone of the comaruman macromolecule was shown to contain branches as side chains consisting of alpha-1,4-linked residues of D-galactopyranosyl uronic acid attached to the 2- and 3-positions of the galacturonic acid residues of the core, in addition to linear regions of alpha-1,4-D-galacturonan. A few side chains appear to attach to 2,3-positions of the D-galacturonic acid residues.

Structural studies on pectin from marsh cinquefoil Comarum palustre 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.

Antiinflammatory activity of the pectic polysaccharide from Comarum palustre.

A pectic polysaccharide named comaruman (CP) was extracted from the aerial part of Comarum palustre with 0.7% aqueous ammonium oxalate and subsequent precipitation with ethanol. Oral administration of comaruman (5-100 mg/kg) was found to reduce a paw edema observed 24 h after injection of 2% formalin in mice. A fraction of comaruman (CP-H9) exhibited a similar antiinflammatory activity. Comaruman, CP deprived of lipid, CP purified by proteins and CP fractions obtained with acidic hydrolysis inhibit spontaneous and phorbol-12-myristate-13-acetate-activated adhesion of peritoneal leukocytes in vitro.

Adhesion of human neutrophils to fibronectin is inhibited by comaruman, pectin of marsh cinquefoil Comarum palustre L., and by its fragments.

Earlier, we detected antiinflammatory action of comaruman, pectin of the marsh cinquefoil Comarum palustre L. This effect can be explained by new data concerning inhibition of adhesion of human neutrophils to fibronectin by comaruman and its fragments. The galacturonan backbone fragment of molecular mass >10 kD appears to be the active region of the comaruman macromolecule. Comaruman CP (50-200 microg/ml) was found to decrease adhesion of neutrophils stimulated by phorbol 12-myristate 13-acetate (PMA, 1.625 microM) and by dithiothreitol (DTT, 0.5 mM). The fragments of comaruman CP-H (100 kD), CP-H1 (10-50 kD), and CP-H2 (100 kD) obtained by acidic hydrolysis and representing regions of linear polygalacturonan are shown to inhibit neutrophil adhesion more than the crude pectin. A fragment CP-E (<10 kD) obtained using pectinolysis and representing a branched region of the comaruman macromolecule failed to influence cell adhesion. The parent comaruman CP as well as fragments of its polygalacturonan backbone diminish PMA-initiated generation of oxygen radicals in neutrophils.

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.

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 alpha-1,4-D-galacturonan. The ramified regions consist of linear alpha-1,2-L-rhamno-alpha-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 beta-galactopyranose residues or a branching beta-1,4-galactopyranan bearing 4,6-substituted beta-D-galactopyranose residues as branched points. In addition, the ramified regions contain side chains of a branched alpha-1,5-arabinofuranan possessing 2,5- and 3,5-substituted alpha-L-arabinofuranose residues as branching points. Some side chains of rhamnogalacturonan appear to be arabinogalactan which contains branched sugar chains of alpha-1,5-arabinofuranan attached to the linear chains of beta-1,4-galactopyranan by 1,3- and 1,6-linkages. The residues of alpha-L-arabinofuranose seem to occupy the terminal positions of the arabinogalactan side chains.