Structural characteristics and biological effects of exopolysaccharide produced by cyanobacterium Nostoc sp.

Complex structure of cyanobacterium Nostoc sp. exopolysaccharide (EPS), with apparent molecular weight 214 × 103 g/mol, can be deduced from its composition. Chemical and NMR analyses found four dominant sugar monomers, namely (1 → 4)-linked α-l-arabinopyranose, ß-d-glucopyranose, ß-d-xylopyranose and (1 → 3)-linked ß-d-mannopyranose, two different uronic acids and a lactyl group, with (1 → 4,6)-linked ß-d-glucopyranose as the only branch point suggest a complex structure of this polymer. The dominant uronic acid is α-linked, but it remained unidentified. ß-d-Glucuronic acid was present in lower amount. Their position as well as that of lactyl remained undetermined too. Different doses of orally administered EPS in guinea pigs evoked a significant decrease in cough effort and a decrease in airway reactivity. The antitussive efficacy and bronchodilator effect of higher doses of EPS were found to be similar to that of the antitussive drug codeine and the antiasthmatic salbutamol. Without significant cytotoxicity on the RAW 264.7 cells, EPS stimulated the macrophage cells to produce pro-inflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), and prostaglandins (PGs) and nitric oxide (NO) via induction of COX-2 and iNOS expression, respectively, suggesting that this biopolymer potentiates an early innate immune response and can therefore be used as a new immune modulator.

Structural characterisation of polysaccharides from roasted hazelnut skins.

Two polysaccharide fractions sequentially extracted with water 1W and alkali 1A, were isolated from the hazelnut skins. The monosaccharide composition together with the FTIR and NMR analyses, indicated that both fractions are formed from a mixture of polysaccharides. The fraction 1W consists of methyl-esterified pectic polysaccharide with rhamnogalacturonan I blocks, branching with arabinose side chains, and with 1,5-, 1,3,5-arabinan and galactan polysaccharides. The fraction 1A is a mixture of deesterified rhamnogalacturonan I and 1,5-, 1,3,5-arabinan and 4-O-Me-glucuronoxylan polysaccharides. The presence of unsaturated galacturonic acid and the heterogeneity of the molecular weights, which Mw ranged between 3.6 and 39 kg mol-1, indicated the pectin degradation during roasting.

Bioactive hemicelluloses alkali-extracted from Fallopia sachalinensis leaves.

Fallopia sachalinensis, regarded as an invasive plant in Europe and designated for disposal, is traditionally used in Japan and China as herbal medicine. Attempted for valorization of the leaves, this paper reports on two protein-free polysaccharide fractions, a neutral (FS-5A) and an acidic (FS-5B) one, obtained via alkali extraction and consecutive purification. Both fractions were characterized by chemical, molecular, structural and bioactive properties. FTIR and 1D/2D NMR analyses revealed that FS-5A consisted of a fucogalactoxyloglucan, whereas, glucuronoxylan was the major hemicellulose in FS-5B accompanied with low proportions of fucosylated xyloglucan and pectic RG-I. Both hemicellulose fractions exhibited significant immunostimulating activity in the complement-fixation test and the latter had noticeable DPPH radical-scavenging ability. The results completed information about neutral and acidic bioactive polysaccharide components present in the leaves of F. sachalinensis.

Non-cellulosic polysaccharides from the leaves of small balsam (Impatiens parviflora DC.).

The leaves of the annual plant Impatiens parviflora DC., a herbal medicine in Asian countries and invasive in managed forests and natural environments in Central Europe, have the potential as a source of bioactive phenolic compounds and polysaccharides. Extractives accounted for ∼22% of the leaves, whereby, the methanolic extract contains mainly caffeic acid, ferulic acid, kaempferol, and quercetin derivatives, and 1,2,4-trihydroxynaphthalene-1-O-glucoside. From the pre-extracted leaves, non-cellulosic polysaccharides were isolated by a five-step extraction procedure using as extractants cold water, 0.05 M EDTA, and DMSO in the first three steps, and 1% and 5% NaOH in the last two steps. The isolated polysaccharide fractions were characterized by chemical, physicochemical, and spectroscopic analyses (FTIR and (1)H NMR). The first three fractions contained mainly pectin and the alkali-extracted ones methylglucuronoxylan and arabinogalactan. The suggested structural features were confirmed using HSQC NMR and COSY experiments for polysaccharides of the EDTA-fraction and the Pronase-treated 5% NaOH-fraction. The EDTA fraction comprised a pectin with low degree of methyl-esterification (DM, 37%) with few rhamnogalacturonan RG I segments bearing ß-1,4-galactan as side chains. The alkali-extracted fraction comprised a degraded methylglucuronoxylan and type II 3,6-arabinogalactan in about equal amounts.

Structural features of two heteroxylan polysaccharide fractions from wheat bran with anti-complementary and antioxidant activities.

Wheat bran is a rich source of bioactive substances ascribed to its arabinoxylan component. Two water-soluble arabinoxylans were sequentially extracted from wheat bran. WB1, released during enzymatic digestion of starch and protein, contained medium-branched arabinoxylan (A/X=0.88) consisting of 3-O-substituted (22%), di-substituted (19.8%) and 58% unsubstituted Xylp residues. It was slightly contaminated with (1→3,1→4)-ß-glucan and arabinogalactan, and free of protein. WB2 extracted with 0.5% NaOH contained ∼95% arabinoxylan (A/X=1.09). WB2 and two 5% NaOH-extracted arabinoxylans were rich in protein and phenolic compounds. All radical-scavenging assays indicated a relation with the protein and total phenolics contents. The protein-free WB1 displayed the highest hydroxyl radical scavenging effect indicating the distinct role of phenolic acids. The immunomodulatory activity of WB1 was somewhat lower, whereas, that of WB2 higher in comparison to the immunogenic polysaccharide PMII. The arabinoxylans have the potential as immuno-enhancing and antioxidant additives in functional foods.

Structural diversity of pectins isolated from the Styrian oil-pumpkin (Cucurbita pepo var. styriaca) fruit.

To evaluate the seeded fruit biomass of the Styrian oil-pumpkin in view of its pectin component, a series of acidic polysaccharides were isolated by a six-step sequential extraction using hot water, EDTA, dilute HCl (twice) and dilute and stronger NaOH solutions. Chemical, physicochemical and spectroscopy analyses revealed that the first four fractions comprised partially methyl-esterified and acetylated pectins with varying proportions of rhamnogalacturonan regions ramified with galactose- and arabinose-containing side chains and showed considerable polymolecularity. The alkali-extracted polysaccharides contained lower amounts of pectins with homogalacturonan and arabinose-rich rhamnogalacturonan regions next to hemicelluloses prevailing in the last polysaccharide. Using (1)H-(13)C HSQC and HMBC spectroscopy, the resonances of free and methylesterified galacturonic acid residues in the purified acid-extracted pectin were unambiguously established and various diads formed by both residues identified. The results might serve as a basis for searching technological conditions to produce pectin from the oil-pumpkin fruit biomass.

Suppressive effect of pectic polysaccharides from Cucurbita pepo L. var. Styriaca on citric acid-induced cough reflex in guinea pigs.

Several water-soluble pectic polysaccharides were isolated from the pumpkin fruit biomass and characterized by composition, structural features and molecular properties. The pectic polysaccharides were tested for antitussive activity by studying the effects of citric acid-induced cough reflex in guinea pigs and reactivity of the airway smooth muscle in vivo conditions in comparison to the narcotic drug codeine. Oral administration of all pectic polysaccharides from pumpkin inhibited the number of coughs induced by citric acid in guinea pigs, but to various extents. The results indicated that the antitussive activity of the pectic polysaccharides is affected by their molecular and structural properties, whereby a synergistic action between the polysaccharide and non-carbohydrate components on the biological response has been suggested as well. The cough depressive efficacy of most of the tested polysaccharides was comparable and even higher than that of codeine. Moreover, the application of these polysaccharides provoked any side effects what is their advantage towards the conventional opioid-derived antitussive agents.

The pharmacological activity of wheat bran polysaccharides.

(Glucurono)arabinoxylans were extracted from the wheat bran with acetate buffer in the first step (WBH1) and with dilute alkali in the second step (WBH2). In both samples xylose and arabinose dominated, accompanied with smaller amounts of galactose, glucose, mannose and uronic acids mainly in WBH1. WBH1 was free of protein and with low content of phenolic compounds. Fraction WBH2 contained relatively low levels of proteins and about 4.5% of the total phenolic. When tested for antitussive activity, the (glucurono)arabinoxylans exhibited comparable cough-suppressing effect with centrally acting codeine. The observed effects of bronchoconstriction are limiting practical application of WBH2.

Norway spruce galactoglucomannans exhibiting immunomodulating and radical-scavenging activities.

Wood-derived naturally acetylated galactoglucomannans (AcGGM) can be recovered even in ton-scale at mechanical pulp mills using spruce as raw material. These cell wall polysaccharides have a great potential as hydrocolloids and bioactive polymers in food and pharmaceutical applications, or as starting material for production of functional polymers. The immunostimulatory activity of both AcGGM and its deacetylated form (GGM) was now in vitro tested. The biological response of both AcGGM and GGM in the lymphocyte transformation test was dose-dependent. The direct mitogenic as well as comitogenic activities of the AcGGM were comparable to those of the immunogenic corn cob xylan used as control, and GGM showed significantly higher biological responses also at lower doses. In contrast to GGM, AcGGM possessed also DPPH radical-scavenging activity. The results suggested that the spruce AcGGM and GGM are potentially important as additives with immuno-potentiating and antioxidant properties in food products and pharmaceutical formulations.

Weak self-association in a carbohydrate system.

The physiological importance of weak interactions between biological macromolecules (molar dissociation constants >10 microM) is now well recognized, particularly with regard to cell adhesion and immunological phenomena, and many weak interactions have been measured for proteins. The concomitant importance of carbohydrate-carbohydrate interactions has also been identified, although no weak interaction between pure carbohydrate systems has ever been measured. We now demonstrate for the first time to our knowledge using a powerful probe for weak interactions--sedimentation velocity in the analytical ultracentrifuge--that at least some carbohydrates (from the class of polysaccharides known as heteroxylans and demonstrated here to be biologically active) can show well-defined weak self-interactions of the "monomer-dimer" type frequently found in protein systems. The weak interaction between the heteroxylans is shown from a temperature dependence study to be likely to be hydrophobic in nature.

Effect of salt stress on the production and properties of extracellular polysaccharides produced by Cryptococcus laurentii.

The composition, main structural features and molecular properties of exopolysaccharides (EP) produced by Cryptococcus laurentii var. laurentii CCY 17-3-16 under optimal (EPo) and NaCI-stress conditions (EPs) as well as their subfractions isolated by gel chromatography were studied using chemical, FT-IR and NMR spectroscopy methods. The results showed that under stress conditions the yeast produced EP with a lower content of protein and phosphorus. In comparison to EPo, the EPs exhibited a substantially larger proportion of high molecular mass populations. NMR analysis of EPs revealed a higher degree of branching with single xylose side chains of the heteromannan components. The increase of the molecular mass and degree of branching of the macromolecular chains of the heteromannan components might in part be related to the function of EPs to protect the yeast cells from water loss and maintain growth conditions under the salt stress.