Polysaccharides

This β-glucan contain D-glucose residues with β-1,3 links and b-1-6 side branches. The frequency, location, and length of the sidechains may play a role in immunomodulation. Differences in molecular weight, shape, and structure of β-glucans can also affect the differences in biological activity. The water-soluble β-D-glucan is extracted from fruiting bodies of Piptoporus betulinus by hot aqueous extraction, followed by freeze-thawing and dialysis. Methylation analysis and NMR spectroscopy, indicated the presence of a β-D-glucan with a main chain (1,3)-linked, substituted at O-6 by single glucose residues. The image was kindly provided by Dr. Chris Lawson.

Bacterial exopolysaccharide from gram negative Flavobacterium spp.

Gellan is a microbial polysaccharide produced by Pseudomonas elodea and generates gels with similar properties to agar. Gellan gum is a linear tetrasaccharide of (1,4)-β-L-rhamnopyranosyl, (1,3)-α-D-glucopyranosyl, (1,4)-β-D-glucuronopyranosyl, (1,4)-β-D-glucopyranosyl- with O(2) L-glyceryl and O(6) acetyl substituents on the 3-linked glucose. Both substituents are located on the same glucose residue, and on average, there is one glycerate per repeat and one acetate per every two repeats. In low acyl gellan gum, the acyl groups are removed completely. The high acyl form produces soft, elastic, non-brittle gels, whereas the low acyl form produces firm, non-elastic, brittle gels.

Sodium carboxymethyl dextran is a white, odourless and tasteless powder, which is freely soluble in water or electrolyte solutions. Applications that have been described for carboxymethyl dextran include carriers of paramagnetic contrast agents, preparation of conjugates of pharmacologically active compounds and carboxymethyl dextrans in biosensors.  A number of other uses in cosmetics, agriculture, foods, paints and textiles have been the subject of patent applications.

Sodium carboxymethyl dextran (CM-dextran) is a white, odourless and tasteless powder, which is freely soluble in water or electrolyte solutions. The product has a pronounced polyanionic character, due to the high degree of carboxyl substitution.  Applications that have been described for CM-dextran include carriers of paramagnetic contrast agents, preparation of conjugates of pharmacologically active compounds and CM-dextrans in biosensors.  A number of other uses in cosmetics, agriculture, foods, paints and textiles have been the subject of patent applications.

A fucan sulphate found in brown marine algae (Phaeophyta-typically Fucus vesiculotus, Ascophyllum nodosum, Alaria and Cladosiphon (illustrated) and has been shown to have anticoagulant activity. The main constituents are α-1,4 and α-1,2 linked L-fucose sulphates although galactose also occurs and there are many variations of the basic structure found in different species of Phaeophyta. The image was kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.

Sodium carboxymethyl dextran is a white, odourless and tasteless powder, which is freely soluble in water or electrolyte solutions. Applications that have been described for carboxymethyl dextran include carriers of paramagnetic contrast agents, preparation of conjugates of pharmacologically active compounds and carboxymethyl dextrans in biosensors.  A number of other uses in cosmetics, agriculture, foods, paints and textiles have been the subject of patent applications.

Chitosan is the deacetylated form of chitin.  The polysaccharide is deacetylated in order to render it soluble, which is then possible at pH values of less than 7 (normally in dilute acid).  This then allows the material to be used in a number of industrial applications as a binder and film former.

Sodium salt of a polysaccharide obtained from the brown seaweeds (e.g. Laminaria hyperborea, Fucus vesiculosus, Ascophyllum nodosum). The chemical structure consists of blocks of (1,4) linked-β-D-polymannuronic acid (poly M), (1,4) linked-α-L-polyguluronic acid (poly G) and alternating blocks of the two uronic acids (poly MG). Alginates form strong gels with divalent metal cations and the egg box model has been used to describe this form of gelation. The main use for alginate is in textile printing as a thickener in the printing of cottons with reactive dyes. In the food industry it is used as a thickener and gelling agent.  Recently, it has been shown that ternary mixtures of Konjac glucomannan, Xanthan gum and Sodium alginate can form a non-covalently linked complex which exhibits enhanced rheological properties of value in, for example, functional foods. The image was kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.High viscosity (500-500mPa.s).

Gum arabic is an exudate gum picked from Acacia trees growing in tropical arid regions (typically Acacia senegal and Acacia laetia). The polysaccharide is branched with a main chain of (1-3) linked β-D-galactopyranosyl units with side chains of (1-3) β-D-galactopyranosyl units joined to it by (1-6) links. The side chains are 2-5 units in length. Both the main chain and the side chains have attached units of α-L-arabinofuranosyl, α-L-rhamnopyranosyl, β-D-glucuronopyranosyl and 4-O-methyl-β-D-glucuronopyranosyl units.

The polysaccharide, known as glucuronoxylomannan - produced by fruit bodies and in pure culture conditions - has been shown to consist of a mannan backbone that is glycosylated with xylan and glucuronic acid chains in a regular repeating structure. Laboratory tests have associated a number of biological activities with Cryptococcus neoformans glucuronoxylomannan, including immunostimulatory, antidiabetic, anti-inflammatory, hypocholesterolemic, hepatoprotective, and antiallergic effects. The image was kindly provided by Dr. Chris Lawson.

Dextran is α-(1,6)-linked α-D-glucan with α-(1,3)-linked glucose branch points produced by fermentation of Leuconostoc mesenteroides via the action of the enzyme dextransucrase on sucrose.  The main use for native dextran is as an extender in blood transfusions and products having a range of sharp cut-off molecular weights are produced commercially for this and other applications.  A complex of Iiron with dextran, known as iron dextran, is used as a source of iron for baby piglets which are often anaemic at birth.

Rhodamine dextran (RD) is widely used as both an anterograde and retrograde tracer in neurons and for numerous other applications. It is biologically rather inert having α-1,6-linked glucose residues resistant to cleavage by most endogenous cellular glycosidases. It has low immunogenicity and makes an ideal long-term tracer for live cells. RD also serves as a valuable marker for cell loading of macromolecules by micro-injection, vesicular fusion, and electroporation, as well as for the uptake and internal processing of exogenous materials by phagocytotic and endocytic pathways.

Sodium carboxymethyl dextran is a white, odourless and tasteless powder, which is freely soluble in water or electrolyte solutions. Applications that have been described for carboxymethyl dextran include carriers of paramagnetic contrast agents, preparation of conjugates of pharmacologically active compounds and carboxymethyl dextrans in biosensors.  A number of other uses in cosmetics, agriculture, foods, paints and textiles have been the subject of patent applications.

Pustulan is a β-1,6-glucan isolated from Lasallia pustulata MW (20 kDa). It is recognized by the membrane bound Dectin-1, a C-type lectin-like pattern recognition receptor. Detection of β-glucans by Dectin-1 receptor leads to the CARD9-dependent activation of NF-κB and MAP kinases.  Studies have shown that pustulan can stimulate innate immune responses, inducing heat shock protein expression, eliciting phagocytosis, and production of pro-inflammatory cytokines. The image was kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.

A fucan sulphate found in brown marine algae (Phaeophyta-typically Fucus serratus, Ascophyllum nodosum, Laminaria japonica (illustrated) and Macrocystis pyrifyra) and has been shown to have anticoagulant activity. The main constituents are α-1,4 and α-1,2 linked L-fucose sulphates although galactose also occurs and there are many variations of the basic structure found in different species of Phaeophyta. The image was kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.

Locust bean (carob) gum is the refined endosperm of the seed of the carob tree, an evergreen of the legume family (Ceretonia siliqua). The tree grows extensively in Spain and is cultivated in many other Mediterranean countries. Locust bean gum, like guar gum, is a galactomannan with a backbone of (1,4) β-D-mannopyranosyl units having branches of (1,6)-linked α-D-galactopyranosyl units. However, locust bean gum has substantially fewer side chains than guar gum and these are clustered in blocks leaving longer regions of unsubstituted mannosyl regions. The gum is only partially soluble in water and suspensions require heating before solubility is achieved. As with guar, the polysaccharide forms gels with other gums such as carrageenan and xanthan. Applications are in the food industry to enhance texture, in paper making and in the textile industry.

Inulin is a prebiotic dietary fibre with a mildly sweet taste that promotes digestive health by supporting growth of healthy and balanced microbiota. In diagnostics, inulin is used for determining the glomerular filtration rate in functional kidney testing. Chemically, inulin is a chain of fructose molecules terminated at the reducing end with glucose. Thus, inulin is a fructan consisting of linear chains of β-(2,1) linked fructose residues, terminated at the reducing end by an α-D-(1,2)-glucopyranoside moiety.  It has a degree of polymerization typically between 2 and 60 (5). The β-(2,1) bond in inulin resists digestion in the gastrointestinal tract and is therefore responsible for its lower caloric value and beneficial effects on colon microbiota. A more functional form of inulin is produced by removing all fractions with chain lengths lower than 10.