Polysaccharides

Dextran sulphate is a dextran derivative whose ulcer (colitis) -causing properties were first reported in hamsters and extrapolated a few years later to mice and rats. The exact mechanisms through which dextran sulphate induces intestinal inflammation are unclear but may be the result of direct damage of the monolayer of epithelial cells in the colon, leading to the crossing of intestinal contents (for e.g. commensal bacteria and their products) into underlying tissue and therefore induction of inflammation.  The dextran sulphate sodium-induced ulceration model in laboratory animals has some advantages when compared to other animal models of colitis due to its simplicity and similarities to human inflammatory bowel disease.  MW is in the range of 40,000Da

Starch is an energy storing polysaccharide produced by higher plants and some algae. Pure starch is a white, tasteless and odorless powder that is insoluble in cold water or alcohol. It consists of two types of polysaccharide: the linear and helical amylose (α-1,4-linked glucose) and the branched amylopectin (α-1,4 and α-1,6-linked glucose). Depending on the plant, starch generally contains 20 to 25% amylose and 75 to 80% amylopectin by weight.

Xylan is the most abundant noncellulosic polysaccharide present in both hardwoods and annual plants. Xylan is found mainly in the secondary cell wall as part of the hemicellulose fraction and is considered to form an interface between lignin and other polysaccharides. In their simplest forms, xylans are linear homopolymers of β-1,4-xylose residues but can also form complex heterogenous and polydispersed glycans.

Glycogen is a highly branched polysaccharide of glucose that serves as a form of energy storage in animals and fungi. It is the main storage form of glucose in the body.  In humans, glycogen is made and stored primarily in liver and muscle cells and functions as the second most important energy storage molecule to fat which is held in adipose tissue. Glycogen is analogous to starch and has a structure similar to amylopectin, but is more extensively branched and compact than starch. It occurs as granules in the cytosol/cytoplasm in many cell types, and plays an important role in the glucose cycle.

In water, hydroxypropyl cellulose forms liquid crystals with many mesophases depending on concentration. These mesophases include isotropic, anisotropic, nematic and cholesteric, the latter resulting in many colors such as violet, green and red. Pharmaceutical applications include treatments for medical conditions such as dry eye syndrome (keratoconjunctivitis sicca), recurrent corneal erosions, decreased corneal sensitivity, exposure and neuroparalytic keratitis. It is also used as a binder in tablets. Hydroxypropylcellulose is also used as a thickener, a binder and emulsion stabiliser in foods with E number E463.  HPC is used as a support matrix for DNA separations by capillary and microchip electrophoresis.

Starch consists of two polysaccharides, amylose and amylopectin and represents approximately 20-25% of the total polysaccharide content in starch. Amylose molecules consist of single mostly unbranched chains of 500-20,000 α-(1->4)-D-glucose residues dependent on source (e.g. wheat, rice, potato, tapioca, etc). Amylose can form an extended shape (hydrodynamic radius 7-22 nm) but generally tends to wind up into a rather stiff left-handed single helix or form even stiffer parallel left-handed double helical junction zones. Hydrogen bonding between aligned chains causes retrogradation and releases some of the bound water (syneresis). The aligned chains may then form double stranded crystallites that are resistant to amylases. These possess extensive inter- and intra-strand hydrogen bonding, resulting in a fairly hydrophobic structure of low solubility. The amylose content of starches is thus the major cause of resistant starch formation.

Cellulose is a linear polysaccharide of β 1-4 linked glucose residues. The polysaccharide chains are bundled as microfibrils in cell walls and provide the essential structural components within growing plants. Each microfibril exhibits a high degree of three-dimensional internal bonding resulting in a crystalline structure that is insoluble in water, resistant to reagents and very strong.

A linear polyuronide obtained from the brown seaweeds (e.g. Laminaria hyperborea, Fucus vesiculosus, Ascophyllum nodosum). In the free acid form, the chemical structure consists of protonated 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).

Psyllium seed gum comes from plants of the Plantago genus and is cultivated mainly in the Mediterranian and in India. Psyllium has been used for many years medical applications and more recently there has been a resurgency of interest because it has been seen as a soluble dietary fibre. The proposed structure is of a backbone of D-xylopyranosyl units linked (1,4) and (1,3) with the 4-linked units bearing side chains. The side chains consist of α-L-arabinofuranosyl units linked (1,3) and (1,2) and β-D-xylopyranosyl units linked (1,3) and (1,2) and the α-D-GalAρ-(1,2)-α-L-Rhaρ aldobiuronic acid units linked (1,2) to the main chain.

Porcine mucosal heparin derivative; no anti-coagulant activity

Arabinoxylans consist of α-L-arabinofuranose residues attached as branch-points to β-(1,4)-linked D-xylopyranose main chains. These may be 2- or 3-substituted or 2- and 3- di-substituted. The arabinose residues may also be linked to other groups attached such as glucuronic acid residues, ferulic acid cross links and acetyl groups. Arabinoxylans generally consist of between 1500 - 5000 residues.

Porphyran is an agar-like polysaccharide with a linear backbone consisting of 3 linked β-D-galactosyl units alternating with either 4-linked α-L-galactosyl 6-sulphate or 3-6-anhydro-α-L-galactosyl units.The composition includes 6-O-sulphated L-galactose, 6-O-methylated D-galactose, L-galactose, 3,6-anhydro-L-galactose, 6-O-methyl D-galactose and ester sulphate. Some of the ester is present as 1,4-linked L-galactose 6-sulphate. The precise composition of porphyran shows seasonal and environmental variations. Porphyran is not used commercially, but the seaweed, Porphyra umbilicalis, is edible and is consumed in Wales (Laver). It is also made into a delicacy called Laverbread. The image was kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.

Chondroitin sulfate A sodium salt is a glycosaminoglycan that is derived from chondroitin. It is a complex carbohydrate with a high molecular weight and an average MW of 10,000 to 50,000 Da. The synthesis of the monosaccharide units in chondroitin sulfate A sodium salt occurs by Methylation, Click modification, Polysaccharide, or Fluorination. Chondroitin sulfate A sodium salt can be custom synthesized according to customer specifications and can be ordered as a CAS No. 39455-18-0 with high purity.

In water, hydroxypropyl cellulose forms liquid crystals with many mesophases depending on concentration. These mesophases include isotropic, anisotropic, nematic and cholesteric, the latter resulting in many colors such as violet, green and red. Pharmaceutical applications include treatments for medical conditions such as dry eye syndrome (keratoconjunctivitis sicca), recurrent corneal erosions, decreased corneal sensitivity, exposure and neuroparalytic keratitis. It is also used as a binder in tablets. Hydroxypropylcellulose is also used as a thickener, a binder and emulsion stabiliser in foods with E number E463.  HPC is used as a support matrix for DNA separations by capillary and microchip electrophoresis.

Laminaran is a polysaccharide that co-occurs with fucoidan and alginate in brown seaweeds such as Laminaria digitata, Laminaria cloustoni, Eisenia bicyclis and Thallus laminariae. It is a β-1,3-linked glucan which it is claimed stimulates the immune system in mammals and fish. The image was kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.

Laminaran is a polysaccharide that co-occurs with fucoidan and alginate in brown seaweeds such as Laminaria digitata, Laminaria cloustoni, Eisenia bicyclis and Thallus laminariae. It is a β-1,3-linked glucan which it is claimed stimulates the immune system in mammals and fish. The image was kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.

Isolichenan is a cold-water soluble (1,3)-(1,4)-α-D-glucan isolated from lichen Cetraria islandica to have MW of about 6-8 kDa. Lichens produce isolichenan-type polysaccharides with considerable variation in linkage ratios as well as MW, even within the same species. Occasionally these α-glucans can be branched at O2, O3 or O6. The immunomodulating activity of isolichenan was tested in in vitro phagocytosis and anti-complementary assays, and proved to be active in both cases. The image was kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.

Sodium polymannuronate is produced from alginates by partial hydrolysis and chromatography of brown algae such as Laminaria digitata, Ascophyllum nodosum and Fucus spp. The image was kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.

Chondroitin sulphate is the most abundant glycosaminoglycan in mammalian tissues and occurs both in skeletal and soft connective tissue. The disaccharide repeat unit consists of N-acetyl galactosamine sulphate linked β1,4 to glucuronic acid.

In their simplest forms, xylans are linear homopolymers of β-1,4-xylose residues. In nature they are partially substituted by acetyl, 4-O-methyl-D-glucuronosyl and α-1,3 L-arabinofuranosyl residues, forming complex heterogenous and polydispersed glycans. An example of this is in the L-arabino (methyl-D-glucurono) xylan from corn cob.

Low calcium heparin is a glycosaminoglycan, which occurs in many mammalian tissues and has important anticoagulant and thrombolytic properties. The chemical structure is composed mainly of two disaccharide repeating units A and B. A is L-iduronic acid 2-suplhate linked α-(1,4) to 2-deoxy-2-sulfamido-D-galactose 6-sulphate, while B is D-glucuronic acid β-(1,4) linked to 2-deoxy-2-sulfamido-D-glucose 6-sulphate.

In addition to the β-glucans from cereals, another group of β-glucans are found in the cell walls of yeast (Saccharomyces cerevisiae), bacteria and fungi, with significantly differing physicochemical properties dependent on source. Typically these β-glucans form a linear backbone with 1,3 β-glycosidic bonds but vary with respect to molecular mass, solubility, viscosity, branching structure, and gelation properties, causing diverse physiological effects in animals.  They are structural components in the cell walls of Saccharomyces cerevisiae and to provide stability, they have a few b-1,6 branch points that lock into other cell wall components (1 in 5 glucose residues). So in any extraction you get a few 1,6 linked glucose residues ~5%. The yeast and fungal β-glucans have been investigated for their ability to modulate the immune system. They are also used in various nutraceutical and cosmetic products, as texturing agents, and as fibre supplements. Their detailed molecular structures are key to the physical properties that they exhibit, such as water solubility, viscosity, gelation properties and physiological functions. The image was kindly provided by Dr. Chris Lawson.

In water, hydroxypropyl cellulose forms liquid crystals with many mesophases depending on concentration. These mesophases include isotropic, anisotropic, nematic and cholesteric, the latter resulting in many colors such as violet, green and red. Pharmaceutical applications include treatments for medical conditions such as dry eye syndrome (keratoconjunctivitis sicca), recurrent corneal erosions, decreased corneal sensitivity, exposure and neuroparalytic keratitis. It is also used as a binder in tablets. Hydroxypropylcellulose is also used as a thickener, a binder and emulsion stabiliser in foods with E number E463.  HPC is used as a support matrix for DNA separations by capillary and microchip electrophoresis.

Dextran sulphate is a dextran derivative whose ulcer (colitis) -causing properties were first reported in hamsters and extrapolated a few years later to mice and rats. The exact mechanisms through which dextran sulphate induces intestinal inflammation are unclear but may be the result of direct damage of the monolayer of epithelial cells in the colon, leading to the crossing of intestinal contents (e.g., commensal bacteria and their products) into underlying tissue and therefore induction of inflammation.  The dextran sulphate sodium induced ulceration model in laboratory animals has some advantages when compared to other animal models of colitis, due to its simplicity and has many similarities to human inflammatory bowel disease.

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.

Gycosaminoglycan in many organs; joint lubricant and shock absorber

Welan gum is a microbial polysaccharide produced by a species of Alcaligenes and shows interesting rheological properties of use in the oil and agricultural industries. The structure is similar to gellan based on repeating glucose, rhamnose and glucuronic acid units but with a single side chain of either an α-L-rhamnopyranosyl or an α-L-mannopyranosyl unit linked (1,3) to the 4-O-substituted β-D-glucopyranosyl unit in the backbone.

Amylopectin is composed of between 2,000 to 200,000 glucose residues linked α (1→4) with α (1→6) branching. The molecule is highly branched, every 24 to 30 glucose units, resulting in a soluble molecule with many terminal residues. Starch is made of about 70% amylopectin by weight, though it varies depending on the source (higher in medium-grain rice to 100% in glutinous rice, waxy potato starch, waxy corn, and lower in long-grain rice, amylomaize, and russet potatoes).

Polymannuronic acid is produced from alginates by partial hydrolysis and chromatography of brown algae such as Laminaria digitata, Ascophyllum nodosum and Fucus spp. The image was kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.

Cellulose is a linear polysaccharide of β 1-4 linked glucose residues. The polysaccharide chains are bundled as microfibrils in cell walls and provide the essential structural components within growing plants. Each microfibril exhibits a high degree of three-dimensional internal bonding resulting in a crystalline structure that is insoluble in water, resistant to reagents and very strong. The crystalline region of cellulose is isolated to produce microcrystalline cellulose. Microcrystalline cellulose is a term for refined wood pulp and is used as a texturizer, an anti-caking agent, a fat substitute, an emulsifier, an extender, and a bulking agent in food production.

Water thickener; rheological control additive; has industrial appplications

Starch is a two component polysaccharide mixture of amylose and amylopectin. Amylose is a linear polysaccharide of α (1,4)-linked glucose residues and averages 20 to 30% of the total in most native starches. Amylopectin is a highly branced glucan containing both a (1,4) and a (1,6) linkages. The number of glucose residues in a single starch molecule can vary from five hundred to several hundred thousand, depending on the type of starch. Starch is the major storage form of energy in plants, just as glycogen is the storage form of energy for animals. The plant directs the starch molecules to the amyloplasts, where they are deposited to form granules. Thus, both in plants and in the extracted concentrate, starch exists as granules varying in diameter from 2 to 130 μm.

A sulphated galactan from the red seaweeds (Gelidium spp.). The major gel-forming component agarose consisting of a linear chain of sequences of (1,3) linked β -D-galactopyranosyl units and (1,4 ) linkages to 3,6-anhydro-α-D-galactopyranosyl units. Gelation is via the formation of double helices. Both Gelidium latifolium and Gelidium amansii are sources of both Agar (mixture of agarose and agaropectin) and Agarose. The images were kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.

Chitin forms the tough fibrous exoskeletons of insects, crustaceans and other arthropods, and, in addition to its presence in some fungi, it occurs in at least one alga. The structure of chitin is similar to that of cellulose but with glucose replaced with N-acetyl-D-glucosaminyl units linked β-D-(1,4) in a linear chain. Chitin is normally produced from the shells of lobster, crab or shrimp.

Galactomannan, food additive, fracking fluids, complex formation with Xanthan

Starch is a two component polysaccharide mixture of amylose and amylopectin. Amylose is a linear polysaccharide of α (1,4)-linked glucose residues and averages 20 to 30% of the total in most native starches. Amylopectin is a highly branced glucan containing both a (1,4) and a (1,6) linkages. The number of glucose residues in a single starch molecule can vary from five hundred to several hundred thousand, depending on the type of starch. Starch is the major storage form of energy in plants, just as glycogen is the storage form of energy for animals. The plant directs the starch molecules to the amyloplasts, where they are deposited to form granules. Thus, both in plants and in the extracted concentrate, starch exists as granules varying in diameter from 2 to 130 μm.

Fluorescein isothiocyanate carboxymethyl dextran (FITC-CM Dextran) has been reported to provide a valuable carrier for nanoparticles of iron oxide.  These products provide a potent tool for contrast enhancement in magnetic resonance imaging.

Viscoelastic polymer; excipient; food additive

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’.

Tara gum is a galactomannan that is obtained from the seeds of the tara shrub Caesalpinia spinosa which is a native of the northern regions of Africa and South America. The gum is described as having a backbone of (1,4)-linked β-D-mannopyranosyl units one third of which possess a single unit side chain of (1,6)-linked α-D-galactopyranose. The gum forms gels with carrageenan and xanthan in a similar manner to guar and locust bean gum. Currently, only small quantities of tara gum are sold for use as food thickeners and stabilisers.

A linear β-(1,4)-galactan from Acacia gum. Other linear β-(1,4)-galactans have been isolated from lemon peel, potato tubers and Norwegian spruce compresssion wood.

The disaccharide repeating unit of chondroitin sulphate consists of N-acetyl galactosamine sulphate linked β1,4 to glucuronic acid. Each monosaccharide may be left unsulphated, sulphated once, or sulphated twice. The most common pattern is that the hydroxyl groups of the 4 and 6 positions of the N-acetyl-galactosamine are sulphated, with some chains having the position 2 of the glucuronic acid sulphated.

Hydroxypropyl methylcellulose (HPMC or hypromellose) is a semisynthetic, inert and viscoelastic polymer that is used as eye drops and as semi-synthetic substitute for tear-films. When applied, a hypromellose solution acts to swell and absorb water, by increasing the thickness of the tear-film, resulting in decreased eye irritation.  In addition to its use in ophthalmic liquids, hypromellose has been used as an excipient in oral tablet and capsule formulations, where, depending on the grade, it functions as controlled-release agent. It is also used as a binder and as a component of tablet coatings.  Hypromellose in aqueous solution, unlike methylcellulose, exhibits thermal gelation properties. HPMC is approved as a food additive, emulsifier, thickening and suspending agent, and as an alternative to animal gelatin (Codex Alimentarius code (E number) is E464).

A fucan sulphate found in brown marine algae (Phaeophyta-typically Fucus vesiculotus, Sargassum (illustrated), Alaria and Cladosiphon) 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’.

Heparin is a glycosaminoglycan which occurs in many mammalian tissues and has important anticoagulant and thrombolytic properties. The chemical structure is composed mainly of two disaccharide repeating units A and B. A is L-iduronic acid 2-suplhate linked α-(1,4) to 2-deoxy-2-sulfamido-D-galactose 6-sulphate while B is D-glucuronic acid β-(1,4) linked to 2-deoxy-2-sulfamido-D-glucose 6-sulphate.

In water, hydroxypropyl cellulose forms liquid crystals with many mesophases depending on concentration. These mesophases include isotropic, anisotropic, nematic and cholesteric, the latter resulting in many colors such as violet, green and red. Pharmaceutical applications include treatments for medical conditions such as dry eye syndrome (keratoconjunctivitis sicca), recurrent corneal erosions, decreased corneal sensitivity, exposure and neuroparalytic keratitis. It is also used as a binder in tablets. Hydroxypropylcellulose is also used as a thickener, a binder and emulsion stabiliser in foods with E number E463.  HPC is used as a support matrix for DNA separations by capillary and microchip electrophoresis.

Nigeran is a polysaccharide found in the cell wall of lower fungi. In certain Aspergillus and Penicillium spp., nigeran was first isolated from Penicillium expansum and Aspergillus niger (illustrated). The polysaccharide contains unbranched α-D- glucopyranose residues linked 1,3 and 1,4. Nigeran is part of the hyphal cell wall, where it can contribute up to 40 % of the cell dry weight. The polysaccharide occupies several domains or location on the hyphal wall and is highly crystalline in vivo. Deposition of nigeran is primarily at the outer surface of the hyphal wall.

A linear β-(1,4)-galactan from potato tubers. Other linear β-(1,4)-galactans have been isolated from lemon peel, potato tubers and Norwegian acacia gum.