Polisacáridos

<p>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.</p>

<p>N-Acetyl-de-O-sulphated 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.</p>

<p>The sodium salt of hyaluronic acid is a glycosaminoglycan found in many organs, where it functions as a joint lubricant and shock absorber. It is obtained principally from synovial fluid, vitreous humor of the eye, umbilical tissue and cocks comb. The chemical structure of hyaluronic is a disaccharide repeat of β-(1,3) glucuronic acid and β-(1,4) N-acetyl glucosamine.</p>

<p>Ulvans are structural polysaccharides present in the cell walls of green algae such as Ulva armoricana, Ulva rotondata, Ulva rigida, Ulva lacterca and Ulva pertusa.  They are highly sulphated and contain rhamnose 3-sulphate, xylose, xylose 2-sulphate, glucuronic acid and iduronic acid residues.  Ulvan has several potentially valuable functionalities such as gel formation for agricultural and food applications and possible anticoagulant, antioxidant, antihyperlipidemic and antitumor activities for pharmaceutical applications.<br>The image was kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.</p>

<p>Gycosaminoglycan in many organs; joint lubricant and shock absorber</p>

<p>Chitosan from fungal cell walls.  It is made by treating cell walls of fungi (agaricus bisporus) with sodium hydroxide.Viscosity typically 20-100 mPa.sMushroom OriginMolecular Weight: 13000Da</p>

Gycosaminoglycan in many organs; joint lubricant and shock absorber

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.

<p>Levan is a (2,6)-linked fructan produced by Erwinia herbicola. The polysaccharide contains branches every 10-12 fructose residues linked (1,2) and is reported to have a molecular weight in excess of 1000 KDa.  Potential industrial applications of levan have been proposed as an emulsifier, formulation aid, stabilizer and thickener, surface-finishing agent, encapsulating agent, and carrier for flavor and fragrances. In addition, levan is promising in medicine as a plasma substitute, drug activity prolongator and antihyperlipidemic agent.</p>

<p>Chitin is a polysaccharide which is found widely in nature, where it functions in a manner similar to collagen in chordates. It 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. It is normally produced from the shells of lobster, crab or shrimp.</p>

<p>The sodium salt of hyaluronic acid is a glycosaminoglycan found in many organs, where it functions as a joint lubricant and shock absorber. It is obtained principally from synovial fluid, vitreous humor of the eye, umbilical tissue and cocks comb. The chemical structure of hyaluronic is a disaccharide repeat of β-(1,3) glucuronic acid and β-(1,4) N-acetyl glucosamine.</p>

<p>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.</p>

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.

<p>Gycosaminoglycan in many organs; joint lubricant and shock absorber</p>

<p>Carboxymethyl chitosan has good solubility in water and unique chemical, physical and biological properties such as high viscosity, large hydrodynamic volume, low toxicity, biocompatibility and good ability to form films, fibres and hydrogels. For this reason, it has been extensively used in many biomedical fields such as a moisture-retention agent, bactericide, wound dressing agent, in artificial bone and skin, as blood anticoagulant and as a component in different drug delivery matrices. The reactive ligands COOH and NH2 groups are available for metal chelation and dye binding.</p>

<p>N-Acetyl 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.</p>

Gycosaminoglycan in many organs; joint lubricant and shock absorber

<p>Gycosaminoglycan in many organs; joint lubricant and shock absorber</p>

<p>Polyguluronic acid is produced from alginates by partial hydrolysis and chromatography of brown algae such as Laminaria digitata, Ascophyllum nodosum and Fucus spp.<br>The image was kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.MW is ca 6000 - 8000Da.poly-M levels are ca 3%</p>

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.