Polissacáridos

<p>Polymannuronic 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’.</p>

<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. Average molecular weight of 23,000 to 41,000</p>

<p>Sodium polymannuronate 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’.</p>

<p>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.</p>

<p>Xanthan gum is a polysaccharide produced by the Gram negative bacteria Xanthomonas campestris. It has unique rheological and gel forming properties and finds many applications particularly in the food and oil industries. 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 structure of xanthan is based on a cellulosic backbone of β-(1,4)-linked glucose units which have a trisaccharide side chain of mannose-glucuronic acid-mannose linked to every second glucose unit in the main chain. Some terminal mannose units are pyruvylated and some of the inner mannose units are acetylated.</p>

<p>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>Bacterial exopolysaccharide from gram negative Bacillus polymixa</p>

<p>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.</p>

<p>Octyl-agarose is a type of agarose gel that has been modified to contain 20% ethanol solution. It is used in the purification of oligosaccharides and monosaccharides, as well as in the synthesis of complex carbohydrate. Octyl-agarose can be custom synthesized or modified with glycosylation, methylation, sugar, or carbohydrate modifications.</p>

<p>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.</p>

<p>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).</p>

<p>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.</p>

<p>Hypromellose phthalate (hydroxypropyl methylcellulose phthalate, or HPMCP) is a phthalic acid ester of hydroxypropyl methylcellulose.  Hypromellose phthalate was introduced in 1971 as a cellulose derivative for enteric coatings, used to protect drugs from degradation by gastric acid or to prevent them from causing side effects in the stomach.  HPMCP is also used in sustained-release preparations, in binders and as microcapsule bases.</p>

<p>Lichenin, the poly β-D-Glucan of Cetraria islandica (Iceland moss), is found by enzymic degradation to differ in fine structure from the poly β-D-glucans of cereal grains. Thus, the basic structure of lichenin is a tetrameric unit in which two adjacent 1,4 linkages alternate with an isolated 1,3 linkage; occasionally four consecutive monomers are linked by 1,4 bonds. The immunomodulatory activity of isolichenan was tested in in vitro phagocytosis and anti-complementary assays, and proved to be active in both cases.<br>The image was kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.</p>

<p>Schizophyllan is a neutral extracellular polysaccharide produced by the fungus Schyizophyllum commune. Schizophyllan is a β-1,3 beta glucan with β-1,6 branches and a molecular weight of around 450 kDa. It is reported that this polysaccharide can stimulate the immune system, chelate metals, act as an adjuvant in delivering drugs and aid in the production of nanofibres.<br>The image was kindly provided by Dr. Chris Lawson.</p>

<p>A fucan sulphate found in brown marine algae (Phaeophyta-typically Fucus serratus, Ascophyllum nodosum, Laminaria digitata (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.<br>The image was kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.</p>

<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>

<p>Lambda-Carrageenan is a non-gelling sulphated galactan extracted from red seaweed (typically Gigartina stellata and Chondrus crispus). The structure of all carrageenans consists of a strictly alternating masked repeating unit of 1,3-linked α-D-galactose and 1,4-linked β-D-galactose. λ-Carrageenan has the α-linked unit 2-6-disulphated and the β-linked unit is 2-sulphated.<br>The image was kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.</p>

<p>Gum tragacanth is an exudate gum from species of Astragalus trees mainly grown in Iran and Turkey. Tragacanth finds applications as an effective emulsifying and thickening agent in the food and pharmaceutical industries. The gum is a slightly acidic salt consisting of two fractions namely the water soluble tragacanthin and the fraction bassorin which swells in water to form a gel. Water soluble tragacanthin is reported as a branched arabiogalactan which is soluble in 70% ethanol. The acidic bassorin has a chain of (1,4)-linked a-D-galacturonic acid units some of which are substituted at O-3 with β-D-xylopyranosyl units and some of these being terminated with galactose or fucose.</p>

<p>Starch component; highly branched glucan</p>

<p>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.</p>

<p>The fluorescence intensity of these Rhodamine B isothiocyanate-dextrans varies much less than with FITC-dextrans.</p>

<p>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.</p>

<p>Carboxymethyl cellulose is used in food as a viscosity modifier, thickener, to stabilise emulsions and are found in gluten-free and reduced-fat products. It is also a constituent of toothpaste, laxatives, diet pills, water-based paints, detergents, textile sizing, and various paper products.  In laundry detergents, it is used as a soil suspension polymer. It is also used in pharmaceuticals as a thickening agent and in the oil-drilling industry as a viscosity modifier and water-retaining agent.</p>

<p>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.</p>

<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. <br>MW is in the range of 40,000Da</p>

<p>Hyaluronic acid, a polysaccharide with alternating β (1,3) glucuronide and β (1,4) glucosamine residues labelled with 5-amino-fluorescein gives a yellow fibrous product, which is soluble in both water and electrolytes.  Fluorescein-labelled hyaluronic acid can be used as a probe to follow the fate of hyaluronan in vitro and greatly enhances the visualisation of the permeation of substrates through skin and other tissues. Other applications of fluorescein-labelled hyaluronic acid have been reported in cancer research.</p>

<p>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.</p>

<p>A fucan sulphate found in brown marine algae (Phaeophyta-typically Fucus vesiculotus, Ascophyllum nodosum, Alaria and Macrocystis pyrifyra (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.<br>The fucose content of this fucan is approx. 31% and it also contains galactose (approx. 2.2%), uronic acid (approx. 12.4%) and sulfate (approx. 32.5%).<br>The image was kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.</p>

<p>An apiose-rich pectic polysaccharide zosterin is found in the sea grass Zostera marina and is typical of similar structures occurring in higher plants. The structure consists of an α-1,4-D-galactopyranosyluronan backbone substituted by 1,2-linked apiofuranose oligosaccharides and single apiose residues. The average molecular mass of the polysaccharide has been shown to be about 4100 Da with a low polydispersity.</p>

<p>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 iron with dextran, known as iron dextran, is used as a source of iron for baby piglets which are often anaemic at birth.</p>

<p>Pullulan is a glucan elaborated by the fungus Aureobasidium pullulans. The chemical structure is essentially repeating units of maltotriose joined by α-1,6 linkages. Pullulan dissolves readily in water to form stable, viscous solutions that do not gel. The polysaccharide can be moulded, made into fibres and forms clear soluble films. Applications are in foods as a low calorie ingredient and the polysaccharide forms water soluble films that have been used as seed coatings and to coat fruit. Pullulan can also be used in industrial applications as a binder, film former and in pharmaceutical applications.  Average MW is typically 100-200kDa.  Viscosity is ca 120 mm2/s.<br>The image was kindly provided by Dr. Chris Lawson.</p>

<p>A fucan sulphate found in brown marine algae (Phaeophyta-typically Fucus serratus, Ascophyllum nodosum (illustrated), Laminaria japonica 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.<br>The image was kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.</p>

<p>Pectins are derived from citrus fruits such as lemons and limes. Amidated pectin is a modified form of pectin in which some of the galacturonic acid residues are converted with ammonia to amides. These pectins are more tolerant to varying calcium concentrations that occur in use and behave like low-ester pectins, need less of and are more tolerant to excess calcium. In addition, these gels are thermoreversible.</p>

<p>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 iron with dextran, known as iron dextran, is used as a source of iron for baby piglets which are often anaemic at birth.</p>

<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>

<p>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.<br>The image was kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.</p>

<p>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.<br>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’.</p>

<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>

<p>Larch arabinogalactan is extracted from the heartwood of the western larch Larix occidentalis. This compound has a backbone of 1,3-linked β-D-galactopyranosyl units each of which contains a side chain at position C-6. Arabinogalactans are used as emulsifiers, stabilizers and binders in the food, pharmaceutical and cosmetic industries, as low viscosity dietary fibres and as a prebiotic fibres.</p>

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

<p>Iota-Carageenan is a gelling sulphated galactan extracted from red seaweed (typically Euchuma cottonii and Euchuma spinosum). The structure of all carrageenans consists of a strictly alternating masked repeating unit of (1,3) linked α-D-galactose and (1,4) linked β-D-galactose. The α-linked galactose occurs as a 3,6-anhydro-2-sulphate unit and the β-linked sugar occurs as the 4-sulphate.<br>The image was kindly provided by Prof Mike Guiry from Cork who runs ‘The Seaweed Site’.</p>

<p>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-&gt;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.</p>

<p>Konjac glucomannan is an acetylated (1,4)-β-D-glucomannan obtained from the tubers of Amorphophallus konjac or Konnyaku root. It is widely used in foods, pharmaceuticals paints and explosives. 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.</p>

<p>Carboxymethyl curdlan is widely used in the preparation of nanoparticles for biomedical applications. Following the synthesis of superparamagnetic iron oxide nanoparticles (SPIN) capped with carboxymethyl curdlan for use in cellular and in vivo imaging applications, the stability and dispersibility of SPIN in water were greatly improved with the introduction of the carboxymethyl curdlan moiety. Recently, a green and simple route was proposed to synthesize Ag nanoparticles using carboxymethylcurdlan under UV irradiation.</p>

<p>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.</p>

<p>Galactomannan, food additive, fracking fluids, complex formation with Xanthan</p>

<p>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).</p>

<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>

<p>Compression wood is a type of reaction wood formed on the underside of softwood stems when they are tilted from the vertical and on the underside of branches, which unlike normal wood contains significant amounts of β-(1,4)-galactan.</p>