Neutral polysaccharides

This chapter will give you an overview of recent approaches for drug development, focusing on the function and roles of carbohydrates. O Section 2 will outline the biochemical functions of polysaccharide (neutral polysaccharide, chitin and chitosan, glycosaminoglycan, and synthetic polysaccharides) and glycopolymers and the perspectives of their medicinal/medical use. O Section 3 will outline recent biopharmaceutical research and development, utilizing... 

Mono- and di saccharides are colourless solids or sjrrupy liquids, which are freely soluble in water, practically insoluble in ether and other organic solvents, and neutral in reaction. Polysaccharides possess similar properties, but are generally insoluble in water because of their high molecular weights. Both poly- and di-saccharides are converted into monosaccharides upon hydrolysis. 

Psyllium Seed Gum. PsyUium seed gum [8036-16-9] is derived from plants of the genus Plantago several species of which are used as commercial sources. However, most current production is from Plantago ovata grown in India. The gum is located in the coat which is removed by cracking. The gum is then extracted with boiling water and separated from the insoluble residue by filtration. It consists of mixtures of both neutral and acidic polysaccharides, the composition of which is species dependent (66). 

Every polysaccharide contains glycosyl units with unsubstituted hydroxyl groups available for esterification or etherification. Polysaccharide derivatives are described by their degree of substitution (DS), which is the average number of substituent groups per glycosyl unit. Because each monomeric unit of cellulose molecules has free hydroxyl groups at C-2, C-3, and C-6, the maximum DS for cellulose, and all polysaccharides composed exclusively of neutral hexosyl units, the majority of polysaccharides, is 3.0. 

Molecular Interactions. Various polysaccharides readily associate with other substances, including bile acids and cholesterol, proteins, small organic molecules, inorganic salts, and ions. Anionic polysaccharides form salts and chelate complexes with cations some neutral polysaccharides form complexes with inorganic salts and some interactions are stmcture specific. Starch amylose and the linear branches of amylopectin form inclusion complexes with several classes of polar molecules, including fatty acids, glycerides, alcohols, esters, ketones, and iodine/iodide. The absorbed molecule occupies the cavity of the amylose helix, which has the capacity to expand somewhat to accommodate larger molecules. The starch—Hpid complex is important in food systems. Whether similar inclusion complexes can form with any of the dietary fiber components is not known. 

Detergent Methods. The neutral detergent fiber (NDF) and acid detergent fiber (ADF) methods (2), later modified for human foods (13), measure total insoluble plant cell wall material (NDF) and the cellulose—lignin complex (ADF). The easily solubilized pectins and some associated polysaccharides, galactomaimans of legume seeds, various plant gums, and seaweed polysaccharides are extracted away from the NDF. They caimot be recovered easily from the extract, and therefore the soluble fiber fraction is lost. 

For the hydrolyses of neutral muco-polysaccharide, the activity of Amberlite IR-120 was 3 turns higher than HC1 89,, 42 Painter et al reported, interestingly enough, that both deglucoside bond and N-deacylation occurred in the presence of HC1, whereas N-deacylation did not occur in the presence of the resins142 As an... 

Separations of polysaccharides by fractionation on a preparative scale were also examined. Stemming from earlier work in his laboratory on the isolation of acidic polysaccharides by precipitation as their insoluble Cetavlon salts, Stacey and coworkers showed that it was possible to fractionate neutral polysaccharides by selective precipitation with Cetavlon after the formation of borate complexes. 

The rheological behavior of storage XGs was characterized by steady and dynamic shear rheometry [104,266]. Tamarind seed XG [266] showed a marked dependence of zero-shear viscosity on concentration in the semi-dilute region, which was similar to that of other stiff neutral polysaccharides, and ascribed to hyper-entanglements. In a later paper [292], the flow properties of XGs from different plant species, namely, suspension-cultured tobacco cells, apple pomace, and tamarind seed, were compared. The three XGs differed in composition and structural features (as mentioned in the former section) and... 

Arabinogalactans (AGs) are widely spread throughout the plant kingdom. Many edible and inedible plants are rich sources of these polysaccharides. AGs occur in two structurally different forms described as type I and type II, associated with the pectin cell-wall component by physical bonds and some of them are covalently linked to the complex pectin molecule as neutral side chains. Commercial pectins always contain AG 10-15%). AG of type I has a linear (1 4)-y0-o-Galp backbone, bearing 20-40% of of-L-Ara/ residues (1 5)-linked in short chains, in general at position 3. It is commonly found in pectins from citrus, apple and potato [6]. Recently, this AG type has been isolated from the skin of Opuntia ficus indica pear fruits [372]. 

Acanthus ebracteatus is a plant traditionally used for various ailments, amongst those skin diseases in Thai traditional medicine. The stem of the plant was shown to contain neutral and acidic polysaccharides with effect in... 

The first paper on the bioactive polysaccharides from Glycyrrhiza uralensis roots was published in 1996 by Kiyohara et al. [57]. They isolated a pectic type polymer with anti-complementary and mitogenic activity that was an acidic pectin, possibly containing rhamnogalacturonan type I as part of the total structure. Degradation of the uronic acid part of the molecule decreased both types of bio activities. The neutral oligosaccharide chains were shown to retain some of the activities of the native polymer, but it was suggested that they should be attached to the acidic core to retain maximum activity. 

Already in 1988 and 1991, Gao et al. [65,66] detected four different polysaccharides present in the leaves of Panax ginseng that had an effect on the complement system, but only two of them, the neutral, GL-NIa, and one of the acidic ones, GL-AIa, had potent activities at low concentrations. GL-NIa was found to be mainly an arabinigalactan type II polymer. GL-AIa was a polysaccharide with a rhamnogalacturonan core with neutral side chains of the AG-II type, confirmed by a strong reaction with the Yariv reagent and the methylation results. It was shown that the crude polysaccharide fraction contained KDO and DHA, suggesting the presence of Rhamnogalacturonan II in... 

These low-polysaccharide concentrations were preferred to avoid excessive viscosity. Neutral polysaccharide. 

Po and rio are the densities and viscosities of the solvent, P2o,w and rj2o,w the corresponding values at 20.0 °C in water, v is the partial specific volume, which for neutral polysaccharides can often be reasonably estimated from the carbohydrate content [31] and takes on values between 0.5-0.7 ml/g for... 

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