Polysaccharides neutral polysaccharide

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... 

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. 

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... 

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... 

The FTIR spectra of citrus pectin and wheat straw XRPP (Figure 1) appeared to be similar. Both of the spectra have absorptions at 1740, 1608, 1430, 1360, 1244, 1080, 1060, 1035, 890 and 524 cm. The pectic substances belong to a class of carboxy poly saccharides which differ from neutral polysaccharides, with an intense band in the region 1740 cm l (for salts 1608 cm ) related to vibrations of the carboxyl group... 

Although the glycosidic bonds of uronic acid residues are usually more resistant to acid hydrolysis than those of neutral polysaccharides,218 these linkages in heparin are more readily cleavable then those between the hexosamine and the uronic acid residues. Disaccharides obtained by exhaustive hydrolysis of heparin with 0.5 MHC1 at 80° contained hexu-... 

Nishi has found that chondroitin sulfate A and C are more effective in the resolution of basic drugs than dextran or dextrin and even dextran sulfate because of additional ionic interactions with sulfate or carboxylic groups. The small ionic character of chondroitin sulfate C leads to large enantiose-lectivity under acidic conditions, whereas heparin was not so effective. Using neutral polysaccharides, only hydrophobic interactions and hydrogen bonding may occur (117). 

H Nishi. Enantiomer separation of basic drugs by capillary electrophoresis using ionic and neutral polysaccharides as chiral selectors. J Chromatogr A 735 345-351, 1996. 

Gum tragacanth is a mixture consisting of a salt of a complex acidic polysaccharide (tragacanthic acid) and a neutral polysaccharide which contains arabinose units. It is the latter which probably accounts for the isolation of arabinose from the crude gum. ... 

The crude gum tragacanth is a mixture of the salt of a complex acid polysaccharide and a neutral polysaccharide composed principally of L-arabinose residues. Starch is also present in the gum. The acid character of this gum is due to units of D-galacturonic acid and not D-glucuronic acid and it is of interest to note that in its ability to form gels it resembles pectin and the plant mucilages, which also contain D-galacturonic acid. 

The neutral polysaccharide is of the nature of an araban, but whether this polysaccharide is in physical admixture with the acid complex or is chemically bound to it is not yet certain. 

A method for purifying certain neutral polysaccharides by precipitation in borate buffer with cetyltrimethylammonium bromide was developed by Stacey and coworkers,118 but it does not appear to have been used for the isolation of galactomannan gums. It has, however, been claimed119 that guar gum and locust-bean gum can be separated by carefully controlled precipitation of the cetylpyridinium bromide complexes by 0.1 M sodium hydroxide. Guar gum is precipitated between pH 7.0 and 8.3, and locust-bean gum between 8.6 and 9.3. 

The results of a conductivity study on locust-bean gum (a neutral polysaccharide) in aqueous salt solutions led Barry and Halsey28 to conclude that there is no interaction between this carbohydrate and the many ions employed (H , Na , K , Ag , Ba2 , OAc , Cl , NO, , SO,2 , and HSO, ). Hydroxide ion was an exception. The electrolyte concentrations ranged from 0.0005 to 0.1 N, and the maximum concentration of polysaccharide was 0.0277 M (on a monosaccharide-residue bans). The specific conductivity of each polysaccharide-salt solution was identical to that of the corresponding salt solution containing no polysaccharide, strongly indicating the absence of significant adduct formation under the conditions... 

Carbohydrate chains of teichuronic acids and neutral polysaccharides linked to the carbohydrate chains of peptidoglycans are fragments of macromolecules of Gram-positive cell-wall. Only two examples of the biosynthesis of these polymers have been studied in detail. Evidence for both block and monomeric mechanisms of the chain assembly was obtained. 

The situation that exists in the case of the biosynthesis of neutral polysaccharide chains of streptococcal cell-wall is still very uncertain. In S. sanguis, assembly of the trisaccharide derivative (45, X = an unidentified, hydro-phobic group) from UDP-GlcNAc, dTDP-Rha, and UDP-Glc on an... 

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