Structures of Natural Polysaccharides

Besides simple monosaccharides, a large number of associated compounds are found in the structure of natural polysaccharides. Among these are the deoxysugars. The structural formulas of two common deoxyhexoses are shown below ... 

Muhlethaler K (1969) Fine structure of natural polysaccharide systems. In Marchessault RH (ed), Proceedings of 6th cellulose conference. Wiley, New York, 57-67 Murphy RJ, Barnes HM and Dickinson DJ (2002) Vapor boron technology. In Enhancing the durability of lumber and engineered wood products. Forest Prodncts Society, Madison, Wisconsin, 251-6... 

Miihlenthaler, R., 1969. Fine structure of natural polysaccharide systems. J. Polym. Sci. C 28, 305-316. 

This chapter has been written in order to investigate natural polysaccharides in terms of their use as pharmaceutical excipients. The focus has been given to the chemical structure of natural polysaccharides, which is of paramount importance for their utilization in drug delivery systems during stages of manufacturing, storage and human intake. 

Eylers, J. P. (2008). Mucus and slime Structure and rheology of natural polysaccharides. 

The use of carbohydrases for the elucidation of the structure of naturally occurring polysaccharides has been reviewed.257 The present discussion will be limited to their use in analyzing the structures of synthetic polysaccharides. 

The currently known structures of bacterial polysaccharides may be separated into several, biosynthetic types according to the nature of the activated forms of the monosaccharide residues in the main chain (for example, the UGT type means that UDP-, GDP-, and dTDP-activated sugars are present in the main chain). Table VIII shows the total number... 

The structural analysis of red algal galactans is similar in many respects to that of other groups of natural polysaccharides, but has some important peculiarities. First of all, the possible presence of both d- and L-galactose derivatives in the same... 

Comparison of the properties of fractions obtained from the cell and from the metabolism liquid indicates that they are of similar nature. It is not known what part the extracellular enzymes play in modifying the structure of the polysaccharides from the culture medium. The occurrence of D-arabinose in nature is rare, and its presence in the polysaccharides of M. tuberculosis indicates the unique metabolic activity of this organism. In other natural materials, arabinose occurs in the L-form (as for example in arabic acid). 

Polysaccharides are naturally occurring polymers, which can be considered as derived from aldoses or ketoses by condensation polymerization. A polysaccharide derived from hexoses, for example, has the general formula (C6H]oOs)n. This formula, of course, tells us very little about the structure of the polysaccharide. We need to know what the monosaccharide units are and how many there are in each molecule how they are joined to each other and whether the huge molecules thus formed are straight-chained or branched, looped or coiled. 

Because poiysaccharides are natural macromolecules occurring in all living organisms, the structure of some polysaccharides can be much more complex, as they are not made only from simple monosaccharides. In the composition of natural polymeric carbohydrates, a wide variety of sugars are found. Among these, the most common are pentoses and hexoses. The structural formulas of three common pentoses are shown below. They frequently form cyclic structures with five-member rings (furanoses). 

Acids related to monosaccharides are also common for the formation of natural polysaccharides. There are three types of acids associated with monosaccharides aldonic acids generated by the oxidation of the aldehyde group of a monosaccharide, uronic acids generated by the replacement of the primary alcohol group of a monosaccharide by a carboxyl group, and saccharic acids generated by simultaneous oxidation and replacement. Aldonic acids have a marked tendency to eliminate water and form lactones. The structural formulas of two common hexuronic acids are... 

Helicity (e.g., helical nature of tertiary structure of proteins, polysaccharides, and nucleotides)... 

Synthetic polysaccharides are prepared mainly to obtain models which may be helpful in establishing the biological functions of natural polysaccharides. It is desirable to find systems in which the polymerization of anhydro sugars proceeds stereospecifi-cally, i.e. to prepare uniform and well defined structures. 

Many years of persistent effort were spent by Professor Wolfrom in the determination of the structure of various polysaccharides. The most challenging of these was heparin, the natural blood anticoagulant. Methods were found for modifying the intractable backbone chain of this polymer, notably by use of diborane to reduce the... 

Besides application to the analysis of polysaccharides of unknown structure, enzymes are also often used for routine measurements on polysaccharides of essentially established structure, such as the starch components and the glycogens. Enzymes provide extremely quick and accurate information for the characterization of polysaccharides of this type, including the products synthesized in vitro diuring studies on their mechanism of biosynthesis. There is also increasing application to the characterization of other types of polysaccharide, synthesized enzymically in vitro. A further important use is for investigation of the nature of the products formed by the action of other catabolic enzymes on polysaccharides such applications may give information on either the structure of the polysaccharide or the specificity of the catabolic enzyme under investigation. 

Analytical Techniques to Evaluate the Structure and Function of Natural Polysaccharides, Glycosaminoglycans, ed. N. Volpi, Research Signpost Trivandrum, India, 2002... 

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