Polysaccharides animal

Chitin is a natural polysaccharide including amino and acetyl groups [3]. Chitin is considered one of the most abxmdant natural polysaccharides on earth [96] and is found in species of lower plants and animals. It can be obtained from fungi, yeast, green, brown and red algae, as well as from insects and crustaceans. In insects and crustaceans, chitin is the main component of the exoskeleton [4]. It is composed of 2-acetamido-2-deoxy-(3-Dglucose 

Chitin exhibits very ordered, crystalline structure that is stabilized by a high number of intermolecular H-bonds [24]. Chitin exhibits highly hydrophobic character and is insoluble in water and most organic solvents. It is soluble in hexafluoroisopropanal, hexafluoroacetone and chloroalcohols in conduction with aqueous solutions of mineral acids and dimethylacetamide (DMAc) containing 5% lithium chloride (LiCl) [98,99], Upon hydrolysis of chitin with concentrated acids under harsh conditions, a relatively pure amino sugar D glucosamine is produced [96]. 

Derivatization of chitin occurs by utilizing the primary amino group and the primary and secondary hydroxyl groups. Glycol chitin, which is a partially o-hydroxyeth-ylated chitin, was the first derivative of practical importance [100]. 

Chitin has been investigated in terms of its use as a sustained release agent in different forms, including microspheres [101], nanogels [20] and nanofibers [21,102]. 

In a trial, microspheres of acrylamide-modified chitin were produced via ionically crosslinking with Fe3+ and then complexed with polycationic polysaccharide chito-san. The microspheres presented a fast responsive and pH-sensitive release behavior [101]. 

Agar is used in treating acute diarrhea. It is administered as a solid or as a thick slurry and provides a nonirritating bulking material that absorbs water and swells in the bowel, giving form to the stool. It is also used as an ingredient in slow-release capsules, in suppositories, and as a carrier in topical ointments. 

Dietary fibers are polysaccharides from natural foods found primarily in plant cell walls, and include cellulose, hemicelluloses, and pectins. They are P-glucans that are not digestible by humans, and thereby provide noncaloric bulk in the diet. Dietary fibers also include polysaccharides such as pectins, alginates, exudate gums, carrageenans, and agar that are added to foods and are not digestible. 

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In two articles published in this Series in 1946, the chemistry of bacterial polysaccharides was discussed. All the sugar and non-sugar components of such polysaccharides that were known at that time had previously been isolated from plant or animal polysaccharides. It was thus not known that... 

Chitin, a homopolymer from pi 4-linked N-acetylglucosamine, is the most important structural substance in insect and crustacean shells, and is thus the most common animal polysaccharide. It also occurs in the cell wall of fungi. 

Animal polysaccharides containing D-glucuronic acid include heparan sulfate,108 chondroitin 4- and 6-sulfates,109 and hyaluronic acid.109... 

Most of the known oligoglycuronic acids are aldobiouronic acids. Because of the stability of the glycosidic linkage of aldobiouronic acids toward acid hydrolysis, they are readily isolated after vigorous hydrolysis of polysaccharides that contain uronic acid residues. They have been obtained from wood hemicelluloses, plant mucilages, gums, bacterial and animal polysaccharides, and by synthesis. 

Polysaccharides may be attached to proteins, in which case they are known as protein-polysaccharides, when they originate from plants, or proteoglycans, when they originate from animals. Polysaccharides may also contain lipid components. Lipopolysaccharides and other mycobacterial constituents are covered in Chap. 6.5 and Chap. 7. 

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