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Chitosan

Chitosan is a natural, polymeric carbohydrate made through the deaceylation of chitin. Chitin is a natural polysaccharide present in various marine and terrestrial organisms, including crustacea, insects, mollusks, and microorganisms, such as fungi. The structure of chitin is that of an unbranched polymer of 2-acetoamido-2-deoxy-D-glucose (N-acetyl-D-glucosamine). Chitin is typically an amorphous solid that is largely insoluble in water, dilute acids, and alkali. Although chitin has various commercial applications, greater commercial utility is found by converting chitin to the deacetylated product chitosan. Chitosan can be created by N-deacetylation of the chitin polymer. Chitosan is derived from chitin and can be formed by deacetylation of chitin. Chitosan is commercially available in a wide variety of molecular weights and usually has a degree of deacetylation ranging between 70% and 90%. Chitosan is used for a wide variety of purposes including plant care, cosmetics additives, food and nutrition supplements and medical care. Chitosan is a polymer having a strong positive charge, which most polysaccharides lack. Such charge readily permits interaction with negatively charged surfaces. In addition, chitosan includes both hydroxyl functionality and amine functionality, lending itself to reactive chemistry on either side group. Chitosan has the properties of allowing permeation of water and low-molecular compounds therethrough, exhibiting a good anticoagulant action, and shows a good affinity with tissues of living organisms, rarely causing an undesirable tissue reaction. In view of such characteristics, application of chizosan as a biomaterial has been conducted and its utilization in microcapsule materials, dialysis membrane, artificial organs, surgical materials, etc. has been attempted. Chitosan is non-toxic and displays the desired properties of absorptivity, moisturizing property, emulsifiability and biodegradability. Chitosan is known to have various therapeutic functions, including antimicrobial activity, deacidification activity, anti-ulcer activity, cholesterol and neutral lipid reducing activity, antitumor activity, promotion of growth intestinal bacteria, activation of plant cells and restoration of the immune response. Currently popular as a dietary supplement, chitosan is capable of binding fat, both triaceylgylcerols (TGs) as well as fatty acids. Based upon in vitro data, it has the potential to assist in weight loss and thereby reduce the incidence of obesity-associated conditions such as cardiovascular disease and type II or non-insulin dependent diabetes. With the use of chitosan as a dietary supplement, chitosan is often used to reduce the blood serum level of cholesterol, and to promote weight loss by impeding dietary fat absorption in the gastrointestinal tract. Chitosan can be encapsulated or tabletized either alone or in combination with other ingredients including vitamins C, E, B6, beta-carotene, folic acid, and a variety of binders. The properties and applications of chitosan are strongly linked to its morphology, structure and size and these are directly related to the process used for obtaining chitosan. Chitosan is present extensively in the natural world and, therefore, can be prepared through extraction from natural products and purification of the extract. Industrially, chitosan has been prepared by subjecting shells of crustaceans such as shrimps and/or crabs to decalcification and deproteination to isolate chitin and then deacetylating the resulting chitin with a hot concentrated alkali solution.

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