ABSTRACT
Chitosan (poly-d-glucosamine) is a natural polymer derived from chitin, the second most abundant polysaccharide after cellulose. Chitosan can be obtained by either chemical deacetylation by treating with 40% sodium hydroxide for several hours or enzymatic deacetylation by N-deacetylase (EC3.5.1.41) (Tokuyasu et al. 1996), and it generally contains less than 50% of N-acetylglucosamine units. Chitosan possesses special properties for use in pharmaceutical, biomedical, food industry, health, and agriculture due to biocompatibility, biodegradability, and a nontoxic nature. However, the high molecular weight and poor solubility at neutral pH values of chitosan limit its industrial applications. Therefore, chemical and enzymatic modifications were employed to improve water solubility at a wide range of pH values and to enhance biological activities. Chitooligosaccharides (COSs) by enzymatic hydrolysis of chitosan and substitution of functional groups by chemical modification on three reactive groups, a free amino group, and both primary and secondary hydroxyl groups at C6 and C3 in chitosan were developed in order to overcome most of limitations (Vinšová and Vavřiková 2011). This chapter, therefore, reviews some bioactivities of chitosan and its derivatives for potential use as nutraceuticals.
