ABSTRACT
The naturally occurring biopolymer, chitin, is a well-known mucopolysaccharide abundantly distributed in the shell of crustaceans, in the cuticle of insects, and also in the cell walls of some fungi and microorganisms. Chitin consists of 2-acetamido-2-deoxy-(1-4)-β-d-glucopyranose residues (N-acetyl-d-glucosamine units) that has intra-and intermolecular hydrogen bonds and is a water-insoluble material resembling cellulose in its solubility. Chitosan is an N-deacetylated derivative of chitin and consists of 2-amino-2-deoxy-(1-4)-β-d-glucopyranose residues (d-glucosamine units). Chitosan has many interesting properties such as biocompatibility, biodegradability, less toxic nature, and versatile chemical and physical properties that make it attractive for a wide variety of applications in many elds such as food (Lin et al. 2009), cosmetics (Majeti and Kumar 2000), biomedicine (Felt et al. 1998), agriculture, and wastewater management (Kim et al. 2007). Due to its versatile biological activities such as antibacterial activity (Allan and Hadwiger 1979, Hirano and Nagao 1989, Jeon and Kim 2000, Jeon et al. 2001), hypocholesterolemic activity (Hirano et al. 1990), antitumor activity (Sugano et al. 1992), immumostimulating effect (Jeon and Kim 2001), and antioxidant activity (Park et al. 2004), chitosan has been under much attention to develop as new physiological bioactive materials. In spite of its unique biological aspects, the water-insoluble property is a major limiting factor for its wide application. Moreover, biofunctionalities of chitosans are highly related to its molecular weight (MW) and the degree of deacetylation (DD). To this end, recent progress in basic and application studies about chitosan chemistry has been achieved, which develops ways to improve not only water-soluble property but also biological activities by using both chemical and enzymatic modications. This chapter provides an overview of antihypertensive effects of chitosan and its derivatives prepared by enzymatic and chemical modications.
