Modification of chitosan to improve its hypocholesterolemic capacity.

Cholestyramine is the most widely used bile acid sequestrant in the treatment of hypercholesterolemia. However, cholestyramine has unpleasant side effects as a consequence of its hydrophobic backbone. Therefore, high-capacity bile acid sequestering biopolymers with cationic chitosan derivatives were developed, because electrostatic interactions are important for binding with bile acid anions. Dialkylaminoalkylation and reductive amination of chitosan were done to add dialkylaminoalkyl and an additional free amino group at a hydroxyl site in the chitosan backbone respectively and the amino-derivatized chitosan derivatives were quaternized with methyl iodide to produce a cationic polyelectrolyte. The in vitro bile acid binding capacity of the chitosan derivatives in aqueous NaCl was measured by reversed-phase HPLC. The binding capacities of sodium glycocholate (a major bile acid) to chitosan, DEAE-chitosan, quaternized DEAE-chitosan, and cholestyramine were 1.42, 3.12, 4.06, and 2.78 mmol/g resin, respectively. With quaternized DEAE-chitosan, the bile acid binding capacity increased approximately 50% over that of cholestyramine. The bile acid binding capacity of dialkylaminoalkyl chitosan derivatives increased with the number of carbons in the alkyl groups, indicating that hydrophobic interaction is a secondary factor for the sequestration of bile acids.