Structural factors affecting radical scavenging activity of chitooligosaccharides (COS) and its derivatives

Two chitooligosaccharides (COS) derivatives were synthesised by introducing carboxyl (-COCH2CH2COO-) and quaternized amino (-CH2CH(OH)CH2N(CH3)(3)(+)) groups to the amino position of COS with different substitution degrees (CCOS-1-3 and QCOS-1-3) for the purpose of altering total amount of hydrogen atoms capable of reacting with radicals and modifying their metal ion chelating ability. Scavenging of carbon-centered and DPPH radicals was directly affected by the amount of abstractable hydrogen atoms in COS molecules. In contrast, structure-activity relationships revealed that chelation of Fe2+ ions indirectly contributed for their observed hydroxyl radical scavenging activity apart from hydrogen abstraction. (c) 2005 Elsevier Ltd. All rights reserved.