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 ( – CH 2 CH ( OH ) CH 2 N ( CH 3 ) 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.