The Effect of the Molecular Architecture on the Antioxidant Properties of Chitosan Gallate

To elucidate the structure-antioxidant activity relationships of chitosan gallate (CG), a series of CG derivatives with different degrees of substitution (DS's) and molecular weights (MWs) were synthesized from chitosan (CS) and gallic acid (GA) via a free radical graft reaction. A higher MW led to a lower DS of CG. The structures of CG were characterized by FT-IR and H-1 NMR, and results showed that GA was mainly conjugated to the C-2 and C-6 positions of the CS chain. The antioxidant activity (the DPPH radical scavenging activity and reducing power) were enhanced with an increased DS and a decreased MW of CG. A correlation between antioxidant activities and the DS and MW of CG was also established. In addition, a suitable concentration (0 similar to 250 mu g/mL) of CG with different MWs (32.78 similar to 489.32 kDa) and DS's (0 similar to 92.89 mg.GAE/g CG) has no cytotoxicity. These results should provide a guideline to the application of CG derivatives in food or pharmacology industries.