Comparison in antioxidant action between α-chitosan and β-chitosan at a wide range of molecular weight and chitosan concentration

Antioxidant activity in alpha- and beta-chitosan at a wide range of molecular weight (Mw) and chitosan concentration (CS) was determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, reducing ability, chelating ability, and hydroxyl radical scavenging activity. The form of chitosan (FC) had significant (P < 0.05) effect on all measurements except DPPH radical scavenging activity, and antioxidant activity was dependent on Mw and CS. High Mw (280-300 kDa) of beta-chitosan had extremely lower half maximal effective concentrations (EC50) than alpha-chitosan in DPPH radical scavenging activity and reducing ability. The 22-30 kDa of alpha- and beta-chitosan showed significantly (P < 0.05) higher activities in DPPH radical scavenging, reducing ability, and hydroxyl radical scavenging than samples at other Mw, while chelating ability was the highest in 4-5 kDa chitosan. CS had significant effect on all measurements and the effect was related to Mw. The antioxidant activity of 280-300 kDa chitosan was affected by coil-overlap concentrations (C*) in the CS range of 4-10 mg/mL, forming entanglements. Reducing ability and hydroxyl radical scavenging activity were more predominant action in antioxidant activity of chitosan as shown by the lower EC alpha- values than those in other antioxidant measurements. (C) 2012 Elsevier Ltd. All rights reserved.