ORAC of chitosan and its derivatives

Chitosan and chitosan derivatives are receiving a lot of attention as materials of natural origin which possess radical scavengers, antioxidants and antimicrobial properties, especially in food applications. With the aim to apply the Oxygen-Radical Absorbance Capacity assay (ORAC), to detect the polysaccharides capacity to scavenge the peroxyl radical, four different grafted chitosan derivatives were synthesized. Among the synthesized derivatives, N-acetyl cysteine-g-chitosan was found to have the highest ORAC value, while gallic acid-g-chitosan and p-hydroxybenzoic acid-g-chitosan had respective 70% and 42% of ORAC values of the former. On the contrary, p-methoxybenzoic acid-g-chitosan did not show any significant difference in antioxidant activity from the unmodified chitosan. A linear correlation between ORAC values and total phenols measured with the Folin–Ciocalteau reagent was shown. The combination of ORAC and Folin–Ciocalteau assays is a useful system to monitor the growth of the acquired antioxidant capacity in relation to the type of phenolic compound used for grafting.