Heterogeneous Method for Grafting of Syringaldehyde onto Chitosan by Laccase Oxidation

Abstract

Heterogeneous method for grafting of syringaldehyde (SD) onto chitosan by laccase oxidation, yielding a product with improved antioxidant activities. The results showed that about 1.1% amino groups participated in this reaction. The FTIR showed that the absorption of amino groups were decreased, the absorption of benzene ring structures were disappeared and a new band appeared at 1637 cm-1 corresponding to C=N vibrations that were due to the Schiff base reaction between the chitosan and syringaldehyde. Additionally, the chitosan had insignificant reducing power and DPPH free radical scavenging activity, SD-chitosan had reducing power of A700=0.684, DPPH free radical scavenging activity of 53.2%. SD-chitosan presented improved antioxidant properties.