Modulating antioxidant activity and the controlled release capability of laccase mediated catechin grafting of chitosan

[Display omitted] •Laccase mediated enzymatic grafting of catechin to chitosan is presented.•Coupling reaction of o-quinones and free amines is detected by UV–vis and FT-IR.•Antioxidant activity of flavonoid is successfully transferred to chitosan films.•Type of loading molecule is a decisive parameter on the release profile of CS films. Laccase from ascomycete Myceliophthora thermophila was used for the oxidation and grafting of catechin (CA) and chitosan (CS). The enzymatic grafting of CA into CS resulted in the improvement of natural properties of chitosan films. The successful grafting of CA to CS was supported by UV–vis and Fourier transform infrared (FT-IR) spectroscopies. The differences in the molecular weight and the degree of deacetylation of the CS affected on the enzymatic grafting rate and thus on the film properties like swelling behaviour, erosion rate, thermal property, tensile strength and breaking strain. The CS films prepared by enzymatic grafting presented high antioxidant activity compared to native CS films. The controlled release profiles of methylene blue and coomassie brilliant blue dye, having different acidity/basicity properties, loaded films were also studied with different release medium. The types of molecule loaded into films, the preparation manner of films and the release medium were decisive parameters affecting the release rate.