Innovative antioxidant thermo-responsive hydrogels by radical grafting of catechin on inulin chain

Abstract The synthesis of thermo-sensitive antioxidant hydrogels by grafting of an antioxidant molecule and a thermo-responsive monomer into inulin, in the presence of a crosslinker. In particular, catechin and NIPAAm, as antioxidant and thermo-responsive species, respectively, were inserted in a polymeric network employing a redox pair as an eco-friendly radical initiator system. Calorimetric, FT-IR, UV–Vis and fluorescence analyses were performed to verify both the formation of the inulin–antioxidant covalent bond and the insertion of bioactive molecules and monomers in the network. The hydrogels showed transition temperatures in the range 31.3–33.1 °C and a water affinity depending on the temperature of the surrounding medium. The antioxidant activity of the conjugates was evaluated measuring the scavenger properties of the hydrogels against the 2,2′-diphenyl-1-picrylhydrazyl radical and the total flavonoid content at different temperatures. The thermo-responsive antioxidant properties of the hydrogels confirmed the efficiency of the proposed synthetic strategy and demonstrated as the antioxidant–carbohydrate thermo-responsive conjugates possess peculiar features for specific applications in the food industry.