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

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.