Novel coumarin-functionalized inulin derivatives: Chemical modification and antioxidant activity assessment

In this paper, a series of target derivatives were synthesized by introducing coumarin into inulin structure using three-step chemical modification, and their structures were characterized by FTIR, ¹H NMR, and ¹³C NMR. At the same time, the antioxidant activities of inulin derivatives were determined, including DPPH-radical scavenging activity, superoxide-radical scavenging activity, PTIO-radical scavenging activity and reducing ability. The test results showed that the antioxidant activities of inulin derivatives containing coumarin were significantly increased. Especially, inulin derivatives showed excellent DPPH radical-scavenging ability (IC₅₀ 0.09-0.11 mg/mL). Meanwhile, the scavenging ability of PTIO-radical was increased by more than 80%, and the IC₅₀ values were all between 0.23 and 0.26 mg/mL. At the concentration below 1 mg/mL, the scavenging rate of all inulin derivatives could even reach 100%. This study provides a feasible way to synthesize inulin derivatives with significant activity, which may be developed into new antioxidants in medicine and cosmetics.