Preparation, characterization, and functional evaluation of proanthocyanidin-chitosan conjugate

In this study, chitosan (CS) was conjugated with proanthocyanidin (PA) by a free radical grafting reaction. The successful synthesis of PA-CS conjugate was confirmed by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance. The optimal molar ratio of PA to CS repeat unit for the preparation of PA-CS was 0.13:1, which led to a high PA content of 381.76 mg PAE/g in PA-CS. The antioxidant assays demonstrated that PA-CS had much stronger radical scavenging activity and reducing power than the native CS. Especially, the half-inhibition concentrations of PA-CS against DPPH and ABTS radicals were only 6.2 μg/mL and 5.9 μg/mL, respectively. In addition, PA-CS showed an alteration in antibacterial activity compared with CS, and the alteration varied with bacterial strain.