Synthesis of protocatechuic acid grafted chitosan copolymer: Structure characterization and in vitro neuroprotective potential

Excessive free radicals can cause oxidative damage to human tissues, which results in a variety of diseases. Therefore, the development of antioxidant materials is one of the great projects in biomedical field. In this work, antioxidant protocatechuic acid (PCA) monomers were grafted onto chitosan (CS) backbones to develop a PCA grafted chitosan (PCA-g-CS) antioxidant copolymer via the method of free radical-induced grafting reaction. The formation of covalent bonds between PCA and CS were confirmed by FTIR, 1H NMR, XRD and UV-vis. The antioxidant activity of PCA-g-CS was analyzed by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical scavenging assays. In addition, the cytotoxicity of PCA-g-CS on neuron-like rat phaeochromocytoma (PC12) cells was evaluated by using MTT assay. The neuroprotective effects against hydrogen peroxide (H2O2) and l-glutamic acid (GLU) induced apoptosis in PC12 cells were also investigated. Our results demonstrated that the PCA-g-CS antioxidant copolymer had the ability to scavenge DPPH and hydroxyl radical in vitro. Furthermore, the PCA-g-CS was biocompatible and had neuroprotective effects against free radical-induced apoptosis in PC12 cells. This PCA-g-CS copolymer is firstly synthesized for neuroprotection and the results suggest the PCA-g-CS may be a potential antioxidant material in the treatment of oxidative damage related diseases.