Modification of different molecular weights of chitosan by p-Coumaric acid: Preparation, characterization and effect of molecular weight on its water solubility and antioxidant property

In this study, we modified three different molecular weights of chitosan by using p-Coumaric acid (p-CA) for enhancing their water solubility and antioxidant property. The chemical and physical properties of all native chitosan and its modified products were determined by Fourier transform spectroscopy (FTIR), ninhydrin assay, Folin-Ciocalteu reagent procedure, thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), high performance of liquid chromatography (HPLC), X-ray diffraction (XRD), water solubility and antioxidant property (both DPPH assay and reducing power assay). Results showed that the water solubility and antioxidant property of modified product decreases, when molecular weight of corresponding native chitosan increases. The obtained modified product had good solubility over a wide range of pH. Thermal analysis (TGA and DSC) showed the lower thermal stability of the modified product than that of corresponding native chitosan. XRD pattern revealed that the crystallinity was less in modified product than that of respective chitosan. The enhanced partially water solubility and antioxidant property of all modified chitosan products might be a great advantage, while applied in a wide range of applications in the form antioxidant property in food, biomedical and cosmetic industry.