Preparation, characterization and antioxidant property of water-soluble ferulic acid grafted chitosan

The objective of the present work was to improve the antioxidant activity and water solubility of chitosan by grafting with ferulic acid through a carbodiimide-mediated coupling reaction. UV-vis spectrophotometry, FTIR, 1H NMR and ninhydrin assay confirmed the grafting of ferulic acid onto chitosan at the C-2 position. Ferulic acid grafted chitosan - prepared using a mole ratio of chitosan to ferulic acid of 1:1, reaction temperature of 60 °C, and reaction time of 3 h - possessed the highest ferulic acid substitution degree, i.e. 0.37. Although ferulic acid grafted chitosan showed reduced crystallinity (∼10%) and decreased decomposition temperature (∼55 °C) as compared to chitosan, it exhibited greater radical scavenging activity (∼55%) and was soluble in water (up to 1.3 mg/mL). The improved antioxidant property and water solubility of this chitosan derivative could open a wide range of applications, particularly its use as an antioxidant in food, food packaging, biomedical, pharmaceutical and cosmetics industries.