Polyphenol-chitosan conjugates: Synthesis, characterization, and applications

• Three different methods to fabricate polyphenol-chitosan conjugates are reviewed and discussed in detail.
• Conjugation of polyphenol greatly improves physicochemical properties of the resultant chitosan derivatives.
• Conjugation of polyphenol to chitosan brings many novel functionalities for various applications.
• Challenges and limitations of each polyphenol-chitosan conjugate are highlighted.
• Perspectives on future development of polyphenol-chitosan conjugate are provided.

Chitosan, the only positively charged polysaccharide in the world, is very attractive for food, medicinal and pharmaceutical applications because of its promising properties, including non-toxicity, superb biodegradability, high biocompatibility, abundant availability and low cost. In order to overcome the poor water solubility and widen the applications of chitosan, various polyphenol-chitosan conjugates have been synthesized in recent years. The present review focuses on the chitosan-based conjugates formed using different polyphenols, including gallic acid, caffeic acid, ferulic acid, salicylic acid, catechin, and EGGE, etc. Three major synthesis techniques, namely, activated ester-mediated modification, enzyme-mediated strategy, and free radical induced grafting approach are introduced in detail. In addition, the new physicochemical and biological properties of polyphenol-chitosan conjugates are introduced, including water solubility, thermo stability, in vitro and in vivo antioxidant activity, antimicrobial and anticancer activity. Furthermore, the novel applications of each conjugate are discussed in detail. Lastly, the challenges and prospective areas of study related to polyphenol-chitosan are summarized.

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