Recent advances in the preparation, structural characteristics, biological properties and applications of gallic acid grafted polysaccharides

Natural polysaccharides are important biopolymers with unique physicochemical properties and valuable biological activities. Due to the lack of sufficient functional groups, the applications of natural polysaccharides are incomparable to synthetic biopolymers. In order to broaden the applications of polysaccharides, gallic acid (GA, one kind of phenolic acid with numerous functional properties) has been grafted onto polysaccharides through several chemical and enzymatic methods. The structural characteristics and physical properties (e.g. water solubility, thermal stability, crystalline character and viscosity) of polysaccharides are greatly changed by grafting with GA. Meanwhile, GA grafted polysaccharides (GA-g-polysaccharides) show improved biological activities (e. g. antioxidant, antimicrobial, antitumor, anti-inflammatory, anti-allergic, enzyme inhibitory, prebiotic, and calcium oxalate crystals formation inhibitory effects) and broadened applications in the fields of active packaging, edible coating, encapsulation, delivery and bioadsorption. Notably, the structural characteristics, physical properties, biological activities and applications of GA-g-polysaccharides are affected by the grafting ratio and grafting method. Herein, recent advances of GA-g-polysaccharides in terms of preparation methods, structural characteristics, biological activities and potential applications are summarized. This review will provide a guideline for the scientific community towards more rational design and targeted use of GA-g-polysaccharides in the future.