Polysaccharide-catechin conjugates: Synthesis methods, structural characteristics, physicochemical properties, bioactivities and potential applications in food industry

Natural polysaccharides and plant-derived catechins are two types of food ingredients. Natural polysaccharides and catechins, restricted by their intrinsic molecular structures, individually have weak bioactivity and low stability. The drawbacks of natural polysaccharides and catechins can be overcome by conjugating them through graft copolymerization reactions. The reaction products, often called as polysaccharide-catechin conjugates, show strong bioactivity, high stability and good application potentials in food industry. This review comprehensively summarizes the synthesis methods, structural characteristics, physicochemical properties, bioactivities and potential applications of polysaccharide-catechin conjugates in food industry. The future research and prospects of polysaccharide-catechin conjugates are also discussed. Polysaccharide-catechin conjugates can be synthesized through free radical mediated reaction, acid condensation reaction, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide mediated reaction and enzyme catalyzed reaction. The spectroscopic characteristics of polysaccharides and catechins are changed after conjugation. As compared with polysaccharides, polysaccharide-catechin conjugates exhibit better solubility but lower viscosity and crystallinity. Importantly, the oxidative stability of catechins is elevated by conjugating with polysaccharides. At the same time, the antioxidant, antimicrobial, anticancer, hepatoprotective and enzyme inhibitory properties of polysaccharides are enhanced by conjugating with catechins. In food industry, polysaccharide-catechin conjugates can be developed into food packaging materials and the encapsulation agents of functional food ingredients. Notably, the structural characteristics, physicochemical properties, bioactivities and applications of polysaccharide-catechin conjugates are closely associated with synthesis method, reaction condition, and the type of polysaccharides and catechins. Future studies are needed to reveal the detailed structural characteristics, in vivo bioactivities, and the mechanism of action of polysaccharide-catechin conjugates.