A comprehensive review on polysaccharide conjugates derived from tea leaves: Composition, structure, function and application

Tea polysaccharide conjugates (TPS conjugates) are receiving worldwide attention in the recent decades, after they were recognized as critical components of coarse tea, and were responsible for their therapeutic effects in patients with diabetes. Existing evidences indicate that TPS conjugates not only benefit human health, but also can be used as carriers for drugs and as films for food packaging, and as emulsifiers. Despite their many practical applications, molecular structures of TPS conjugates are not well worked out yet, making their mechanisms of action difficult to understand. Their structural variations are attributed mainly to the differences in the processing of different tea. This comprehensive review summarises the compositions, structural characteristics, and bioactivities of TPS conjugates from different tea-leaf products, discusses the relationships between their compositions and structures, and the specific functions, and suggests the conjugation among polysaccharides, proteins and polyphenols occurring in tea leaves during processing which is mainly responsible for the alteration in composition and structure of TPS conjugates derived from different kinds of tea.