Theasinensin A: Formation, preparation, and bioactivities of a promising functional polyphenol in tea

Background

Theasinensin A (TSA), a type of ester-linked catechin dimer, is a polyphenolic compound formed through oxidative condensation of catechins during tea processing, particularly in the fermentation stage. As the most representative dimeric flavanol among the theasinensins (TSs), TSA is abundantly present in black tea and oolong tea. In recent years, TSA has attracted considerable attention due to its remarkable bioactivities, demonstrating promising applications in the fields of food, pharmaceuticals, and health. However, the natural abundance of TSA in tea is relatively low, making its extraction costly. Moreover, its synthesis and analytical characterization are technically challenging due to the presence of multiple chiral centers requiring stereoselective control. Therefore, an in-depth investigation into the formation mechanism of TSA, as well as the development of efficient methods for its preparation and analysis, is of great significance for advancing its practical applications.

Scope and approach

This review provides a comprehensive summary of the structural characteristics, formation mechanisms, synthetic approaches, analytical methods, and biological activities of TSA. In addition, the potential mechanisms underlying its bioactivities are briefly discussed.

Key findings and conclusions

Despite recent advances in the extraction, synthesis, analytical techniques, and health-related studies of TSA, research on TSA remains limited compared to other well-characterized polyphenols in tea. The inability to achieve large-scale production has hindered its availability for high-dose animal studies, thereby restricting in-depth investigations into its clinical health benefits and the mechanisms underlying its high bioactivity at low concentrations. Future research should focus on developing targeted synthetic strategies, establishing efficient systems for integrated extraction, purification, and analysis, and elucidating the molecular targets and mechanisms of TSA's biological activities. These efforts will be essential for advancing the functional development and practical application of TSA.