Importance of the Nucleophilic Property of Tea Polyphenols

Tea is the second most popular beverage in the world after water. Vast accumulative evidence attest that tea consumption may promote human health, such as antioxidant, anti-obesity, and anticancer activities. Therefore, tea phytochemicals have drawn exceeding attention from researchers in structure confirmation, formation mechanism, component clarification, and bioactivity screening of interested constituents. Particularly, most investigations of chemical or biochemical reactions of catechins have concentrated on the B ring of the C6–C3–C6 skeleton. Hence, in this perspective, we reviewed the profound findings of the carbon–carbon (C–C) connection from the unambiguous characterization of novel A-ring addition derivatives of tea catechins, including catechin–carbonyl and catechin–theanine conjugates and the C–C formation mechanisms, and offered our view of the potential effects of catechin–carbonyl interactions on flavor generation and bioactive action in tea.