Comprehensive Understanding of the Relationship between Bioactive Compounds of Black Tea and its Angiotensin Converting Enzyme (ACE) Inhibition and Antioxidant Activity.

Long term regular intake of black tea (BT) can lower blood pressure, which is probably due to its antioxidant activity and angiotensin converting enzymes (ACE) inhibitory activity. This study achieves a comprehensive understanding of the relationship between bioactive compounds of BT and its ACE inhibitory activity and antioxidant activity. Phenolic compounds are closely related to antioxidant activity and ACE inhibitory activity. Catechin (C) exhibits stronger inhibitory activity on ACE enzyme than that of other compounds. Molecular docking demonstrates that C could directly bind to ACE active site pockets and Zn(II). Other bioactive compounds are involved in antioxidant and ACE inhibitory activity in varying degrees but no obvious trend is established. Our study proposes a conjecture that some bioactive compounds of BT regulate antioxidant defenses through mechanisms that involve ACE. The mixed mode of in vitro inhibition of ACE and oxidant of BT bioactive compounds needs to be further investigated.