title: Inhibitory effects of epigallocatechin-3-gallate on microsomal cyclooxygenase-1 activity in platelets.
abstract: In this study, we investigated the effect of (-)-epigallocatechin-3-gallate (EGCG), a major component of green tea catechins from green tea leaves, on activities of cyclooxygenase (COX)-1 and thromboxane synthase (TXAS), thromboxane A2 (TXA2) production associated microsomal enzymes. EGCG inhibited COX-1 activity to 96.9%, and TXAS activity to 20% in platelet microsomal fraction having cytochrome c reductase (an endoplasmic reticulum marker enzyme) activity and expressing COX-1 (70 kDa) and TXAS (58 kDa) proteins. The inhibitory ratio of COX-1 to TXAS by EGCG was 4.8. These results mean that EGCG has a stronger selectivity in COX-1 inhibition than TXAS inhibition. In special, a nonsteroid anti-inflammatory drug aspirin, a COX-1 inhibitor, inhibited COX-1 activity by 11.3% at the same concentration (50 μM) as EGCG that inhibited COX-1 activity to 96.9% as compared with that of control. This suggests that EGCG has a stronger effect than that of aspirin on inhibition of COX-1 activity. Accordingly, we demonstrate that EGCG might be used as a crucial tool for a strong negative regulator of COX-1/TXA2 signaling pathway to inhibit thrombotic disease-associated platelet aggregation.
authors.affiliation: Department of Biomedical Laboratory Science, College of Biomedical Science and Engineering and Regional Research Center, Inje University, Gimhae 621-749, Republic of Korea.
authors.forename: Dong-Ha
authors.initials: DH
authors.lastname: Lee
authors.forename: Yun-Jung
authors.initials: YJ
authors.lastname: Kim
authors.forename: Hyun-Hong
authors.initials: HH
authors.lastname: Kim
authors.forename: Hyun-Jeong
authors.initials: HJ
authors.lastname: Cho
authors.forename: Jin-Hyeob
authors.initials: JH
authors.lastname: Ryu
authors.forename: Man Hee
authors.initials: MH
authors.lastname: Rhee
authors.forename: Hwa-Jin
authors.initials: HJ
authors.lastname: Park
keywords: (–)-Epigallocatechin-3-gallate (EGCG); Aspirin; Cyclooxygenase-1; Microsomal fraction; Thromboxane synthase