Direct scavenging of nitric oxide and superoxide by green tea

• Published in: Food and chemical toxicology Vol. 40; no. 12; pp. 1745 - 1750
• Main Authors: Nakagawa, T, Yokozawa, T
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-12-2002; New York, NY Elsevier Science
• Subjects: (−)-Epicatechin 3- O-gallate; (−)-Epigallocatechin 3- O-gallate; (−)-Gallocatechin 3- O-gallate; Biological and medical sciences; Catechin - analogs & derivatives; Catechin - pharmacology; Dose-Response Relationship, Drug; Flavonoids - pharmacology; Free Radical Scavengers - metabolism; General pharmacology; Green tea; In Vitro Techniques; Medical sciences; Nitric oxide; Nitric Oxide - metabolism; Oxidants - metabolism; Oxidation-Reduction; Pharmacognosy. Homeopathy. Health food; Pharmacology. Drug treatments; Structure-Activity Relationship; Superoxide; Superoxides - metabolism; Tannin; Tannins - pharmacology; Tea - chemistry; EGC; O 2; PBS; NBT; NO; C; EC, (−)-epicatechin; EGCg; ECg; FAB-MS; Superoxide; GCg; (−)-Epicatechin 3- O-gallate; Tannin; Nitric oxide; (−)-Epigallocatechin 3- O-gallate; ROS; OH; ONOO; (−)-Gallocatechin 3- O-gallate; GC; Green tea; Extract; Plant leaf; Antioxidant; In vitro; Radical scavenger; Biological activity; (-)-Epicatechin 3-O-gallate; (-)-Epigallocatechin 3-O-gallate; (-)-Gallocatechin 3-O-gallate; Plant origin
• ISSN: 0278-6915; 1873-6351
• DOI: 10.1016/S0278-6915(02)00169-2

In the present study, we investigated the free radical scavenging effects of green tea extract and green tea tannin mixture and its components using a nitric oxide (NO) and superoxide (O
2
−) generating system in vitro. Green tea extract showed direct scavenging activity against NO and O
2
− and green tea tannin mixture, at the same concentration, showed high scavenging activity. Comparison of the activities of seven pure compounds isolated from green tea tannin mixture showed that (−)-epigallocatechin 3-
O-gallate (EGCg), (−)-gallocatechin 3-
O-gallate (GCg) and (−)-epicatechin 3-
O-gallate (ECg) had higher scavenging activities than (−)-epigallocatechin (EGC), (+)-gallocatechin (GC), (−)-epicatechin (EC) and (+)-catechin (C), showing the importance of the structure of flavan-3-ol linked to gallic acid for this activity. Among the gallate-free tannins, EGC and GC were more effective O
2
− scavengers than EC and C, indicating the
O-trihydroxy structure in the B ring is an important determinant of such activity. However, this structure did not affect the NO scavenging activity. These findings confirm that green tea tannin has excellent antioxidant properties, which may be involved in the beneficial effect of this compound.