Tea Catechin Supplementation Increases Antioxidant Capacity and Prevents Phospholipid Hydroperoxidation in Plasma of Humans Kiyotaka Nakagawa, † Manabu Ninomiya, ‡ Tsutomu Okubo, ‡ Nobuyuki Aoi, ‡ Lekh Raj Juneja, ‡ Mujo Kim, ‡ Kenji Yamanaka, § and Teruo Miyazawa* ,† Laboratory of Biodynamic Chemistry, Tohoku University Graduate School of Life Science and Agriculture, Sendai 981-8555, Japan, Central Research Laboratories, Taiyo Kagaku Co., Ltd., Yokkaichi, Japan, and Sasakawa Clinic of Gastroenterology, Yokkaichi, Japan The effect of green tea catechin supplementation on antioxidant capacity of human plasma was investigated. Eighteen healthy male volunteers who orally ingested green tea extract (254 mg of total catechins/subject) showed 267 pmol of epigallocatechin-3-gallate (EGCg) per milliliter of plasma at 60 min after administration. The plasma phosphatidylcholine hydroperoxide (PCOOH) levels attenuated from 73.7 pmol/mL in the control to 44.6 pmol/mL in catechin-treated subjects, being correlated inversely with the increase in plasma EGCg level. The results suggested that drinking green tea contributes to prevent cardiovascular disease by increasing plasma antioxidant capacity in humans. Keywords: Tea catechin; antioxidant; lipid peroxidation; phosphatidylcholine hydroperoxide; human plasma INTRODUCTION Green tea is consumed as a popular beverage in Japan and throughout the world. During the past decade, epidemiological studies have shown that tea catechin intake is associated with lower risk of cardiovascular disease (Hertog et al., 1993; Keli et al., 1996). In vitro biochemical studies have reported that catechins, par- ticularly epigallocatechin-3-gallate (EGCg, for chemical structure see Table 1), help to prevent oxidation of low- density lipoprotein (LDL) (De Walley et al., 1990; Zhenhua et al., 1991; Miura et al., 1995). LDL oxidation has been recognized to be an important step in the formation of atherosclerotic plaques and subsequent cardiovascular disease (Steinberg et al., 1989). Previous metabolic studies have shown that EGCg supplement is incorporated into human plasma at a maximum concentration of 4400 pmol/mL (Lee et al., 1995; Unno et al., 1996; Nakagawa and Miyazawa, 1997a; Nakagawa et al., 1997). Such concentrations would be enough to exert antioxidant activity in the blood stream. The potent antioxidant property of tea catechin may be beneficial in preventing the oxidation of LDL. It is therefore of interest to examine whether tea catechin supplementation increases antioxidant capacity in humans. In this study, the effect of green tea catechin supple- mentation on antioxidant capacity of plasma was in- vestigated in humans by measuring plasma phosphati- dylcholine hydroperoxide (PCOOH) levels as a marker of oxidized lipoproteins. EXPERIMENTAL PROCEDURES Chemicals. Green tea extract (Sunphenon DCF-1®) and EGCg (above 95% purity) were obtained from Taiyo Kagaku Co. (Yokkaichi, Japan). R- and γ-tocopherol were a gift from Eisai Co. (Tokyo, Japan). -Carotene was purchased from Sigma Chemical Co. (St. Louis, MO). Lycopene was from Wako Pure Chemical Co. (Osaka, Japan). Other reagents and chemicals were commercially available extra-pure grade prod- ucts. Subjects and Protocol. Eighteen healthy male volunteers, aged 23-41 years, participated in this study. Body weight ranged from 52 to 81 kg (body mass index, 21.4 ( 2.3 kg/m 2 ). All subjects were generally healthy as evidenced by their medical history and a physical examination. All were non- smokers. The subjects were employees of the laboratory of Taiyo Kagaku Co. and gave written informed consent to the experimental protocol which was approved by the local re- search ethics committee. * Author to whom correspondence should be addressed (telephone 81-22-717-8904; fax 81-22-717-8905; e-mail miyazawa@biochem.tohoku.ac.jp). † Tohoku University Graduate School of Life Science & Agriculture. ‡ Taiyo Kagaku Co. § Sasakawa Clinic of Gastroenterology. Table 1. Catechin Composition of Green Tea Extract variable % by wt dose (mg)/subject epigallocatechin gallate (EGCg) a 24.6 82 epicatechin gallate 11.4 38 gallocatechin gallate 11.1 37 epicatechin 10.0 33 epigallocatechin 8.1 27 gallocatechin 7.7 26 catechin 3.3 11 total 76.2 254 a The chemical structure of EGCg is 3967 J. Agric. Food Chem. 1999, 47, 3967-3973 10.1021/jf981195l CCC: $18.00 © 1999 American Chemical Society Published on Web 09/25/1999