title: Green tea metabolite EGCG protects membranes against oxidative damage in vitro.
abstract: Green tea polyphenols like epigallocatechin gallate (EGCG) have been proposed as a cancer chemopreventative. Several studies have shown that EGCG can act as an antioxidant by trapping proxyl radicals and inhibiting lipid peroxidation. The main propose of this study is to investigate the antioxidant capacity of EGCG using erythrocyte membrane-bound ATPases as a model. The effects of EGCG on t-butylhydroperoxide-induced lipid peroxidation and the activity of membrane-bound ATPases in human erythrocyte membranes were studied. The extent of oxidative damage in membranes was assessed by measuring lipid peroxidation, (TBARS, thiobarbituric acid reactive substances formation) and the activity of ATPases (Na(+)/K(+), Ca(2+), and CaM-activated Ca(2+) pump ATPases). EGCG blocked t-BHP induced lipid peroxidation in erythrocyte membranes, significantly (0.45 +/- 0.02 vs 0.20 +/- 0.01; t-BHP vs t-BHP + EGCG respectively, microm/L TBARS) (p < 0.05). EGCG also protected ATPases against t-BHP induced damage; for Na/K ATPase (2.4 +/- 0.2 vs 1.6 +/- 0.1 vs 2.44 +/- 0.2, nmol Pi/min/mg protein, control vs t-BHP vs t-BHP and EGCG respectively), for Ca ATPase (5.8 +/- 0.4 vs 3.9 +/- 0.3 vs 5.6 +/- 0.34, nmol Pi/min/mg protein, control vs t-BHP vs t-BHP and EGCG respectively) and for CaM-Ca ATPase (14.7 +/- 0.7 vs 7.3 +/- 0.4 vs 11.6 +/- 0.55, nmol Pi/min/mg protein, control vs t-BHP vs t-BHP and EGCG respectively) (p < 0.05). In conclusion our results indicate that EGCG is a powerful antioxidant that is capable protecting erythrocyte membrane-bound ATPases against oxidative stress.
authors.affiliation: Department of Laboratory Medicine, University of Washington, Harborview Medical Center, 325 9th Avenue, Seattle, WA 98104, USA.
authors.forename: Yasi
authors.initials: Y
authors.lastname: Saffari
authors.forename: S M Hossein
authors.initials: SM
authors.lastname: Sadrzadeh
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000972:Antineoplastic Agents, Phytogenic / Q000737:chemistry / Q000378:metabolism*; D000975:Antioxidants / Q000737:chemistry / Q000378:metabolism*; D002392:Catechin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D004910:Erythrocyte Membrane / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D015227:Lipid Peroxidation; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010936:Plant Extracts / Q000378:metabolism*; D013662:Tea / Q000737:chemistry*; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D000975:Antioxidants; D010936:Plant Extracts; D013662:Tea; D017392:Thiobarbituric Acid Reactive Substances; D002392:Catechin; C045651:epigallocatechin gallate; D000251:Adenosine Triphosphatases