title: (-)-Epicatechin inhibits nitration and dimerization of tyrosine in hydrophilic as well as hydrophobic environments.
abstract: The flavanol (-)-epicatechin is known to protect against peroxynitrite-induced nitration and oxidation reactions. This study investigated the protection afforded by (-)-epicatechin against both these reaction types on one target molecule, the aminoacid tyrosine, in a hydrophilic milieu as well as with a lipophilic tyrosine derivative, N-t-BOC l-tyrosine tert-butyl ester (BTBE), bound to liposomes. The flavanol efficiently attenuated both tyrosine nitration and tyrosine dimerization (which is based on an initial oxidation reaction) and was active in the hydrophilic and hydrophobic systems at similar IC(50) values, approximately 0.02-0.05 mol (-)-epicatechin/mol peroxynitrite. Related procyanidin oligomers of different chain-length (dimer to octamer) were also tested for their protective properties, and exhibited protection that, on a monomer basis, was in the same order of magnitude as those for (-)-epicatechin.
authors.affiliation: Institut für Physiologische Chemie I, Heinrich-Heine-Universität Düsseldorf, Düsseldorf, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Schroeder
authors.forename: H
authors.initials: H
authors.lastname: Zhang
authors.forename: L O
authors.initials: LO
authors.lastname: Klotz
authors.forename: B
authors.initials: B
authors.lastname: Kalyanaraman
authors.forename: H
authors.initials: H
authors.lastname: Sies
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D002392:Catechin / Q000494:pharmacology*; D019281:Dimerization; D066298:In Vitro Techniques; D008081:Liposomes; D009566:Nitrates / Q000737:chemistry; D030421:Peroxynitrous Acid / Q000737:chemistry; D017382:Reactive Oxygen Species / Q000737:chemistry; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000187:drug effects*
chemical_list: D000975:Antioxidants; D008081:Liposomes; C434144:N-t-BOC-tyrosine-t-butyl ester; D009566:Nitrates; D017382:Reactive Oxygen Species; D030421:Peroxynitrous Acid; C002744:3-nitrotyrosine; D014443:Tyrosine; D002392:Catechin; C007543:dityrosine