title: Short-lived phenoxyl radicals formed from green-tea polyphenols and highly reactive oxygen species: an investigation by time-resolved EPR spectroscopy.
abstract: Polyphenols are effective antioxidants and their behavior has been studied in depth. However, a structural characterization of the species formed immediately upon hydrogen-atom transfer (HAT), a key reaction of oxidative stress, has not been achieved. The reaction of catechin and green-tea polyphenols with highly reactive O-centered H-abstracting species was studied at the molecular level and in real time by using time-resolved electron paramagnetic resonance (EPR) spectroscopy. This mirrors the reaction of highly reactive oxygen species with polyphenols. The results show that all phenolic OH groups display essentially identical reactivity. Accordingly, there is no site specificity for HAT and initial antioxidative events are demonstrated to be largely ruled by statistical (entropic) factors.
authors.affiliation: Institute of Physical and Theoretical Chemistry, Graz University of Technology, NAWI Graz, Stremayrgasse 9, 8010 Graz (Austria).
authors.forename: Dmytro
authors.initials: D
authors.lastname: Neshchadin
authors.forename: Stephen N
authors.initials: SN
authors.lastname: Batchelor
authors.forename: Itzhak
authors.initials: I
authors.lastname: Bilkis
authors.forename: Georg
authors.initials: G
authors.lastname: Gescheidt
mesh_terms: D001688:Biological Products; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D008958:Models, Molecular; D018384:Oxidative Stress; D010636:Phenols / Q000737:chemistry*; D059808:Polyphenols; D017382:Reactive Oxygen Species; D013662:Tea / Q000737:chemistry*
chemical_list: D001688:Biological Products; D010636:Phenols; D059808:Polyphenols; D017382:Reactive Oxygen Species; D013662:Tea; C042329:phenoxy radical
keywords: EPR spectroscopy; antioxidants; oxidative stress; polyphenols; radicals