title: pH-Dependent radical scavenging capacity of green tea catechins.
abstract: The effect of pH on the radical scavenging capacity of green tea catechins was investigated using experimental as well as theoretical methods. It was shown that the radical scavenging capacity of the catechins, quantified by the TEAC value, increases with increasing pH of the medium. Comparison of the pKa values to theoretically calculated parameters for the neutral and deprotonated forms indicates that the pH-dependent increase in radical scavenging activity of the catechins is due to an increase of electron-donating ability upon deprotonation. The data also reveal that the radical scavenging activity of the catechins containing the pyrogallol (or catechol) and the galloyl moiety over the whole pH range is due to an additive effect of these two independent radical scavenging structural elements. Altogether, the results obtained provide better insight into the factors determining the radical scavenging activity of the catechins and reveal that the biological activity of green tea catechins will be influenced by the pH of the surrounding medium or tissues.
authors.affiliation: Faculty of Commodity Science, The Poznań University of Economics, al. Niepodległości 10, 60-967 Poznań, Poland.
authors.forename: Małgorzata
authors.initials: M
authors.lastname: Muzolf
authors.forename: Henryk
authors.initials: H
authors.lastname: Szymusiak
authors.forename: Anna
authors.initials: A
authors.lastname: Gliszczyńska-Swigło
authors.forename: Ivonne M C M
authors.initials: IM
authors.lastname: Rietjens
authors.forename: Bozena
authors.initials: B
authors.lastname: Tyrakowska
mesh_terms: D002392:Catechin / Q000494:pharmacology*; D016166:Free Radical Scavengers / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D013662:Tea / Q000737:chemistry*
chemical_list: D016166:Free Radical Scavengers; D013662:Tea; D002392:Catechin