title: Complexation of epigallocatechin gallate (a green tea extract, egcg) with Mn2+: nuclear spin relaxation by the paramagnetic ion.
abstract: Metal-binding sites in epigallocatechin gallate (egcg) were identified by measuring (1)H nuclear spin relaxation time T(1) under the coexistence of paramagnetic Mn(2+). The T(1) of the proton of gallate ring (D-ring) was shortened by the paramagnetic ion to a greater extent than the proton in gallocatechin ring (B-ring); the D-ring OH groups occupy the first coordination sphere around a metal ion to form a diolate chelate ring, while B-ring OH groups have a weak interaction with the metal ion. Comparison of changes in T(1) of egcg and epigallocatechin (egc) indicates that the gallate ring has a higher coordination capability than that of the gallocatechin ring so that the former plays a predominant role in the complex formation of egcg.
authors.affiliation: Departamento de Investigación en Polímeros y Materiales, Universidad de Sonora, Apartado Postal 130, Hermosillo, Sonora 83000, México. rnavarro@guaymas.uson.mx
authors.forename: Rosa E
authors.initials: RE
authors.lastname: Navarro
authors.forename: Hisila
authors.initials: H
authors.lastname: Santacruz
authors.forename: Motomichi
authors.initials: M
authors.lastname: Inoue
mesh_terms: D001665:Binding Sites; D002392:Catechin / Q000031:analogs & derivatives* / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008345:Manganese / Q000737:chemistry*; D015394:Molecular Structure; D010936:Plant Extracts / Q000737:chemistry; D013662:Tea / Q000737:chemistry
chemical_list: D010936:Plant Extracts; D013662:Tea; D008345:Manganese; D002392:Catechin; C045651:epigallocatechin gallate; C057580:gallocatechol