title: Analysis of oxidized epigallocatechin gallate by liquid chromatography/mass spectrometry.
abstract: (-)-Epigallocatechin gallate (EGCG) of catechins changes from non-colored at around neutral pH to yellow at higher pH region in aqueous solution. The pH-dependent oxidation of EGCG was analyzed by liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS). LC/MS/MS analysis of EGCG and its related compounds, (-)-epicatechin gallate (ECG) and (-)-epigallocatechin (EGC), successfully elucidated the structure relationship of EGCG solution involving the color change reaction at different pH conditions. The oxidation species produced at alkaline pH was detected at a different retention time from EGCG in the chromatograms of the EGCG sample. The oxidation species was found to correspond to M+14 (where M is the molecular weight of EGCG), which has two hydrogen atoms removed and addition of one oxygen atom to the gallyl moiety in the B-ring of EGCG.
authors.affiliation: Department of Applied Chemistry, Kansai University, Suita, Osaka 564-8680, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Mizooku
authors.forename: Muneyoshi
authors.initials: M
authors.lastname: Yoshikawa
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Tsuneyoshi
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Arakawa
mesh_terms: D002392:Catechin / Q000031:analogs & derivatives* / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D002392:Catechin; C045651:epigallocatechin gallate