Analysis of oxidized epigallocatechin gallate by liquid chromatography/mass spectrometry.
(-)-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.
Mizooku
Yasuo
Y
Department of Applied Chemistry, Kansai University, Suita, Osaka 564-8680, Japan.
Yoshikawa
Muneyoshi
M
Tsuneyoshi
Toshihiro
T
Arakawa
Ryuichi
R
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*
D002392:Catechin; C045651:epigallocatechin gallate