Analysis of urinary metabolites of tea catechins by liquid chromatography/electrospray ionization mass spectrometry

Tea has been proposed to have beneficial health effects which have been att ributed tu the polyphenolic compounds known as catechins, The bioavailabili ty and biotransformation of these compounds, however, are not clearly under stood. In this study, we used liquid chromatography/ electrospray ionizatio n-mass spectrometry (LC/ESI-MS) to determine urinary glucuronidated and sul fated tea catechins and their metabolites (including methylated and ring-fi ssion metabolites) based on the detection of deprotonated molecular ions an d aglycone fragment ions. The compound resolution was achieved both chromat ographically and mass spectroscopically. After green tea administration, th e major conjugates appeared in human, mouse, and rat urine samples were ide ntified as monoglucuronides and monosulfates of(-)-epigallocatechin (EC;C) and (-)-epicatechin. We also found O-methyl-EGC-O-glucuronides and -O-sulfa tes and O-methyl-epicatechin-O-sulfates in human urine. (-)-5-(3',4',5'-Tri hydroxyphenyl)-gamma -valero- (M4) and (-)-5-(3',4'-dihydroxyphenyl gamma - y-valerolaconte (M6), the ring-fission metabolites of EGC and (-)-epicatech in, respectively, were also predominantly in monoglucuronide and monosulfat e for ms in the urine. In comparison to rats, the urinary metabolite profil es of tea catechins in mice resemble more closely to those in humans. This is the first report describing direct simultaneous analysis of multiple tea catechin conjugates in urine samples. This method will allow more thorough investigations of the biotransformation of tea polyphenols.