Determination of catechins in human urine subsequent to tea ingestion by high-performance liquid chromatography with electrochemical detection

The title determination was conducted by HPLC with electrochemical detectio n using an ODS column and a mobile phase of acetonitrile: 0.1 M phosphate b uffer (pH 2.5) (15:85, v/v). The eight catechins, gallocatechin (GC), epiga llocatechin (EGC), catechin (C), epicatechin (EC), epigallocatechin gallate (EGCg), gallocatechin gallate (GCg), epicatechin gallate (ECg), and catech in gallate (Cg), were detected at 0.6 V vs Ag/AgCl. Good linear relationshi ps between current and amount were noted for 0.5-250 pmol of each catechin, with a correlation coefficient of 0.999 in each case. The detection limit for any one was 0.5 pmol (signal to noise ratio, S/N = 3). After the ingest ion of 340 ml canned green tea, GC, EGG, C, and EC, mostly in conjugated fo rm, were determined in urine samples. Conjugated catechins were hydrolyzed by enzymes using sulfatase and beta-glucuronidase. The time courses of the above four catechins showed a maxima at 1-3 h after tea ingestion. (+), (-) -EC and (+), (-)-C were present in canned tea. (C) 2000 Academic Press.