Simultaneous determination of twelve tea catechins by high-performance liquid chromatography with electrochemical detection

摘要

A high-performance liquid chromatographic method with electrochemical detection was developed for the determination of twelve tea catechins including four major catechins: epicatechin (BC), epigallocatechin (EGC), epicatechin gallate (ECG) and epigallocatechin gallate (EGCG); four of their epimers at the C-2 position, C, GC, CG and GCG; and four methylated catechin derivatives, epigallocatechin-3-O-(3-O-methyl)gallate, gallocatechin-3-O-(3-O-methyl)gallate, epigallocatechin-3-O-(4-O-methyl)gallate and epicatechin-3-O-(3-O-methyl)gallate. These catechins were separated on an ODS C~8 reversed-phase column by isocratic elution with 0.1 M NaH2PO4 buffer (pH 2.5)—acetonitrile (87:13) containing 0.1 mM EDTA·2Na. The detection limits (S/N 3) of these catechins were approximately 10—40 pmol mV’ at an applied voltage of 600 mV. Extracting these catechins from tea leaf powder with H20—acetonitrile (1:1) at 30 0C for 40 mm inhibited the epimerization at C-2 significantly from these epicatechins compared to extraction with hot water at 90 0C. This analytical method is sensitive to and appropriate for the simultaneous determination of various biologically active catechins in green tea.