M. Sano et al., Simultaneous determination of twelve tea catechins by high-performance liquid chromatography with electrochemical detection, ANALYST, 126(6), 2001, pp. 816-820
A high-performance liquid chromatographic method with electrochemical detec
tion was developed for the determination of twelve tea catechins including
four major catechins: epicatechin (EC), epigallocatechin (EGC), epicatechin
gallate (ECG) and epigallocatechin gallate (EGCG); four of their epimers a
t the C-2 position, C, GC, CG and GCG; and four methylated catechin derivat
ives, epigallocatechin-3-O-(3-O-methyl)gallate, gallocatechin-3-O-(3-O-meth
yl)gallate, epigallocatechin-3-O-(4-O-methyl)gallate and epicatechin-3-O-(3
-O-methyl)gallate. These catechins were separated on an ODS C-18 reversed-p
hase column by isocratic elution with 0.1 M NaH2PO4 buffer (pH 2.5)-acetoni
trile (87:13) containing 0.1 mM EDTA.2Na. The detection limits (S/N = 3) of
these catechins were approximately 10-40 pmol ml(-1) at an applied voltage
of 600 mV. Extracting these catechins from tea leaf powder with H2O-aceton
itrile (1:1) at 30 degreesC for 40 min inhibited the epimerization at C-2 s
ignificantly from these epicatechins compared to extraction with hot water
at 90 degreesC. This analytical method is sensitive to and appropriate for
the simultaneous determination of various biologically active catechins in
green tea.