Investigation of epigallocatechin-3-O-caffeoate and epigallocatechin-3-O-p-coumaroate in tea leaves by LC/MS-MS analysis.

ABSTRACT

(-)-Epigallocatechin-3-O-gallate (EGCG), the major catechin present in green tea, exhibits potent antioxidant activity. We thereby investigated the presence of unknown components bearing the (-)-epigallocatechin (EGC) moiety in fresh tea leaf samples. Initially, liquid chromatography tandem mass spectrometry (LC-MS/MS) was employed to examine fresh tea leaves of the Yabukita, the most popular tea cultivar in Japan, which suggested the presence of the EGC phenylpropanoid derivatives, (-)-epigallocatechin-3-O-p-coumaroate (EGCpCA) and (-)-epigallocatechin-3-O-caffeoate (EGCCA). The structures of the detected EGCpCA and EGCCA were then confirmed by LC-MS/MS using synthesized EGCpCA and EGCCA as standards. In addition, EGCpCA and EGCCA were evaluated for their antioxidant activity in the ORAC (oxygen radical antioxidant capacity) and DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assays, where EGCCA (8.60µmolTE/µmol, TE=Trolox equivalents) exhibited a stronger antioxidant activity than EGCG (5.52µmolTE/µmol) in the ORAC assay. Finally, EGCpCA and EGCCA were quantitated in several tea leaf samples using LC-MS/MS, and it was found that these compounds were present in lower quantities (EGCpCA, 16.8-345.8µg/g, EGCCA, 4.3-75.1µg/g in the dry tea leaves) than the major catechins. In this study, we found the potent antioxidant EGCCA using LC-MS/MS and revealed its wide existence in various tea leaves.