Analytical method of measuring tea catechins in human plasma by solid-phase extraction and HPLC with electrochemical detection

Keizo Umegaki*, Ayako Sugisawa, Kazuhiko Yamada, Mitsuru Higuchi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

37 Citations (Scopus)


We developed an analytical method for measuring tea catechins in plasma by solid-phase extraction (SPE), followed by HPLC with a coulometric electrochemical detector. The plasma was mixed with an equal volume of acetonitrile to precipitate protein, and catechins in the resulting supernatant were extracted by SPE, using a C18 cartridge. To correct the extraction efficiency, ethyl gallate was simultaneously added with acetonitrile as an internal standard. Plasma samples were treated in microtubes, and evaporation and SPE were performed by the use of a vacuum centrifuge and vacuum manifold for SPE. The use of these instruments allowed the handling of a large number of samples simultaneously. In this method, (-)-epicatechin (EC), (-)-epicatechin-3-O-gallate (ECg), (-)-epigallocatechin (EGC), (-)-epigallocatechin-3-O-gallate (EGCg), and ethyl gallate could be detected as a single peak with high sensitivity. For an analysis of the conjugated form of catechins, plasma samples were treated with glucuronidase and sulfatase. Type H-2 β-glucuronidase effectively digested the conjugated forms, and the enzyme also converted EGCg and ECg to their nongallated form. When the concentrations of catechins in plasma were analyzed in subjects who took a single dose of catechin liquid, the concentration of free EGCg in plasma reached a maximum of 300 nM at 1 h after intake; those of the other free form of catechins increased only slightly after the intake. The concentration of total catechins (free+conjugated forms) in plasma increased up to 2 h after the intake.

Original languageEnglish
Pages (from-to)402-408
Number of pages7
JournalJournal of Nutritional Science and Vitaminology
Issue number6
Publication statusPublished - 2001
Externally publishedYes


  • Analytical method
  • Catechins
  • Electrochemical detection
  • Solid phase extraction

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Food Science


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