Analysis of (+)-catechin, (-)-epicatechin and their 3'- and 4'-O-methylated analogs. A comparison of sensitive methods.

(+)-Catechin and (-)-epicatechin are found in many foods and may have important effects on human health. These compounds, like many other catechols, are thought to be converted to methylated metabolites after ingestion. This paper describes the synthesis of the 3'- and 4'-methyl ethers and their unambiguous identification. These products, along with catechin, epicatechin and an internal standard, (+)-taxifolin, were separated using RP-HPLC with ultraviolet, electrochemical and fluorescence detection. The trimethylsilylated derivatives of the seven compounds were also separated by GC with mass spectrometric detection. The limits of detection and selectivity of the analytical methods were compared with respect to their application in complex matrices such as human plasma.