THE SEPARATION OF CATECHINS IN GREEN TEA BY MICELLAR ELECTROKINETIC CAPILLARY ELECTROPHORESIS. Bryant C. Nelson and Joseph J. Dalluge, Building 222, Room B208, National Institute of Standards and Technology, Analytical Chemistry Division, Gaithersburg, MD USA (301-975-4485, email: bryant.nelson@nist.gov)

Capillary electrophoresis (CE) is a highly efficient technique for the separation and quantitative determination of a wide range of charged and uncharged biomolecules. With the introduction (1989) of commercial CE instrumentation, the technique has become increasingly established as a primary analytical tool in the clinical, biomedical and pharmaceutical fields. CE has been applied to the separation of biologically active catechins, e.g., (-)epigallocatechin-3-gallate (EGCG), (-)epicatechin gallate (ECG), (-)epigallocatechin (EGC) and (-)epicatechin (EC) extracted from green tea (Camellia sinesis). Tea catechins are polyphenolic compounds which have been shown to have positive anticarcinogenic properties in various strains of mice. Crude tea catechins were extracted from green tea leaves using a water/chloroform/ethyl acetate liquid-liquid extraction procedure. The lyophilized extract was analyzed on a Beckman P/ACE CE system using a borate/micellar separation buffer with direct UV absorbance detection. Good resolution and peak efficiency for the catechins was observed using a borate/sodium dodecyl sulfate buffer system. The catechins were identified on the basis of their migration times and on spiking experiments. Interference from unknown polyphenolic species did not occur. The method limit of detection for each of the catechins was shown to be < 20 ppm. A rapid, sensitive and reliable CE method has been developed and optimized for the separation and determination of low (ppm) levels of catechins in tea. The method requires no analyte derivatization or complex pre-analysis steps. With further refinement, the method may be applicable to the determination of catechins in blood plasma samples. The information gathered from these analyses may be useful for assessing the effects of tea consumption on preventing various cancers in humans.