Abstract: Using the HPLC technique, changes of concentration of eight catechin monomers versus time in boiling infusion were measured. Extraction kinetics of epicatechins and trans-catechins were systematically studied by applying a two-phase model in determining the kinetic and equilibrium data. Dynamic changes of ratios of EGCG and GCG to total catechin were studied, too. The results showed that epicatechins infused faster than trans-catechins dramaticlly, the former reached its maximum at 5min, then the value declined with time. While trans-catechins extraction rate increased steadily with time, reaching the peak value at the end of infusing. According to the rate constant K_obs, the order of extraction velocity of eight catechin monomers was as follows: EC>EGC>EGCG>ECG>GC>C>GCG>CG.

Key words: trans-catechin, epicatechin, extraction rate, rate constant K_obs