DETERMINATION OF D-CATECHIN PLASMA CONCENTRATION AND PHARMACOKINETIC PARAMETERS USING HPLC METHOD

d- Catechin (α-( 3,4-dihydroxyphenyl )-3,4-dihydro-2H-1-benzopyran-3,5,7-triol )is an important hepatotropic drug. It has been extensively used in 1980 's .A few methods for quantitative analysis of d-catechin in biological fluids have been reported , but they are not so sensitive or specific for pharmacokinetic interest.In this study, a specific, sensitive and reproducible RPHPLC-DAD method for quantifying d-catechin in plasma is established. Sep- Pak C₁₈ cartridge is used for sample preparation. HPLC separation is performed on Waters HPLC system consisting of a Model 990 diode array detector .A 150× 5 mm ID column containing YWG C₁₈, held at 25±0.5℃,and a mobile phase of methanol- 0.03 mol/L citric buffer solution containing 0.04% TEMED ,pH 4.7 (16:84, v/v ) at a flow rate of 2 ml/min is used. Under the studied conditions, the t_R for d- catechin is 7.74 min, that of the internal standard (cefetaxime, CTX)is 9.32 min .The peak of d- catechin is identified with the DAD and MS techniques .The limit of detection of the method is 9 ng, and the minimal detectable concentration in plasma is 17.4 ng/ml. There is a linear relationship between the peak area ratio over the range of 69.6～1160 ng/ml with r=0.9993. The method has been applied to determine the d-catechin concentration in rabbit plasma. The pharmacokinetic characteristics and parameters are studied.