[Determination of D-catechin plasma concentration and pharmacokinetic parameters using HPLC method]

d-Catechin (alpha-(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 x 5 mm ID column containing YWG C18, held at 25 +/- 0.5 degrees C, 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 tR 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.