High-performance liquid chromatographic method for determination of clinofibrate and its application to a pharmacokinetic study in healthy volunteers.

A convenient and rapid HPLC method was developed for the determination of clinofibrate in human plasma using simple protein precipitation with the mixture of acetonitrile and 1M hydrochloric acid (95:5, v/v) followed by separation using an Inspire C(18) column with isocratic elution. The detection wavelength was 232nm and the flow rate was 1.0ml/min. The mobile phase consisted of acetonitrile and water containing 0.4% ortho-phosphoric acid (73:27, v/v). Linear calibration curve was obtained over the concentrations ranging from 0.5µg/ml to 32µg/ml (r(2)=0.999) with LLOQ of 0.5µg/ml. The RSD in both the intra-run and inter-run precision study was less than 5.4% and the extraction recoveries were above 90.7%. The HPLC method is reproducible and suitable for the quantification of clinofibrate in plasma. This method was successfully applied to the pharmacokinetic studies of clinofibrate in healthy volunteers. The elimination half-lives (t(1/2)) were (20.47±3.44), (18.19±2.62) and (21.51±4.78)h after single oral administration of 200, 400 and 600mg clinofibrate, respectively. The results of WinNonlin software showed that the area under the plasma concentration versus time curve from time 0 to 72h (AUC(0-72)) and peak plasma concentration (C(max)) were linearly related to dose (P>0.05).

Inhibition of human cytochrome P-450 CYP1A2 by flavonoids: a quantitative structure-activity relationship study / 药学学报

The inhibition activity of 36 flavonoids against CYP1A2 was determined by our previously developed in vitro method. The Comparative Molecular Similarity Indexes Analysis (CoMSJA) approach was used to probe the quantitative relationships between the flavonoids' molecular structural descriptors and their inhibitory activities. A reliable CoMSIA model with the combined electrostatic and hydrophobic fields was derived with the regression coefficient R2 of 0.948 and the cross-validation regression coefficient q2 of 0.630, separately, which is capable of elucidating the quantitative relationship between the 3D structural descriptors of the flavones and their bioactivities. Comparing with flavone, the larger pi-pi conjugated system of alpha-naphthoflavone significantly improved the biologically inhibitory ability. Based on the core structure of the latter, either electropositive substituents or hydrophobic groups at the 6, 3', and 4' ring positions or electronegative counterparts at the 5 ring position, can enhance the inhibitory potency against CYP1 A2 according to the CoMSIA contour maps.