Influence of jinlingzi powder with different compatibility on activity of cytochrome P1 A2 from rat liver microsomes / 中国中药杂志

To illustrate the compability rule of Jinlingizi powder, by investigating the effects of Jinlingzi Powder with different compatibility on the enzymatic activity of cytochrome P1 A2 (CYP1A2) from rat liver microsome. The different compability of Jinlingizi powder is designed, based on the orthogonal array L9 (3(4)). In vitro test, rat liver microsomes incubation system is applied to detect the 50% inhibitory concentraton of Jinlingzi powder with different compatibility to cytochrome P1A2 (CYP1A2) enzyme. In vivo experiments, rats is treated orally with the different compability of Jinlingizi powder for 5 days, then be injected with probe drug phenacetin. The biosample from liver tissue is obtained by microdialysis probe, then analysisd by HPLC. The concentration-time data are modulated by software WinNonlin. IC50 data show no significant inhibitory activty to cytochrome P1 A2. Acetaminophen and phenacetin PK parameters indicate that the different compability of Jinlingizi powder can modulate the CYP 1A2 mediated metabolism, which is associate with the compatibility of Jinlingzi powder.

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.

Mechanism of mono-hydroxylation of daidzein in human liver microsomes / 药学学报

<p><b>AIM</b>To identify the cytochrome P450 (CYP) isoform (s) involved in daidzein mono-hydroxylated metabolites using human liver microsomes.</p><p><b>METHODS</b>Kinetic analysis of the rates of formation of mono-hydroxylated metabolites of daidzein, including 7,8,4'-trihydroxyisoflavone (7,8,4'-THI), 7,3',4'-trihydroxyisoflavone (7,3',4'-THI) and 6,7,4'-trihydroxyisoflavone (6,7,4'-THI), was performed using human liver microsomes (HLM) and recombinant enzymes at substrate concentrations ranging from 0.5 to 400 micromol x L(-1). Nine selective inhibitors or substrate probes specific for different CYP isoforms were applied for screening the isoform(s) responsible for mono-hydroxylated metabolism of daidzein.</p><p><b>RESULTS</b>Michaelis-Menten kinetic parameters were best fitted to one-component enzyme kinetic model. The mean Km (micromol x L(-1) ) and V(max) (micromol x g(-1) x min(-1)) values were 27 +/- 10 and 4. 8 +/- 2.1, 54 +/- 22 and 2.3 +/- 1.0, 51 +/- 29 and 2.2 +/- 0.8, for the formation rates of 7,8,4'-THI, 7,3',4'-THI, and 6,7,4'-THI, respectively. Furafylline, the CYP1A2 specific inhibitor, estrogen, and monoclonal antibody raised against human CYP1A2 (MAB-1A2) apparently inhibited the formation of mono-hydroxylated metabolites, The IC50 of Fur for the formation of 7,3',4'-THI, 6,7,4'-THI and 7,8,4'-THI was 1.0, 0.9 and 0. 8 mol x L(-1), respectively. The IC50 of estrogen for the formation of 7,3',4'-THI, 6,7,4'-THI and 7,8,4'-THI were 51, 60 and 64 mol x L(-1) respectively. The IC50 of MAB-1A2 for the formation of the mono-hydroxylated products was 1 mol x L(-1), but neither other selective inhibitor nor substrate probes, including coumarin (CYP2D6), sulphaphenzole ( CYP2C9/10), omeprazole ( CYP2C19), quinidine (CYP2D6), diethyldithiocarbamate (CYP2E1), troleandomycin (CYP3A4) and keteconazole (CYP3A4), did so with human liver microsomes.</p><p><b>CONCLUSION</b>The in vitro studies indicated that daidzein mono-hydroxylated products were principally metabolized by CYP1A2 in human.</p>