Novel natural inhibitors of CYP1A2 identified by in silico and in vitro screening.

Inhibition of cytochrome P450 (CYP) is a major cause of herb-drug interactions. The CYP1A2 enzyme plays a major role in the metabolism of drugs in humans. Its broad substrate specificity, as well as its inhibition by a vast array of structurally diverse herbal active ingredients, has indicated the possibility of metabolic herb-drug interactions. Therefore nowadays searching inhibitors for CYP1A2 from herbal medicines are drawing much more attention by biological, chemical and pharmological scientists. In our work, a pharmacophore model as well as the docking technology is proposed to screen inhibitors from herbal ingredients data. Firstly different pharmaphore models were constructed and then validated and modified by 202 herbal ingredients. Secondly the best pharmaphore model was chosen to virtually screen the herbal data (a curated database of 989 herbal compounds). Then the hits (147 herbal compounds) were continued to be filtered by a docking process, and were tested in vitro successively. Finally, five of eighteen candidate compounds (272, 284, 300, 616 and 817) were found to have inhibition of CYP1A2 activity. The model developed in our study is efficient for in silico screening of large herbal databases in the identification of CYP1A2 inhibitors. It will play an important role to prevent the risk of herb-drug interactions at an early stage of the drug development process.

In-vitro and in-vivo evaluations of cytochrome P450 1A2 interactions with nuciferine.

OBJECTIVES: The effects of nuciferine, a major active aporphine alkaloid from the leaves of Nelumbo nucifera Gaertn, on a cytochrome P450 1A2 (CYP1A2) probe substrate were investigated in vitro and in vivo. METHODS: Nuciferine and recombinant human CYP1A2 were incubated together to study the impact of nuciferine on CYP1A2 in vitro. Nuciferine was administered orally to Wistar rats at a dose of 20 mg/kg to further estimate the impact of nuciferine on CYP1A2 in vivo. A probe substrate, phenacetin, was used to index the activity of CYP1A2. KEY FINDINGS: The IC50 value for nuciferine was determined to be 2.12 mmol/l. When phenacetin was intravenously coadministered with nuciferine compared with phenacetin alone, the elimination rate constant and total body clearance of phenacetin were decreased by 24.0% (P < 0.01) and 43.0% (P < 0.05), respectively. The mean residence time, apparent elimination half-time and area under the plasma concentration-time curve were increased by 22% (P < 0.005), 26.9% (P < 0.02) and 74.6% (P < 0.05), respectively. Similarly, when phenacetin was coadministered orally with nuciferine, the apparent elimination half-time in the nuciferine pretreated group was increased by 16.7% (P < 0.05) and the elimination rate constant was decreased by 15.4% (P < 0.05). CONCLUSIONS: The results suggest that nuciferine inhibited CYP1A2 activity in vitro and caused changes in the pharmacokinetic parameters of phenacetin in vivo.

Qualitative and quantitative analysis of traditional Chinese medicine Niu Huang Jie Du Pill using ultra performance liquid chromatography coupled with tunable UV detector and rapid resolution liquid chromatography coupled with time-of-flight tandem mass spectrometry.

An ultra performance liquid chromatography coupled with tunable UV detector (UPLC-TUV) and rapid resolution liquid chromatography coupled with time-of-flight tandem mass spectrometry (RRLC-Q-TOF) method was developed for the quality assessment of Niu Huang Jie Du Pill (NHJDP), a commonly used traditional Chinese medicine (TCM). Ten compounds were simultaneously identified by electrospray ion mass spectrometry (ESI/MS) and comparison with reference standards and literature data. All of them were quantified by UPLC method. Baseline separation was achieved on an ODS-140HTP C(18) column (2.3mum, 100mmx2.1mm I.D.) with linear gradient elution of acetonitrile-0.1% formic acid. This developed method provides good linearity (r(2)>0.9996), repeatability (RSD<3.63%), intra- and inter-day precisions (RSD<0.86%) with accuracies (97.88-101.56%) and recovery (98.88-101.92%) of 10 major constituents, namely baicalin, baicalein, wogonoside, wogonin, glycyrrhizic acid, liquiritin, rhein, emodin, chrysophanol and physcion. In addition, the principal component analysis (PCA) coupled with the UPLC fingerprint was applied to classify the NHJDP samples according to their manufacture corporation. This proposed method with high sensitivity and selectivity was successfully utilized to analyze 10 major bioactive compounds in 30 batches of NHJDPs, and the results demonstrate that this analytical method is simple and suitable for the original discrimination and quality control of this TCM.

Bufalin inhibits CYP3A4 activity in vitro and in vivo.

AIM: To investigate the inhibitory interactions of bufalin and CYP3A4. METHODS: Recombinant human CYP3A4 was incubated with bufalin in vitro. Bufalin was administered ig and iv to Wistar rats to further estimate its impact on CYP3A4, and midazolam was given to index the activity of CYP3A4. RESULTS: The IC(50) of bufalin was 14.52 micromol/L. Bufalin affected CYP3A4 activity with increases in AUC(0-t) and t(1/2), and decreases in CL and the formation of 1-hydroxy-midazolam after ig or iv administration of midazolam (P<0.05). An increase in C(max) after ig bufalin administration (P<0.05) was observed. CONCLUSION: Bufalin showed a modest but significant inhibition of CYP3A4 both in vitro and in vivo. The likelihood of an interaction between bufalin and the CYP3A4-metabolized drugs in human might not be negated.