Baolian Wang

Inhibitory effects of herbal constituents on P-glycoprotein in vitro and in vivo: herb-drug interactions mediated via P-gp.

Modulation of drug transporters via herbal medicines which have been widely used in combination with conventional prescription drugs may result in herb-drug interactions in clinical practice. The present study was designed to investigate the inhibitory effects of 50 major herbal constituents on P-glycoprotein (P-gp) in vitro and in vivo as well as related inhibitory mechanisms. Among these herbal medicines, four constituents, including emodin, 18β-glycyrrhetic acid (18β-GA), dehydroandrographolide (DAG), and 20(S)-ginsenoside F₁ [20(S)-GF₁] exhibited significant inhibition (>50%) on P-gp in MDR1-MDCKII and Caco-2 cells. Emodin was the strongest inhibitor of P-gp (IC₅₀=9.42 μM), followed by 18β-GA (IC₅₀=21.78 μM), 20(S)-GF₁ (IC₅₀=76.08 μM) and DAG (IC₅₀=77.80 μM). P-gp ATPase activity, which was used to evaluate the affinity of substrates to P-gp, was stimulated by emodin and DAG with Km and Vmax values of 48.61, 29.09 μM and 71.29, 38.45 nmol/min/mg protein, respectively. However, 18β-GA and 20(S)-GF₁ exhibited significant inhibition on both basal and verapamil-stimulated P-gp ATPase activities at high concentration. Molecular docking analysis (CDOCKER) further elucidated the mechanism for structure-inhibition relationships of herbal constituents with P-gp. When digoxin was co-administered to male SD rats with emodin or 18β-GA, the AUC(₀₋t) and Cmax of digoxin were increased by approximately 51% and 58%, respectively. Furthermore, 18β-GA, DAG, 20(S)-GF₁ and Rh₁ at 10 μM significantly inhibited CYP3A4/5 activity, while emodin activated the metabolism of midazolam in human liver microsomes. In conclusion, four herbal constituents demonstrated inhibition of P-gp to specific extents in vitro and in vivo. Taken together, our findings provided the basis for the reliable assessment of the potential risks of herb-drug interactions in humans.

Effects of capsaicin and dihydrocapsaicin on human and rat liver microsomal CYP450 enzyme activities in vitro and in vivo

Capsaicin and dihydrocapsaicin, the two most abundant members of capsaicinoids in chili peppers, are widely used as food additives and for other purposes. In this study, we examined the inhibitory potentials of capsaicin and dihydrocapsaicin against CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4/5 activities in human liver microsomes. The effects of these two capsaicinoids on CYP450 enzymes were also evaluated in vivo in rats. The results demonstrated that capsaicin and dihydrocapsaicin moderately inhibited five isozymes (IC50 values ranging from 4.4 to 61.8 μM), with the exception of CYP2E1 (IC50>200 μM). Both capsaicinoids exhibited competitive, mixed, and noncompetitive inhibition on these isozymes (K i = 3.1 ± 0.5 − 78.6 ± 8.4 μM). Time-dependent inhibition of CYP3A4/5 by capsaicin was found. After multiple administrations of capsaicin and dihydrocapsaicin (1, 4, and 10 mg/kg) to rats, chlorzoxazone 6-hydroxylase activity and the expression of CYP2E1 were increased in liver microsomes. Our findings indicated that the possibility of food–drug interactions mediated by capsaicin and dihydrocapsaicin could not be excluded, and provided the useful information for evaluating the anticarcinogenic potentials of these two capsaicinoids.

Simultaneous quantification of three active alkaloids from a traditional Chinese medicine Ramulus Mori (Sangzhi) in rat plasma using liquid chromatography-tandem mass spectrometry.

Fagomine, 1-deoxynojirimycin (DNJ) and 1,4-dideoxy-1,4-imino-d-arabinitol (DAB) are the major bioactive constituents in the active fraction of alkaloids from the traditional Chinese medicine mulberry twig (Ramulus Mori, Chinese name Sang Zhi), which has a strong activity on α-glucosidase in vitro and in vivo. A rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the simultaneous determination of DNJ, fagomine and DAB in rat plasma. Plasma samples were prepared using a simple protein precipitation by the addition of 1% volume of Tris and two volumes of methanol-acetonitrile. The analytes and internal standard (IS, miglitol) were chromatographed in an XBridge™ amide column with a gradient mobile phase of acetonitrile-water (0.1% ammonium hydroxide) at a flow rate of 0.7mL/min. The detection was performed on a triple quadrupole tandem mass spectrometer equipped with electrospray ionization (ESI) source in positive ion mode by multiple reaction monitoring (MRM) mode. Linear detection responses were obtained for DNJ ranging from 5.00 to 5000.00ng/mL, 10.00 to 2500.00ng/mL for fagomine and DAB. The lower limits of quantification (LLOQs) were 5.00, 10.00, 10.00ng/mL for DNJ, fagomine and DAB, respectively. Intra-day and inter-day precisions (R.S.D.%) were within 10% for three analytes with accuracies (R.E.%) less than 12%. The mean recoveries of analytes were greater than 85%. All analytes were proved to be stable during the sample storage, preparation and analytic procedures. The method was successfully applied to the pharmacokinetic study of the three alkaloids in rats after oral administration of the active fraction of alkaloids from mulberry twig.

Multifaceted interaction of the traditional Chinese medicinal herb Schisandra chinensis with cytochrome P450-mediated drug metabolism in rats

ETHNOPHARMACOLOGICAL RELEVANCE Schisandra chinensis (SC), officially listed as a sedative and tonic in the Chinese Pharmacopoeia, has been used as a common component in various prescriptions in Traditional Chinese Medicine (TCM) and more recently in western medicine for its antihepatotoxic effect. To assess the possible herb-drug interaction, effects of SC extracts on hepatic cytochrome P450 (P450, CYP) enzymes were studied. MATERIAL AND METHODS Effects of SC extracts on rat hepatic CYP450 enzymes in vitro and in vivo were investigated by probe substrates method, real-time RT-PCR assay and Western blotting analysis. Furthermore, the effects of SC alcoholic extract on the PK of four SC lignans and the drugs possibly co-administrated in vivo were studied in male Sprague-Dawley rat. RESULTS SC aqueous extract and alcoholic extract showed significant inhibitory effect on the activities of rat liver microsomal CYP1A2, 2C6, 2C11, 2D2, 2E1 and 3A1/2 in vitro. Multiple administrations of SC aqueous extract (1.5g/kg, qd×7d) and alcoholic extract (1.5g/kg, qd×7d) increased the activities, mRNA and protein expressions of CYP2E1 and CYP3A1/2, and meanwhile, inhibited the activities and mRNA expression of CYP2D2 in vivo. The in vivo metabolism of four SC lignans, such as schisandrin, schisantherin A, deoxyshisandrin and γ-schisandrin, and chlorzoxazone was significantly accelerated, exhibited by the reduced AUC and increased CLz/F, by 7-day pretreatment with SC alcoholic extract. However, both single and multiple dosing treatments of SC alcoholic extract remarkably decreased the in vivo metabolism of tacrolimus indicated by the enhanced AUC (7-12 fold) and elevated Cmax (10 fold). CONCLUSION These results revealed that the SC extracts exhibited multifaceted effects on rat hepatic CYP450 enzymes. Herb-drug interaction should be paid intense attention between SC components and drugs metabolized by different CYP450 enzymes.

Effect of buagafuran on liver microsomal cytochrome P450 in rats

Buagafuran (BF), derived from α-agarofuran, is a promising anti-anxiety drug in phase I clinical trials. The present study was undertaken to examine the regulation of BF on liver cytochrome P450 (CYP) isoforms in rats. After being administered (4, 16, and 64 mg/kg) by gavage for 7 continuous days, the activities of CYP isoforms were measured by the qualification of six metabolites from CYP probe substrates using LC-MS/MS analysis. The mRNA and protein levels of CYPs were detected by reverse transcription polymerase chain reaction and Western blotting assay, respectively. Using phenacetin and chlorzoxazone as probe drugs, the activities of CYP1A2 and CYP2E1 were monitored in vivo. The result indicated that BF significantly increased the activity and protein levels of CYP1A2 and CYP2E1, while the mRNA levels were elevated to a certain extent. CYP2C6 and CYP2C11 were also slightly induced by BF, but no effect on liver CYP3A was detected in rats. Treatment of BF orally resulted in the decreasing of AUC, MRT and increasing of CL/F of phenacetin as well as production of acetaminophen in rats. The similar pharmacokinetic changes were also observed when using chlorzoxazone as a probe drug. Collectively, BF has inducing potential of liver CYP1A2 and CYP2E1 and may influence the corresponding pharmacokinetics of other drugs.

Metabolism of F18, a Derivative of Calanolide A, in Human Liver Microsomes and Cytosol

10-Chloromethyl-11-demethyl-12-oxo-calanolide (F18), an analog of calanolide A, is a novel potent nonnucleoside reverse transcriptase inhibitor against HIV-1. Here, we report the metabolic profile and the results of associated biochemical studies of F18 in vitro and in vivo. The metabolites of F18 were identified based on liquid chromatography-electrospray ionization mass spectrometry and/or nuclear magnetic resonance. Twenty-three metabolites of F18 were observed in liver microsomes in vitro. The metabolism of F18 involved 4-propyl chain oxidation, 10-chloromethyl oxidative dechlorination and 12-carbonyl reduction. Three metabolites (M1, M3-1, and M3-2) were also found in rat blood after oral administration of F18 and the reduction metabolites M3-1 and M3-2 were found to exhibit high potency for the inhibition of HIV-1 in vitro. The oxidative metabolism of F18 was mainly catalyzed by cytochrome P450 3A4 in human microsomes, whereas flavin-containing monooxygenases and 11β-hydroxysteroid dehydrogenase were found to be involved in its carbonyl reduction. In human cytosol, multiple carbonyl reductases, including aldo-keto reductase 1C, short-chain dehydrogenases/reductases and quinone oxidoreductase 1, were demonstrated to be responsible for F18 carbonyl reduction. In conclusion, the in vitro metabolism of F18 involves multiple drug metabolizing enzymes, and several metabolites exhibited anti-HIV-1 activities. Notably, the described results provide the first demonstration of the capability of FMOs for carbonyl reduction.

Simultaneous quantification of MTC-220 and its metabolites in beagle dog plasma by liquid chromatography-tandem mass spectrometry.

A sensitive LC-ESI-MS/MS method for simultaneous determination of MTC-220 and its metabolites (paclitaxel and MDA-linker) in dog plasma has been developed and validated. After addition of docetaxel (internal standard), plasma samples containing MTC-220, paclitaxel and MDA-linker were prepared based on a simple protein precipitation by adding two volumes of acetonitrile. The separation was performed on a ZorbaxSB-C18 column (3.5μm, 2.1mm×100mm) at a flow rate of 0.2ml/min, using acetonitrile/water containing 0.1% formic acid (v/v) as mobile phase. The detection was performed on a triple quadrupole tandem mass spectrometer equipped with electrospray ionization (ESI) by selected reaction monitoring (SRM). The MS/MS ion transit ions monitored were 1444.4→623.8 for MTC-220, 876.4→307.9 for paclitaxel, 631.2→531.2 for MDA-linker and 830.2→549.1 for the internal standard. Linear detection responses were obtained for MTC-220, paclitaxel and MDA-linker ranging from 10 to 5000, 5 to 2500 and 5 to 500ng/ml, respectively. The lower limits of quantitation (LLOQs) for MTC-220, paclitaxel and MDA-linker were 10, 5 and 5ng/ml, respectively. The intra-day and inter-day precisions (RSD, %) of the three analytes do not exceed 10.9% except for LLOQs (≤17.50), and the accuracy (RE, %) were within ±17.5% for LLOQs and ±12.6% for the others. The average recoveries of three compounds were greater than 85.0%. The analytes were proved to be stable during all sample storage, preparation and analytic procedures. The validated method was successfully applied to pharmacokinetic studies of MTC-220 and its metabolites in beagle dogs after intravenous infusion of MTC-220 at 2.5mg/kg.

Pharmacokinetics, Tissue Distribution, and Elimination of Three Active Alkaloids in Rats after Oral Administration of the Effective Fraction of Alkaloids from Ramulus Mori, an Innovative Hypoglycemic Agent

In this study, we systematically investigated the plasma pharmacokinetics, tissue distribution, and elimination of three active alkaloids after oral administration of the effective fraction of alkaloids from Ramulus Mori (SZ–A)—an innovative hypoglycemic agent—in rats. Moreover, the influences of other components in SZ–A on dynamic process of alkaloids were explored for the first time. The results showed that 1-deoxynojirimycin (DNJ), fagomine (FGM) and 1,4-dideoxy-1,4-imino-d-arabinitol (DAB) exhibited nonlinear pharmacokinetics following oral administration of SZ–A (40–1000 mg/kg). The prolonged t1/2 and greater area under concentration-time curve (AUC) versus time (AUC0–t) of DNJ for SZ–A than for purified DNJ has been observed after both oral and intravenous administration. It was found that other components in SZ–A could enhance the absorption of DNJ through the intestinal barrier. The major distribution tissues of DNJ, FGM, and DAB were the gastrointestinal tract, liver, and kidney. Three alkaloids were mainly excreted into urine and feces, but less into bile. Interestingly, the excess excretion of FGM was revealed to be partly due to the biotransformation of other components in SZ–A via gut microbiota. These information provide a rational basis for the use of SZ–A in clinical practice.

Determination of IMM-H004, a novel neuroprotective agent, in rat plasma and brain tissue by liquid chromatography–tandem mass spectrometry

A rapid and sensitive liquid chromatography-tandem mass spectrometry method for determination of IMM-H004, a novel neuroprotective agent, in rat plasma and brain was developed. Plasma and brain tissue homogenate samples containing IMM-H004 and propranolol (internal standard, IS) were prepared by using a direct protein precipitation of acetonitrile. Separation was carried out in Zorbax SB-C18 column at a flow rate of 0.3mL/min utilizing acetonitrile/water as mobile phases which contain 0.5% formic acid (v/v). Triple quadrupole mass spectrometer was used for detection with selective reaction monitoring. The mass transition ion-pairs were 305→248 for IMM-H004 and 260→183 for IS in positive ion mode. The linear ranges of IMM-H004 were 5-1000ng/mL in plasma and 1-200ng/mL in brain tissue homogenate. The intra- and inter-day precisions were within ±14.9% for analyte in both matrices (±17.0% at the lowest limit of quantification level), while the deviation of assay accuracy was within ±12.9%. No obvious matrix effect was observed. The recovery of the analyte was higher than 85.3%. IMM-H004 was stable during the whole analytic process. The method was applied successfully to the plasma and brain pharmacokinetic study of IMM-H004 in rats after a single intravenous administration.

Determination of 10-chloromethyl-11-demethyl-12-oxo-calanolide A in rat plasma using liquid chromatography-tandem mass spectrometry and its application to pharmacokinetics.

A rapid and specific liquid chromatography-tandem mass spectrometry for the quantitation of 10-chloromethyl-11-demethyl-12-oxo-calanolide A (F18), a small-molecule nonnucleoside reverse transcriptase inhibitor, was developed and validated in rat plasma. F18 was monitored by positive electrospray ionization in the selected reaction monitoring mode. The standard curve was linear over the range of 2-1000 ng/mL. The method was used to determine the plasma concentration of F18 after a single oral dose of 50 mg/kg in rats.