Telmisartan increases systemic exposure to rosuvastatin after single and multiple doses, and in vitro studies show telmisartan inhibits ABCG2-mediated transport of rosuvastatin.

PURPOSE: The ATP-binding cassette transporter G2 (ABCG2) plays an important role in the disposition of rosuvastatin. Telmisartan, a selective angiotension-II type 1 (AT1) receptor blocker, inhibits the transport capacity of ABCG2, which may result in drug interactions. This study investigated the pharmacokinetic interaction between rosuvastatin and telmisartan and the potential mechanism. METHODS: In this two-phase fixed-order design study, healthy subjects received single doses of 10 mg rosuvastatin at baseline and after telmisartan 40 mg daily for 14 days. Patients with hyperlipidaemia who had been taking rosuvastatin 10 mg daily for at least 4 weeks were given telmisartan 40 mg daily for 14 days together with rosuvastatin. Plasma concentrations of rosuvastatin were measured over 24 h before and after telmisartan administration. In vitro experiments using a bidirectional transport assay were performed to investigate the involvement of ABCG2 in the interaction. RESULTS: Co-administration of telmisartan significantly increased the maximum plasma concentration (C max) and the area under the plasma concentration-time curve (AUC) of rosuvastatin by 71 and 26 %, respectively. The T max values were reduced after administration of telmisartan. There was no significant difference in the interaction of rosuvastatin with telmisartan between healthy volunteers and patients receiving long-term rosuvastatin therapy or among subjects with the different ABCG2 421 C>A genotypes. The in vitro experiment demonstrated that telmisartan inhibited ABCG2-mediated efflux of rosuvastatin. CONCLUSION: This study demonstrated that telmisartan significantly increased the systemic exposure to rosuvastatin after single and multiple doses.

Effect of common polymorphisms of the farnesoid X receptor and bile acid transporters on the pharmacokinetics of ursodeoxycholic acid.

Ursodeoxycholic acid (UDCA), a natural, dihydroxy bile acid, promotes gallstone dissolution and has been attributed with several other beneficial effects. The farnesoid X receptor (FXR) may influence the pharmacokinetics of UDCA by modulating the expression of bile acid transporters. This exploratory study examined whether common functional polymorphisms in FXR and in bile acid transporter genes affect the pharmacokinetics of exogenous UDCA. Polymorphisms in genes for transporters involved in bile acid transport, solute carrier organic anion 1B1 (SLCO1B1) 388A>G and 521T>C, solute carrier 10A1 (SLC10A1) 800 C>T and ATP-binding cassette B11 (ABCB11) 1331T>C, and the FXR -1G>T polymorphism were genotyped in 26 male Chinese subjects who ingested single oral 500-mg doses of UDCA. Plasma concentrations of UDCA and its major conjugate metabolite glycoursodeoxycholic acid (GUDCA) were determined. The mean systemic exposure of UDCA was higher in the five subjects with one copy of the FXR -1G>T variant allele than in those homozygous for the wild-type allele (n = 21) (AUC0-24 h : 38.5 ± 28.2 vs. 20.9 ± 8.0 µg h/mL, P = 0.021), but this difference appeared mainly due to one outlier with the -1GT genotype and elevated baseline and post-treatment UDCA concentrations. After excluding the outlier, body weight was the only factor associated with plasma concentrations of UDCA and there were no significant associations with the other polymorphisms examined. None of the polymorphisms affected the pharmacokinetics of GUDCA. This study showed that the common polymorphisms in bile acid transporters had no significant effect on the pharmacokinetics of exogenous UDCA but an effect of the FXR polymorphism cannot be excluded.

Hydrolysis is the dominating in vivo metabolism pathway for arctigenin: identification of novel metabolites of arctigenin by LC/MS/MS after oral administration in rats.

The phenylpropanoid dibenzylbutyrolactone lignan arctigenin, a key component found in Arctium lappa, or burdock, has been reported with a variety of therapeutic effects including anticancer, anti-inflammation, and antivirus effects. Using LC/MS/MS, three novel metabolites of arctigenin, namely, arctigenic acid, arctigenin-4-O'-glucuronide, and 4-O-demethylarctigenin were identified after oral administration of arctigenin in rats for the first time. Another potential metabolite of arctigenin, arctigenin-4'-O-sulfate, was identified in vitro but not in vivo. Structure of arctigenic acid, the major metabolite of arctigenin, was confirmed by 13C-NMR and 1H-NMR. Rapid hydrolysis in plasma was identified as the major metabolic pathway of arctigenin after its oral administration, with Vmax, Km, and Clint in rat plasma determined to be 2.21 ± 0.12 nmol/min/mg, 89.12 ± 9.44 µM, and 24.74 µL/min/mg, respectively. Paraoxonase 1 was further confirmed to be the enzyme responsible for arctigenin hydrolysis, with Vmax, Km, and Clint determined to be 55.39 ± 1.49 nmol/min/mg, 300.3 ± 10.86 µM, and 184.45 µL/min/mg, respectively.

Pharmacokinetic interactions among major bioactive components in Radix Scutellariae via metabolic competition.

Baicalein (B), wogonin (W) and oroxylin A (OA) are major components in Radix Scutellariae with similar pharmacokinetic properties. Due to the co-presence of these three flavones in herbal formulations for Radix Scutellariae, they are likely consumed together. The aim of this study is to investigate whether the pharmacokinetics of individual flavones is influenced by each other and the underlying mechanism of the interaction. Various systems were utilized in the current study including a rat in vivo study, a Caco-2 cell monolayer model and a rat in situ single-pass intestinal perfusion as well as in vitro enzymatic kinetics studies. The B, W and OA given singly as well as in a mixture were administered and the corresponding pharmacokinetic parameters were calculated and compared. After co-administration of the three flavones to rats, OA absorption increased significantly in comparison with when OA was administered alone. Mechanistic studies on the Caco-2 cell monolayer and rat in situ single-pass intestinal perfusion models revealed that co-administration of B, W and OA could significantly enhance their absorption and decrease the extent of phase II metabolism. Further in vitro enzymatic study and a transport study in transfected MDCK cells revealed that metabolic competition rather than membrane transporters might contribute to the pharmacokinetic interactions. The co-presence of multiple active components would result in metabolic interactions, which may induce further changes in pharmacodynamics.

Nitrile assisted, Brønsted acid catalyzed regio and stereoselective diarylphosphonylation of allyl silyl ethers.

We have discovered a mild, catalytic protocol for the regio- and stereoselective synthesis of trisubstituted allyl diarylphosphonates from the corresponding disubstituted allyl silyl ethers, circumventing the challenges related to the preparation and availability of stereodefined trisubstituted olefins. A closely related arylation reaction was also discovered during the methodology development. By simply switching the reaction medium, high phosphonylation/arylation ratios and vice versa can be achieved. This may not be a direct result of changing solvent polarity. The allyl diarylphosphonates were evaluated as carboxylesterase inhibitors, and the screening results revealed that the inhibitory efficiency is highly related to the choice of alkenes and aryl substituents.

Novel algorithm for simultaneous component detection and pseudo-molecular ion characterization in liquid chromatography-mass spectrometry.

Resolving components and determining their pseudo-molecular ions (PMIs) are crucial steps in identifying complex herbal mixtures by liquid chromatography-mass spectrometry. To tackle such labor-intensive steps, we present here a novel algorithm for simultaneous detection of components and their PMIs. Our method consists of three steps: (1) obtaining a simplified dataset containing only mono-isotopic masses by removal of background noise and isotopic cluster ions based on the isotopic distribution model derived from all the reported natural compounds in dictionary of natural products; (2) stepwise resolving and removing all features of the highest abundant component from current simplified dataset and calculating PMI of each component according to an adduct-ion model, in which all non-fragment ions in a mass spectrum are considered as PMI plus one or several neutral species; (3) visual classification of detected components by principal component analysis (PCA) to exclude possible non-natural compounds (such as pharmaceutical excipients). This algorithm has been successfully applied to a standard mixture and three herbal extract/preparations. It indicated that our algorithm could detect components' features as a whole and report their PMI with an accuracy of more than 98%. Furthermore, components originated from excipients/contaminants could be easily separated from those natural components in the bi-plots of PCA.

Elucidation of arctigenin pharmacokinetics after intravenous and oral administrations in rats: integration of in vitro and in vivo findings via semi-mechanistic pharmacokinetic modeling.

Although arctigenin (AR) has attracted substantial research interests due to its promising and diverse therapeutic effects, studies regarding its biotransformation were limited. The current study aims to provide information regarding the pharmacokinetic properties of AR via various in vitro and in vivo experiments as well as semi-mechanistic pharmacokinetic modeling. Our in vitro rat microsome incubation studies revealed that glucuronidation was the main intestinal and liver metabolic pathway of AR, which occurred with V max, K m, and Clint of 47.5 ± 3.4 nmol/min/mg, 204 ± 22 µM, and 233 ± 9 µl/min/mg with intestinal microsomes and 2.92 ± 0.07 nmol/min/mg, 22.7 ± 1.2 µM, and 129 ± 4 µl/min/mg with liver microsomes, respectively. In addition, demethylation and hydrolysis of AR occurred with liver microsomes but not with intestinal microsomes. In vitro incubation of AR and its metabolites in intestinal content demonstrated that glucuronides of AR excreted in bile could be further hydrolyzed back to the parent compound, suggesting its potential enterohepatic circulation. Furthermore, rapid formation followed by fast elimination of arctigenic acid (AA) and arctigenin-4'-O-glucuronide (AG) was observed after both intravenous (IV) and oral administrations of AR in rats. Linear pharmacokinetics was observed at three different doses for AR, AA, and AG after IV administration of AR (0.48-2.4 mg/kg, r (2) > 0.99). Finally, an integrated semi-mechanistic pharmacokinetic model using in vitro enzyme kinetic and in vivo pharmacokinetic parameters was successfully developed to describe plasma concentrations of AR, AA, and AG after both IV and oral administration of AR at all tested doses.

Extensive intestinal first-pass metabolism of arctigenin: evidenced by simultaneous monitoring of both parent drug and its major metabolites.

The current study aims to investigate intestinal absorption and metabolism of arctigenin (AR) through simultaneous monitoring of AR and its major metabolites in rat plasma. An UPLC/MS/MS assay was developed with chromatographic separation of all analytes achieved by a C18 Column (3.9mm×150mm, 3.5µm) and a gradient elution with acetonitrile and 0.1% formic acid within 9min. Sample extraction with acetonitrile was optimized to achieve satisfactory recovery for both AR and its major metabolites. The lower limit of quantification (LLOQ) for all analytes was 25ng/ml. The intra-day and inter-day precision and accuracy of each analyte at LLOQ and three quality control (QC) concentrations (low, middle and high) in rat plasma was within 15.0% RSD and 15.0% bias. The extraction recoveries were within the range of 83.8-94.0% for all analytes. The developed and validated assay was then applied to the absorption study of AR in both Caco-2 cell monolayer model and in situ single-pass rat intestinal perfusion model. High absorption permeability of AR was demonstrated in both models with Papp of (1.76±0.48)×10(-5) (A→B) (Caco-2) and Pblood of (8.6±3.0)×10(-6)cm/s (intestinal perfusion). Extensive first-pass metabolism of AR to arctigenic acid (AA) and arctigenin-4'-O-glucuronide (AG) was identified in rat intestinal perfusion study with Cummins's extraction ratios of 0.458±0.012 and 0.085±0.013, respectively. The current assay method demonstrated to be a practical tool for pharmacokinetics investigation of AR with complicated metabolism pathways and multiple metabolites.

Bench to bed evidences for pharmacokinetic and pharmacodynamic interactions involving oseltamivir and chinese medicine.

Oseltamivir (OA), an ethyl ester prodrug of oseltamivir carboxylate (OC), is clinically used as a potent and selective inhibitor of neuraminidase. Chinese medicines have been advocated to combine with conventional drug for avian influenza. The current study aims to investigate the potential pharmacokinetic and pharmacodynamic interactions of a Chinese medicine formula, namely, Yin Qiao San and Sang Ju Yin (CMF1), commonly used for anti-influenza in combination with OA in both rat and human, and to reveal the underlined mechanisms. It was found that although C max, AUC and urinary recovery of OC, as well as metabolic ratio (AUCOC/AUCOA), were significantly decreased in a dose-dependent manner following combination use of CMF1 and OA in rat studies (P < 0.01), such coadministration in 14 healthy volunteers only resulted in a trend of minor decrease in the related parameters. Further mechanistic studies found that although CMF1 could reduce absorption and metabolism of OA, it appears to enhance viral inhibition of OA (P < 0.01). In summary, although there was potential interaction between OA and CMF1 found in rat studies, its clinical impact was expected to be minimal. The coadministration of OA and CMF1 at the clinical recommended dosages is, therefore, considered to be safe.

A bio-activity guided in vitro pharmacokinetic method to improve the quality control of Chinese medicines, application to Si Wu Tang.

The purpose of this study was to demonstrate the feasibility of using a bio-activity guided in vitro pharmacokinetic (BAPK) method in identifying relevant (absorbable and bioactive) markers for quality control (QC) of Chinese medicines (CM), using Si Wu Tang (SWT), a popular CM for women's health, as an example. A stepwise BAPK approach was utilized for relevant marker determination and evaluating of six SWT products: (1) data mining to identify active components of SWT, (2) quantification of the identified active components in each SWT product, (3) determination of in vitro dissolution and metabolism of the components under simulated gastrointestinal conditions, (4) identification of absorbable components or marker(s) via in vitro Caco-2 cell model, (5) stability testing of the permeable marker(s). Our results showed considerable variations in the amount of active components in different SWT products. Of the nine active components identified from data mining, three (ferulic acid, ligustilide, senkyunolide A) were found to be well permeated and stable over three months. Paeoniflorin, the marker designated by Chinese Pharmacopoeia, was poorly permeable and thus could not be considered a relevant marker for SWT. Our preliminary evaluation of the BAPK method appears to be feasible and may offer as a useful approach for identifying relevant markers of other TCM products in the future.

Simultaneous quantification of active components in the herbs and products of Si-Wu-Tang by high performance liquid chromatography-mass spectrometry.

Si-Wu-Tang (SWT), comprising Paeoniae, Angelicae, Chuanxiong and Rehmanniae, is one of the most popular Traditional Chinese Medicine (TCM) formulae for woman's health. Data mining from the available Chinese and English literatures indicated that the major bioactive components of SWT consist of paeoniflorin, paeonol, gallic acid, ferulic acid, Z-ligustilide, ligustrazine, butylphthalide, senkyunolide A and catalpol. Since content determination of the marker compounds is generally considered as an initial step for quality control of TCM product, a high performance liquid chromatography-mass spectrometric method employing both positive and negative electrospray ionization was developed for the simultaneous determination of the nine identified compounds in the raw herbs and products of SWT. The LOQ of the developed assay method for the tested components was 10ng/ml for ligustrazine, 200ng/ml for catalpol, and 100ng/ml for the other seven compounds. The intra-day and inter-day variations of the current assay were within 17.5%. Paeoniflorin, ferulic acid, gallic acid, Z-ligustilide and senkyunolide A were found in all SWT products investigated. Variations in the contents of the studied compounds were observed among batches of raw herbs and SWT products. The currently developed method provides a sensitive and rapid quantification approach that can be useful in the quality control of raw herbs and products of SWT.

Analytical application of acetate anion in negative electrospray ionization mass spectrometry for the analysis of triterpenoid saponins--ginsenosides.

Ginsenosides containing different numbers of glycosyl groups can be easily differentiated based on the formation of characteristic ginsenoside-acetate adduct anions and deprotonated ginsenosides generated by electrospray ionization (ESI) of methanolic solutions of ginsenosides (M) and ammonium acetate (NH4OAc). Ginsenosides containing two glycosyl groups gave a characteristic mass spectral pattern consisting of [M+2OAc]2-, [M-H+OAc]2- and [M-2H]2- ions with m/z values differing by 30 Th, while this mass spectral pattern was not observed for ginsenosides containing one glycosyl group. Formation of [M+2OAc]2- was influenced by the chain length of glycosyl groups and was used to differentiate the ginsenosides containing different combinations of monosaccharide and disaccharide units in the glycosyl groups. Under identical collisional activation conditions, [M+OAc]-, [M-H+OAc]2- and [M+2OAc]2- underwent proton abstractions predominantly to generate [M-H]-, [M-2H]2- and [M-H+OAc]2- ions, respectively. The ion intensity ratios, I[M-H](-/I) [M+OAc]-, I[M-2H](2-/I) [M-H+2OAc]2- and I[M-H+OAc](2-/I) [M+OAc]2-, being sensitive to the structural differences of ginsenosides, could differentiate the isomeric ginsenosides, including (i) Rf, F11 and Rg1, (ii) Rd and Re, and (iii) Rb2 and Rc. Additionally, NH4OAc was found to enhance the sensitivity of detection of ginsenosides in the form of [M-H]- down to the femtomole level.