An automated streamlined method for the therapeutic drug monitoring of digoxin based on the online-solid-phase extraction liquid chromatography tandem high-resolution mass spectrometry.

RATIONALE: Digoxin is widely used in the clinical treatment of cardiovascular diseases. However, due to its extremely narrow therapeutic window, therapeutic drug monitoring (TDM) is vitally important. In consideration of the time-consuming and labor-intensive nature of the traditional techniques, an automated and efficient method was required for the clinical individualized TDM of digoxin. METHODS: An online solid-phase extraction liquid chromatography tandem high-resolution mass spectrometry (online-SPE-LC-HRMS) method was developed and applied for the determination of digoxin in plasma. The online SPE-LC steps included pretreatment and separation of plasma samples that were carried out using a Waters Oasis HLB cartridge and XBridge Shield RP18 column, respectively. A high-resolution Q Orbitrap mass spectrometer with targeted-selected ion monitoring in negative scan mode was applied to monitor formate-adduct ions [M + HCOO]- m/z 825.42781 for digoxin. RESULTS: Linearity was shown over the range 0.1-10 ng mL-1 for digoxin with correlation coefficients of R2 > 0.999. The lower limit of quantitation (LLOQ) for digoxin was 0.1 ng mL-1 . Extraction recoveries ranged from 82.61% to 94.28% for digoxin. The intra- and inter-day precision values were < 5.53% with accuracy ranging from 84.97% to 96.75%. The total running time was 10 min for each sample. CONCLUSION: The established method displayed satisfactory recoveries, accuracy, precision, and stability, and successfully applied on the TDM of digoxin. This automated streamlined method provides a powerful tool to guide the individualized administration of digoxin, which is significant for the practice of precision medicine.

Protective Effects of 3,4-Seco-Lupane Triterpenes from Food Raw Materials of the Leaves of Eleutherococcus Senticosus and Eleutherococcus Sessiliflorus on Arrhythmia Induced by Barium Chloride.

As a traditional wild vegetable and food raw material, the leaves of Eleutherococcus senticosus and Eleutherococcus sessiliflorus are rich in 3,4-seco-lupane triterpenes, including chiisanoside (CSS), divaroside (DVS), sessiloside-A (SSA), and chiisanogenin (CSG). This study was conducted to evaluate the anti-arrhythmic effects of these 3,4-seco-lupane triterpenes. Evaluation of the cytotoxicity of compounds was performed by measuring cell viability and apoptosis with the CCK-8 assay. In vivo, arrhythmia was induced by rapid injection of BaCl2 via rat caudal vein. The occurrence time and duration of arrhythmias in rats were studied. The levels of SOD and MDA in serum, and Na+ -K+ -ATPase and Ca2+ -Mg2+ -ATPase in myocardial homogenate were detected by ELISA. The histopathological changes of rats myocardial were observed by HE staining. Changes in the expression of PKA and related proteins were detected by Western blot. The 3,4-seco-lupane triterpenes interactions with protein kinase A were analyzed by molecular docking. In the present study, we found that 3,4-seco-lupane triterpenes exhibited powerful anti-arrhythmic activity, especially DVS completely relieved the ventricular arrhythmia induced by BaCl2 . This study suggests that the leaves of E. senticosus and E. sessiliflorus might be used as functional food materials to prevent arrhythmia, and DVS can potentially be further developed as an anti-arrhythmic drug.

Antiarrhythmic Properties of Elsholtzia ciliata Essential Oil on Electrical Activity of the Isolated Rabbit Heart and Preferential Inhibition of Sodium Conductance.

Elsholtzia ciliata essential oil (E. ciliata) has been developed in Lithuania and internationally patented as exerting antiarrhythmic properties. Here we demonstrate the pharmacological effects of this herbal preparation on cardiac electrical activity. We used cardiac surface ECG and a combination of microelectrode and optical mapping techniques to track the action potentials (APs) in the Langendorff-perfused rabbit heart model during atrial/endo-/epi-cardial pacing. Activation time, conduction velocity and AP duration (APD) maps were constructed. E. ciliata increased the QRS duration and shortened QT interval of ECG at concentrations of 0.01-0.1 µL/mL, whereas 0.3 µL/mL (0.03%) concentration resulted in marked strengthening of changes. In addition, the E. ciliata in a concentration dependent manner reduced the AP upstroke dV/dtmax and AP amplitude as well as APD. A marked attenuation of the AP dV/dtmax and a slowing spread of electrical signals suggest the impaired functioning of Na+channels, and the effect was usedependent. Importantly, all these changes were at least partially reversible. Our results indicate that E. ciliata modulates cardiac electrical activity preferentially inhibiting Na+ conductance, which may contribute to its effects as a natural antiarrhythmic medicine.

Preparation and comparison of Fe3O4@graphene oxide nanoclusters for analysis of glimepiride in urine by surface-assisted laser desorption/ionization time-of-flight mass spectrometry.

Graphene oxide (GO) has the ability to absorb certain compounds, and it can be modified with functional groups for different purposes; for instance, iron oxide (IO) nanoparticles can be used to concentrate analyte by a magnet. Recently, many kinds of GO have been developed, such as single-layer GO (SLGO), two-to-four layers of GO (i.e., few-layer GO, FLGO2-4), and four-to-eight layers of GO (i.e., multi-layer GO, MLGO4-8). However, the abilities of these layered GO coated with IO nanoparticles have not been investigated. In this study, we conducted a novel analysis of glimepiride by using layered GO-coated magnetic clusters of IO nanoparticles that were synthesized through a simple and facile emulsion-solvent evaporation method. The methodology is based on (i) enrichment of glimepiride using the layered GO-coated magnetic clusters of IO nanoparticles (IO@SLGO, IO@FLGO2-4, and IO@MLGO4-8), and (ii) rapid determination using magnetic cluster-based surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOFMS). We found that IO@MLGO4-8, the magnetic cluster with the greatest number of GO layers, had the best limit of detection (28.6 pmol/µL for glimepiride). The number of GO layers played a significant role in increasing the sensitivity of the SALDI-MS, indicating that the size of GO in the magnetic clusters contributed to the desorption/ionization efficiency. To the best of our knowledge, this is the first study to enrich glimepiride using magnetic clusters of different GO types and to show that the glimepiride in HLB purified urine adsorbed by magnetic clusters can be analyzed by SALDI-TOFMS.

Arnebiae Radix prevents atrial fibrillation in rats by ameliorating atrial remodeling and cardiac function.

ETHNOPHARMACOLOGICAL RELEVANCE: Arnebiae Radix, a common herbal medicine in China, is often utilized to treat blood-heat syndrome and has been reported to exert an effect on the heart. AIM OF THE STUDY: The combination of acetylcholine (Ach) and CaCl2 has been widely used to induce atrial fibrillation (AF) in animals. However, whether Arnebiae Radix displays any preventive action on Ach-CaCl2 induced AF in rats remains uncertain. In our study, we attempted to investigate the protective effects of Arnebiae Radix on Ach-CaCl2 induced AF compared to amiodarone, which was employed as the positive control. MATERIALS AND METHODS: To establish the AF model, SD rats were treated with a mixture of 0.1 mL/100 g Ach-CaCl2 (60 µg/mL Ach and 10 mg/mL CaCl2) by tail vein injection for 7 days. Rats were also given a gavage of Arnebiae Radix (0.18 g/mL) one week before or concurrently with the establishment of the AF model. At the end of the experimental period, the induction, duration and timing of AF were monitored using electrocardiogram recordings. Left atrial tissues were stained to observe the level of fibrosis. Electrophysiological measurements were used to examine atrial size and function. RESULTS: In Ach-CaCl2-induced AF rats, Arnebiae Radix decreased AF induction, duration and susceptibility to AF. In addition, Arnebiae Radix significantly reduced atrial fibrosis and inhibited atrial enlargement induced by Ach-CaCl2. Moreover, there was an apparent improvement in cardiac function in the Arnebiae Radix-treated group. CONCLUSIONS: Our findings indicate that Arnebiae Radix treatment can attenuate Ach-CaCl2-induced atrial injury and serve as an effective therapeutic strategy for the treatment of AF in the future.

Dynamics of Pivoting Electrical Waves in a Cardiac Tissue Model.

Through a detailed mathematical analysis we seek to advance our understanding of how cardiac tissue conductances govern pivoting (spiral, scroll, rotor, functional reentry) wave dynamics. This is an important problem in cardiology since pivoting waves likely underlie most reentrant tachycardias. The problem is complex, and to advance our methods of analysis we introduce two new tools: a ray tracing method and a moving-interface model. When used in combination with an ionic model, they permit us to elucidate the role played by tissue conductances on pivoting wave dynamics. Specifically we simulate traveling electrical waves with an ionic model that can reproduce the characteristics of plane and pivoting waves in small patches of cardiac tissue. Then ray tracing is applied to the simulated pivoting waves in a manner to expose their real displacement. In this exercise we find loci with special characteristics, as well as zones where a part of a pivoting wave quickly transitions from a regenerative to a non-regenerative propagation mode. The loci themselves and the monitoring of the ionic model state variables in this zone permit to elucidate several aspects of pivoting wave dynamics. We then formulate the moving-interface model based on the information gathered with the above-mentioned analysis. Equipped with a velocity profile v(s), s: distance along of the pivoting wave contour and the steady- state action potential duration (APD) of a plane wave during entrainment, APDss(T), at period T, this simple model can predict: shape, orbit of revolution, rotation period, whether a pivoting wave will break up or not, and whether the tissue will admit pivoting waves or not. Because v(s) and APDss(T) are linked to the ionic model, dynamical analysis with the moving-interface model conveys information on the role played by tissue conductances on pivoting wave dynamics. The analysis conducted here enables us to better understand previous results on the termination of pivoting waves. We surmise the method put forth here could become a means to discover how to alter tissue conductances in a manner to terminate pivoting waves at the origin of reentrant tachycardias.

Highly effective and safe intermediate based on deep eutectic medium for carrier less-three phase hollow fiber microextraction of antiarrhythmic agents in complex matrices.

For the first time, three phase hollow fiber liquid phase microextraction using an influential, and green middle phase comprised a new relatively-hydrophobic deep eutectic solvent (three-phase HF-LPME-DES) was developed for trace analyses of antiarrhythmic drugs in biological and environmental samples. The extraction solvent was easily synthesized by mixing the green and cheap raw materials, namely choline chloride and 1-phenylethanol (ChCl: Ph-ETOH), in the ambient temperature. Good compatibility to pores of hollow-fiber, high ability for extraction of ionizable organic compounds with no need to any carrier agents, and easy availability in the laboratory environment turned this new proposed deep eutectic intermediate to a worthy generation of the supported liquid membrane (SLM). Final determination was accurately done by high performance liquid chromatography-ultraviolet detection (HPLC-UV). After effective statistical optimization of main parameters, the valid analytical features were found to be: wide linear dynamic ranges (LDRs) of 0.8 to 500 ng mL-1 with the determination coefficients (R2s) higher than 0.98, low detection limits (LODs) of 0.3-0.8 ng mL-1, and logical precision (relative standard deviations (%RSDs, n = 3) of 5.2-6.5%). Also, enrichment factors and extraction recoveries were 110-135 and 44-54%, respectively. These satisfactory results confirmed the potent effectiveness of the proposed microextraction procedure for achievement to clean and proper enrichment of the aforesaid compounds in highly complex real samples.

Effect of Water-Soluble Echinochrome Analog on Arrhythmia Severity in Experimental Model of Acute Myocardial Ischemia.

The effects of therapeutic or preventive-therapeutic administration of water-soluble echinochrome analog U-441 on arrhythmia severity assessed by a set of myocardial spatio-temporal depolarization and repolarization parameters were examined on the model of acute myocardial ischemia in cats. Coronary occlusion increased activation time and decreased repolarization time in the ischemic zone; in addition, it increased both global and borderline (local) dispersions of repolarization. The linear regression model showed that only activation time values measured at the initial state and at termination of occlusion were associated with total arrhythmia score during ischemia (regression coefficient ß=0.338, 95%CI=0.074-0.602, p=0.015 and ß=0.720, 95%CI=0.323-1.117, p=0.001, respectively). The study revealed no association between administration of echinochrome analog U-441 and arrhythmia severity.

Rhodiola Inhibits Atrial Arrhythmogenesis in a Heart Failure Model.

INTRODUCTION: Rhodiola, a popular plant in Tibet, has been proven to decrease arrhythmia. The aim of this study was to elucidate the molecular mechanism and electrophysiological properties of rhodiola in the suppression of atrial fibrillation. METHODS: This study consisted of 3 groups as follows: Group 1: normal control rabbits (n = 5); Group 2: rabbits with heart failure (HF) created by coronary ligation and who received 2 weeks of water orally as a placebo (n = 5); and Group 3: rabbits with HF who received 2 weeks of a rhodiola 270 mg/kg/day treatment orally (n = 5). The monophasic action potential, histology, and real-time polymerase chain reaction (RT-PCR) analysis of ionic channels and PI3K/AKT/eNOS were examined. RESULTS: Compared with the HF group, attenuated atrial fibrosis (35.4 ± 17.4% vs. 16.9 ± 8.4%, P = 0.05) and improved left ventricular (LV) ejection fraction (51.6 ± 3.4% vs. 68.0 ± 0.5%, P = 0.001) were observed in the rhodiola group. The rhodiola group had a shorter ERP (85.3 ± 6.8 vs. 94.3 ± 1.2, P = 0.002), APD90 (89.3 ± 1.5 vs. 112.7 ± 0.7, P < 0.001) in the left atrium (LA), and decreased AF inducibility (0.90 ± 0.04 vs. 0.42 ± 0.04, P < 0.001) compared with the HF group. The mRNA expressions of Kv1.4, Kv1.5, Kv4.3, KvLQT1, Cav1.2, and SERCA2a in the HF LA were up-regulated after rhodiola treatment. The rhodiola-treated HF LA demonstrated higher mRNA expression of PI3K-AKT compared with the HF group. CONCLUSIONS: Rhodiola reversed LA electrical remodeling, attenuated atrial fibrosis and suppressed AF in rabbits with HF. The beneficial electrophysiological effect of rhodiola may be related to upregulation of Kv1.4, Kv1.5, Kv4.3, KvLQT1, Cav1.2, SERCA2a, and activation of PI3K/AKT signaling.

Electromembrane extraction through a virtually rotating supported liquid membrane.

Electromembrane extraction (EME) of model analytes was carried out using a virtually rotating supported liquid membrane (SLM). The virtual (nonmechanical) rotating of the SLM was achieved using a novel electrode assembly including a central electrode immersed inside the lumen of the SLM and five counter electrodes surrounding the SLM. A particular electronic circuit was designed to distribute the potential among five counter electrodes in a rotating pattern. The effect of the experimental parameters on the recovery of the extraction was investigated for verapamil (VPL), trimipramine (TRP), and clomipramine (CLP) as the model analytes and 2-ethyl hexanol as the SLM solvent. The results showed that the recovery of the extraction is a function of the angular velocity of the virtual rotation. The best results were obtained at an angular velocity of 1.83 RadS(-1) (or a rotation frequency of 0.29 Hz).The optimization of the parameters gave higher recoveries up to 50% greater than those of a conventional EME method. The rotating also allowed the extraction to be carried out at shorter time (15 min) and lower voltage (200 V) with respect to the conventional extraction. The model analytes were successfully extracted from wastewater and human urine samples with recoveries ranging from 38 to 85%. The RSD of the determinations was in the range of 12.6 to 14.8%.

Pharmacokinetics of dronedarone in rat using a newly developed high-performance liquid chromatographic assay method.

A sensitive and selective high-performance liquid chromatographic method for the determination of dronedarone in rat plasma was developed. Dronedarone was extracted using one-step liquid-liquid extraction. The separation of dronedarone was accomplished using a C18 analytical column. The mobile phase was composed of a combination of monobasic potassium phosphate and acetonitrile. The UV detection was at 254 nm for ethopropazine, the internal standard, and after its elution, changed to 290 nm for dronedarone detection. The total analytical run time was 20 min. Mean recovery was >80%; the assay had excellent linear relationships (>0.999) between peak height ratios and plasma concentrations; the lower limit of quantification 25 was ng/mL, based on 100 µL of rat plasma. Accuracy and precision were <18% over the concentration range of 25-500 ng/mL. The assay was applied successfully to the measurement of dronedarone plasma concentrations in rats given the drug orally.

An impact of the ring substitution in nicorandil on its adsorption on silver nanoparticles. Surface-enhanced Raman spectroscopy studies.

The substituent effect on structure and surface activity of biologically active nicorandil was investigated by means of surface-enhanced Raman spectroscopy (SERS). Vibrational characterization was a basis for investigation of the adsorption profile of nicorandil and 1-methylnicorandil on silver nanoparticles. An assignment of SERS bands was performed by the comparison of the Raman spectra of both compounds in the solid state and in solutions, complemented by DFT calculations. Even though the nitro group was found to be the most attractive to the silver surface, the strong impact of the methyl substituent changed this preferable adsorption mechanism in 1-methylnicorandil. Protonation of the nitrogen atom in the pyridinium ring was also found to have an impact on absorption mechanism.

New diterpenoid alkaloids from Aconitum coreanum and their anti-arrhythmic effects on cardiac sodium current.

Two new diterpenoid alkaloids, Guan-Fu base J (GFJ, 1) and Guan-Fu base N (GFN, 2) along with nineteen known alkaloids (3-21) were isolated from the roots of Aconitum coreanum (Lèvl.) Rapaics, which is the raw material of a new approval anti-arrhythmia drug "Acehytisine Hydrochloride". The structures of isolated compounds were established by means of 1D, 2D NMR spectroscopic and chemical methods. All isolates obtained in the present study were evaluated for their inhibitory effects on blocking the ventricular specific sodium current using a whole-cell patch voltage-clamp technique. Among these 21 compounds, Guan-Fu base S (GFS, 3) showed the strongest inhibitory effect with an IC50 value of 3.48 µM, and only hetisine-type C20 diterpenoid alkaloids showed promising IC50 values for further development.

Microfluidic chip capillary electrophoresis coupled with electrochemiluminescence for enantioseparation of racemic drugs using central composite design optimization.

Optimization based on central composite design (CCD) for enantioseparation of anisodamine (AN), atenolol (AT), and metoprolol (ME) in human urine was developed using a microfluidic chip-CE device. Coupling the flexible and wide working range of microfluidic chip-CE device to CCD for chiral separation of AN, AT, and ME in human urine, a total of 15 experiments is needed for the optimization procedure as compared to 75 experiments using the normal one variable at a time optimization. The optimum conditions obtained are found to be more robust as shown by the curvature effects of the interaction factors. The developed microfluidic chip-CE-ECL system with adjustable dilution ratios has been validated by satisfactory recoveries (89.5-99% for six enanotiomers) in urine sample analysis. The working range (0.3-600 µM), repeatability (3.1-4.9% RSD for peak height and 4.0-5.2% RSD for peak area), and detection limit (0.3-0.6 µM) of the method developed are found to meet the requirements for bedside monitoring of AN, AT, and ME in patients under critical conditions. In summary, the hyphenation of CCD with the microfluidic chip-CE device is shown to offer a rapid means for optimizing the working conditions on simultaneous separation of three racemic drugs using the microfluidic chip-CE device developed.

Prophylactic and therapeutic effects of garlic extract on Nerium oleander-induced arrhythmia: a new approach to antiarrhythmic therapy in an ovine model.

CONTEXT: Oleander is a potent cardiotoxic plant and is a common cause of poisoning in human and animals. There is no affordable and cost-effective treatment for oleander poisoning. Objective. To evaluate the prophylactic and therapeutic effects of garlic extract (Allium sativum) on Nerium oleander (a potent cardiotoxic plant) intoxication in sheep. MATERIALS AND METHODS: Eight sheep were intravenously infused with an unsterilized hydro-ethanol extract of garlic (50 mg/kg) before or after receiving a lethal dose of dried leaves (as a powder) of oleander (100 mg/kg, orally). The cardiac rhythm was continuously monitored using biopotential wireless transmitters and telemetry system. For evaluation of therapeutic effects, six sheep received the lethal dose of oleander and were administered with garlic extract after development of cardiac arrhythmias. Subsequently, the survived animals from the therapeutic study (four sheep) were administered with oleander without receiving any medication. Some blood constituents, including total antioxidant capacity, malondialdehyde, and troponin I, were compared between treated and untreated animals. RESULTS: Pretreatment with garlic extract reversed the arrhythmia caused by oleander to its previous normal rhythm in seven sheep, but, one sheep died of ventricular fibrillation. On therapeutic treatment, four sheep survived while two died of ventricular fibrillation. Dosing with oleander without receiving garlic extract resulted in death of all sheep due to ventricular fibrillation. Blood constituents did not show any significant changes between treated and untreated sheep, and before and after intoxication. CONCLUSIONS: Garlic extract reduced the case fatality from 100% to 12.5% and 33.3% as a prophylactic or therapeutic agent, respectively. Additionally, garlic extract delayed the time of onset of arrhythmias and prolonged the interval between intoxication and death of the animals. Garlic extract could be considered to be a potential and affordable antidote in oleander poisoning. However additional studies with a larger sample size and in other species need to be performed to confirm the results in this study.

Capillary zone electrophoresis for separation and quantitative determination of mexiletine and its main phase I metabolites.

The simultaneous separation and quantification of the analytes within the minimum analysis time and the maximum resolution and efficiency are the main objectives in the development of a capillary electrophoretic method for the determination of solutes. In this paper we describe a specific, sensitive and robust method, using capillary zone electrophoresis with internal standard and UV detection, for the separation and quantification of the anti-arrhythmic drug mexiletine, its main phase I metabolites, and its main nitrogenous degradation product.

Protective effects of saffron (Crocus sativus) against lethal ventricular arrhythmias induced by heart reperfusion in rat: a potential anti-arrhythmic agent.

CONTEXT: Saffron (Crocus sativus L.) has been used as a cuisine spice in eastern and western societies for thousands of years. In traditional medicine, saffron is recommended for the treatment of various kinds of disorders including heart palpitations. OBJECTIVE: We investigated the hypothesis of the protective effect of saffron on lethal cardiac arrhythmias induced by heart ischemia-reperfusion in rat. MATERIALS AND METHODS: Animals were divided into a control (CTL) group that received tap water, Saf50, Saf100 and Saf200 groups that were orally treated with aqueous extracts of saffron, at dosages of 50, 100 and 200 mg/kg/day, respectively, and amiodarone (Amio) group that orally received 30 mg/kg/day for seven days. On day 8, heart ischemia-reperfusion was induced by ligation and releasing of the left anterior descending coronary artery. RESULTS: During reperfusion, the numbers and durations of ventricular fibrillation (VF) decreased in all groups compared to the CTL group (p < 0.05). Ventricular tachycardia (VT)/VF numbers (3.2 ± 1.2), durations (4.9 ± 2.6) and also arrhythmia severity (1.9 ± 0.35) were decreased significantly in the Saf100 group versus CTL group values (18.4 ± 11.6, 52 ± 31 and 3.3 ± 0.3, respectively). The PR and QTcn intervals of ECG were significantly longer in the Saf200 group (p < 0.001 versus CTL). The other doses of saffron only significantly prolonged the QTcn interval. CONCLUSION: The results suggest that pretreatment with saffron, especially at the dosage of 100 mg/kg/day, attenuates the susceptibility and incidence of fatal ventricular arrhythmia during the reperfusion period in the rat. This protective effect is apparently mediated through reduction of electrical conductivity and prolonging the action potential duration.

Dispersive liquid-liquid microextraction of propranolol enantiomers from human plasma based on the solidification of a floating organic droplet.

BACKGROUND: A dispersive liquid-liquid microextraction based on the solidification of a floating organic droplet was developed and validated for the extraction of propranolol enantiomers from human plasma. The studied enantiomers were extracted from diluted and alkalized plasma samples using 1-undecanol as the extracting solvent. HPLC-fluorescence detection analyses were carried out on a chiral column, using n-hexane-ethanol (80:20, v/v) plus 0.2% triethylamine as the mobile phase, at a flow rate of 0.8 ml/min. The significant factors in the microextraction procedure, including extracting and disperser solvents volume, solution pH and salt contents were optimized by using a central composite design and the response surface methodology. RESULTS: Under optimized conditions, the mean recoveries were approximately 14% with linear responses over the 0.5-100 ng/ml concentration range for both enantiomers. The LOQ was 0.5 ng/ml (S/N = 10). Intra-day (n = 5) and inter-day (n = 3) assay precision (1 and 50 ng/ml) showed RSD lower than 8 and 9.5% for studied enantiomers, respectively. Finally, the method was successfully used for the determination of propranolol enantiomers in plasma samples obtained after single drug administration of racemic propranolol tablet to three healthy volunteers. The plasmatic concentrations of (-)-(S)-PROP were higher than those of (+)-(R)-PROP in all times after oral administration of the racemic drug. CONCLUSION: The obtained results proved that the proposed method is a powerful technique for sample preparation, providing suitable recoveries, efficient cleanup, high selectivity and sensitivity and low consumption of organic solvent for determination of the studied enantiomers in plasma samples after oral administration of the racemic drug to volunteers.

Effect of daurisoline on HERG channel electrophysiological function and protein expression.

Daurisoline (1) is a bis-benzylisoquinoline alkaloid isolated from the rhizomes of Menispermum dauricum. The antiarrhythmic effect of 1 has been demonstrated in different experimental animals. In previous studies, daurisoline (1) prolonged action potential duration (APD) in a normal use-dependent manner. However, the electrophysiological mechanisms for 1-induced prolongation of APD have not been documented. In the present study, the direct effect of 1 was investigated on the hERG current and the expression of mRNA and protein in human embryonic kidney 293 (HEK293) cells stably expressing the hERG channel. It was shown that 1 inhibits hERG current in a concentration- and voltage-dependent manner. In the presence of 10 µM 1, steady-state inactivation of V(1/2) was shifted negatively by 15.9 mV, and 1 accelerated the onset of inactivation. Blockade of hERG channels was dependent on channel opening. The expression and function of hERG were unchanged by 1 at 1 and 10 µM, while hERG expression and the hERG current were decreased significantly by 1 at 30 µM. These results indicate that 1, at concentrations below 30 µM, exerts a blocking effect on hERG, but does not affect the expression and function of the hERG channel. This may explain the relatively lower risk of long QT syndrome after long-term usage.

Identification of amiodarone metabolites in human bile by ultraperformance liquid chromatography/quadrupole time-of-flight mass spectrometry.

Amiodarone is recognized as an effective drug in the treatment of arrhythmias. Previous experiments demonstrated that mono-N-desethylamiodarone (MDEA) was the major circulating metabolite in humans. In addition, dealkylation, hydroxylation, and deamination were minor metabolic pathways. The purpose of this study was to identify the metabolites of amiodarone in the bile obtained from patients with T-tube drainage after oral drug administration. Amiodarone metabolism in vitro was also investigated using human liver microsomes (HLMs) and S9 fraction. Ultraperformance liquid chromatography/quadrupole time-of-flight mass spectrometry (UPLC-Q/TOF MS) revealed 33 metabolites in human bile, including 22 phase I and 11 phase II metabolites. The major metabolites were MDEA (M7) and ω-carboxylate amiodarone (M12). Metabolite M12 was isolated from human bile, and the chemical structure was confirmed using UPLC-Q/TOF MS and ¹H NMR. Moreover, the authentic standards of two hydroxylated metabolites, 2-hydroxylamiodarone and 3'-hydroxylamiodarone, were obtained through microbial transformation. Several novel metabolic pathways of amiodarone in human were proposed, including ω-carboxylation, deiodination, and glucuronidation. The in vitro study demonstrated that incubation of HLMs with amiodarone did not give rise to any carboxyl metabolites. In contrast, M12 and its metabolites were detected in human liver S9 incubation samples, and the production of these metabolites were inhibited almost completely by 4-methylpyrazole, an inhibitor of alcohol dehydrogenase, suggesting the involvement of alcohol dehydrogenase in the ω-carboxylation of amiodarone. Overall, UPLC-Q/TOF MS analysis leads to the discovery of several novel amiodarone metabolites in human bile and underscores the importance of bile as an excretion pathway.