Enhanced Oxidation of Simvastatin at a Multi‐Walled Carbon Nanotubes‐Dihexadecyl Hydrogen Phosphate Composite Modified Glassy Carbon Electrode and the Application in Determining Simvastatin in Pharmaceutical Dosage Forms

A sensitive electrochemical method for the determination of simvastatin (SV) was established, based on the enhanced oxidation of SV at a multi‐walled carbon nanotubes‐dihexadecyl hydrogen phosphate composite modified glassy carbon electrode (MWNTs‐DHP/GCE). The voltammetric studies showed that MWNTs instead of DHP or GCE could effectively catalyze the oxidation of SV. The dependence of oxidation current on SV concentration was explored under optimal conditions, which exhibited a good linear relationship in the range of 1.0×10^?7–7.5×10^?6 M. The detection limit of SV was also examined and a low value of 5.0×10^?8 M was obtained for 5 min accumulation (σ=3). This electrode was applied to the detection of SV in drug forms and the results were in accordance with those obtained by UV spectroscopy.     

Inverse screening of Simvastatin kinase targets from glioblastoma druggable kinome

The statin drug Simvastatin is a HMG-CoA reductase inhibitor that has been widely used to lower blood lipid. However, the drug is clinically observed to reposition a significant suppressing potency on glioblastoma (GBM) by unexpectedly targeting diverse kinase pathways involved in GBM tumorigensis. Here, an inverse screening strategy is described to discover potential kinase targets of Simvastatin. Various human protein kinases implicated in GBM are enriched to define a druggable kinome; the binding behavior of Simvastatin to the kinome is profiled systematically via an integrative computational approach, from which most kinases have only low or moderate binding potency to Simvastatin, while only few are identified as promising kinase hits. It is revealed that Simvastatin can potentially interact with certain known targets or key regulators of GBM such as ErbB, c-Src and FGFR signaling pathways, but exhibit low affinity to the well-established GBM target of PI3K/Akt/mTOR pathway. Further assays determine that Simvastatin can inhibit kinase hits EGFR, MET, SRC and HER2 at nanomolar level, which are comparable with those of cognate kinase inhibitors. Structural analyses reveal that the sophisticated T790 M gatekeeper mutation can considerably reduce Simvastatin sensitivity to EGFR by inducing the ligand change between different binding modes.     

Stability-Indicating HPTLC Method for Simultaneous Determination of Ezetimibe and Simvastatin

Simvastatin and ezetimibe are used to treat hyperlipidemia. A simple, selective and stability-indicating HPTLC method has been established for analysis of simvastatin and ezetimibe. The method has been validated so that both drugs can routinely be analyzed simultaneously. The method uses aluminum-backed silica gel 60F₂₅₄ TLC plates as stationary phase with n-hexane–acetone 6:4 (v/v) as mobile phase. Densitometric analysis of both drugs was carried out in absorbance mode at 234 nm. This system was found to give compact bands for simvastatin and ezetimibe (R _F 0.39 ± 0.05 and 0.50 ± 0.05, respectively). Linear relationships were obtained between response and amount of drug in the range 200–1,600 ng per band with high correlation coefficients (r ² = 0.9917 ± 0.0018 for simvastatin and r ² = 0.9927 ± 0.0021 for ezetimibe). The method was validated for precision, robustness, and recovery. The limits of detection and quantitation were 25 and 150 ng per band, respectively. Simvastatin and ezetimibe were subjected degradation by acid, pH 6.8 phosphate buffer, oxidation, dry heat, and wet heat. The degradation products were well resolved from the pure drug with significantly different R _F values. Because the method could effectively separate the drug from its degradation products, it can be used for stability-indicating analysis.     

High-throughput salting-out assisted liquid/liquid extraction with acetonitrile for the simultaneous determination of simvastatin and simvastatin acid in human plasma with liquid chromatography

Simvastatin (SS) is an effective cholesterol-lowering medicine, and is hydrolyzed to simvastatin acid (SSA) after oral administration. Due to SS and SSA inter-conversion and its pH and temperature dependence, SS and SSA quantitation is analytically challenging. Here we report a high-throughput salting-out assisted liquid/liquid extraction (SALLE) method with acetonitrile and mass spectrometry compatible salts for simultaneous LC-MS/MS analysis of SS and SSA. The sample preparation of a 96-well plate using SALLE was completed within 20 min, and the SALLE extract was diluted and injected into an LC-MS/MS system with a cycle time of 2.0 min/sample. The seamless interface of SALLE and LC-MS eliminated drying down step and thus potential sample exposure to room or higher temperature. The stability of SS and SSA in various concentration ratios in plasma was evaluated at room and low (4 °C) temperature and the low temperature (4 °C) was found necessary to maintain sample integrity. The short sample preparation time along with controlled temperature (2-4 °C) and acidity (pH 4.5) throughout sample preparation minimized the conversion of SS → SSA to ≤0.10% and the conversion of SSA → SS to 0.00% The method was validated with a lower limit of quantitation (LLOQ) of 0.094 ng mL⁻¹ for both SS and SSA and a sample volume of 100 μL. The method was used for a bioequivalence study with 4048 samples. Incurred sample reproducibility (ISR) analysis of 362 samples from the study exceeded ISR requirement with 99% re-analysis results within 100 ± 20% of the original analysis results.     

Solubility and limiting activity coefficient of simvastatin in different organic solvents

Equilibrium mole fraction solubility of Zocor^® (simvastatin) a pharmaceutically important compound, was measured between 279 and 315 K, in fifteen different industrial-relevant organic solvents including: methyl acetate, ethyl acetate, propyl acetate, iso-propyl acetate, butyl acetate, iso-butyl acetate, sec-butyl acetate, tert-butyl acetate, and ethanol, propanol, 1-butanol, 2-butanol, 1-pentanol, 1-hexanol, and 1-octanol. Fusion enthalpy, Δ_fusH, melting point temperature, T_m, were measured to be 32,169 J/mol, 412.6 K, respectively; and the difference in the molar heat capacity (at constant pressure) of the liquid, and solid form of simvastatin, ΔC_P, was approximated (by extrapolation) to be 230 J/mol K. Dissolution of simvastatin was found to be endothermic, and entropically favorable. The activity coefficient at infinite dilution of simvastatin in each solvent was calculated from the experimental data, then fitted to Gibbs–Helmholtz equation to estimate the limiting partial molar excess enthalpies, , and the limiting partial molar excess entropies, . The data was also fitted to the non-random-two-liquid (NRTL) activity coefficient equation to generate the model interaction parameters for dissolution of simvastatin in the organic solvents studied here.     

Ultrasound assisted ionic liquid dispersive liquid phase extraction of lovastatin and simvastatin: A new pretreatment procedure

A fast and novel sample preparation procedure: ultrasound assisted ionic liquid (IL) dispersive liquid extraction for the concentration of lovastatin and simvastatin in aqueous samples was developed. An IL ([C₆MIM][PF₆]) was used as the extraction solvent, and the factors affecting the extraction efficiency such as initial temperature, the volume of IL, pH of water samples, cooling time, and salt concentration were optimized. In combination with HPLC‐UV, both lovastatin and simvastatin exhibited a good linear range of 1–100 ng/mL. The limits of detection (LODs) of lovastatin and simvastatin were 0.17 and 0.29 ng/mL, respectively. Precisions of the proposed method (RSDs, n = 9) were 4.12 and 4.52%, respectively. This method has been successfully applied for the analysis of target compounds in three real water samples and good spiking recoveries were obtained in the range of 90.0–102.2% for lovastatin and 80.5–112.0% for simvastatin. These results indicated that ultrasound assisted IL dispersive liquid phase extraction would have good application prospect in the pretreatment of environmental samples.     

Liquid Chromatographic Determination of 3-Hydroxy-3-methylglutaryl Coenzyme A Reductase Inhibitors

Reversed-phase high-performance liquid chromatography (RP-HPLC) was used as a tool to explore the retention behavior and separation of four 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, namely compactin, lovastatin, simvastatin, and pravastatin in their hydroxy acid and lactone forms. The contribution of C-6 and C-2′ methyl groups and lactonization to the molecular hydrophobicity among these four structurally related HMG-CoA reductase inhibitors were elucidated. Eight components (four lactones and four hydroxy acids) could be resolved by RP-HPLC with isocratic elution. In a binary mobile phase system of acetonitrile-water containing 0.5% acetic acid, the free hydroxy acids and corresponding lactone forms remained intact and were completely separated. This study demonstrated that RP-HPLC is suitable for simultaneous determination of active and prodrug forms of these HMG-CoA reductase inhibitors.     

HPLC methods for the determination of simvastatin and atorvastatin

We review high-performance liquid chromatography (HPLC) methods for the determination of two major statins used in clinical treatment – simvastatin and atorvastatin – in various fields of application, including bio-analytical assays, pharmaceutical assays and environmental applications.

Statin molecules are known to be susceptible to interconversion of the lactone and acidic forms, so it is necessary to consider this phenomenon during method development. We highlight liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) methods, as they have become a method of choice in bio-analytical and environmental applications. We compare the methods from the point of view of sensitivity. We discuss selection of the precursor ion for performing selected reaction monitoring (SRM) in MS detection and sample preparation.     

线性扫描极谱法测定辛伐他汀

用线性扫描极谱法研究辛伐他汀的电化学行为。在pH 6.88的0.12mol·L-1磷酸氢二钠-磷酸二氢钾缓冲溶液中,辛伐他汀于-1.188V(vs.SCE)处产生一灵敏的吸附波,其一次微分线性扫描峰电流与辛伐他汀质量浓度在0.01～5.0mg·L-1范围内呈线性关系,检出限(3S/N)为7.0μg·L-1。对5.0mg·L-1辛伐他汀溶液进行6次平行试验,相对标准偏差(n=6)为0.53%,方法可用于测定其片剂中辛伐他汀含量。     

Comparison of UV and charged aerosol detection approach in pharmaceutical analysis of statins

CAD (charged aerosol detector) has recently become a new alternative detection system in HPLC. This detection approach was applied in a new HPLC method for the determination of three of the major statins used in clinical treatment—simvastatin, lovastatin and atorvastatin.The method was optimized and the influence of individual parameters on CAD response and sensitivity was carefully studied. Chromatography was performed on a Zorbax Eclipse XDB C18 (4.6 mm × 75 mm, 3.5 μm), using acetonitrile and formic acid 0.1% as mobile phase. The detection was performed using both CAD (20 pA range) and DAD (diode array detector—238 nm) simultaneously connected in series. In terms of linearity, precision and accuracy, the method was validated using tablets containing atorvastatin and simvastatin.The CAD is designated to be a non-linear detector in a wide dynamic range, however, in this application and in the tested concentration range its response was found to be perfectly linear. The limits of quantitation (0.1 μg/ml) were found to be two times lower than those of UV detection.