Nitrosamine Contamination in Pharmaceuticals: Threat,Impact, and Control

Nitrosamine-contaminated medicinal products have raised safety concerns towards the use of various drugs, not only valsartan and all tetrazole-containing angiotensin II receptor blockers, but also ranitidine, metformin, and other medicines, many of which have been recalled and prone to shortage. At any stages, from drug substance synthesis throughout each product's lifetime, these impurities may evolve if an amine reacts with a nitrosating agent coexisting under appropriate conditions. Consequently, drug regulatory authorities worldwide have established stringent guidelines on nitrosamine contamination for all drug products in the market. This review encompasses various critical elements contributing to successful control measures against current and upcoming nitrosamine issues, ranging from accumulated knowledge of their toxicity concerns and potential root causes, precise risk evaluation, as well as suitable analytical techniques with sufficient sensitivity for impurity determination. With all these tools equipped, the impact of nitrosamine contamination in pharmaceuticals should be mitigated. An evaluation aid to tackle challenges in risk identification, as well as suitable industry-friendly analytical techniques to determine nitrosamines and other mutagenic impurities, are among unmet needs that will significantly simplify the risk assessment process.     

Type 2C protein phosphatases directly regulate abscisic acid-activated protein kinases in Arabidopsis

Abscisic acid (ABA) signaling is important for stress responses and developmental processes in plants. A subgroup of protein phosphatase 2C (group A PP2C) or SNF1-related protein kinase 2 (subclass III SnRK2) have been known as major negative or positive regulators of ABA signaling, respectively. Here, we demonstrate the physical and functional linkage between these two major signaling factors. Group A PP2Cs interacted physically with SnRK2s in various combinations, and efficiently inactivated ABA-activated SnRK2s via dephosphorylation of multiple Ser/Thr residues in the activation loop. This step was suppressed by the RCAR/PYR ABA receptors in response to ABA. However the abi1–1 mutated PP2C did not respond to the receptors and constitutively inactivated SnRK2. Our results demonstrate that group A PP2Cs act as ‘gatekeepers’ of subclass III SnRK2s, unraveling an important regulatory mechanism of ABA signaling.     

化妆品中6种雌激素的液相色谱串联质谱检测方法研究

目的建立化妆品中六种雌激素的液相色谱串联质谱(LC-MS/MS)测定方法。方法分别优化选择合适的质谱及色谱条件,确定最佳分析条件。样品用甲醇溶解,涡流震荡,超声抽提,0.45μm滤膜过滤,采用LC-MS/MS测定。结果6种雌激素β-雌二醇(E2),雌三醇(E3),雌酮(E1),己烯雌酚(DES)和己烷雌酚(HE)的最低检出限(LOD)分别为2.4、0.2、0.7、12、6和5ng/g;最低定量限(LOQ)分别为8、0.7、2.4、40、20和17ng/g;6种雌激素在浓度(0～1000ng/mL)的范围内均呈现良好线性(相关系数≥0.9990),平均加标回收率在85.2%～102.8%之间,相对标准偏差均在2.76%～8.69%之间。测定市场抽检的28个样品,结果满意。结论该方法能在较短时间内同时检测化妆品中6种雌激素,灵敏度高,选择性好。     

Distinction of constitutional isomers of mephedrone by chromatographic and spectrometric methods

Many new psychoactive substances (NPS) have similar chemical structures. Separation and unequivocal identification of structural isomers is an important issue due to the fact that they can differ in pharmacology, toxicology, effects and action on the human body, as well as legal status. This paper is aimed at comparing the abilities of different analytical methods (GC-MS, UHPLC-DAD, LC-MS/MS), to distinguish mephedrone and its isomers: 3-MMC, 2-MMC, buphedrone, metamfepramone and ethcathinone. These techniques allowed for distinction between the isomers of mephedrone. In the GC-MS method, combining retention times with the mass spectra made the differentiation efficient. In the UHPLC-DAD conditions, it was impossible to distinguish the isomers based on their retention times, but the UV/VIS spectra were useful in identification. The separation conditions were optimised for the LC-MS/MS method. The identification of isomers was supported by the different intensity of product ions. The LODs for the GC-MS method (1000–2500 ng/mL) in scan mode were definitely the worst. The values for the UHPLC-DAD method were much better (1.4–2.7 ng/mL) making this assay suitable for the analysis of biological material. The LC-MS/MS method was sensitive enough (LODs = 0.03–0.39 ng/mL) for the analysis of biological material even a long time after the initial drug use.     

肠道菌群对硫酸氢氯吡格雷及其活性代谢产物在大鼠体内药动学的影响

目的：探究肠道菌群变化对硫酸氢氯吡格雷及其活性代谢产物在大鼠体内药动学的影响。方法：24只健康大鼠随机分为益生菌组、抗生素组和对照组,每组8只,分别灌胃双歧杆菌乳杆菌三联活菌（0.8 g·kg^-1）、阿莫西林克拉维酸钾片（125 mg·kg^-1）和等体积的纯化水,连续7 d。第8天给予硫酸氢氯吡格雷片,并于给药前和给药后不同时间点取血于含有衍生试剂的抗凝管中,LC-MS/MS法测定血药浓度,绘制药时曲线,使用DAS 2.1.1拟合药动学参数,SPSS 21.0进行统计学比较。结果：益生菌组、抗生素组和对照组硫酸氢氯吡格雷和活性代谢产物衍生物（CAMD）的主要药动学参数AUC_0-t、AUC_0-∞、t_1/2、t_max、CL、V、C_max均没有统计学差异（P>0.05）。结论：肠道菌群变化对硫酸氢氯吡格雷及其活性代谢产物的药动学参数没有影响。     

不同种植基地滇重楼根茎中甾体皂苷有效成分差异的研究

目的:探讨不同种植基地滇重楼根茎中甾体皂苷有效成分的差异。方法:采用超高效液相色谱法(UHPLC)测定不同种植基地滇重楼根茎中重楼皂苷Ⅰ、Ⅱ、Ⅵ、Ⅶ及总皂苷的含量,并用液质联用(LC-MS)技术定性分析其甾体皂苷有效成分的差异。结果:不同种植基地滇重楼根茎中重楼皂苷Ⅰ及总皂苷含量差异较小,重楼皂苷Ⅱ、Ⅵ、Ⅶ含量差异较大;重楼皂苷Ⅰ、重楼皂苷Ⅲ(薯蓣皂苷)、重楼皂苷Ⅴ、重楼皂苷Ⅶ是不同种植基地滇重楼根茎中甾体皂苷的主要存在形式,不同种植基地滇重楼根茎中重楼皂苷Ⅱ、重楼皂苷H、重楼皂苷Ⅵ、纤细薯蓣皂苷差异较大;根据不同种植基地滇重楼根茎正离子模式下液质数据的主成分分析(PCA)模型可将其分为四类。结论:不同种植基地滇重楼根茎中重楼皂苷Ⅰ、Ⅱ、Ⅵ、Ⅶ及总皂苷的含量、甾体皂苷有效成分及化学成分种类差异较大。     

固相萃取-液相色谱-串联质谱法测定氯化消毒副产物二氯对苯醌

目的 建立饮水中新型氯化消毒副产物二氯对苯醌的固相萃取-液相色谱-串联质谱检测方法。方法 水样经0.45 μm滤膜过滤,用 Oasis HLB 固相萃取小柱富集进样,以含0.25%甲酸甲醇溶液-0.25%甲酸的水溶液为流动相,梯度洗脱,经Agilent ZORBAX Eclipse XDB-C18色谱柱（2.1 mm×50 mm,1.8 μm） 分离后,采用四极杆串联质谱仪电喷雾负离子模式和多反应监测（MRM）模式进行检测。结果 二氯对苯醌在2～100 μg/L的范围内回归方程为Y = 12.978x + 0.285,线性相关系数r = 0.9937;方法检出限为0.01 μg/L,定量下线限为0.03 μg/L。管网末梢自来水加标回收率为80.0％～85.0％,相对标准偏差(RSD)为3.4%～4.1%。结论 方法的灵敏度和准确度较高,适用于饮用水中二氯对苯醌的测定。     

A liquid chromatography-tandem mass spectrometric method for the determination of axitinib in nude mouse plasma: development,validation and application to a pharmacokinetic study

In the present study, a simple, rapid, and sensitive liquid chromatography-tandem mass spectrometric method for the determination of axitinib in nude mouse plasma was developed, validated, and applied to a pharmacokinetic study. Plasma samples were pre-treated by protein precipitation with acetonitrile spiked with erlotinib as an internal standard. The chromatographic separation was accomplished by using a reversed phase C₁₈ column (50 mm×2 mm, 5 μm) with a simple mobile phase system composed of methanol and water (60:40, v/v) at an isocratic flow rate of 0.4 mL/min. The analyte was detected by a triple-quadrupole tandem mass spectrometer via electrospray ionization and multiple reaction monitoring was employed to select both axitinib and erlotinib in the positive ion mode. The calibration curves were linear (r>0.99) ranging from 1 to 1000 ng/mL, and the lowest level of this range was the lower limit of quantification. The intra­ and inter­day precision were 7.7%-12.0%, and the accuracies ranged from 88.6% to 110.4%. This method was successfully applied to a preclinical pharmacokinetic study on female nu/nu nude mice administrated with a single oral dose of axitinib at 120 mg/kg, and the pharmacokinetics was characterized by a one-compartment model with first-order absorption.     

A simple and sensitive gradient elution liquid chromatography with tandem mass spectrometry (LC-MS/MS) method for the quantification of doxorubicin in rabbit plasma

In the present study, we developed and validated a simple and sensitive gradient elution liquid chromatography tandem mass spectrometry (LC-MS/MS) method for quantification of doxorubicin in rabbit plasma. Daunorubicin was used as an internal standard (IS). The doxorubicin and IS were extracted with ethyl acetate from plasma samples. The chromatographic separations were achieved on a C₁₈ column (2.1 mm×50 mm, 2.5 μm) configured with a C₁₈ guard column (2.1 mm×10 mm, 2.5 μm). The mobile phase of 0.1% formic acid-water solution and acetonitrile was delivered using a gradient elution program at a flow rate of 0.4 mL/min. The temperature for column was maintained at 40 ºC. The electrospray ionization (ESI) source was operated in the positive ion mode, and the quantification was conducted using multiple reaction monitoring (MRM) of the transitions m/z 544.07→396.96 and m/z 528.06→321.05 for doxorubicin and IS, respectively. The calibration curve of doxorubicin was linear (r > 0.999) within the range of 2-600 ng/mL. The lower limit of quantification was 2 ng/mL. The relative errors of intra­day and inter-day accuracies ranged from -2.48% to 0.18% and from -3.78% to 1.94%, respectively. The relative standard deviations of intra­day and inter-day precisions were less than 8.65% and 6.41%, respectively. The method exhibited satisfactory results in terms of specificity, sensitivity, matrix effect, recovery and stability. The newly developed LC-MS/MS method was reliable to monitor doxorubicin concentrations in rabbit plasma.