Carboxylesterase catalyzed 18O-labeling of carboxylic acid and its potential application in LC-MS/MS based quantification of drug metabolites

LC-MS quantification of drug metabolites is sometimes impeded by the availability of internal standards that often requires customized synthesis and/or extensive purification. Although isotopically labeled internal standards are considered ideal for LC-MS/MS based quantification, de novo synthesis using costly isotope-enriched starting materials makes it impractical for early stage of drug discovery. Therefore, quick access to these isotope-enriched compounds without chemical derivatization and purification will greatly facilitate LC-MS/MS based quantification. Herein, we report a novel ¹⁸O-labeling technique using metabolizing enzyme carboxylesterase (CES) and its potential application in metabolites quantification study. Substrates of CES typically undergo a two-step oxygen exchange with H₂¹⁸O in the presence of the enzyme, generating singly- and doubly-¹⁸O-labeled carboxylic acids; however, unexpected hydrolytic behavior was observed for three of the test compounds – indomethacin, piperacillin and clopidogrel. These unusual observations led to the discovery of several novel hydrolytic mechanisms. Finally, when used as internal standard for LC-MS/MS based quantification, these in situ labeled compounds generated accurate quantitation comparable to the conventional standard curve method. The preliminary results suggest that this method has potential to eliminate laborious chemical synthesis of isotope-labeled internal standards for carboxylic acid-containing compounds, and can be developed to facilitate quantitative analysis in early-stage drug discovery.     

LC-MS/MS法测定人血浆中布康唑浓度的不确定度评定

目的：评定LC-MS/MS法测定人血浆中布康唑浓度的不确定度。方法：分析测定过程中不确定度的来源，包括对照品的称量、仪器误差、标准溶液的配制、含药血浆样品的配制、血浆样品的处理、标准曲线的拟合、基质效应、重复性等，评定各来源分量的不确定度，计算合成不确定度和扩展不确定度。结果：人血浆中低（60.0 pg·mL^-1）、中（600.0 pg·mL^-1）、高（6 400.0 pg·mL^-1）浓度布康唑的扩展不确定度分别为5.62，63.90，626.26 pg·mL^-1（k=2，P=95%）。结论：LC-MS/MS法测定人血浆中布康唑浓度的不确定度主要由基质效应、血浆样品的处理（提取回收率），仪器误差、重复性（精密度）引入。     

基于LC-MS的甘草炮制雷公藤降低肝毒性的代谢组学研究

目的 观察甘草炮制雷公藤Tripterygium wilfordii后对小鼠血清中代谢产物的影响，初步探讨其降低肝毒性的可能代谢通路。方法 将C57BL/6小鼠随机分为对照（Con）组、雷公藤（Raw）组、甘草炮制雷公藤（Pro）组，观察小鼠肝组织病理变化，检测小鼠肝功能生化指标、炎症因子水平；利用液质联用（LC-MS）技术结合代谢组学方法，对各组间的代谢差异进行表征。结果 与Raw组相比，Pro组小鼠肝组织损伤显著改善，肝功能生化指标、炎症因子水平显著降低，表明甘草炮制雷公藤后可以降低小鼠肝毒性；共筛选出脂肪酸、磷脂酸、甘油酯、磷脂酰胆碱、胆酸等12个潜在生物标志物，主要涉及脂肪酸生物合成、甘油磷脂代谢、花生四烯酸代谢等9个代谢通路。结论 甘草炮制雷公藤可有效降低小鼠的肝毒性，其机制可能与调节脂肪酸代谢等通路相关，为其临床合理应用提供参考依据。     

四种大宗常用中药饮片中黄曲霉毒素污染状况分布比较研究

目的 测定不同来源的4种大宗常用中药饮片中黄曲霉毒素（AFB₁、AFB₂、AFG₁和AFG₂）的含量，比较不同基质中药饮片中黄曲霉毒素的分布状况。方法 基于免疫亲和柱净化-高效液相色谱分离-荧光检测器（IAC-HPLC-FLD）方法，分析不同产地共75批中药样品。结果 柏子仁、薏苡仁、决明子及党参共计75批中药饮片中，阳性检出：26批柏子仁（AFs 1.22-46.67 μg·kg^-1，AFB₁ 1.22-31.40 μg·kg^-1）、4批薏苡仁（AFs 1.97-41.13 μg·kg^-1，AFB₁ 1.97-36.40 μg·kg^-1）、1批决明子（AFs 13.65 μg·kg^-1，AFB₁ 12.60 μg·kg^-1），阳性率41%，超标率15%。阳性样品经 LC-MS/MS确证，排除假阳性。4种大宗常用中药饮片柏子仁、薏苡仁、决明子、党参中黄曲霉毒素的污染水平依次降低，阳性检出率分别为77%、29%、7%、0%，表明中药材中黄曲霉毒素的污染状况与药材基质密切相关。结论 针对易污染AFs的中药品种，需进一步加强其污染状况的全面检测分析，为黄曲霉毒素的有效防控以及完善中药的质量标准提供科学依据，从而保障中药用药安全。     

The Selection of a Pharmaceutical Salt—The Effect of the Acidity of the Counterion on Its Solubility and Potential Biopharmaceutical Performance

A roadmap for the selection of a pharmaceutical salt form for a development candidate is presented. The free base of the candidate did not have sufficient chemical stability for development. The initially selected salt form turned out to be undevelopable because it was unstable during scale-up synthesis and storage. The rationale for the new solid form screening and the criteria for selection are discussed. Before the final selection, the pH solubility profiles of the 2 new salts, a benzoate and a besylate, were compared. Atypical solubility behavior was observed for the benzoate salt in hydrochloric acid with and without normal saline. A scheme is proposed illustrating how the pKas of the counterion and active pharmaceutical ingredient, the medium composition, and final pH affect the solubility and solution equilibria of the 2 selected salt forms. This scheme also includes the equilibria between solution and solid phases in different pH ranges. The pharmaceutical importance of this research is that it sheds light on how the acidity of the counterion can affect the solubility of the selected salt form in the gastric environment. With a well-designed formulation strategy, this property potentially can be translated to optimal biopharmaceutical performance of the drug product.     

Inhibition of Organic Anion Transporting Polypeptide 1B1 and 1B3 by Betulinic Acid: Effects of Preincubation and Albumin in the Media

Betulinic acid (BA), a plant-derived pentacyclic triterpenoid, may interact with the members of the organic anion transporting polypeptide 1B subfamily. Here, we investigated the interactions of BA and its analogs with OATP1B1/3 and rat Oatp1b2 in vitro and in vivo. BA inhibited the activity of OATP1B1/3 and rat Oatp1b2 in vitro. Systemic exposure of atorvastatin was substantially altered with the intravenous co-administration of BA (20 mg/kg). Preincubation (incubation with inhibitors, followed by washout) with BA led to a sustained inhibition of OATP1B3, which recovered rapidly in the media containing 10% fetal bovine serum. The addition of albumin to the media decreased intracellular concentrations of BA and expedited the recovery of OATP1B3 activity following preincubation. For asunaprevir and cyclosporin A (previously known to inhibit OATP1B3 upon preincubation), the addition of albumin to the media shortened recovery time with asunaprevir, but not with cyclosporin A. Overall, our results showed that BA inhibits OATP1B transporters in vitro and may incur hepatic transporter-mediated drug interactions in vivo. Our results identify BA as another OATP1B3 inhibitor with preincubation effect and suggest that the preincubation effect and its duration is impacted by altered equilibrium of inhibitors between intracellular and extracellular space (e.g., albumin in the media).     

基于液相色谱-质谱技术的乳腺癌转移相关 代谢标志物的筛选

摘要：目的 应用代谢组学技术筛选与乳腺癌转移相关的代谢标志物。方法 收集100例乳腺癌患者和50例 健康志愿者的血清标本,采用高效液相色谱-轨道离子阱质谱联用（HPLC-LTQ Orbitrap XL MS）代谢组学研究平台分 析乳腺癌未转移患者、乳腺癌转移患者和健康人群血清标本的代谢轮廓,并通过模式识别方法结合非参数检验对数 据进行分析。结果 由乳腺癌未转移组、乳腺癌转移组和健康对照组的代谢轮廓构建的正交偏最小二乘判别分析 （OPLS-DA）模型具有很好的判别能力（R2=95.2%,Q2=86.7%）,可以鉴别出用于区分乳腺癌转移与否的8个代谢标志 物,包括溶血磷脂酸［18∶1（9Z）/0∶0］、溶血磷脂酰胆碱（18∶0）、溶血磷脂酰胆碱［20∶3（5Z,8Z,11Z）］、胆碱、磷酸二羟 丙酮（18∶0e）、2R,3S-番石榴酸、芥酸、L-氢化乳清酸。结论 利用代谢组学方法获得的血清代谢轮廓可以用来构建 区分模型和寻找乳腺癌转移相关的代谢标志物,为乳腺癌的早期诊治、预后评估和药物治疗靶点的选择提供支持和 依据。     

Effect of residual doxycycline concentrations on resistance selection and transfer in porcine commensal Escherichia coli

Pig feed may contain various levels of antimicrobial residues due to cross-contamination. A previous study showed that a 3% carry-over level of doxycycline (DOX) in the feed results in porcine faecal concentrations of approximately 4?mg/L.The aim of this study was to determine the effect of residual DOX concentrations (1 and 4?mg/L) in vitro on selection of DOX–resistant porcine commensal Escherichia coli and transfer of their resistance plasmids.Three different DOX–resistant porcine commensal E. coli strains and their plasmids were characterised. These strains were each brought in competition with a susceptible strain in a medium containing 0, 1 and 4?mg/L DOX. Resistant bacteria, susceptible bacteria and transconjugants were enumerated after 24?h and 48?h.The tet(A)–carrying plasmids showed genetic backbones that are also present among human E. coli isolates. Ratios of resistant to susceptible bacteria were significantly higher at 1 and 4?mg/L DOX compared with the blank control, but there was no significant difference between 1 and 4?mg/L. Plasmid transfer frequencies were affected by 1 or 4?mg/L DOX in the medium for only one of the resistance plasmids.In conclusion, DOX concentrations of 1 and 4?mg/L can select for resistant E. coli in vitro. Further research is needed to determine the effect of these concentrations in the complex environment of the porcine intestinal microbiota.     

保健食品中新型二硫代卡地那非类似物的分析鉴定

目的 鉴定保健食品中非法添加的一个未知结构的二硫代卡地那非类似物。方法 采用高效液相色谱-二极管阵列检测器联用（HPLC-DAD）技术进行补肾壮阳类保健食品非法添加筛查时发现一个未知结构的二硫代卡地那非类似物,经过正相硅胶薄层色谱分离纯化得到目标化合物后,用超高效液相色谱-二级质谱联用（UPLC-MS/MS）技术获得其准分子离子和二级质谱图,用核磁共振得到碳谱和氢谱数据,结合文献分析,最终鉴定该化合物的结构。结果 在保健食品中发现了一个新型二硫代卡地那非类似物,结构为3,5-二甲基哌嗪基二硫代去甲卡地那非。结论 该化合物不在现有补肾壮阳类中成药检验标准的13种目标化合物范围内,是一种新的非法添加化学物质。     

复方卡托普利片中未知杂质的来源与结构分析

目的 对复方卡托普利片中新发现的未知杂质进行来源分析和结构的初步确认,以期为该制剂改进工艺和提高标准提供依据。方法 采用Kromasil苯基色谱柱（250 mm×4.6 mm,5 μm）,以水-磷酸（550︰0.5）和甲醇为流动相进行梯度洗脱,检测波长为210 nm。对市售的复方卡托普利片中的该未知杂质的含量进行系统的评价;同时采用液质联用的方法对该未知杂质的结构进行确认。结果 该未知杂质为复方制剂的2种原料卡托普利和氢氯噻嗪在受热过程中产生的二聚物,分子式为C₁₆H₂₃N₄O₇S₃Cl;市售产品多数含有该杂质。结论 本研究为复方卡托普利片的质量控制和工艺优化提供了参考依据。