Enzyme-based assay for quantification of chlorpyrifos oxon in human plasma

Chlorpyrifos oxon (CPO) is the active metabolite of the pesticide chlorpyrifos that inhibits cholinesterases at high reaction rates. Chlorpyrifos is of major concern because it causes some ten thousand fatalities each year, mostly due to suicidal attempts. Notwithstanding, toxicokinetic studies on chlorpyrifos in humans are scarce and CPO has not been detected hitherto in human blood. Knowledge of the concentration and the time course of CPO in poisonings would be helpful to better design antidotal strategies, particularly with oximes. Owing to the exceptionally fast covalent binding to butyrylcholinesterase we searched for an enzyme-based assay for CPO determination. We succeeded in a simple procedure where CPO is titrated with purified equine butyrylcholinesterase. The assay requires less than 0.2mL EDTA plasma and allows the quantification of CPO down to 0.5nM. CPO is first extracted from plasma with n-pentane, thereby largely excluding the majority of the more hydrophilic pesticide oxons from possible cross-reactions. When chlorpyrifos incorporation is ascertained the assay may be considered largely specific. The new procedure enabled the assessment of the extent of reversible binding of CPO to human albumin, amounting to 85% under physiological conditions. The assay allowed the quantification of CPO in the plasma of a poisoned patient, where the active metabolite was about two orders of magnitude lower than chlorpyrifos. Similar to the parent compound its oxon showed the same tendency to persist for longer periods, thus calling for a change of the usual oxime dosage regimen.     

Carbofuran poisoning detected by mass spectrometry of butyrylcholinesterase adduct in human serum

Carbofuran is a pesticide whose acute toxicity is due to inhibition of acetylcholinesterase. Butyrylcholinesterase (BChE) in plasma is inhibited by carbofuran and serves as a biomarker of poisoning by carbofuran. The goal was to develop a method to positively identify poisoning by carbofuran. Sera from an attempted murder and an attempted suicide were analyzed for the presence of carbofuran adducts on BChE. The BChE from 1 ml of serum was rapidly purified on a 0.2 ml procainamide-Sepharose column. Speed was essential because the carbofuran-BChE adduct decarbamylates with a half-life of about 2 h. The partially purified BChE was boiled to denature the protein, thus stopping decarbamylation and making the protein vulnerable to digestion with trypsin. The labeled peptide was partially purified by HPLC before analysis by LC/MS/MS in the multiple reaction monitoring mode on the QTRAP 2000 mass spectrometer. Carbofuran was found to be covalently bound to Ser 198 of human BChE in serum samples from two poisoning cases. Multiple reaction monitoring triggered MS/MS spectra positively identified the carbofuran-BChE adduct. In conclusion a mass spectrometry method to identify carbofuran poisoning in humans has been developed. The method uses 1 ml of serum and detects low-level exposure associated with as little as 20% inhibition of plasma butyrylcholinesterase.     

An evaluation of the inhibition of human butyrylcholinesterase and acetylcholinesterase by the organophosphate chlorpyrifos oxon

Acetylcholinesterase (EC 3.1.1.7) and butyrylcholinesterase (EC 3.1.1.8) are enzymes that belong to the superfamily of α/β-hydrolase fold proteins. While they share many characteristics, they also possess many important differences. For example, whereas they have about 54% amino acid sequence identity, the active site gorge of acetylcholinesterase is considerably smaller than that of butyrylcholinesterase. Moreover, both have been shown to display simple and complex kinetic mechanisms, depending on the particular substrate examined, the substrate concentration, and incubation conditions. In the current study, incubation of butyrylthiocholine in a concentration range of 0.005–3.0 mM, with 317 pM human butyrylcholinesterase in vitro, resulted in rates of production of thiocholine that were accurately described by simple Michaelis–Menten kinetics, with a K_m of 0.10 mM. Similarly, the inhibition of butyrylcholinesterase in vitro by the organophosphate chlorpyrifos oxon was described by simple Michaelis–Menten kinetics, with a k_i of 3048 nM⁻¹ h⁻¹, and a K_D of 2.02 nM. In contrast to inhibition of butyrylcholinesterase, inhibition of human acetylcholinesterase by chlorpyrifos oxon in vitro followed concentration-dependent inhibition kinetics, with the k_i increasing as the inhibitor concentration decreased. Chlorpyrifos oxon concentrations of 10 and 0.3 nM gave k_is of 1.2 and 19.3 nM⁻¹ h⁻¹, respectively. Although the mechanism of concentration-dependent inhibition kinetics is not known, the much smaller, more restrictive active site gorge of acetylcholinesterase almost certainly plays a role. Similarly, the much larger active site gorge of butyrylcholinesterase likely contributes to its much greater reactivity towards chlorpyrifos oxon, compared to acetylcholinesterase.     

Methamidophos,dichlorvos, O‐methoate and diazinon pesticides used in Turkey make a covalent bond with butyrylcholinesterase detected by mass spectrometry

Organophosphorus pesticides used most commonly in Turkey include methamidophos, dichlorvos, O‐methoate and diazinon. These toxic chemicals or their metabolites make a covalent bond with the active site serine of butyrylcholinesterase. Our goal was to identify the adducts that result from the reaction of human butyrylcholinesterase with these pesticides. Highly purified human butyrylcholinesterase was treated with a 20‐fold molar excess of pesticide. The protein was denatured by boiling and digested with trypsin. MS and MSMS spectra of HPLC‐purified peptides were acquired on a MALDI‐TOF‐TOF 4800 mass spectrometer. It was found that methamidophos added a mass of +93, consistent with addition of methoxy aminophosphate. A minor amount of adduct with an added mass of +109 was also found. Dichlorvos and O‐methoate both made dimethoxyphosphate (+108) and monomethoxyphosphate adducts (+94). Diazinon gave a novel adduct with an added mass of +152 consistent with diethoxythiophosphate. Inhibition of enzyme activity in the presence of diazinon developed slowly (15 h), concomitant with isomerization of diazinon via a thiono‐thiolo rearrangement. The isomer of diazinon yielded diethoxyphosphate and monoethoxyphosphate adducts with added masses of +136 and +108. MSMS spectra confirmed that each of the pesticides studied made a covalent bond with serine 198 of butyrylcholinesterase. These results can be used to identify the class of pesticides to which a patient was exposed.     

Extreme variability in the formation of chlorpyrifos oxon (CPO) in patients poisoned by chlorpyrifos (CPF)

Chlorpyrifos (CPF) is a pesticide that causes tens of thousands of deaths per year worldwide. Chlorpyrifos oxon (CPO) is the active metabolite of CPF that inhibits acetylcholinesterase. However, this presumed metabolite has escaped detection in human samples by conventional methods (HPLC, GC-MS, LC-MS) until now. A recently developed enzyme-based assay allowed the determination of CPO in the nanomolar range and was successfully employed to detect this metabolite. CPO and CPF were analysed in consecutive plasma samples of 74 patients with intentional CPF poisoning. A wide concentration range of CPO and CPF was observed and the ratio of CPO/CPF varied considerably between individuals and over time. The ratio increased during the course of poisoning from a mean of 0.005 in the first few hours after ingestion up to an apparent steady-state mean of 0.03 between 30 and 72 h. There was a hundred-fold variation in the ratio between samples and the interquartile range (between individuals) indicated over half the samples had a 5-fold or greater variation from the mean. The ratio was independent of the CPF concentration and the pralidoxime regimen. CPO was present in sufficient quantities to explain any observed acetylcholinesterase inhibitory activity. The effectiveness of pralidoxime in reactivating the inhibited acetylcholinesterase is strongly dependent on the CPO concentration. Differences in clinical outcomes and the response to antidotes in patients with acute poisoning may occur due to inter-individual variability in metabolism.     

Nanoimages show disruption of tubulin polymerization by chlorpyrifos oxon: Implications for neurotoxicity

Organophosphorus agents cause cognitive deficits and depression in some people. We hypothesize that the mechanism by which organophosphorus agents cause these disorders is by modification of proteins in the brain. One such protein could be tubulin. Tubulin polymerizes to make the microtubules that transport cell components to nerve axons. The goal of the present work was to measure the effect of the organophosphorus agent chlorpyrifos oxon on tubulin polymerization. An additional goal was to identify the amino acids covalently modified by chlorpyrifos oxon in microtubule polymers and to compare them to the amino acids modified in unpolymerized tubulin dimers. Purified bovine tubulin (0.1 mM) was treated with 0.005-0.1 mM chlorpyrifos oxon for 30 min at room temperature and then polymerized by addition of 1 mM GTP to generate microtubules. Microtubules were visualized by atomic force microscopy. Chlorpyrifos oxon-modified residues were identified by tandem ion trap electrospray ionization and matrix-assisted laser desorption/ionization mass spectrometry of tryptic peptides. Nanoimaging showed that low concentrations (0.005 and 0.01 mM) of chlorpyrifos oxon yielded short, thin microtubules. A concentration of 0.025 mM stimulated polymerization, while high concentrations (0.05 and 0.1 mM) caused aggregation. Of the 17 tyrosines covalently modified by chlorpyrifos oxon in unpolymerized tubulin dimers, only 2 tyrosines were labeled in polymerized microtubules. The two labeled tyrosines in polymerized tubulin were Tyr 103 in EDAANNY?R of alpha tubulin, and Tyr 281 in GSQQY?R of beta tubulin. In conclusion, chlorpyrifos oxon binding to tubulin disrupts tubulin polymerization. These results may lead to an understanding of the neurotoxicity of organophosphorus agents.     

液质联用法测定人血浆中米格列奈的浓度

目的建立LC-MS/MS法测定人血浆中米格列奈的浓度,并研究其在健康男性受试者体内的药动学。方法血浆经液-液萃取。色谱柱:Agilent TC-C18柱,流动相:乙腈-水-甲酸(体积比为70.0∶30.0∶0.3),质谱检测采用多反应监测模式(multiple reaction monitoring,MRM),电喷雾离子源,分析时间:2.0 min。结果米格列奈线性为5.0～4 000.0μg.L-1,定量下限为5.0μg.L-1。日内、日间精密度(relative standard deviation,RSD)均不大于10.5%,准确度(relative error,RE)为-0.8%～-2.0%。健康男性受试者口服含米格列奈10 mg的受试制剂(规格:10 mg/片)和参比制剂(规格:5 mg/片)后主要药动学参数为:tmax分别为(0.375±0.079)和(0.396±0.166)h,ρmax分别为(887±292)和(902±298)μg.L-1,t1/2分别为(1.37±0.45)和(1.49±0.57)h,AUC0-t分别为(1047±379)和(1 067±430)μg.h.L-1,AUC0-∞分别为(1 070±394)和(1 092±433)μg.h.L-1。结论该法适用于米格列奈的药动学及生物等效性研究。     

液相色谱-串联质谱法测定人血浆中罗格列酮

目的:建立测定人血浆中罗格列酮的液相色谱-质谱-质谱联用法,并用于临床药动学研究。方法: 血浆样品经液-液萃取后,以乙腈-水-甲酸(90:10:0．5)为流动相,采用Zorbax SB—C18柱分离,通过电喷雾离子化四极杆串联质谱,以选择反应监测(SRM)方式进行检测。用于定量分析的离子反应分别为m／z 358→ 135(罗格列酮)和m／z 256→167(内标苯海拉明)。结果:标准曲线线性范围为0．50～1 000μg·L-1,定量下限为0．50μg·L-1,日内、日间精密度(RSD)均小于7．4％。应用此法测试了20名男性健康受试者口服酒石酸罗格列酮片(相当于罗格列酮4 mg)后血浆中罗格列酮的浓度。结论:该法灵敏、快速、准确,操作简便、线性范围宽,适用于罗格列酮的临床药动学研究。     

液相色谱-串联质谱法测定人血浆中培哚普利及其活性代谢物培哚普利拉

目的:建立人血浆中培哚普利及其活性代谢物培哚普利拉的高效液相-串联质谱测定法.方法:采用不同的沉淀法对血浆样品进行处理,分别对培哚普利和培哚普利拉进行测定,采用Phenomenex Cu-rosil-PFP柱对样品和内标进行分离,以不同比例的甲醇和醋酸盐缓冲液为流动相,通过电喷雾离子化四级杆串联质谱,以选择反应监测(SRM)正离子方式进行检测.用于定量分析的离子反应分别为m/z 369→172.2(培哚普利)和m/z 377.0→234.1(内标依那普利);m/z 341→170.2(培哚普利拉)和m/z 349.0→206.0(内标依那普利拉).结果:培哚普利标准曲线范围为0.5～200μg·L-1,定量下限为0.5μg·L-1;培哚普利拉标准曲线范围为0.2～20μg·L-1,定量下限为0.2 μg·L-1.原药和代谢物的批内批间精密度(RSD)均<15%.应用该法测试了18名健康男性受试者口服培哚普利片后血浆中培哚普利和培哚普利拉的浓度.结论:该法灵敏、快速、准确,适用于培哚普利的临床药动学研究.     

液相色谱-串联质谱法测定人血浆中的龙胆苦苷浓度

目的:建立测定人血浆中龙胆苦苷浓度的液相色谱-串联质谱法。方法:血浆加入内标咖啡因后经固相萃取处理,采用 RESCEK C_8柱(150 mm×2.1 mm,5μm)分离,流动相为甲醇-10 mmol·L~(-1)醋酸铵溶液-乙腈(50:40:10),流速为0.2mL·min~(-1)。样品在三级四极杆串联质谱中经 ESI 源离子化后以多反应离子监测方式测定。结果:龙胆苦苷在3～5000 ng·mL~(-1)线性良好(r=0.9985),检测限为3 ng·mL~(-1),回收率为94.4%～104.2%,绝对回收率为92.4%～98.0%,日内、日间变异(RSD)均≤15%,色谱峰保留时间为2.25 min。结论:方法灵敏、准确、快速、特异性强,适用于中药龙胆苦苷的血药浓度测定和临床药代动力学研究。     

Determination of eperisone in human plasma by liquid chromatography-ESI-tandem mass spectrometry

A sensitive and selective method for the determination of 4′-ethyl-3-methyl-3-piperidinopro-piophenone hydrochloride (eperisone hydrochloride) in human plasma was developed and validated. The procedure employed an internal standard and a solvent extraction step followed by chromatography on a Xterra C₁₈ minibore column. Detection was by electrospray ionization tandem mass spectrometry with multiple reaction monitoring. The mass transitions of eperisone and tolperisone (IS) were m/z 260 → 98 and m/z 246 → 98, respectively. The method has a limit of detection of 0.1 pg/mL for eperisone based on the three times signal-to-noise value with a linear range from 0.01 to 10.0 ng/mL for the analyte. Extraction recovery was on average 98.6±7.2% (SD) for eperisone. The Intra- and inter-day assay accuracy ranged from 93 to 114% and precision (RSD) was better than 8.5%. The method was successfully employed to analyze plasma samples and evaluate pharmacokinetics of eperisone in healthy male volunteers.     

液相色谱-串联质谱法测定人血浆中的伪麻黄碱浓度

建立了测定人血浆中伪麻黄碱浓度的液相色谱 串联质谱法。血浆样品经液 液萃取处理后 ,以甲醇 水 甲酸 (体积比 6 0∶40∶2 )为流动相 ,采用ZorbaxC18柱分离 ,通过电喷雾四极杆串联质谱 ,正离子方式检测 ;采用SRM转化m/z 16 6→ 147(伪麻黄碱 )和m/z 2 75→ 12 5 (内标罗哌卡因 )进行定量分析。线性范围为 5 0～ 2 5 0 0ng/mL ,定量限为 5 0ng/mL。应用本法测试了 2 0名健康受试者口服 6 0mg盐酸伪麻黄碱后不同时刻的血浆药物浓度     

液相色谱-串联质谱法测定人血浆中氟氯西林的含量

目的为临床制定安全有效的给药方案提供参考。方法采用液相色谱-串联质谱(LC-MS-MS)法。血浆样品经液-液萃取处理后,以乙腈-水(体积比25∶75)为流动相,采用Zorbax Ec lipseXDB C8柱(150 mm×4.6 mm,5μm)分离;通过电喷雾三重四级杆串联质谱,以负离子、选择反应监测方式进行检测,用于定量的离子反应分别为m/z452→m/z311(氟氯西林)和m/z468→m/z327(内标双氯西林)。结果氟氯西林线性范围为20.0~15000μg.L-1,定量下限为20.0μg.L-1,提取回收率均大于70%,日内、日间精密度均小于7%。结论该法适用于注射用氟氯西林钠的单次肌内注射给药的药物动力学研究。     

液相色谱-串联质谱法同时测定人血浆中二甲双胍和格列吡嗪

建立了快速、灵敏的液相色谱-串联质谱法测定人血浆中的二甲双胍和格列吡嗪。血浆样品经0.3%甲酸-乙腈(v/v)沉淀蛋白后，以乙腈-水-甲酸(70∶30∶0.3，v/v/v)为流动相，流速为0.50 mL·min^-1。Zorbax Extend C₁₈柱分离，采用大气压化学电离源；以选择反应监测(SRM)方式进行正离子检测。用于定量分析的离子反应分别为m/z 130→m/z 60(二甲双胍)，m/z 446→m/z 321(格列吡嗪)和m/z 256→m/z 167(内标，苯海拉明)。测定血浆中二甲双胍的线性范围为2.00～2 000 ng·mL^-1， 定量下限为2.00 ng·mL^-1； 格列吡嗪的线性范围为1.00～1 000 ng·mL^-1， 定量下限为1.00 ng·mL^-1。该方法专属性好，灵敏度高，准确快捷，适用于二甲双胍和格列吡嗪的临床药代动力学研究。     

液相色谱-串联质谱法同时测定人血浆中伪麻黄碱和苯海拉明

伪麻黄碱 (ｐｓｅｕｄｏｅｐｈｅｄｒｉｎｅ)为拟交感神经类药物 ,临床常用于治疗感冒、支气管炎等上呼吸道感染疾病。苯海拉明 (ｄｉｐｈｅｎｈｙｄｒａｍｉｎｅ)为Ｈ1 受体拮抗剂 ,具抗组胺活性 ,同时还具镇静、止呕和抗副交感神经生理作用等特点。临床上常将二者复方用药 ,既能发挥伪麻黄碱消除上呼吸道粘膜充血的功能 ,又可利用苯海拉明促进睡眠、有助于机体自身免疫系统发挥作用等特点。有文献报道单独测定人血浆中的伪麻黄碱[1～ 4]或苯海拉明的方法[5～ 7] ,但这些方法均有一定局限性 ,无法满足同时测定两种成分的需要。本文旨在建立…     

液相色谱-串联质谱法测定人血浆中匹伐他汀

目的:建立灵敏、快速的液相色谱-串联质谱(LC-MS-MS)法测定人血浆中匹伐他汀,并用于药动学研究。方法:血浆样品经乙腈沉淀蛋白后,以乙腈-5 mmol·L~(-1)醋酸铵溶液(90:10,V:V)为流动相,Zorbax XDB C_8柱分离。采用电喷雾电离源(ESI),以多反应监测(MRM)方式进行正离子检测。用于定量分析的离子分别为m/z 422→m/z 290(匹伐他汀)和m/z 515→m/z 276(内标,替米沙坦)。结果:测定血浆中匹伐他汀的线性范围为0.1～100μg·L~(-1),定量下限为0.1μg·L~(-1)。日内、日间精密度(RSD)均小于12.0%,准确度(RE)在±2.4%以内。结论:该方法选择性好、灵敏度高、操作简便,适用于匹伐他汀的临床药动学研究。     

紫杉醇及其人血浆中代谢物的电喷雾串联质谱研究

目的:采用电喷雾串联质谱(ESI-MSn)法研究紫杉醇的离子化方式、结构裂解方式及在人血浆中的主要代谢物。方法:紫杉醇对照品溶液经质谱进样,探索其一级质谱的电离规律和二级质谱的裂解规律。通过液相色谱-质谱联用技术分离和鉴定紫杉醇在人体中的代谢物。结果:溶液中的添加剂对紫杉醇的离子化效率有明显促进作用,在ESI正离子模式下紫杉醇以m/z854的[M+H]+丰度最高。紫杉醇裂解过程以脱水和酯键断裂为主,产生多个碎片离子,其中m/z286信号最强并具有较好的稳定性。紫杉醇在人血浆中的代谢物有3个,以6α-羟基紫杉醇为主。结论:紫杉醇及其人血浆中代谢物的质谱行为研究,可为紫杉醇的质谱定性和定量分析以及药物代谢研究提供重要参考。     

液-质联用测定人血浆中罗红霉素浓度

目的:建立高效液相色谱-质谱联用法测定人血浆中罗红霉素浓度。方法:以克拉霉素为内标,血浆样品经乙腈沉淀后,经HPLC-MS/MS分离分析。采用Waters ODS C18柱(2.1mm×50mm,3.5μm),以甲醇-5mmol.L-1醋酸铵(含0.03%甲酸)(55∶45)为流动相;流速:0.2mL.min-1,采用电喷雾离子源(ESI),以多离子反应监测方式(MRM)进行正离子监测,罗红霉素和内标克拉霉素的定量分析离子对分别为m/z837.5→679.4和m/z748.5→590.3。结果:罗红霉素血浆浓度测定方法线性范围为0.02025~13.500mg.L-1,r=0.999 0。定量下限为0.02025mg.L-1,方法回收率在85%~115%之间。日内和日间RSD均小于15%。结论:本试验所建立的方法灵敏、准确、可靠,适于罗红霉素的人体内药动学研究。     

液相色谱-质谱-质谱联用法快速测定人血浆中法莫替丁含量

目的建立测定人血浆中法莫替丁含量的液相色谱 质谱 质谱联用法。方法取 0 2mL血浆样品经液 液萃取后 ,以乙腈 水 甲酸 (3 0∶70∶1 ,V∶V∶V)为流动相 ,采用ZorbaxSBC8柱分离 ,通过电喷雾离子化四极杆串联质谱 ,以选择反应监测 (SRM)方式进行检测。用于定量分析的离子反应分别为m/z 3 3 8→m/z1 88(法莫替丁 )和m/z2 40→m/z1 47(内标 ,沙丁胺醇 )。结果法莫替丁线性范围是 2 5～ 5 0 0 0ng/mL ,最低定量限为 2 5ng/mL。日内、日间精密度 (RSD)小于 8% ,准确度(RE)在± 2 %范围内。每个样品测试时间仅为 4min,应用此法每天可以测试 1 0 0多个样品。结论该法灵敏度高 ,样品处理简单 ,分析测试速度快 ,适用于临床药物动力学研究。     

同位素稀释-超高效液相色谱-串联质谱法测定人血浆中仑伐替尼的浓度

目的 建立同位素稀释-超高效液相色谱-串联质谱法测定人血浆中仑伐替尼的浓度.方法 血浆样品用甲基叔丁醚进行液液萃取,取上清液后氮气吹干,50％甲醇水复溶后进样检测,同位素为内标用于定量,色谱柱为ZORBAX SB-C18(2.1 mm×100.0 mm,3.5μm),乙腈、0.1％甲酸水为流动相进行梯度洗脱,进样体积为...