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Targeted mass spectrometry is extensively used for the quantitative measurement of various molecules present in complex matrices. It is certainly one of the most important analytical duties in a mass spectrometry laboratory. Systematic development of selected-reaction monitoring (SRM), multiple-reaction monitoring (MRM) and parallel-reaction monitoring (PRM) methods for targeted mass spectrometry-based analysis was performed without considering future opportunities. The advancement of hardware and software technologies has resulted in greater resolution, accuracy, speed and depth. For sure, SRM, MRM or PRM acquisitions can quantify molecules very accurately at trace levels. However, they do not provide datasets allowing future data mining. Obviously, we cannot truly quantify something that we do not know is there. However, using non-targeted data acquisition for target analysis, we can generate a MS 1 and MS 2 digital libraries of each sample, providing future proof datasets. This is instrumental for data mining following new questions potentially arising in time permitting new and deeper processing and interpretation. This perspective article provides thoughts on why we believe it is time to question the status quo in targeted mass spectrometry., (© 2022 John Wiley & Sons Ltd.)

A rapid, selective and sensitive method was developed and validated for the determination of LY-404,039 concentration in rat plasma using a butylation derivatization step to improve chromatographic characteristics and enhance signal intensity. The method consisted of a protein precipitation extraction followed by derivatization with butanol/HCl and analysis by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The separation was achieved using a 100 × 2.1 mm (2.6 μm) Thermo Scientific Accucore RP-MS column combined with an isocratic mobile phase composed of 40:60 acetonitrile-0.1% formic acid in water. An analytical range of 2.0-1,000 ng/ml was validated and used to quantify LY-404,039 in rat plasma. The novel method met all of the requirements of specificity, sensitivity, linearity, precision, accuracy and stability. A pharmacokinetic study was performed in rats and the novel analytical method was used as a routine analysis method to provide enhanced measurements of plasma concentrations of LY-404,039. The plasma pharmacokinetic results indicate very short terminal half-life (0.27 h ± 0.8) and high clearance (0.97 L/h/kg ± 0.12), suggesting that LY-404,039 is rapidly eliminated in the rat. Dose-dependent pharmacokinetics were observed following subcutaneous administration of LY-404,039 at doses of 0.1, 0.3 and 1.0 mg/kg., (© 2022 John Wiley & Sons Ltd.)

Targeted peptide quantitation by mass spectrometry is a rapidly emerging field. Traditionally it relied on the development and validation of multiple reaction monitoring assays that could comply with a high level of sensitivity, specificity, accuracy and reproducibility in complex biological samples. However, with the introduction of high-resolution mass spectrometers, other acquisition modes could provide more comprehensive datasets for identification and quantification but also for in-depth data mining. The objective of this study was to evaluate two analytical approaches, parallel-reaction monitoring (PRM) and data-independent analysis (DIA) using a hybrid Quadrupole-Orbitrap mass spectrometer for the quantification of neuropeptides in animal spinal cord tissues. Mouse spinal cord tissues were harvested, homogenized and neuropeptides extracted using a C 18 solid-phase extraction protocol. Chromatography was achieved using a Thermo Biobasic C 8 100 × 1 mm (5 μm) column. The initial mobile phase conditions consisted of acetonitrile and water (both containing 0.1% of formic acid) at a ratio of 5:95. An 11 min linear gradient was applied up to a ratio of 50:50 and maintained for 3 min. The flow rate was fixed at 75 μL/min and 2 μL of sample was injected. Mass spectrometry analyses were performed using a Thermo Q Exactive Plus MS using PRM and DIA approaches. Quantitative data using an isotopic dilution and a label-free strategy were obtained for both methods and statistically compared. Using both approaches, we were able to clearly detect endogenous neuropeptides. However, with DIA, mass spectra alone could not distinguish Leu-Enk and Met-Enk. We used a Bland-Altman plot (Difference plot) to analyze the agreement between both approaches and no systematic bias was observed. Further statistical analyses, including variance analysis, showed more variability in DIA compared with PRM mode. Further analyses were performed using a label-free approach and confirmed an increase of the variance using a DIA approach., (© 2019 John Wiley & Sons, Ltd.)

Tachykinins are a family of pronociceptive neuropeptides with a specific role in pain and inflammation. Several mechanisms regulate endogenous tachykinins levels, including the differential expression of protachykinin mRNA and the controlled secretion of tachykinin peptides from neurons. We suspect that proteolysis regulates extracellular neuropeptide K (NPK) and neurokinin A (NKA) concentrations and NPK is a precursor of NKA. Here, we provide evidence that proteolysis controls NPK and NKA levels in the spinal cord, leading to the formation of active C-terminal peptide fragments. Using high-resolution mass spectrometry, specific tachykinin fragments were identified and characterized. The metabolic stability in rat spinal cord fractions of NPK and NKA was very short, resulting in half-lives of 1.9 and 2.2 min respectively. Following the degradation of NPK, several C-terminal fragments were identified, including NPK 1-26 , NKA, NKA 2-10 , NKA 3-10 , NKA 5-10 and NKA 6-10 , which conserve affinity for the neurokinin 2 receptor but also for the neurokinin 1 receptor. Interestingly, the same fragments were identified following the degradation of NKA. A specific proprotein convertases inhibitor was used and showed a significant reduction in the rate of formation of NKA, providing strong evidence that proprotein convertase is involved in C-terminal processing of NPK in the spinal cord, leading to the formation of NKA., (Copyright © 2018 John Wiley & Sons, Ltd.)

Codeine and oxycodone are opioids used to alleviate pain. The outcome of the treatment is ultimately related to their metabolism by Cytochromes P450 (CYPs). Depending on the drugs used, alterations in the metabolism of drugs by CYPs can lead to severe consequences including alterations in their efficacy, safety and toxicity. The objectives of this study were to develop a novel HPLC-MS/MS method capable of quantifying codeine and oxycodone along with specific metabolites using an isotopic dilution strategy and study the rate of formation of morphine (CYP2D), norcodeine (CYP3A), oxymorphone (CYP2D) and noroxycodone (CYP3A). The chromatographic separation was achieved using a Biobasic C 18 100 × 1 mm column combined with an isocratic mobile phase composed of methanol and 10 mm ammonium acetate (40:60) at a flow rate of 75 μL/min. The mass spectrometer was operating in scan mode MS/MS and the analytical range was set at 10-10 000 nm. The precision (RSD) and accuracy (RE) observed were 4.4-11.5 and -9.1-6.1% respectively. Liver S9 fractions from 3-, 6-, 12- and 18-month-old male Sprague-Dawley rats were prepared and Michaelis-Menten parameters were determined. The derived maximum enzyme velocity suggested a rapid saturation of the CYP2D and CYP3A active sites in the liver S9 fractions of 18-month-old rats. Moreover, metabolic stabilities of codeine and oxycodone in rat liver S9 fractions were significantly greater for the 18-month-old rats. This study suggests that there is an impairment of CYP2D and CYP3A metabolism in aging rats., (Copyright © 2016 John Wiley & Sons, Ltd.)

Triple quadrupole mass spectrometers coupled with high performance liquid chromatography are workhorses in quantitative bioanalyses. They provide substantial benefits including reproducibility, sensitivity and selectivity for trace analysis. Selected reaction monitoring allows targeted assay development but datasets generated contain very limited information. Data mining and analysis of nontargeted high-resolution mass spectrometry profiles of biological samples offer the opportunity to perform more exhaustive assessments, including quantitative and qualitative analysis. The objectives of this study were to test method precision and accuracy, to statistically compare bupivacaine drug concentration in real study samples and to verify if high-resolution and accurate mass data collected in scan mode can actually permit retrospective data analysis, more specifically, extract metabolite related information. The precision and accuracy data presented using both instruments provided equivalent results. Overall, the accuracy ranged from 106.2 to 113.2% and the precision observed was from 1.0 to 3.7%. Statistical comparisons using a linear regression between both methods revealed a coefficient of determination (R(2)) of 0.9996 and a slope of 1.02, demonstrating a very strong correlation between the two methods. Individual sample comparison showed differences from -4.5 to 1.6%, well within the accepted analytical error. Moreover, post-acquisition extracted ion chromatograms at m/z 233.1648 ± 5 ppm (M - 56) and m/z 305.2224 ± 5 ppm (M + 16) revealed the presence of desbutyl-bupivacaine and three distinct hydroxylated bupivacaine metabolites. Post-acquisition analysis allowed us to produce semi-quantitative evaluations of the concentration-time profiles for bupicavaine metabolites., (Copyright © 2015 John Wiley & Sons, Ltd.)

Ketamine is widely used in medicine in combination with several benzodiazepines, including midazolam. The objectives of this study were to develop a novel HPLC-MS/selected reaction monitoring (SRM) method capable of quantifying ketamine and norketamine using an isotopic dilution strategy in biological matrices and study the formation of norketamine, the principal metabolite of ketamine with and without the presence of midazolam, a well-known CYP3A substrate. The chromatographic separation was achieved using a Thermo Betasil Phenyl 100 × 2 mm column combined with an isocratic mobile phase composed of acetonitrile, methanol, water and formic acid (60:20:20:0.4) at a flow rate of 300 μL/min. The mass spectrometer was operating in selected reaction monitoring mode and the analytical range was set at 0.05-50 μm. The precision (CV) and accuracy (NOM) observed were 3.9-7.8 and 95.9-111.1% respectively. The initial rate of formation of norketamine was determined using various ketamine concentrations and Km values of 18.4, 13.8 and 30.8 μm for rat, dog and human liver S9 fractions were observed, respectively. The metabolic stability of ketamine on liver S9 fractions was significantly higher in human (T1/2  = 159.4 min) compared with rat (T1/2  = 12.6 min) and dog (T1/2  = 7.3 min) liver S9 fractions. Moreover significantly lower IC50 and Ki values observed in human compared with rat and dog liver S9 fractions. Experiments with cDNA expressed CYP3A enzymes showed that the formation of norketamine is mediated by CYP3A but results suggest an important contribution from other isoenzymes, most likely CYP2C particularly in rat., (Copyright © 2014 John Wiley & Sons, Ltd.)

[6]-Gingerol, a structural analog of capsaicin, is an agonist of the transient receptor potential vanilloid 1 channel, which is known to have therapeutic properties for the treatment of pain and inflammation. The main objective of this study was to determine the central effect of [6]-gingerol on neuropathic pain when injected intrathecally at the level of the lumbar spinal cord. [6]-Gingerol distribution was evaluated following a 40 mg/kg intraperitoneal injection, and the brain-to-plasma and spinal cord-to-plasma ratios (0.73 and 1.7, respectively) suggest that [6]-gingerol penetrates well the central nervous system of rats. Induction of pain was performed using the sciatic nerve ligation model on rats, and a 10-µg intrathecal injections of [6]-gingerol was performed to evaluate its central effect. The results suggest a significant decrease of secondary mechanical allodynia after 30 min, 2 h and 4 h (p < 0.05, p < 0.01 and p < 0.001) and thermal hyperalgesia after 30 min, 2 h and 4 h (p < 0.05, p < 0.01 and p < 0.01). These promising results illustrate that [6]-gingerol could alleviate neuropathic pain by acting centrally at the level of the spinal cord., (Copyright © 2012 John Wiley & Sons, Ltd.)

Xylazine is an α2 -adrenoceptor agonist and it is widely used in veterinary anesthesia in combination with ketamine. There is limited information on the metabolism of xylazine. A quantitative method for the determination of xylazine by HPLC-ESI/MS/MS was developed. The method consisted of a protein precipitation extraction followed by analysis using liquid chromatography electrospray tandem mass spectrometry. The chromatographic separation was achieved using a Thermo Betasil Phenyl 100 × 2 mm column combined with an isocratic mobile phase composed of acetonitrile, methanol, water and formic acid (60:20:20:0.4) at a flow rate of 300 μL/min. The mass spectrometer was operating in selected reaction monitoring mode and the analytical range was set at 0.05-50 μm. The precision (%CV) and accuracy (%NOM) observed were 2.3-7.2 and 88.2-96.4%. In vitro metabolism studies were performed in rat liver microsomes and results showed moderate cytochrome P450 affinity (Km = 10.1 μm) and a low metabolic stability of xylazine with a half-life of 4.1 min in rat liver microsomes. Five phase 1 metabolites were observed. The main metabolite observed was an oxidation of the thiazine moiety at m/z 235 and, to a lesser extent, we observed the formation of N-(2,6-dimethylphenyl)thiourea at m/z 181 and three distinctive hydroxylated metabolites at m/z 237. Further experiments with ketamine and ketoconazole strongly supported that the metabolism of xylazine to its main metabolite is mediated by CYP3A in rat liver microsomes., (Copyright © 2013 John Wiley & Sons, Ltd.)

Substance P (SP) belongs to the tachykinin family and plays an essential role in pain transmission and in neurogenic inflammation. It can be detected in the central and peripheral nervous systems. The objectives of this study were to establish SP metabolic stability in liver microsomes in three species (rat, mouse and human), and identify and characterize SP metabolites by LC-MS/MS. Endogenous peptide metabolism is not well documented and this is particularly true for neuropeptides participating in neurogenic inflammation. In vitro, T(1/2) results in pooled liver microsomes were 9.2, 5.6 and 18.6 min for rat, mouse and human liver microsomes, respectively. Five major SP metabolites were identified and quantified, including C-terminal SP fragments SP(3-11) , SP(5-11) , SP(6-11) , SP(8-11) as well as N-terminal fragment SP(1-7) . The results suggest significant differences between species in SP metabolite concentrations. Consequently, the metabolic profile of each species is distinctive and may have a significant impact on biomolecular mechanisms involved in specific pathophysiological changes., (Copyright © 2012 John Wiley & Sons, Ltd.)

The aim of the present study was to evaluate whether eugenol, the main constituent of clove oil, has the capacity to provide analgesia in the monoiodoacetate-induced rat model of osteoarthritis. Animals (n = 6/group) received either eugenol (20 or 40 mg/kg) or a vehicle by gavage. Daily administrations were initiated 2 days post osteoarthritis induction and continued for the duration of the study (4 weeks). Gait analysis was performed using the CatWalk method and secondary mechanical allodynia was assessed with von Frey filaments. Selected spinal cord peptides (substance P, calcitonin gene-related peptide and dynorphin) were quantified by mass spectrometry. Significant changes were identified in dynamic gait parameters (swing speed, swing phase duration and duty cycle) of the affected limb following 40 mg/kg eugenol treatment compared with the vehicle (p < 0.05). Von Frey results revealed significant differences between the 40 mg/kg treatment and the vehicle group during the first and the third week of the study (p < 0.02). Spinal pain-related peptide analysis revealed a decreased content of substance P and CGRP accompanied by an increase of dynorphin in animals treated with 40 mg/kg eugenol. These results suggest a therapeutic potential of eugenol to alleviate osteoarthritis-related pain., (Copyright © 2012 John Wiley & Sons, Ltd.)

Staphylococcus aureus produces enterotoxins, which are causative agents of foodborne intoxications. Enterotoxins are single-chain polypeptides and have a molecular weight of about 26-28 kDa. The consumption of food contaminated with Staphylococcus aureus enterotoxins results in the onset of acute gastroenteritis within 2-6 h. The objective of this study was the development of a new method for the quantification of Staphylococcal enterotoxin B (SEB) in food matrices. Tryptic peptide map was generated and nine proteolytic fragments were clearly identified (sequence coverage of 35%). Among these, three specific tryptic peptides were selected to be used as surrogate peptides and internal standards for quantitative analysis using an isotopic tagging strategy along with analysis by LC-MS/MS. The linearity of the measurement by LC-MS/MS was evaluated by combining mixtures of both isotopes at 0.1, 0.2, 0.5, 1.0 and 2.0 ¹H/²H molar ratios with a slope near to 1, values of R² above 0.98 and %CV obtained from six repeated measurement was below 8%. The precision and accuracy of the method were assessed using SEB spiked in chicken meat homogenate samples. SEB was fortified at 0.2, 1 and 2 pmol/g. The accuracy results indicated that the method can provide accuracy within a 84.9-91.1% range. Overall, the results presented in this manuscript show that proteomics-based methods can be effectively used to detect, confirm and quantify SEB in food matrices., (Copyright © 2011 John Wiley & Sons, Ltd.)

The development of LC-MS/MS instruments and related applications improved the large-scale analyses of proteins and peptides in complex biological mixtures. The historical factor limiting these types of studies was the lack of sensitivity and reproducibility. However, the capacity of these analyses to detect proteins and peptides was significantly enhanced to a point where they are routinely performed in specialized laboratories in support to drug development programs as well as prognostic and diagnostic investigations. The analytical strategy used in peptidomic analyses needs to minimize the fluctuation in data measurements that might mask or reduce the precision of the determinations and consequently reduce the sensitivity of the assay. Inherently, it outlines the importance of careful standardization to reduce technical and instrumental variation. Therefore, this review will focus on the strengths and the limitations of the different experimental approaches used for the integration of internal standards in peptidomic studies. This review will examine a wide variety of methods, reagents, instrumentations and data analysis tools available to design peptidomic experiments. Moreover, this review will focus on the importance of precision and accuracy in order to adequately establish analysis threshold to detect peptide expression differences., (Copyright © 2012 John Wiley & Sons, Ltd.)

[6]-Gingerol is a structural analog of capsaicin, an agonist of the transient receptor potential channel vanilloid 1, which is known to have therapeutic properties for the treatment of pain and inflammation. A selective and sensitive quantitative method for the determination of [6]-gingerol by HPLC-ESI/MS/MS was developed. The method consisted of a protein precipitation extraction followed by analysis using liquid chromatography electrospray tandem mass spectrometry. The chromatographic separation was achieved using a Thermo 100 × 2.1 mm C(8) column combined with an isocratic mobile phase composed of acetonitrile, water and formic acid (80:20:0.1) at a flow rate of 250 μL/min. The mass spectrometer was operating in SRM mode and an analytical range set at 20-5000 ng/mL was used to construct a calibration curve in rat plasma. The interbatch precision (%CV) and accuracy (%NOM) observed were 2.9-10.8% and 98.1-102.1% in rat plasma. Similarly, precision and accuracy in rat liver microsomal suspension were also evaluated at nominal concentrations of 1, 25 and 100 μm; the precision (%CV) was <3.4% and the accuracy (%NOM) observed ranged from 89.7 to 109.4%. An in vitro metabolic stability study using rat liver microsomes was performed to determine intrinsic clearance of [6]-gingerol. The results show slow degradation with a T(1/2) of 163 min and relatively low intrinsic clearance suggesting that phase I metabolism may not be a major contributor of the drug clearance. Further analyses were performed to characterize in vitro and in vivo metabolites. Three main phase I metabolites and four phase II metabolites were identified by HPLC-MS/MS and HPLC-MSD TOF. However, the results suggest that glucuronidation of hydroxylated [6]-gingerol is the primary metabolite excreted in rat urine., (Copyright © 2011 John Wiley & Sons, Ltd.)

Capsazepine is an antagonist of the transient receptor potential channel vanilloid 1 (TRPV1), which is known to play an important role in the regulation of pain and inflammation. A selective and sensitive quantitative method for the determination of capsazepine by HPLC-ESI/MS/MS was developed. The method consisted of a protein precipitation extraction followed by analysis using liquid chromatography electrospray quadrupole ion trap mass spectrometry. The chromatographic separation was achieved using a 100 × 2 mm C(18) Waters Symmetry column combined with a gradient mobile phase composed of acetonitrile and 0.1% formic acid aqueous solution at a flow rate of 220 µL/min. The mass spectrometer was operating in full-scan MS/MS mode using two-segment analysis. An analytical range of 10-5000 ng/mL was used in the calibration curve constructed in rat plasma. The inter-batch precision and accuracy observed were 10.1, 6.4 and 6.1% and 100.8, 98.5 and 106.2% at 50, 500 and 5 000 ng/mL, respectively. An in vitro metabolic stability using rat, dog or mouse liver microsomes was performed to determine the intrinsic clearance of capsazepine. The results suggest a very rapid degradation with T(1/2) ranging from 2.6 to 4.3 min and a high clearance, suggesting that drug bioavailability is considerably reduced following extravascular administrations, consequently affecting drug response. Three metabolites were identified by HPLC-MS/MS. S-hydroxylation (M + 16), oxidative desulfuration (M - 16) and desulfuration (M - 32) metabolites of capsazepine were observed following exposure to rat, dog and mouse microsomes., (Copyright © 2010 John Wiley & Sons, Ltd.)

The main objective of this study was to determine the central effect of eugenol on neuropathic pain when injected intrathecally at the level of the lumbar spinal cord. In a preliminary study the penetrability of eugenol was evaluated in the CNS of rats. Blood, brain and spinal cord samples were collected at selected time points following eugenol administration and concentrations were determined by tandem liquid chromatography-mass spectrometry. Brain-to-plasma and spinal cord-to-plasma ratios (3.3 and 6.7, respectively) suggest that eugenol penetrates relatively well the CNS of rats, with a preferential distribution in the spinal cord. Following the induction of neuropathic pain in rats using the sciatic nerve ligation model, intrathecal injections of eugenol were done to evaluate the central effect of eugenol. Treatment with 50 μg of eugenol significantly decreased secondary mechanical allodynia after 15 min, 2 h and 4 h (p < 0.05; <0.005; <0.05, respectively) and improved thermal hyperalgesia after 2 h and 4 h (p < 0.001 and p < 0.05). The results support the hypothesis that eugenol may alleviate neuropathic pain, both allodynia and hyperalgesia, by acting centrally most probably at the level of the dorsal horn of the spinal cord where vanilloid receptors can be found., (Copyright © 2010 John Wiley & Sons, Ltd.)

Medetomidine is a potent and selective alpha2-adrenergic agonist. The activation of alpha2-adrenergic receptor mediates a variety of effects including sedation, analgesia, relief of anxiety, vasoconstriction and bradycardia. However, our main interest is the sedative effects of medetomidine when used as a premedicant prior surgery in companion animals, especially in dogs. Recently, data suggested that following intravenous infusion at six dosing regiments non-linear pharmacokinetics was observed. Major causes of non-linear pharmacokinetics are the elimination of the drug not following a simple first-order kinetics and/or the elimination half-life changing due to saturation of an enzyme system. The goal of this study was to establish the metabolic stability and determine the metabolic pathway of medetomidine in dog liver microsomes. Consequently, Michaelis-Menten parameters (V(max), K(m)), T(1/2) and CL(i) were determined. The incubations were performed in a microcentrifuge tube and containing various concentrations of medetomidine (10-5000 nM), 1 mg/mL of microsomal proteins suspended in 0.1 M phosphate buffer, pH 7.4. Microsomal suspensions were preincubated with NADPH (1 mM) for 5 min at 37 degrees C prior to fortification with medetomidine. Samples were taken at various time points for kinetic information and the initial velocity (v(i)) was determined after 10 min incubation. The reaction was stopped by the addition of an internal standard solution (100 ng/mL of dextrometorphan in acetone). Medetomidine concentrations were determined using a selective and sensitive HPLC-ESI/MS/MS method. Using non-linear regression, we determined a K(m) value of 577 nM, indicating relatively low threshold enzyme saturation consistent with previous in vivo observation. The metabolic stability was determined at a concentration of 100 nm (<

The analgesic effects of vanillin on neuropathic pain was evaluated using thermal sensitivity and mechanical allodynia using the sciatic nerve constriction model (n = 30 rats). To determine the pharmacokinetics of vanillin, rats (n = 6/administration route) received either 20 or 100 mg/kg of vanillin i.v. and p.o., respectively. For the pharmacodynamic study, baseline levels for hyperalgesia and allodynia were taken for 5 days prior to surgery. Following surgery each group (n = 6 rats/group) received either vanillin (50 mg/kg or 100 mg/kg), morphine (2 mg/kg or 6 mg/kg) or the vehicle only. Pharmacokinetic results following p.o. administrations are C(max) 290.24 ng/mL, T(max) 4 h, relative clearance 62.17 L/h/kg and T(1/2) 10.3 h. The bioavailability is 7.6%. Mechanical allodynia was decreased on treatment days 1, 2, 3, 5 (p < 0.003) and not on day 4 (p > 0.02) with 50 mg/kg vanillin, whereas at 100 mg/kg p.o. a decrease was noted only on days 7 and 8 (p < 0.003). No effect on hyperalgesia was seen following vanillin administration. In conclusion, vanillin is bioavailable and seems to have an alleviating effect on mechanical allodynia, and not on hyperalgesia, when evaluated with a chronic constriction nerve injury rat model of neuropathic pain., (Copyright (c) 2009 John Wiley & Sons, Ltd.)

Substance P and CGRP play a central role in neuropathic pain development and maintenance. Additionally, dynorphin A is an endogenous ligand of opioid receptors implicated in the modulation of neurotransmitters including neuropeptides, such as substance P and CGRP. This manuscript proposes a method to characterize, identify and quantify substance P, CGRP and dynorphin A in rat spinal cord by HPLC-ESI/MS/MS. Rat spinal cords were collected and homogenized into a TFA solution. Samples were chromatographed using a microbore C(8) 100 x 1 mm column and a 19 min linear gradient (0:100 --> 40:60; ACN:0.2% formic acid in water) at a flow rate of 75 microL/min for a total run time of 32 min. The peptides were identified in rat spinal cord based on full-scan MS/MS spectra. Substance P, CGRP and dynorphin A were predominantly identified by the presence of specific b CID fragments. Extracted ion chromatogram (XIC) suggested selected mass transitions of 674 --> [600 + 254], 952 --> [1215 + 963] and 717 --> [944 + 630] for substance P, CGRP and dynorphin A can be used for isolation and quantitative analysis. A linear regression (weighted 1/x) was used and coefficients of correlations (r) ranging from 0.990 to 0.999 were observed. The precision (%CV) and accuracy (%NOM) observed were 10.9-14.4% and 8.9-14.2%, 8.8-13.0% and 91.0-110.2% and 97.2-107.3% and 91.8-97.3% for substance P, CGRP and dynorphin A respectively. Following the analysis of rat spinal cords, the mean endogenous concentrations were 110.7, 2541 and 779.4 pmol/g for substance P, CGRP and dynorphin A respectively. The results obtained show that the method provides adequate figures of merit to support targeted peptidomic studies aimed to determine neuropeptide regulation in animal neuropathic and chronic pain models., (Copyright (c) 2009 John Wiley & Sons, Ltd.)

Capsaicin is the most abundant pungent molecule present in red peppers and it is widely used for food flavoring, in pepper spray in self-defense devices and more recently in ointments for the relief of neuropathic pain. Capsaicin is a selective agonist of transient receptor potential channel, vanilloid subfamily member 1. A selective and sensitive quantitative method for the determination of capsaicin by LC-ESI/MS/MS was developed. The method consisted of a protein precipitation extraction followed by analysis using liquid chromatography electrospray quadrupole ion trap mass spectrometry. The chromatographic separation was achieved using a 100 x 2 mm C(18) Waters Symmetry column combined with a gradient mobile phase composed of acetonitrile and 0.1% formic acid aqueous solution at a flow rate of 220 microL/min. The mass spectrometer was operating in full-scan MS/MS mode using two-segment analysis. An analytical range of 10-5000 ng/mL was used in the calibration curve constructed in rat plasma. The interbatch precision and accuracy observed were 6.5, 6.7, 5.3 and 101.2, 102.7, 103.5% at 50, 500 and 5000 ng/mL, respectively. An in vitro metabolic stability study was performed in rat, dog and mouse liver microsomes and the novel analytical method was adapted and used to determine intrinsic clearance of capsaicin. Results suggest very rapid degradation with T(1/2) ranging from 2.3 to 4.1 min and high clearance values suggesting that drug bioavailability will be considerably reduced, consequently affecting drug response and efficacy., (Copyright (c) 2008 John Wiley & Sons, Ltd.)

Glucosamine is an amino sugar involved in the biosynthesis of glycosylated proteins and lipids. Recently, with increased public interest in natural products medicine, glucosamine has been widely used to treat osteoarthritis, even though demonstrations of its actual efficacy remain relatively unknown. Information related to the pharmcokinetics of glucosamine is sparse. A recent analytical method published used 13C-glucosamine as an internal standard to analyse study samples. The method lacked accuracy owing to an important natural isotopic contribution of glucosamine to 13C-glucosamine ion abundance. This manuscript describes a simple method to quantify glucosamine in horse plasma. Glucosamine was extracted by protein precipitation with acetonotrile containing 0.1% formic acid. The chromatography was performed on a Agilent Hypersil-ODS 100x2.1 mm column with a mobile phase composed of acetonitrile and 0.5% formic acid in water (45:55) at a flow rate of 0.3 mL/min. A linear (1/x) relationship was used to perform the calibration over an analytical range of 10-1000 ng/mL. The inter-batch precision and accuracy ranged from 5.3 to 11.3% and from 87.8 to 107.2% in horse plasma, respectively. The mean endogenous level of glucosamine in horse plasma was 14.4 ng/mL (n=6). This LC-ESI/MS/MS method for the determination of glucosamine in horse plasma provided results within generally accepted criteria used for bioanalytical assay., (Copyright (c) 2007 John Wiley & Sons, Ltd.)

Vanillin is responsible for producing the familiar smell of vanilla. Vanillin has many similarities with other flavor phenolic compounds and could potentially show similar pharmacological activity. A previously published analytical method was adapted, developed and tested. Vanillin was extracted from rat plasma using protein precipitation with acetone. Prior to LC-ESI/MS/MS analysis, an aliquot of the supernatant was used to proceed to the derivatization of vanillin and the internal standard with dansyl chloride to enhance signal intensity in positive electrospray mode. The chromatography was performed on a 100 x 2.1 mm C8 column and an isocratic mobile phase composed of 75:25 acetonitrile:0.5% formic acid in water with a flow rate fixed at 500 microL/min. A linear (weighted 1/concentration) relationship was used to perform the calibration over an analytical range of 10-10,000 ng/mL. The intra-batch precision and accuracy at the limit of quantitation (10 ng/mL), medium (500 ng/mL) and high (10,000 ng/mL) concentrations were 10.7, 7.0 and 7.2% and 103.5, 108.0 and 100.1%, respectively. The observed recovery was greater than 87% and no significant ionization suppression or matrix effect was observed. This LC-ESI/MS/MS method for the determination of vanillin in rat plasma provided results within generally accepted criteria used for bioanalytical assay., (Copyright 2007 John Wiley & Sons, Ltd.)

Substance P is a neuropeptide that belongs to the tachykinin neuropeptide family. It is an 11-amino acid polypeptide with the amino acid sequence: Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met. It is synthesized as a larger protein and then enzymatically converted into the active undecapeptide. Substance P is widely distributed in the central and peripheral nervous systems. In the central nervous system, substance P participates in various behavioral responses and in regulating neuronal survival and degeneration. In the spinal cord, substance P participates in neurotransmission of pain and modulates autonomic reflexes. A rapid and selective method was developed for the determination of substance P concentration in rat spinal cord. The method consisted of a tissue homogenization, dilution, centrifugation and analysis by full-scan liquid chromatography electrospray quadrupole ion trap mass spectrometry (LC-ESI-QIT). The separation was achieved using a 50 x 2.1 mm C(18) analytical column combined with a gradient mobile phase composed of methanol: 0.1% formic acid in water set at a flow rate of 0.2 mL/min. An analytical range of 10-500 pmol/g was tested to analyze rat spinal cord. The LOD observed was 10 fmol injected on column. The novel method met all requirements of specificity, sensitivity, linearity, precision, accuracy and stability. In conclusion, a rapid and sensitive LC-ESI/MS/MS method was developed to identify and quantify substance P in rat spinal cord., (Copyright (c) 2006 John Wiley & Sons, Ltd.)

A rapid, selective and sensitive method was developed for the determination of eugenol concentration using an off-line dansyl chloride derivatization step to enhance signal intensity. The method consisted of a protein precipitation extraction followed by derivatization with dansyl chloride and analysis by full scan liquid chromatography electrospray quadrupole ion trap mass spectrometry (LC-ESI-QIT). The separation was achieved using a 100 x 2 mm C(8) analytical column combined with an isocratic mobile phase composed of 75:25 acetonitrile: 0.1% formic acid in water set at a flow rate of 0.25 mL/min. Signal intensity of the eugenol-dansyl chloride derivative was increased up to 100-fold as compared with the underivatized eugenol in positive electrospray mode. An analytical range of 100-20,000 ng/mL was used in the calibration curve of plasma and blood samples. The LOD observed was 0.5 pg injected on column. The novel method met all requirements of specificity, sensitivity, linearity, precision, accuracy and stability. In conclusion, a rapid and sensitive LC-ESI/MS/MS method using a derivatization agent was developed to enhance signal intensity of eugenol., (Copyright (c) 2006 John Wiley & Sons, Ltd.)

Mass spectrometry is a powerful qualitative and quantitative analytical technique that has been introduced in many bioanalytical and research laboratories in the last 10 years. The combination of HPLC with tandem MS yields a particularly powerful tool and it is now the method of choice for the analysis drugs, metabolites, biomarkers and proteins. However, HPLC-MS methods are not completely without problems that can compromise the quality of the results. An important phenomenon that can affect the quantitative performance of a mass detector is ion suppression. In this study, we measured the influence of the observed current (I) vs signal intensity and the variation of the observed current (I) when analyzing biological samples. Our experiment suggests that, despite the fact that it is possible for other chemicals to compete for protons in the droplets, the increase in the observed current (I) during the signal suppression is important and indicates that the conductivity of the liquid increases significantly. The salts and the charged species influence the conductivity and the surface tension of the droplets and modify the equilibrium between the two main forces involved during the electrospray process, resulting in an erratic spray behavior., (Copyright (c) 2005 John Wiley & Sons, Ltd.)

A rapid and selective method has been developed for the determination of theophylline in horse serum by LC-ESI/MS/MS. The analytical method includes a protein precipitation extraction for sample preparation, liquid chromatography separation technique and ionspray tandem mass spectrometry. The drug was extracted from serum using a protein precipitation with acetonitrile and the supernatants were analyzed using an LC-ESI/MS/MS instrument. The chromatography was performed using a 50 x 2.1 mm C(8) analytical column and an isocratic mobile phase composes of 60:40 acetonitrile-0.5% formic acid in water with a flow rate fixed at 350 microL/min. A linear (weighted 1/concentration) relationship was used to perform the calibration over an analytical range of 0.1-20 ppm. The intra-batch precision and accuracy at LLOQ, medium and high concentration were 11.7, 6.9 and 5.4% and 95.8, 107.8 and 95.8%, respectively, and the inter-batch precision and accuracy at LLOQ, medium and high concentration were 10.4, 7.9 and 7.3% and 97.3, 105.2 and 95.9%, respectively. This LC-ESI/MS/MS method for the determination of theophylline in horse serum has been proved to within generally accepted criteria used for bioanalytical assay and was used successfully during clinical investigation.

A rapid, selective and sensitive method has been developed for the determination of chlortetracycline in swine plasma by LC-ESI/MS/MS. The method consists of a protein precipitation extraction for sample preparation and liquid chromatography ionspray tandem mass spectrometry for analysis. The plasma samples were extracted with acetonitrile and the supernatants were analyzed using an LC-ESI/MS/MS instrument. Separation was achieved using a C(8) analytical column and an isocratic mobile phase composed of 70:30 acetonitrile:0.5% formic acid in water at a flow rate of 500 microL/min. A linear (weighted 1/concentration) relationship was used to perform the calibration over an analytical range 20--2000 ppb (ng/mL). The intra-batch precision and accuracy at LLOQ, medium and high concentrations were 9.0, 11.3 and 9.9% and 97.7, 100.3 and 98.4%, respectively, and the inter-batch precision and accuracy at LLOQ, medium and high concentrations were 9.1, 8.4 and 7.4% and 95.1, 102.1 and 97.1%, respectively. This LC-ESI/MS/MS method for the determination of chlortetracycline in swine plasma has been proven to be within generally accepted criteria used for bioanalytical assay., (Copyright (c) 2005 John Wiley & Sons, Ltd.)

A fast and sensitive method has been developed and validated for the determination of bucillamine in human blood by derivatizing the free sulfhydryl groups with isobutyl acrylate (IA), by APCI-LC/MS/MS. The collected blood sample was immediately mixed with a mixture of IA and 0.05 m Tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl) buffer, pH 9.2, to stabilize the sulfyhydryl moieties. The derivatized samples were then extracted by protein precipitation, evaporated, reconstituted and injected using an LC-APCI/MS/MS instrument. Separation was achieved using a C18 analytical column and a gradient mobile phase within a chromatographic run time of 5 min. A quadratic (weighted 1/concentration(2)) relationship was observed during validation over a concentration range of 0.4-40 microg/mL with a correlation value of r > or = 0.9966. The inter-batch precision and accuracy at low, medium and high concentrations were 8.1, 8.4 and 7.3%; 113.3, 104.9 and 103.9%, respectively, and the intra-batch precision and accuracy at low, medium and high concentrations were 7.7, 5.4 and 2.7%; 105.1, 111.9 and 113.2%, respectively., (Copyright 2004 John Wiley & Sons, Ltd.)

Reversible attachment to serum proteins plays a significant role in pharmacokinetics and pharmacodynamics, and a clear understanding of this process is fundamental in the development of the rational use of many therapeutics agents. Over the last few years, it has been demonstrated that immobilized human serum albumin (HSA) could be used to estimate plasma protein binding. A series of 40 structurally unrelated pharmaceutical compounds were chromatographed on an immobilized HSA column in order to construct a protein binding 'calibration curve' and multiple linear regression system. When studying the relationship between the chromatographic retention and the percentage of binding determined in vitro, a good correlation can be observed (r(2) = 0.799) using a wide variety of compounds with different binding affinities (from 0 to 99% binding). Using a quantitative structure-retention relationships (QSRR) approach to analysing chromatographic data, the correlation was improved compared to the traditional approach (r(2) = 0.824)., (Copyright 1999 John Wiley & Sons, Ltd.)

Metabolite profiling is one of the most challenging fields in applied mass spectrometry. Mass spectrometry was used to characterize the metabolites of propranolol, a beta-adrenergic receptor antagonist containing numerous oxidation sites. Propranolol is extensively metabolized, with most metabolites appearing in urine. Urine samples were collected from young adult male Sprague-Dawley rats. Structural identification of various metabolites was performed by LC/MS/MS, using a PE SCIEX triple quadrupole instrument (PE SCIEX API 3000). Metabolites were itemized using several LC/MS/MS techniques, including Q3 full scan and precursor and constant neutral loss experiments. A looped experiment technique revealed the presence of mono- and di-hydroxylated metabolites as well as regio isomers of hydroxy- and dihydroxy-propranolol glucuronides and propranolol glucuronic acid. Propranolol glucuronide was not observed, while the presence of dealkylated metabolites was suggested but not confirmed., (Copyright 1999 John Wiley & Sons, Ltd.)