Metabolite profiling study of propranolol in rat using LC/MS/MS analysis

Systematic, Modifying Group-Assisted Strategy Expanding Coverage of Metabolite Annotation in Liquid Chromatography-Mass Spectrometry-Based Nontargeted Metabolomics Studies

From microbes to human beings, nontargeted metabolic profiling by liquid chromatography (LC)-mass spectrometry (MS) has been commonly used to investigate metabolic alterations. Still, a major challenge is the annotation of metabolites from thousands of detected features. The aim of our research was to go beyond coverage of metabolite annotation in common nontargeted metabolomics studies by an integrated multistep strategy applying data-dependent acquisition (DDA)-based ultrahigh-performance liquid chromatography (UHPLC)-high-resolution mass spectrometry (HRMS) analysis followed by comprehensive neutral loss matches for characteristic metabolite modifications and database searches in a successive manner. Using pooled human urine as a model sample for method establishment, we found 22% of the detected compounds having modifying structures. Major types of metabolite modifications in urine were glucuronidation (33%), sulfation (20%), and acetylation (6%). Among the 383 annotated metabolites, 100 were confirmed by standard compounds and 50 modified metabolites not present in common databases such as human metabolite database (HMDB) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were structurally elucidated. Practicability was tested by the investigation of urines from pregnant women diagnosed with gestational diabetes mellitus vs healthy controls. Overall, 83 differential metabolites were annotated and 67% of them were modified metabolites including five previously unreported compounds. To conclude, the systematic modifying group-assisted strategy can be taken as a useful tool to extend the number of annotated metabolites in biological and biomedical nontargeted studies.

Assessment of Tissue Distribution and Metabolism of MP1, a Novel Pyrrolomycin, in Mice Using a Validated LC-MS/MS Method

MP1 is a novel marinopyrrole analogue with activity in MYCN amplified neuroblastoma cell lines. A rapid, selective, and sensitive liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method was developed and validated for quantitation of MP1 in mouse plasma. Analyte separation was achieved using a Waters Acquity UPLC^®BEH C18 column (1.7 µm, 100 × 2.1 mm). Mobile phase consisted of 0.1% acetic acid in water (10%) and methanol (90%) at a total flow rate of 0.25 mL/min. The mass spectrometer was operated at unit resolution in the multiple reaction monitoring (MRM) mode, using precursor ion > product ion transitions of 324.10 > 168.30 m/z for MP1 and 411.95 > 224.15 m/z for PL-3. The MS/MS response was linear over the concentration range from 0.2-500 ng/mL for MP1, correlation coefficient (r²) of 0.988. Precision (% RSD) and accuracy (% bias) were within the acceptable limits as per FDA guidelines. MP1 was stable under storage and laboratory handling conditions. The validated method was successfully applied to assess the solubility, in-vitro metabolism, plasma protein binding, and bio-distribution studies of MP1.

A rapid and sensitive bioanalytical LC-MS/MS method for the quantitation of a novel CDK5 inhibitor 20-223 (CP668863) in plasma: Application to in vitro metabolism and plasma protein-binding studies

A rapid, selective, and sensitive liquid chromatography coupled with tandem mass spectrometry (MS/MS) method was developed and validated for the quantitation of the novel CDK5 inhibitor '20-223' in mouse plasma. Separation of analytes was achieved by a reverse-phase ACE Excel C18 column (1.7 μm, 100 × 2.1 mm) with gradient elution using 0.1% formic acid (FA) in methanol and 0.1% FA as the mobile phase. Analytes were monitored by MS/MS with an electrospray ionization source in the positive multiple reaction monitoring mode. The MS/MS response was linear over the concentration range 0.2-500 ng/mL for 20-223. The within- and between-batch precision were within the acceptable limits as per Food and Drug Administration guidelines. The validated method was successfully applied to plasma protein binding and in vitro metabolism studies. Compound 20-223 was highly bound to mouse plasma proteins (>98% bound). Utilizing mouse S9 fractions, in vitro intrinsic clearance (CLint ) was 24.68 ± 0.99 μL/min/mg protein. A total of 12 phase I and II metabolites were identified with hydroxylation found to be the major metabolic pathway. The validate method required a low sample volume, was linear from 0.2 to 500 ng/mL, and had acceptable accuracy and precision.

Biological fate and effects of propranolol in an experimental aquatic food chain

The aim of this study was to evaluate the trophic transfer of the β-blocker propranolol (PRP) in an experimental aquatic food chain involving the green algae Scenedesmus obliquus, the water flea Daphnia magna and the crucian carp Carassius auratus, as well as the metabolism and effects of PRP in the liver of crucian carp. After a 48 h PRP aqueous exposure for algae, with a subsequent 48 h dietary exposure for daphnia and an 8d dietary exposure for crucian carp, PRP was observed in each trophic level, despite significant bioaccumulation did not occur in daphnia and crucian carp. A portion of the absorbed PRP was metabolized by the crucian carp to N-desisopropylated propranolol, propranolol glucuronic acid, monohydroxylated propranolol, hydroxypropranolol glucuronide and dihydroxypropranolol glucuronide, which were similar to those in mammals. In addition, multiple biomarkers in the liver of crucian carp (7-ethoxyresorufin O-deethylase, EROD; 7-benzyloxyresorufin O-dealkylation, BROD; superoxide dismutase, SOD and malondialdehyde, MDA) were measured. BROD and MDA were not significantly affected by PRP, while EROD and SOD did change significantly during the 8d dietary exposure. This work indicated that the trophic transfer of PRP, resulting in biochemical perturbations of fish biological systems, should be a concern for the assessment of the environmental risks to aquatic food chains.

The development of the LC-MS/MS method based on S-9 biotransformation for detection of metabolites of selected β-adrenolytics in surface water

Pharmaceuticals consumption in Poland is high. One of the most frequently prescribed is cardiovascular drugs. Due to their relatively high hydrophilic properties, they are not completely eliminated during wastewater treatment processes. In contrast to parent compounds, the presence of cardiovascular metabolites is rarely investigated in surface waters. The goal of this paper was to develop the methodology for detection of metabolites of selected beta-blockers: metoprolol, bisoprolol and propranolol. These metabolites were obtained by the incubation of parent compounds with S9 rat's liver fraction and used for the development and optimization of the low resolution LC-MS/MS method. Accurate mass spectrometry measurements were applied for validation of this method. The incubation of the parent compound with S9 fraction resulted only in propranolol's metabolites generation. However, on the basis of hydroxypropranolol, theoretically transitions for mono- and dihydroxy-metoprolol and bisoprolol derivatives were generated for MRM mode and applied for surface water analysis. The analysis revealed the presence of some of the target metabolites in the Vistula river. This work is the first one proposing the application of biotrasformation in the methodology of low resolution LC-MS-MS analysis of metabolites of cardiovascular drugs in surface water.

A systems biology approach toward understanding seed composition in soybean

BACKGROUND

The molecular, biochemical, and genetic mechanisms that regulate the complex metabolic network of soybean seed development determine the ultimate balance of protein, lipid, and carbohydrate stored in the mature seed. Many of the genes and metabolites that participate in seed metabolism are unknown or poorly defined; even more remains to be understood about the regulation of their metabolic networks. A global omics analysis can provide insights into the regulation of seed metabolism, even without a priori assumptions about the structure of these networks.

RESULTS

With the future goal of predictive biology in mind, we have combined metabolomics, transcriptomics, and metabolic flux technologies to reveal the global developmental and metabolic networks that determine the structure and composition of the mature soybean seed. We have coupled this global approach with interactive bioinformatics and statistical analyses to gain insights into the biochemical programs that determine soybean seed composition. For this purpose, we used Plant/Eukaryotic and Microbial Metabolomics Systems Resource (PMR, http://www.metnetdb.org/pmr, a platform that incorporates metabolomics data to develop hypotheses concerning the organization and regulation of metabolic networks, and MetNet systems biology tools http://www.metnetdb.org for plant omics data, a framework to enable interactive visualization of metabolic and regulatory networks.

CONCLUSIONS

This combination of high-throughput experimental data and bioinformatics analyses has revealed sets of specific genes, genetic perturbations and mechanisms, and metabolic changes that are associated with the developmental variation in soybean seed composition. Researchers can explore these metabolomics and transcriptomics data interactively at PMR.

Grapefruit juice markedly increases the plasma concentrations and antiplatelet effects of ticagrelor in healthy subjects

AIM

This study examined the effects of grapefruit juice on the new P2Y12 inhibitor ticagrelor, which is a substrate of CYP3A4 and P-glycoprotein.

METHODS

In a randomized crossover study, 10 healthy volunteers ingested 200 ml of grapefruit juice or water thrice daily for 4 days. On day 3, they ingested a single 90 mg dose of ticagrelor.

RESULTS

Grapefruit juice increased ticagrelor geometric mean peak plasma concentration (Cmax ) to 165% (95% confidence interval 147, 184%) and area under the concentration-time curve (AUC(0,∞)) to 221% of control (95% confidence interval 200, 245%). The Cmax and AUC(0,34 h) (P < 0.05) but not the AUC(0,∞) of the active metabolite C12490XX were decreased significantly. Grapefruit juice had a minor effect on ticagrelor elimination half-life prolonging it from 6.7 to 7.2 h (P = 0.036). In good correlation with the elevated plasma ticagrelor concentrations, grapefruit juice enhanced the antiplatelet effect of ticagrelor, assessed with VerifyNow® and Multiplate® methods, and postponed the recovery of platelet reactivity.

CONCLUSIONS

Grapefruit juice increased ticagrelor exposure by more than two-fold, leading to an enhanced and prolonged ticagrelor antiplatelet effect. The grapefruit juice-ticagrelor interaction seems clinically important and indicates the significance of intestinal metabolism to ticagrelor pharmacokinetics.

Microbial production of phase I and phase II metabolites of propranolol

1. The production in multimilligram amounts of 4- and 5-hydroxylated metabolites of (R)- or (S)-propranolol by biotransformation with two fungal strains, an Absidia sp. M50002 and a Cunninghamella sp. M50036, was carried out, starting from either the racemic drug or pure enantiomers. 2. While both enantiomers of propranolol were hydroxylated in the 5-position by incubation with strain M50002, the strain M50036 operated a chiral discrimination, resulting in the exclusive formation of the 4-hydroxy-(R)-enantiomer. 3. In addition, a Streptomyces sp. strain M52104, isolated from a soil sample, was selected for the high-yield regioselective β-glucuronidation of propranolol and its 4- and 5-hydroxylated derivatives. 4. NMR and mass spectroscopic data have been extensively used for the unambiguous characterization of 4- and 5-hydroxylated and glucuronidated derivatives, all of them corresponding to the major animal and human metabolites of propranolol, a typical substrate of CYP2D6.

Metabolic stability and determination of cytochrome P450 isoenzymes' contribution to the metabolism of medetomidine in dog liver microsomes

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 (<<K(m)) and the observed T(1/2) was 90 min with a CL(i) of 0.008 mL/min indicating moderately low clearance in dog liver microsomes, also consistent with previous in vivo data. Moreover, results suggest that principally medetomidine is metabolized by the CYP3A with a small contribution from CYP2D and CYP2E. The participation of CYP3A is an important discovery since medetomidine is used as a premedicant in combination with fentanyl, ketamine and/or midazolam. These findings combined with a low K(m) value may indicate that medetomidine can competitively inhibit the metabolism of these drugs and consequently significantly impair metabolic clearance.

Combining genomics, metabolome analysis, and biochemical modelling to understand metabolic networks

Now that complete genome sequences are available for a variety of organisms, the elucidation of gene functions involved in metabolism necessarily includes a better understanding of cellular responses upon mutations on all levels of gene products, mRNA, proteins, and metabolites. Such progress is essential since the observable properties of organisms – the phenotypes – are produced by the genotype in juxtaposition with the environment. Whereas much has been done to make mRNA and protein profiling possible, considerably less effort has been put into profiling the end products of gene expression, metabolites. To date, analytical approaches have been aimed primarily at the accurate quantification of a number of pre-defined target metabolites, or at producing fingerprints of metabolic changes without individually determining metabolite identities. Neither of these approaches allows the formation of an in-depth understanding of the biochemical behaviour within metabolic networks. Yet, by carefully choosing protocols for sample preparation and analytical techniques, a number of chemically different classes of compounds can be quantified simultaneously to enable such understanding. In this review, the terms describing various metabolite-oriented approaches are given, and the differences among these approaches are outlined. Metabolite target analysis, metabolite profiling, metabolomics, and metabolic fingerprinting are considered. For each approach, a number of examples are given, and potential applications are discussed.

In vitro formation of phase I and II metabolites of propranolol and determination of their structures using chemical derivatization and liquid chromatography-tandem mass spectrometry

Derivatization with 1,2-dimethylimidazole-4-sulfonyl chloride (DMISC) has been successfully used as a tool to differentiate between aromatic and aliphatic O-glucuronides of hydroxypropranolol. The analyses were performed with liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) with both a triple quadrupole and an ion trap instrument. Hydroxylated forms of propranolol can be glucuronidated in aliphatic as well as aromatic positions. These isoforms are not distinguishable by tandem MS alone, as they both initially lose 176 Da, i.e. monodehydrated glucuronic acid, giving back the aglycone. Two in vitro systems were set up for the production of propranolol metabolites. The obtained isomers of 4'-hydroxypropranolol glucuronide were determined to correspond to one aliphatic and one aromatic form, using chemical derivatization with DMISC and LC-MS(n). DMISC was shown to react with the secondary amine in the case where the naphtol was occupied by the glucuronyl moiety, resulting in a different fragmentation pattern compared with that of the aliphatic glucuronide, where the naphtol group was accessible to derivatization.

Comparison of sub-2-μm particle columns for fast metabolite ID

The use of sub-2-microm particle columns for fast high throughput metabolite ID applications was investigated. Three LC-MS methods based on different sub-2-microm particle size columns using the same analytical 3 min gradient were developed (Methods A, B, and C). Method A was comprised of a 1.8 microm particle column coupled to an MS, methods B and C utilized a 1.7 microm particle column (BEH 50 x 2.1 mm2 id) and 1.8 microm particle column coupled to a Q-TOF MS. The precision and the separation efficiency of the methods was compared with repeated standard injections (N=10) of reference compounds verapamil (VP), propranolol, and fluoxetine. Separation efficiency and MS/MS spectral quality were also evaluated for separation and detection of VP and its two major metabolites norverapamil (NVP) and O-demethylverapamil (ODMVP) in human-liver microsomal incubates. Results show that 1.8 microm particle columns show similar performance for separation of VP and its major metabolites and comparable spectral quality in MS(E) mode of the Q-TOF instrument compared to 1.7 microm particle columns. Additionally, the study also confirmed that sub-2-microm particle size columns can be operated with standard analytical HPLC but that performance is maximized by integrating column in UPLC method with reduced void volumes. All the methods are suitable for the determination of major metabolites for compounds with high metabolic turnover. The high throughput metabolite profile analysis using 384-well plate format of up to 48 compounds in incubates of human-liver microsomes was discussed.

Wild-type CYP102A1 as a biocatalyst: turnover of drugs usually metabolised by human liver enzymes

This work provides functional data showing that the bacterial CYP102A1 recognises compounds metabolised by human CYP3A4, CYP2E1 and CYP1A2 and is able to catalyse different reactions. Wild-type cytochrome CYP102A1 from Bacillus megaterium is a catalytically self-sufficient enzyme, containing an NADPH-dependent reductase and a P450 haem domain fused in a single polypeptidie chain. An NADPH-dependent method (Tsotsou et al. in Biosens. Bioelectron. 17:119-131, 2002) together with spectroscopic assays were applied to investigate the catalytic activity of CYP102A1 towards 19 xenobiotics, including 17 commercial drugs. These molecules were chosen to represent typical substrates of the five main families of drug-metabolising human cytochromes P450. Liquid chromatography-mass spectrometry analysis showed that CYP102A1 catalyses the hydroxylation of chlorzoxazone, aniline and p-nitrophenol, as well as the N-dealkylation of propranolol and the dehydrogenation of nifedipine. These drugs are typical substrates of human CYP2E1 and CYP3A4. The KM values calculated for these compounds were in the millimolar range: 1.21+/-0.07 mM for chlorzoxazone, 2.52 +/- 0.08 mM for aniline, 0.81+/-0.04 mM for propranolol. The values of vmax for chlorzoxazone and propranolol were 46.0+/-9.0 and 7.6+/-3.4 nmol min-1 nmol-1, respectively. These values are higher then those measured for the human enzymes. The vmax value for aniline was 9.4+/-1.3 nmol min-1 nmol-1, comparable to that calculated for human cytochromes P450. The functional data were found to be in line with the sequence alignments, showing that the identity percentage of CYP102A1 with CYP3A4 and CYP2E1 is higher than that found for CYP1A2, CYP2C9 and CYP2D6 families.

High-performance liquid chromatography separations coupled with coulometric electrode array detectors: a unique approach to metabolomics

Metabolomics is the systematic and theoretically comprehensive study of the small molecules that comprise a biological sample, e.g., sera or plasma. The primary analytical tools used in metabolomics are nuclear magnetic resonance and mass spectroscopy. We here address a different tool, high-performance liquid chromatography (HPLC) separations coupled with coulometric electrode array detection. This system has unique advantages, notably sensitivity and high quantitative precision, but also has unique limitations, such as obtaining little structural information on the metabolites of interest and limited scale-up capacity. The system also only detects redox-active compounds, which can be either a benefit or a detriment, depending on the experimental goals and design. Here, we discuss the characteristics of this HPLC/coulometric electrode array system in the context of metabolomics, and then present the method as practiced in our groups.

Use of liquid chromatography-electrospray ionization tandem mass spectrometry to identify diarylheptanoids in turmeric (Curcuma longa L.) rhizome

LC-ESI-MS/MS coupled to DAD analysis was used as an on-line tool for identification of diarylheptanoids in fresh turmeric rhizome extracts. Based on their mass spectra, from both negative and positive mode LC-ESI-MS/MS analysis, and supported by their DAD spectra, 19 diarylheptanoids were identified. Among these 19 compounds, curcumin, demethoxycurcumin, and bisdemethoxycurcumin were identified by comparing their chromatographic and spectral data with those of authentic standard compounds. The other diarylheptanoid compounds were identified or tentatively identified based on comparison to the three curcuminoids and each other. Twelve of the identified diarylheptanoids have not been previously reported from turmeric and six of these are new compounds.

Screening for unknown synthetic steroids in human urine by liquid chromatography-tandem mass spectrometry

Chemically modified steroids (designer steroids), including tetrahydrogestrinone and norbolethone, pose a threat to the integrity of the sport community. These compounds have recently been detected in urine specimens from athletes, resulting in temporary or permanent suspension from amateur and/or professional competition. Triple quadrupole mass spectrometers enable doping control laboratories to screen for unknown, anabolic, androgenic steroids utilizing precursor ion scans. On the basis of common dissociation patterns of steroids with common structural features, characteristic product ions were selected to serve as diagnostic markers for previously unidentified drugs or drug metabolites in human urine samples. An assay was established to complement standard screening procedures. Urine specimens were enzymically hydrolyzed, partitioned into ether, concentrated, and analyzed by precursor ion scanning. Spectra from samples fortified with eight standard compounds (methyltestosterone, ethyltestosterone, 1-testosterone, gestrinone, dihydrogestrinone, tetrahydrogestrinone, norbolethone, and propyltrenbolone) and one deuterium-labeled analog (d(4)-tetrahydrogestrinone) at 50 ng/ml of urine, had precursor ion peaks other than those from common endogenous steroids. Subsequent product ion scan experiments on precursor ions of peaks of unknown origin provided structural identification of the unknown compounds.

The characterisation of selected drugs with amine-containing side chains using electrospray ionisation and ion trap mass spectrometry and their determination by HPLC–ESI-MS

The electrospray ionisation-ion-trap mass spectrometry (ESI-MS(n)) of selected drug compounds with amine-containing side chains has been investigated. Certain characteristic in-source fragmentations have been observed for these molecules. Sequential product ion fragmentation experiments (MS(n)) have been performed in order to elucidate the degradation pathways for the [M + H](+) ions and their predominant fragment ions. These MS(n) experiments also show certain characteristic fragmentations with respect to the amine-containing side chains. QTOF-MS/MS has been used to support the identity of the proposed fragments. The data presented in this paper therefore provides useful information on the structure of these compounds with amine-containing side chains and can be used in the characterisation of such drugs, their structurally related metabolites and unknown molecules of pharmaceutical significance extracted from animal and plant sources, for example. Amphetamine, clenbuterol, flurazepam and methadone can be identified and determined in mixtures at low ng/ml concentrations by the application of HPLC-ESI-MS which can also be used for their analysis in saliva samples.

Functional genomics: high-throughput mRNA, protein, and metabolite analyses

A tremendous amount of DNA sequence information is now available to scientists and engineers. These DNA sequences provide the foundation for studying how the genome of an organism is functioning and they are particularly useful for metabolic engineers interested in manipulating plants for the production of chemicals and enzymes. Functional genomics relies on high-throughput techniques for measuring the mRNA (the transcriptome), protein (the proteome), and metabolite (the metabolome) components of plants as well as their organs and tissues. Microarray technologies, recent advances in protein mass spectrometry, and high-throughput metabolite analyses are beginning to provide detailed information on the total mRNA, protein, and metabolite components of plants. This knowledge will allow scientists to monitor changes in proteins and metabolites in plants. Ultimately, it may allow them to discover new metabolic pathways and to model metabolic and regulatory networks in plants.

Metabolomics--the link between genotypes and phenotypes

Metabolites are the end products of cellular regulatory processes, and their levels can be regarded as the ultimate response of biological systems to genetic or environmental changes. In parallel to the terms 'transcriptome' and proteome', the set of metabolites synthesized by a biological system constitute its 'metabolome'. Yet, unlike other functional genomics approaches, the unbiased simultaneous identification and quantification of plant metabolomes has been largely neglected. Until recently, most analyses were restricted to profiling selected classes of compounds, or to fingerprinting metabolic changes without sufficient analytical resolution to determine metabolite levels and identities individually. As a prerequisite for metabolomic analysis, careful consideration of the methods employed for tissue extraction, sample preparation, data acquisition, and data mining must be taken. In this review, the differences among metabolite target analysis, metabolite profiling, and metabolic fingerprinting are clarified, and terms are defined. Current approaches are examined, and potential applications are summarized with a special emphasis on data mining and mathematical modelling of metabolism.

High speed determination of beta-receptor blocking agents in human urine by liquid chromatography/tandem mass spectrometry

Beta-receptor blocking agents are present on the international market in a huge variety. The International Olympic Committee prohibits the use of these drugs in several sport sections and doping control laboratories analyse urine samples of high-performance athletes with different techniques. Therefore, fast and reliable methods are required to enable a sensitive detection of many drugs and a high throughput of samples. In the present study a screening procedure is described using high speed liquid chromatography and multiple reaction monitoring to identify 32 beta-receptor blocking agents extracted from human urine. Urine specimens (blank urine samples, spiked urine samples and specimens of excretion studies) were hydrolysed, extracted and analysed within 7 min. Quasi-molecular ions (M(+) + H) of the beta-blockers are generated by means of an atmospheric pressure chemical ionization interface followed by collision-induced dissociation in a triple quadrupole mass spectrometer and subsequent detection of daughter ions. Proposals for the origin of common and individual secondary ions are presented.

Determination of an arylether antiarrhythmic and its N-dealkyl metabolite in rat plasma and hepatic microsomal incubates using liquid chromatography-tandem mass spectrometry

A method was developed and validated for the quantification of (+/-)-trans-[2-morpholino-1-(1-naphthalene-ethyloxy]cyclohexane monohydrochloride (RSD1070) and its N-dealkyl metabolite in rat plasma and hepatic microsomal incubates. Chromatographic separations were achieved using reversed-phase high-performance liquid chromatography coupled with positive ion electrospray ionization and detection by tandem mass spectrometry. The assay was linear from 2.5 to 100 ng/ml and this range was used for validation. Inter- and intra-assay variability (n=6), extraction recovery, and stability in plasma were assessed. The estimated limit of quantitation was in the range 2.5-3 ng/ml for both analytes in rat plasma. The analytical method was used in a pharmacokinetic study of RSD1070 in rats after a single i.v. bolus of 12 mg/kg.

Mass spectrometry innovations in drug discovery and development

This review highlights the many roles mass spectrometry plays in the discovery and development of new therapeutics by both the pharmaceutical and the biotechnology industries. Innovations in mass spectrometer source design, improvements to mass accuracy, and implementation of computer-controlled automation have accelerated the purification and characterization of compounds derived from combinatorial libraries, as well as the throughput of pharmacokinetics studies. The use of accelerator mass spectrometry, chemical reaction interface-mass spectrometry and continuous flow-isotope ratio mass spectrometry are promising alternatives for conducting mass balance studies in man. To meet the technical challenges of proteomics, discovery groups in biotechnology companies have led the way to development of instruments with greater sensitivity and mass accuracy (e.g., MALDI-TOF, ESI-Q-TOF, Ion Trap), the miniaturization of separation techniques and ion sources (e.g., capillary HPLC and nanospray), and the utilization of bioinformatics. Affinity-based methods coupled to mass spectrometry are allowing rapid and selective identification of both synthetic and biological molecules. With decreasing instrument cost and size and increasing reliability, mass spectrometers are penetrating both the manufacturing and the quality control arenas. The next generation of technologies to simplify the investigation of the complex fate of novel pharmaceutical entities in vitro and in vivo will be chip-based approaches coupled with mass spectrometry.

Liquid chromatography-mass spectrometry in the study of the metabolism of drugs and other xenobiotics

The application of liquid chromatography-mass spectrometry (LC/MS) to the study of metabolism of drugs and other xenobiotics is reviewed. Original research papers covering the period from 1998 to early 2000 and concerning the use of LC/MS in the study of xenobiotic metabolism in humans and other mammalian species are reviewed. LC/MS interfaces, sample preparation steps, column types, mobile phases and additives, and the type of metabolites detected are summarized and discussed in an attempt to identify the current and future trends in the use of LC/MS for metabolism studies. Applications are listed according to the parent xenobiotic type and include substances used in therapeutics, drug candidates, compounds being evaluated in clinical trials, environmental pollutants, adulterants and naturally occurring substances.