High Performance Thin-Layer Chromatography of Plant Ecdysteroids Coupled with Desorption Electrospray Ionisation–Ion Mobility–Time of Flight High Resolution Mass Spectrometry (HPTLC/DESI/IM/ToFMS)

The use of high performance thin-layer chromatography (HPTLC) in combination with high resolution time of flight mass spectrometry (MS) for the detection, identification and imaging (HPTLC/MSI) of ecdysteroids (insect moulting hormones) present in a number of plant extracts obtained from members of the Silene family is demonstrated. DESI is shown to be a convenient method for the recovery of these polar polyhydroxylated steroids from the silica gel of the HPTLC plate for subsequent MS detection and imaging. The incorporation of an ion mobility separation (IMS) to the system to give HPTLC/IMS/MS provided additional drift time data which enabled more confident identification. Using HPTLC/DESI/IMS/MS, a range of ecdysteroids were detected and characterized in extracts of S. otitis, S nutans, S. maritime, S. viridiflora and S. fimbriata.

The pharmacokinetics and metabolism of diclofenac in chimeric humanized and murinized FRG mice

The pharmacokinetics of diclofenac were investigated following single oral doses of 10 mg/kg to chimeric liver humanized and murinized FRG and C57BL/6 mice. In addition, the metabolism and excretion were investigated in chimeric liver humanized and murinized FRG mice. Diclofenac reached maximum blood concentrations of 2.43 ± 0.9 µg/mL (n = 3) at 0.25 h post-dose with an AUC_inf of 3.67 µg h/mL and an effective half-life of 0.86 h (n = 2). In the murinized animals, maximum blood concentrations were determined as 3.86 ± 2.31 µg/mL at 0.25 h post-dose with an AUC_inf of 4.94 ± 2.93 µg h/mL and a half-life of 0.52 ± 0.03 h (n = 3). In C57BL/6J mice, mean peak blood concentrations of 2.31 ± 0.53 µg/mL were seen 0.25 h post-dose with a mean AUC_inf of 2.10 ± 0.49 µg h/mL and a half-life of 0.51 ± 0.49 h (n = 3). Analysis of blood indicated only trace quantities of drug-related material in chimeric humanized and murinized FRG mice. Metabolic profiling of urine, bile and faecal extracts revealed a complex pattern of metabolites for both humanized and murinized animals with, in addition to unchanged parent drug, a variety of hydroxylated and conjugated metabolites detected. The profiles in humanized mice were different to those of both murinized and wild-type animals, e.g., a higher proportion of the dose was detected in the form of acyl glucuronide metabolites and much reduced amounts as taurine conjugates. Comparison of the metabolic profiles obtained from the present study with previously published data from C57BL/6J mice and humans revealed a greater, though not complete, match between chimeric humanized mice and humans, such that the liver humanized FRG model may represent a model for assessing the biotransformation of such compounds in humans.

Stability in metabolic phenotypes and inferred metagenome profiles before the onset of colitis-induced inflammation

Inflammatory bowel disease (IBD) is associated with altered microbiota composition and metabolism, but it is unclear whether these changes precede inflammation or are the result of it since current studies have mainly focused on changes after the onset of disease. We previously showed differences in mucus gut microbiota composition preceded colitis-induced inflammation and stool microbial differences only became apparent at colitis onset. In the present study, we aimed to investigate whether microbial dysbiosis was associated with differences in both predicted microbial gene content and endogenous metabolite profiles. We examined the functional potential of mucus and stool microbial communities in the mdr1a ^-/- mouse model of colitis and littermate controls using PICRUSt on 16S rRNA sequencing data. Our findings indicate that despite changes in microbial composition, microbial functional pathways were stable before and during the development of mucosal inflammation. LC-MS-based metabolic phenotyping (metabotyping) in urine samples confirmed that metabolite profiles in mdr1a ^-/- mice were remarkably unaffected by development of intestinal inflammation and there were no differences in previously published metabolic markers of IBD. Metabolic profiles did, however, discriminate the colitis-prone mdr1a ^-/- genotype from controls. Our results indicate resilience of the metabolic network irrespective of inflammation. Importantly as metabolites differentiated genotype, genotype-differentiating metabolites could potentially predict IBD risk.

Hyphenated MS-based targeted approaches in metabolomics

Review of targeted metabolomics, with a focus on the description of analytical methods.

1H-NMR Spectroscopy as a Means of Monitoring Nephrotoxicity as Exemplified by Studies with Cephaloridine

1 Male albino rats were dosed intravenously with either 0.9% saline or cephaloridine in saline at doses of 650, 750 or 950 mg kg-1 d-1 for 7 d.

2 Urine analysis on day 3, after two doses of cephaloridine showed dose-related increases in glucose, total protein, N-acetyl β-D-glucosaminidase, y-glutamyltranspeptidase, alkaline phosphatase and lactate dehydrogenase. 1H-NMR spectroscopy showed corresponding disturbed profiles of products of intermediary metabolism indicative of a disruption of renal function.

3 By day 6, after five doses of cephaloridine, analysis by both 1H-NMR and conventional methods showed that all indices had returned to normal. 1H-NMR was demonstrated to provide useful complementary information to conventional techniques on the time course of the onset of the nephrotoxicity and the recovery phase, and was at least as sensitive as conventional urine analysis.

Nitric oxide and ABA in the control of plant function

Abscisic acid (ABA) and nitric oxide (NO) are both extremely important signalling molecules employed by plants to control many aspects of physiology. ABA has been extensively studied in the mechanisms which control stomatal movement as well as in seed dormancy and germination and plant development. The addition of either ABA or NO to plant cells is known to instigate the actions of many signal transduction components. Both may have an influence on the phosphorylation of proteins in cells mediated by effects on protein kinases and phosphatases, as well as recruiting a wide range of other signal transduction molecules to mediate the final effects. Both ABA and NO may also lead to the regulation of gene expression. However, it is becoming more apparent that NO may be acting downstream of ABA, with such action being mediated by reactive oxygen species such as hydrogen peroxide in some cases. However not all ABA responses require the action of NO. Here, examples of where ABA and NO have been put together into the same signal transduction pathways are discussed.

Nitric oxide and ABA in the control of plant function

Abscisic acid (ABA) and nitric oxide (NO) are both extremely important signalling molecules employed by plants to control many aspects of physiology. ABA has been extensively studied in the mechanisms which control stomatal movement as well as in seed dormancy and germination and plant development. The addition of either ABA or NO to plant cells is known to instigate the actions of many signal transduction components. Both may have an influence on the phosphorylation of proteins in cells mediated by effects on protein kinases and phosphatases, as well as recruiting a wide range of other signal transduction molecules to mediate the final effects. Both ABA and NO may also lead to the regulation of gene expression. However, it is becoming more apparent that NO may be acting downstream of ABA, with such action being mediated by reactive oxygen species such as hydrogen peroxide in some cases. However not all ABA responses require the action of NO. Here, examples of where ABA and NO have been put together into the same signal transduction pathways are discussed.

Integrated HPLC-MS and (1)H-NMR spectroscopic studies on acyl migration reaction kinetics of model drug ester glucuronides

Acyl glucuronides (AGs) are common, chemically reactive metabolites of acidic xenobiotics. Concerns about the potential of this class of conjugate to cause toxicity in man require efficient methods for the determination of reactivity, and this is commonly done by measuring transacylation kinetics. High-performance liquid chromatography-mass spectrometry (HPLC-MS) and nuclear magnetic resonance (NMR) spectroscopy were applied to the kinetic analysis of AG isomerization and hydrolysis for the 1-beta-O-AGs of ibufenac, (R)- and (S)-ibuprofen, and an alpha,alpha-dimethylated ibuprofen analogue. Each AG was incubated in either aqueous buffer at pH 7.4 or human plasma at 37 degrees C. Aliquots of these samples, taken throughout the reaction time course, were analysed by HPLC-MS and (1)H-NMR spectroscopy and the results compared. For identification of the AGs incubated in pH 7.4 buffer and for analysis of kinetic rates, (1)H-NMR spectroscopy generally gave the most complete set of data, but for human plasma the use of (1)H-NMR spectroscopy was impractical and HPLC-MS was more suitable. HPLC-MS was more sensitive than (1)H-NMR spectroscopy, but the lack of suitable stable-isotope labelled internal standards, together with differences in response between glucuronides and aglycones, made quantification problematic. Using HPLC-MS a specific 1-beta-O-AG-related ion at m/z 193 (the glucuronate fragment) was noted enabling selective determination of these isomers. In buffer, transacylation reactions predominated, with relatively little hydrolysis to the free aglycone observed. In human plasma incubations the observed rates of reaction were much faster than for buffer, and hydrolysis to the free aglycone was the major route. These results illustrate the strengths and weaknesses of each analytical approach for this class of analyte.

Topics in Xenobiochemistry: Do metabolic pathways exist for xenobiotics? The micro-metabolism hypothesis

1. The relevance of the concept of 'the metabolic pathway' for the understanding of xenobiotic metabolism is discussed in the light of advances in modern analytical methods that have enabled the detection and identification of minor metabolites present at ever lower concentrations. 2. A model is suggested where the overall metabolic fate of a xenobiotic is the sum of all the possible metabolic reactions permitted by the solution chemistry of the compound modulated by factors such as the metabolizing enzyme complement of the organism, the affinity of those enzymes for the xenobiotic substrates and the probabilities of all of these processes. 3. In this probabilistic, rather than deterministic, system, the resulting proportions of particular metabolites will, therefore, depend on the sums of the probabilities of particular biotransformation reactions occurring and the stability (chemical or metabolic) of the resulting metabolite. 4. In this model, all the potential metabolic possibilities that could result for any individual xenobiotic will occur to some extent. However, in actuality, many of the resulting metabolites will be produced or excreted in such small quantities as to defy ready detection with current methods.

Nuclear magnetic resonance (NMR) and quantitative structure–activity relationship (QSAR) studies on the transacylation reactivity of model 1β-O-acyl glucuronides. II: QSAR modelling of the reaction using both computational and experimental NMR parameters

In a previously reported study, a number of 4-substituted benzoic acid acyl glucuronides were synthesized and their degradation rates determined using nuclear magnetic resonance (NMR) spectroscopy. It was shown that this reaction was strongly influenced by the nature of the substituent at the 4-position of the benzoyl moiety. The overall degradation reaction rates for this series of compounds have been modelled successfully using Hammett substituent constants, computational chemistry-derived partial atomic charges and the experimentally determined carbonyl carbon 13C-NMR chemical shifts of the benzoic acids and their ethyl and glucuronide esters. The primary contribution to reactivity is the scale of the electron-donating or -withdrawing effect of the substituent; however, additional contributions such as steric parameters must also be considered when modelling reactions outside a single chemical series. The derived property-reactivity relationships should find utility in medicinal chemistry efforts for optimizing chemical series in pharmaceutical discovery programmes.

Metabolism of [14C]-5-chloro-1,3-benzodioxol-4-amine in male Wistar-derived rats following intraperitoneal administration

[14C]-5-chloro-1,3-benzodioxol-4-amine was administered intraperitoneally (i.p.) to bile duct-cannulated rats (Alpk:ApfSD, Wistar derived) at 25 mg kg-1 to determine the rates and routes of excretion of the compound and to investigate its metabolic fate. A total of 89.1% of the dose was excreted in the 48 h following administration, the majority being recovered in the urine during the first 12 h. The main metabolite in both urine and bile, detected by high-performance liquid chromatography (HPLC) with radioprofiling and mass spectrometry, was identified as a demethylenated monosulfate conjugate. Unchanged parent compound formed a major component of the radiolabel excreted in urine and, in addition to unchanged parent and demethylenated sulphate conjugate, a large number of minor metabolites were detected in urine and bile. The overall metabolic fate of 5-chloro-1,3-benzodioxol-4-amine in the rat was complex, with some similarities to previously studied methylenedioxyphenyl compounds.

Metabolism of 3-chloro-4-fluoroaniline in rat using [14C]-radiolabelling,19F-NMR spectroscopy, HPLC-MS/MS, HPLC-ICPMS and HPLC-NMR

The metabolic fate of 3-chloro-4-fluoroaniline was investigated in rat following intraperitoneal (i.p.) administration at 5 and 50 mg kg(-1) using a combination of HPLC-MS, HPLC-MS/MS, (19)F-NMR spectroscopy, HPLC-NMR spectroscopy and high-pressure liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICPMS) with (35)Cl and (34)S detection. The metabolism of 3-chloro-4-fluoroaniline at both doses was rapid and extensive, to a large number of metabolites, with little unchanged compound excreted via the urine. Dosing at 5 mg kg(-1) with [(14)C]-labelled compound enabled the comparison of standard radioassay analysis methods with (19)F-NMR spectroscopy. (19)F-NMR resonances were only readily detectable in the 0-12 h post-dose samples. Dosing at 50 mg kg(-1) allowed the facile and specific detection and quantification of metabolites by (19)F-NMR spectroscopy. Metabolite profiling was also possible at this dose level using HPLC-ICPMS with (35)Cl-specific detection. The principal metabolites of 3-chloro-4-fluoroaniline were identified as 2-amino-4-chloro-5-fluorophenyl sulfate and 2-acetamido-4-chloro-5-fluorophenyl glucuronide. N-acetylation and hydroxylation followed by O-sulfation were the major metabolic transformations observed.

Kinetic studies on the intramolecular acyl migration of β-1-O-acyl glucuronides: Application to the glucuronides of (R)- and (S)-ketoprofen, (R)- and (S)-hydroxy-ketoprofen metabolites, and tolmetin by1H-NMR spectroscopy

Conjugation of carboxylate drugs with D-glucuronic acid is of considerable interest because of the inherent reactivity of the resulting beta-1-O-acyl glucuronides. These conjugates can degrade by spontaneous hydrolysis and internal acyl migration. beta-1-O-acyl glucuronides and their acyl migration products can also react covalently with macromolecules with potential toxicological consequences. The spontaneous degradation of the diastereoisomeric beta-1-O-acyl glucuronide metabolites of the racemic drug ketoprofen, two of its ring-hydroxylated metabolites and of tolmetin beta-1-O-acyl glucuronide was investigated by (1)H-NMR spectroscopy in buffer solutions, at pH 7.4 and 37 degrees C. A plot of the logarithm of the peak integrals against time revealed first-order kinetics. Degradation rates and half-lives were calculated for each glucuronide using first-order reaction equations. Tolmetin glucuronide had the fastest degradation rate, whilst all of the ketoprofen-related glucuronides had similar degradation rates. The degradation of the diastereoisomeric glucuronides was stereoselective, with the rate for the (S)-isomer always slower compared with the (R)-isomer by approximately a factor of 2.

Characterization and quantification of metabolites of racemic ketoprofen excreted in urine following oral administration to man by1H-NMR spectroscopy, directly coupled HPLC-MS and HPLC-NMR, and circular dichroism

The identity of the human metabolites of ketoprofen (2-(3-benzoylphenyl)-propanoic acid) excreted via urine was investigated after a single oral dose of the racemic drug. Drug metabolites were concentrated and partially purified from urine using solid-phase extraction chromatography before separation and identification by directly coupled HPLC-MS and HPLC-NMR. The metabolites identified were the ester glucuronides of the parent drug and its phase I metabolites, 2-[3-(3-hydroxybenzoyl)phenyl]-propanoic acid, 2-[3-(4-hydroxybenzoyl)phenyl]-propanoic acid and 2-[3-(hydroxy(phenyl)methyl)phenyl]-propanoic acid, the latter formed by reduction of the ketone group of ketoprofen. In addition, two novel minor metabolites were identified as the ether glucuronides of 2-[3-(3-hydroxybenzoyl)phenyl]-propanoic acid and 2-[3-(4-hydroxybenzoyl)phenyl]-propanoic acid. These conjugates were all observed as diastereoisomeric pairs of unequal proportions. Purification of these metabolites by preparative chromatography allowed stereochemistry assignments. Metabolites were quantified by 1H-NMR spectroscopy after spectral simplification achieved by hydrolysis of the conjugates.

Identification of phenacetin metabolites in human urine after administration of phenacetin-C2H3: measurement of futile metabolic deacetylation via HPLC/MS-SPE-NMR and HPLC-ToF MS

The metabolism of acetyl-labelled phenacetin-C2H3 was investigated in man following a single (150 mg) oral dose. Urine samples were collected at predose, 0-2 h and >2-4 h post-dose, and samples from each time-point were then analysed directly using 1H-nuclear magnetic resonance (NMR) spectroscopy. The phenacetin metabolites acetaminophen (paracetamol) glucuronide, sulphate and the N-acetyl-L-cysteinyl conjugate were identified by this method, and all showed clear evidence of the loss of the original 2H3-acetyl label and its replacement with 1H3 (futile deacetylation). The observed percentage futile deacetylation by 1H-NMR spectroscopy was measured as approximately 20% in each metabolite (about 2% of the recovered dose). After sample preparation by solid-phase extraction on a C18 solid-phase extraction (SPE) cartridge, further profiling was performed using high-performance liquid chromatography/mass spectrometry-solid-phase extraction-nuclear magnetic resonance (HPLC/MS-SPE-NMR) confirming futile deacetylation had taken place as indicated by NMR spectroscopy on both the isolated acetaminophen glucuronide and L-cysteinyl-metabolites. Additional analysis by high-performance liquid chromatography-time-of-flight mass spectrometry (HPLC-ToF MS) identified further phenacetin metabolites, and from these data the mean percentage of futile deacetylation was measured as 31% +/- 2% for the acetylated phenacetin metabolites. A number of non-acetylated metabolites were also detected in the sample via HPLC-ToF MS. The results showed that phenacetin underwent a transient formation via a number of toxic intermediates to a much greater extent than had been observed in similar studies on acetaminophen. These results may contribute to the understanding of the analgesic nephropathy reported following chronic phenacetin consumption.

The application of microbore UPLC/oa-TOF-MS and 1H NMR spectroscopy to the metabonomic analysis of rat urine following the intravenous administration of pravastatin

The metabonomic effects of hepatotoxic doses of pravastatin on the urinary metabolic profiles of female rats have been investigated using ultra performance liquid chromatography (UPLC)-oa-TOF-MS and, independently, by (1)H NMR spectroscopy. UPLC was performed using a 1 mm microbore column packed with 1.7 microm particles. Examination of the data obtained from the individual animals, aided by statistical interpretation of the data, made it possible to identify potential markers for toxicological effects, with both NMR and UPLC-MS analysis highlighting distinct changes in the urinary metabolite profiles. These markers, which included elevated taurine and creatine, as well as bile acids, were consistent with hepatotoxicity in some animals, and this hypothesis was supported by histopathological and clinical chemistry findings. The analytical data from both techniques could be used to define a metabolic "trajectory" as toxicity developed and to provide an explanation for the lack of hepatotoxicity for one of the animals. The two analytical approaches (UPLC-MS and NMR) were found to be complementary whilst the use of a 1mm i.d. x 100 mm column reduced the amount of sample required for analysis to 2 microL, compared with 10 microL for a 2.1mm i.d. x 100 mm column. The 1mm i.d. column also provided increased signal-to-noise without loss of chromatographic efficiency.

Statistically Integrated Metabonomic−Proteomic Studies on a Human Prostate Cancer Xenograft Model in Mice

A novel statistically integrated proteometabonomic method has been developed and applied to a human tumor xenograft mouse model of prostate cancer. Parallel 2D-DIGE proteomic and 1H NMR metabolic profile data were collected on blood plasma from mice implanted with a prostate cancer (PC-3) xenograft and from matched control animals. To interpret the xenograft-induced differences in plasma profiles, multivariate statistical algorithms including orthogonal projection to latent structure (OPLS) were applied to generate models characterizing the disease profile. Two approaches to integrating metabonomic data matrices are presented based on OPLS algorithms to provide a framework for generating models relating to the specific and common sources of variation in the metabolite concentrations and protein abundances that can be directly related to the disease model. Multiple correlations between metabolites and proteins were found, including associations between serotransferrin precursor and both tyrosine and 3-D-hydroxybutyrate. Additionally, a correlation between decreased concentration of tyrosine and increased presence of gelsolin was also observed. This approach can provide enhanced recovery of combination candidate biomarkers across multi-omic platforms, thus, enhancing understanding of in vivo model systems studied by multiple omic technologies.

The comparative metabonomics of age-related changes in the urinary composition of male Wistar-derived and Zucker (fa/fa) obese rats

The global metabolite profiles of endogenous compounds excreted in urine by male Wistar-derived and Zucker (fa/fa) obese rats were investigated from 4 to 20 weeks of age using both 1H NMR spectroscopy and HPLC-TOF/MS with electrospray ionisation (ESI). Multivariate data analysis was then performed on the resulting data which showed that the composition of the samples changed with age, enabling age-related metabolic trajectories to be constructed. At 4 weeks it was possible to observe differences between the urinary metabolite profiles from the two strains, with the difference becoming more pronounced over time resulting in a marked divergence in their metabolic trajectories at 8-10 weeks. The changes in metabolite profiles detected using 1H NMR spectroscopy included increased protein and glucose combined with reduced taurine concentrations in the urine of the Zucker animals compared to the Wistar-derived strain. In the case of HPLC-MS a number of ions were found to be present at increased levels in the urine of 20 week old Zucker rats compared to Wistar-derived rats including m/z 71.0204, 111.0054, 115.0019, 133.0167 and 149.0454 (negative ion ESI) and m/z 97.0764 and 162.1147 (positive ion ESI). Conversely, ions m/z 101.026 and 173.085 (negative ion ESI) and m/z 187.144 and 215.103 (positive ion ESI) were present in decreased amounts in urine from Zucker compared to Wistar-derived rats. Metabolite identities proposed for these ions include fumarate, maleate, furoic acid, ribose, suberic acid, carnitine and pyrimidine nucleoside. The utility of applying metabonomics to understanding disease processes and the biological relevance of some of the findings are discussed.

A multi-analytical platform approach to the metabonomic analysis of plasma from normal and zucker (fa/fa) obese rats

Plasma obtained from 20 week old normal Wistar-derived and Zucker (fa/fa) rats was analysed using a number of different analytical methodologies to obtain global metabolite profiles as part of metabonomic investigations of animal models of diabetes. Samples were analysed without sample pre-treatment using 1H NMR spectroscopy, after acetonitrile solvent protein precipitation by ultra-performance liquid chromatography-MS (UPLC-MS) and after acetonitrile protein precipitation and derivatisation for capillary gas chromatography-MS (GC-MS). Subsequent data analysis using principal components analysis revealed that all three analytical platforms readily detected differences between the plasma metabolite profiles of the two strains of rat. There was only limited overlap between the metabolites detected by the different methodologies and the combination of all three methods of metabolite profiling therefore provided a much more comprehensive profile than would have been provided by their use individually.

Metabonomics with 1H-NMR spectroscopy and liquid chromatography-mass spectrometry applied to the investigation of metabolic changes caused by gentamicin-induced nephrotoxicity in the rat

The model nephrotoxin gentamicin was administered to male Wistar-derived rats daily, for 7 days, at 60 mg kg-1 day-1, subcutaneously, twice daily. Conventional clinical chemistry urinalysis showed a significant increase in N-acetyl-beta-D-glucosaminidase (NAG) activity from day 3. At necropsy on day 9, clear histological damage to the kidney was noted with all animals showing a generally severe nephropathy primarily focused on the proximal convoluted tubules. The urinary excretion pattern of endogenous metabolites over the time course of the study was studied using a combination of 1H-NMR spectroscopy and HPLC-TOF-MS/MS using electrospray ionization (ESI). Changes in the pattern of endogenous metabolites as a result of daily administration of gentamicin were readily detected by both techniques with significant perturbations of the urinary profile observed from day 7 onwards. The findings by 1H-NMR included raised glucose and reduced trimethylamine N-oxide (TMAO). Changes in metabonomic profiles were observed by HPLC-MS in both positive and negative ESI. The MS data showed reduced xanthurenic acid and kynurenic acid, whilst neutral loss experiments also revealed a changed pattern of sulphate conjugation on gentamicin administration.

D-Serine-induced nephrotoxicity: a HPLC-TOF/MS-based metabonomics approach

HPLC-MS-based metabonomic analysis was used to investigate urinary metabolic perturbations associated with D-serine-induced nephrotoxicity. D-Serine causes selective necrosis of the proximal straight tubules in the rat kidney accompanied by aminoaciduria, proteinuria and glucosuria. Alderely Park (Wistar-derived) rats were dosed with either D-serine (250 mg/kg ip) or vehicle (deionised water) and urine was collected at 0-12, 12-24, 24-36 and 36-48 h post-dosing. Samples were analysed using a Waters Alliance HT 2795 HPLC system coupled to a Waters Micromass Q-ToF-micro equipped with an electrospray source operating in either positive or negative ion mode. Changes to the urinary profile were detected at all time points compared to control. In negative ion mode, increases were observed in serine (m/z=103.0077), m/z=104.0376 (proposed to be hydroxypyruvate) and glycerate (m/z=105.0215), the latter being metabolites of D-serine. Furthermore, an increase in tryptophan, phenylalanine and lactate and decreases in methylsuccinic acid and sebacic acid were observed. Positive ion analysis revealed a decrease in xanthurenic acid, which has previously been assigned and reported using HPLC-MS following exposure to mercuric chloride and cyclosporine A. A general aminoaciduria, including proline, methionine, leucine, tyrosine and valine was also observed as well as an increase in acetyl carnitine. Investigation of additional metabolites altered as a result of exposure to D-serine is on-going. Thus, HPLC-MS-based metabonomic analysis has provided information concerning the mechanism of D-serine-induced renal injury.

The metabonomics of aging and development in the rat: an investigation into the effect of age on the profile of endogenous metabolites in the urine of male rats using 1H NMR and HPLC-TOF MS

The effect of aging and development in male Wistar-derived rats on the profile of endogenous metabolites excreted in the urine was investigated using both (1)H NMR spectroscopy and HPLC-TOF MS using electrospray ionisation (ESI). The endogenous metabolites were profiled in samples collected from male rats every two weeks from just after weaning at 4 weeks up to 20 weeks of age. Multivariate data analysis enabled clusters to be visualised within the data according to age, with urine collected at 4 and 6 weeks showing the greatest differences by both analytical techniques. Markers detected by (1)H NMR spectroscopy included creatinine, taurine, hippurate and resonances associated with amino acids/fatty acids, which increased with age, whilst citrate and resonances resulting from glucose/myoinositol declined. A number of ions were detected by HPLC-MS that were only present in urine samples at 4 weeks of age in both positive and negative ESI, with a range of ions, including e.g. carnitine, increasing with age. Age predictions by PLS-regression modelling demonstrated an age-related trend within these data, between 4 and 12 weeks for HPLC-MS and 4-16 weeks for NMR. The possible utility of these techniques for metabonomic investigations of age-related changes in the rat is discussed and the importance of employing suitable control animals in pharmacological and toxicological studies is highlighted.

Cyclosporin A-induced changes in endogenous metabolites in rat urine: a metabonomic investigation using high field 1H NMR spectroscopy, HPLC-TOF/MS and chemometrics

The model nephrotoxin cyclosporin A was administered to male Wistar-derived rats daily for 9 days at a dose level of 45 mg/kg per day. Urine samples were collected daily and the excretion pattern of low molecular mass organic molecules in the urine was studied using 1H NMR spectroscopy and HPLC-TOF/MS. Distinct changes in the pattern of endogenous metabolites, as a result of the daily administration of cyclosporin A, were observed by 1H NMR from day 7 onwards. The NMR-detected markers included raised concentrations of glucose, acetate, trimethylamine and succinate and reduced amounts of trimethylamine-N-oxide. In parallel studies by HPLC-TOF/MS a reduction in the quantities of kynurenic acid, xanthurenic acid, citric acid and riboflavin present in the urines was noted, together with reductions in a number of as yet unidentified compounds. In addition, signals resulting from the polyethylene glycol, present in the dosing vehicle, and cyclosporin A metabolites were detected by MS. However, these were excluded from the subsequent multivariate data analysis in order to highlight only changes to the endogenous metabolites. Analysis of both the 1H NMR and HPLC-MS spectroscopic data using pattern recognition techniques clearly identified the onset of changes due to nephrotoxicity.

Metabonomics, dietary influences and cultural differences: a 1H NMR-based study of urine samples obtained from healthy British and Swedish subjects

The aim of this study was to assess the feasibility and comparability of metabonomic data in clinical studies conducted in different countries without dietary restriction. A (1)H NMR-based metabonomic analysis was performed on urine samples obtained from two separate studies, both including male and female subjects. The first was on a group of healthy British subjects (n = 120), whilst the second was on healthy subjects from two European countries (Britain and Sweden, n = 30). The subjects were asked to provide single, early morning urine samples collected on a single occasion. The (1)H NMR spectra obtained for urine samples were visually inspected and analysed chemometrically using principal components analysis (PCA). These inspections highlighted outliers within the urine samples and displayed interesting differences, revealing characteristic dietary and cultural features between the subjects of both countries, such as high trimethylamine-N-oxide (TMAO)-excretion in the Swedish population and high taurine-excretion, due to the Atkins diet. This study suggests that the endogenous urinary profile is subject to distinct cultural and severe dietary influences and that great care needs to be taken in the interpretation of 'biomarkers of disease and response to drug therapy' for diagnostic purposes.

A 1H NMR-based metabonomic study of urine and plasma samples obtained from healthy human subjects

The aim of the study was to assess the feasibility of metabonomics in clinical studies. A 1H nuclear magnetic resonance (NMR)-based metabonomic analysis was performed on plasma and urine samples obtained from a group of 12 healthy male subjects on two separate study days 14 days apart. The subjects were fed a standard diet and plasma and urine samples were obtained on both days. The 1H NMR spectra obtained for urine and plasma samples were analysed using principal components analysis (PCA) in order to generate metabonomic data. In plasma there was relatively little variability between subjects and study days. In the case of endogenous urinary metabolite profiles there was considerable inter-subject variability, but less intra-subject variation. In all subjects diurnal variation was seen with urine samples. This suggests the possibility to collect consistent metabonomics data in clinical studies.

A 1H NMR-based metabonomic study of urine and plasma samples obtained from healthy human subjects

The aim of the study was to assess the feasibility of metabonomics in clinical studies. A 1H nuclear magnetic resonance (NMR)-based metabonomic analysis was performed on plasma and urine samples obtained from a group of 12 healthy male subjects on two separate study days 14 days apart. The subjects were fed a standard diet and plasma and urine samples were obtained on both days. The 1H NMR spectra obtained for urine and plasma samples were analysed using principal components analysis (PCA) in order to generate metabonomic data. In plasma there was relatively little variability between subjects and study days. In the case of endogenous urinary metabolite profiles there was considerable inter-subject variability, but less intra-subject variation. In all subjects diurnal variation was seen with urine samples. This suggests the possibility to collect consistent metabonomics data in clinical studies.

Comparison of extraction of a β-blocker from plasma onto a molecularly imprinted polymer with liquid–liquid extraction and solid phase extraction methods

An optimised solid phase extraction (SPE) method developed for the extraction of a structural analogue of the beta-blocking drug propranolol from plasma utilising a molecularly imprinted polymer (MIP) has been compared with methods based on conventional liquid-liquid extraction (LLE), and SPE using C18-bonded and immobilised phenyl boronic acid (PBA). All four methods could be used for the extraction of the analyte with acceptable accuracy and precision. The MIP-based method, unlike the other methods required a protein precipitation step prior to extraction to eliminate the effects of co-extracted protein. The best performance was seen with the LLE method followed by SPE on the C18 phase. The MIP-based method represented no advantage over the comparator methods for this analyte. Indeed the performance of the MIP-based method was marginally worse as leaching of low level template impurities prevented detection of the target analyte at low concentrations (5 ngmL(-1)). This relatively poorer performance was evident as worse accuracy at low concentrations with a consequent higher limit of quantification than the conventional methods.

A metabonomic investigation of the biochemical effects of mercuric chloride in the rat using 1H NMR and HPLC-TOF/MS: time dependent changes in the urinary profile of endogenous metabolites as a result of nephrotoxicity

The effects of the administration of a single dose of the model nephrotoxin mercuric chloride (2.0 mg kg(-1), subcutaneous) to male Wistar-derived rats on the urinary metabolite profiles of a range of endogenous metabolites has been investigated using (1)H NMR and HPLC-MS. Urine samples were collected daily for 9 days from both dosed and control animals. Analysis of these samples revealed marked changes in the pattern of endogenous metabolites as a result of HgCl(2) toxicity. Peak disturbances in the urinary metabolite profiles were observed (using both NMR and HPLC-MS) at 3 days post dose. Thereafter the urinary metabolite profile gradually returned to a more normal composition. Markers of toxicity identified by (1)H NMR spectroscopy were raised concentrations of lactate, alanine, acetate, succinate, trimethylamine (TMA), and glucose. Reductions in the urinary excretion of citrate and alpha-ketoglutarate were also seen. Markers identified by HPLC-MS, in positive ion mode, were kynurenic acid, xanthurenic acid, pantothenic acid and 7-methylguanine which decreased after dosing. In addition an ion at m/z 188, probably 3-amino-2-naphthoic acid, was observed to increase after dosing. As well as these identified compounds other ions at m/z 297 and 267 decreased after dosing. In negative ion mode a range of sulfated compounds were observed, including phenol sulfate and benzene diol sulfate, which decreased after dosing. As well as the sulfated components an unidentified glucuronide at m/z 326 was also observed to decrease after dosing. The results of this study demonstrate the complementary nature of the NMR and MS-based techniques for metabonomic analysis.

NMR and QSAR studies on the transacylation reactivity of model 1beta-O-acyl glucuronides. I: design, synthesis and degradation rate measurement

1. The products arising from intramolecular acyl migration reactions of drug ester glucuronides are reactive towards cellular proteins and can potentially cause toxic side-effects. The relationship between molecular structure and the degradation rates (kd) of 1beta-O-acyl glucuronides were investigated systematically using a series of model compounds based on 4-substituted benzoic acids. 2. A rational method for selecting suitable compounds for inclusion was used and 10 glucuronide esters, predicted to produce a wide range of transacylation rates, were synthesized via a simple "one-pot" method using an imidazolide intermediate. The 10 substituents, where X = NO2, CN, I, Br, F, H, nPr, Et, OMe, O-nPr, had degradation rate half-lives (t1/2 = loge(2)/kd) ranging from 0.9 to 106.6 h. The reactions resulted in mixtures, which predominantly consisted of the desired 1beta-O-acyl glucuronides. 3. It was demonstrated that further purification was unnecessary for determination of kd of the synthetic 1beta-O-acyl glucuronides. Degradation rates (kd) were calculated by following the disappearance of the 1H-NMR signal from the 1beta-anomeric proton of the glucuronic acid moiety as the reaction progressed in pH 7.4 buffer inside an nuclear magnetic resonance tube. Each measured degradation rate represents a pseudo-first-order rate constant, which is a combination of the transacylation rate (1beta to 2beta isomer) and the hydrolysis rate. 4. Degradation rates show a clear relationship with substituent properties, with half-life increasing as the substituent becomes more electron-donating, e.g. 4-nitro t1/2 = 0.9 h and 4-propoxy t1/2 = 106.6 h.

Detection of mono- and di-hexoses as metabolites of 4-bromoaniline using HPLC-TOF-MS/MS

1. The metabolic fate of 4-bromoaniline (4-BrA) was investigated in rat following intraperitoneal administration at 50 mg kg(-1) using HPLC-TOF-MS/MS. 2. The sensitivity provided by the use of TOF-MS/MS, aided by the distinctive isotope pattern resulting from the presence of the bromine substituent in the molecule, enabled the detection of many previously uncharacterized metabolites in the samples. 3. Several groups of minor metabolites were detected in the urine that corresponded to a number of isomeric hexose and di-hexose-containing conjugates (possibly glucosides and diglucosides) of 4-BrA. 4. As well as hexose and di-hexose conjugates of 4-BrA, several further groups of metabolites that also contained either a sulphamate or sulphate group in addition to the sugar moieties were also detected.

Hyphenation and hypernation the practice and prospects of multiple hyphenation

In the past two decades, combining a chromatographic separation system on-line with a spectroscopic detector in order to obtain structural information on the analytes present in a sample has become the most important approach for the identification and/or confirmation of the identity of target and unknown chemical compounds. In most instances, such hyphenation can be accomplished by using commercially available equipment For most (trace-level) analytical problems encountered today, the combination of column liquid chromatography or capillary gas chromatography with a mass spectrometer (LC-MS and GC-MS, respectively) is the preferred approach. However, it is also true that additional and/or complementary information is, in quite a number of cases, urgently required. This can be provided by, for example, atomic emission, Fourier-transform infrared, diode-array UV-vis absorbance or fluorescence emission, or nuclear magnetic resonance spectrometry. In the present review, the various options are briefly discussed and a few relevant applications are quoted for each combination. Special attention is devoted to systems in which multiple hyphenation, or hypernation, is an integral part of the setup. As regards this topic, the relative merits of various combinations--which turn out to include a mass spectrometer as one of the detectors in essentially all cases--are discussed and the fundamental differences between GC- and LC-based systems are outlined. Finally, the practicability of more extensive hypernation in LC, viz. with up to four spectrometers, is discussed. It is demonstrated that, technically, such multiple hyphenation is possible and that, from a practical point of view, rewarding results can be obtained. In other words, further research in this area is certainly indicated. However, in the foreseeable future, using several separate conventional hyphenated systems will be the commonly implemented solution in most instances.

An NMR study of the metabolic fate of 2-, 3- and 4-fluorobenzyl alcohols in the rat: detection of N-acetylcysteinyl conjugates as minor metabolites in urine

Following the administration of 2-, 3- and 4-fluorobenzyl alcohols, the major metabolites detected in urine corresponded to the glycine conjugates of the corresponding benzoic acids. Little, or no, unchanged parent compound was detected in the samples. In addition to glycine-conjugated benzoic acids, a small proportion of the urinary metabolites for each of the fluorobenzyl alcohols was found to correspond to N-acetylcysteinyl conjugate. These were probably formed as the result of the production of a reactive sulphate ester during metabolism. The overall urinary recoveries of metabolites for the 2- and 3-fluorobenzyl alcohols were lower than that observed for the corresponding benzoic acids whilst that for 4-fluorobenzyl alcohol was similar.

The metabolism of 2-trifluormethylaniline and its acetanilide in the rat by 19F NMR monitored enzyme hydrolysis and 1H/19F HPLC-NMR spectroscopy

The urinary excretion profile and identity of the metabolites of 2-trifluoromethyl aniline (2-TFMA) and 2-trifluoromethyl acetanilide (2-TFMAc), following i.p. administration to the rat at 50 mg kg(-1), were determined using a combination of 19F NMR monitored enzyme hydrolysis, SPEC-MS and 19F/1H HPLC-NMR. A total recovery of approximately 96.4% of the dose was excreted into the urine as seven metabolites. The major routes of metabolism were N-conjugation (glucuronidation), and ring-hydroxylation followed by sulphation (and to a lesser extent glucuronidation). The major metabolites excreted into the urine for both compounds were a labile N-conjugated metabolite (a postulated N-glucuronide) and a sulphated ring-hydroxylated metabolite (a postulated 4-amino-5-trifluoromethylphenyl sulphate) following dosing of 2-TFMA. These accounted for approximately 53.0 and 31.5% of the dose, respectively. This study identifies problems on sample component instability in the preparation and analysis procedures.

Physiological variation in metabolic phenotyping and functional genomic studies: use of orthogonal signal correction and PLS-DA

Metabolic phenotyping, or metabotyping, is increasingly being used as a probe in functional genomics studies. However, such profiling is subject to intrinsic physiological variation found in all animal populations. Using a nuclear magnetic resonance-based metabonomic approach, we show that diurnal variations in metabolism can obscure the interpretation of strain-related metabolic differences in two phenotypically normal mouse strains (C57BL10J and Alpk:ApfCD). To overcome this problem, diurnal-related metabolic variation was removed from these spectral data by application of orthogonal signal correction (OSC), a data filtering method. Interpretation of the removed orthogonal variation indicated that diurnal-related variation had been removed and that the AM samples contained higher levels of creatine, hippurate, trimethylamine, succinate, citrate and 2-oxo-glutarate and lower levels of taurine, trimethylamine-N-oxide, spermine and 3-hydroxy-iso-valerate relative to the PM samples. We propose OSC will have great potential removing confounding variation obscuring subtle changes in metabolism in functional genomic studies and will be of benefit to optimising interpretation of proteomic and genomic datasets.

Application of (1)H- and (19)F-NMR spectroscopy in the investigation of the urinary and biliary excretion of 3,5-, 2,4-ditrifluoromethylbenzoic and pentafluorobenzoic acids in rat

1. The metabolism and excretion of 2,4-, 3,5-ditrifluoromethyl- and pentafluorobenzoic acids were studied in the bile-cannulated rat using (1)H- and (19)F-NMR spectroscopy following intraperitoneal administration at 50 mg kg(-1). 2. Pentafluorobenzoic acid was excreted in the urine entirely unchanged. No detectable compound or metabolites were eliminated in the bile. A total of 63.5 +/- 6.7% of the dose was recovered in the 24-h collection period. 3. In the case of 2,4-ditrifluromethyl benzoic acid, 83.9 +/- 5.2% of the dose was recovered in the 24h after administration, with about 52% being excreted in the urine and 32% in the bile. The majority of the material present in the urine was unchanged parent compound. In bile, some 60% of the compound-related material excreted was present as transacylated ester glucuronide conjugates. 4. For 3,5-ditrifluoromethylbenzoic acid, 49.6 +/- 5.3% of the dose was recovered in the 24-h collection period, with about 22% being excreted in the urine and 28% in the bile. The material excreted in both the urine and bile was a mixture of the parent acid and transacylated ester glucuronides. 5. Urinary excretion in bile-cannulated animals was similar to that found in studies using non-cannulated animals dosed at 100mg kg(-1).

The metabolism of 4-trifluoromethoxyaniline and [13C]-4-trifluoromethoxyacetanilide in the rat: detection and identification of metabolites excreted in the urine by NMR and HPLC-NMR

A combination of 19F, 1H NMR and HPLC-NMR spectroscopic approaches have been used to quantify and identify the urinary-excreted metabolites of 4-trifluoromethoxyaniline (4-TFMeA) and its [13C]-labelled acetanilide following i.p. administration at 50 mg/kg to rats. The major metabolite excreted in the urine for both compounds was a sulphated ring-hydroxylated metabolite (either 2- or 3-trifluoromethyl-5-aminosulphate) which accounted for approximately 32.3% of the dose following the administration of 4-TFMeA and approximately 29.9% following dosing of the acetanilide. The trifluoromethoxy-substituent appeared to be metabolically stable, with no evidence of O-detrifluoromethylation. There was no evidence of the excretion of N-oxanilic acids in urine, of the type seen with 4-trifluoromethylaniline.

Structure-metabolism relationships of substituted anilines: prediction of N-acetylation and N-oxanilic acid formation using computational chemistry

1. The relationship between the in vivo metabolism of substituted anilines, in particular N-acetylation and subsequent formation of oxanilic acids, and their molecular physico-chemical properties has been investigated using computational chemistry and pattern-recognition methods. The methods revealed that the physico-chemical properties most important for N-acetylation and subsequent oxanilic acid formation were electronic descriptors based on partial atomic charges and the susceptibility of the molecules to nucleophilic attack at certain ring positions. 2. The calculated partial atom charge on the amine nitrogen was the parameter most important for predicting that an aniline would be N-acetylated. The calculated nucleophilic susceptibility of the aromatic carbon para to the amino group (NS4) was the most significant parameter for determining oxanilic acid formation following N-acetylation. Thus, highly electron-withdrawing groups substituted at this position gave higher nucleophilic susceptibilities that were related to the presence of an oxanilic acid metabolite. 3. If the parameters relating to N-acetylation were modified by other electron-withdrawing groups in the ring (particularly at the position ortho to the amino group), then acetylation and subsequent oxanilic acid formation did not occur. The introduction of groups that allow the possibility of competing oxidative metabolic pathways elsewhere in the molecule (e.g. CH(3)) also affected the production of oxanilic acids. 4. Using chemometric analysis of the computed physico-chemical properties, the result has been the generation of a model that classifies the metabolism of a number of anilines. This could be used to predict the acetylation and oxanilic formation propensity of a number of substituted anilines whose metabolism was unknown to the system, demonstrating that such techniques may be of use for predicting metabolism and hence could provide support for rational drug design.

A comparison of quantitative NMR and radiolabelling studies of the metabolism and excretion of Statil (3-(4-bromo-2-fluorobenzyl)-4-oxo-3H-phthalazin-1-ylacetic acid) in the rat

The identification and quantitation of the metabolites of Statil in rat bile and urine were investigated by 1H- and 19F-NMR spectroscopy and liquid scintillation counting. Male Wistar rats received a single oral dose of 100 mg/kg of radiolabelled Statil. Statil is known to produce glucuronide conjugates which are predominantly excreted into the bile in male rats. The complex multiphasic matrix of bile has been shown to make identification of the resonances by 1H-NMR spectroscopy very difficult as Statil appeared to be micellar bound giving rise to very broad signals. This not only impaired unambiguous signal characterisation but also quantification. The partial separation by SPEC-(1)H-NMR spectroscopy enabled the disruption of the micellar matrices and hence enabled the identification of Statil predominantly as aglycone, and to a lesser extent as glucuronide conjugate. In addition, minor acyl migration products of Statil glucuronide could also be detected as they were separated during the SPEC-process. 19F-NMR spectroscopic measurements on whole bile confirmed their presence as a number of overlapped signals could be observed. The selectivity, simplicity and signal dispersion characteristic of 19F-NMR spectroscopy also enabled the calculation of dose related recoveries of Statil related material in the bile and urine samples without the need for a radiolabel. The aim of this work was to investigate the usefulness and limitations of NMR spectroscopy of intact bile and urine as a means of quantifying levels of drug metabolites. The results obtained from NMR spectroscopy are compared with those obtained using scintillation techniques. Scintillation counting yields unequivocal quantification results, provided the label is preserved in metabolites as has been the case here. In general, quantification by 19F-NMR results similar to those obtained by scintillation counting (in agreement within about 20%). However, discrepancies have been observed with very small and broad 19F-NMR signals in bile. Nevertheless, 19F-NMR spectroscopy of bile is a rapid and facile method for assessing metabolite levels of fluorinated drugs.

Identification of the urinary metabolites of 4-bromoaniline and 4-bromo-[carbonyl-13C]-acetanilide in rat

1. The urinary excretion of 4-bromoaniline and its [carbonyl-(13)C]-labelled N-acetanilide, together with their corresponding metabolites, have been investigated in the rat following i.p. administration at 50 mg kg(-1). 2. Metabolite profiling was performed by reversed-phase HPLC with UV detection, whilst identification was performed using a combination of enzymic hydrolysis and directly coupled HPLC-NMR-MS analysis. The urinary metabolite profile was quantitatively and qualitatively similar for both compounds with little of either excreted unchanged. 3. The major metabolite present in urine was 2-amino-5-bromophenylsulphate, but, in addition, a number of metabolites with modification of the N-acetyl moiety were identified (from both the [(13)C]-acetanilide or produced following acetylation of the free bromoaniline). 4. For 4-bromoacetanilide, N-deacetylation was a major route of metabolism, but despite the detection of the acetanilide following the administration of the free aniline, there was no evidence of reacetylation (futile deacetylation). 5. Metabolites resulting from the oxidation of the acetyl group included a novel glucuronide of an N-glycolanilide, an unusual N-oxanilic acid and a novel N-acetyl cysteine conjugate.

High resolution 1H NMR spectroscopic studies of the composition of the haemolymph of crowd- and solitary-reared nymphs of the desert locust, Schistocerca gregaria

High resolution 1H NMR spectroscopy provided a rapid and non-invasive means of establishing a multicomponent profile of the low molecular weight organic metabolites present in the haemolymph of crowd-reared and solitary-reared desert locusts. Assignments of the 1H NMR resonances detected in the one-dimensional (1D) spectra were supported by the comparison of chemical shifts with those of commonly found metabolites, the application of 2D NMR spectroscopy, and spiking of authentic standards into the sample. The haemolymph metabolite profile was found to comprise trehalose, a series of amino acids, organic acids, lipids, ethanol and the polyamine putrescine. In total, it was possible to detect simultaneously and potentially quantify over 20 endogenous compounds. An interesting difference between the phases was the higher putrescine concentrations present in solitary-reared nymphs, which may indicate a role of this compound in phase determination. In addition, differences in the concentrations of trehalose, lipids, acetate and ethanol were also observed between solitary-reared and gregarious-reared nymphs enabling the ready differentiation of the two phases based on the NMR spectra of the haemolymph.