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J C Lindon

Publications and source records attributed to J C Lindon.

At least 91 records · Page 5Linked to original sources
PubMed1996

Quantitative structure-metabolism relationships for substituted benzoic acids in the rabbit: prediction of urinary excretion of glycine and glucuronide conjugates.

1. Quantitative relationships between molecular physicochemical properties of 24 substituted benzoic acids and their metabolic fate in the rabbit have been investigated using computational chemistry and multivariate statistical methods. 2. A total of 34 molecular properties were calculated for each compound using computational chemistry and were related statistically to the % molar recovery of glycine and glucuronide conjugates excreted in the urine of rabbits for the 24 compounds. 3. Compounds were successfully classified according to their dominant metabolic fate based on urinary excretion data, where stepwise linear regression analysis of the theoretical property data achieved good predictive fits for observed versus predicted % molar urinary recovery as glucuronide conjugates (r2 = 0.79) and % molar urinary recovery as glycine conjugates (r2 = 0.66). 4. Quantitative prediction of the urinary excretion of glucuronide and glycine conjugates of the parent compounds was achieved based on a statistical model using calculated molecular physicochemical parameters. Interpretation of the molecular properties, which are important for predicting the metabolic class, should give new insights into basic mechanisms of drug metabolism and underlying molecular recognition events that determine disposition and metabolism.

Animals↗
PubMed1996

Hplc-nmr identification of the human urinary metabolites of (-)-cis-5-fluoro-1-[2-(hydroxymethyl)-1,3-oxathiolan-5-yl] cytosine, a nucleoside analogue active against human immunodeficiency virus (HIV).

1. Human urine samples from a clinical trial of the anti-HIV compound (-)-cis-5-fluoro-1-[2-(hydroxymethyl)-1,3-oxathiolan-5-yl]-cyto sin e (BW524W91) have been analysed using 19F-nmr and 1H-hplc-nmr spectroscopy. 2. The identities and relative levels of the xenobiotic species in the urine have been determined by 470-MHz 19F-nmr spectroscopy and by directly coupled 600-MHz 1H-hplc-nmr in the stop-flow mode with confirmation of the metabolite identities being made by comparison with nmr spectra of synthetic standard compounds. 3. The principal urinary xenobiotic was the unchanged drug, but the glucuronide ether conjugate at the 5' position of BW524W91, one of the two diastereomeric sulphoxides and the deaminated metabolite were also characterized. 4. The detection limit of directly coupled hplc-600-MHz 1H-nmr spectroscopy was evaluated by measuring two-dimensional nmr spectra of the glucuronide conjugate of BW524W91 and shown to be approximately 1 microgram material for 1H-1H-TOCSY and 20 micrograms metabolite for 1H-13C-HMQC spectra for overnight (16 h) acquisition.

Antiviral Agents↗
PubMed1996

1H and 19F-nmr spectroscopic studies on the metabolism and urinary excretion of mono- and disubstituted phenols in the rat.

1. 1H and 19F-nmr spectroscopy was used to investigate quantitatively the urinary excretion of the metabolites of 15 substituted phenols in the rat. The compounds studied were: 2-, 3-, and 4-fluorophenols; 2-, 3-, and 4-trifluoromethylphenol; 2,4-, 2,6- and 3,4-difluorophenol; 2-fluoro-5-trifluoromethylphenol, 3-fluoro-5-trifluoromethylphenol, 2-trifluoromethyl-4-fluorophenol; 3-chloro-4-fluorophenol, 3-fluoro-4-chlorophenol, and 3-methyl-4-fluorophenol. All compounds were dosed to the Sprague-Dawley rat (10 mg/kg i.p.) and urine was collected over the periods 0-8, 8-24 and 24-48 h post-dosing and analyzed using nmr spectroscopy. 2. The compounds were excreted in the urine mainly as glucuronide or sulphate conjugates or as the unchanged parent compound. There was considerable variation in the urinary excretion of the compounds over 48 h ranging from 22.1 to 93.6% of the dose. There was no apparent relationship between the molecular weight of compounds or their metabolites and the percentage molar recovery of each in the urine. 3. Ortho-substituted phenols in general showed a greater propensity for glucuronidation than did either meta- or para-substituted compounds, irrespective of the substituent group. The molar glucuronide-to-sulphate ratio for ortho-substituted compounds was found to be 2.2 +/- 0.9 whereas the ratio for both meta- and para-substituted compounds was 0.8 +/- 0.2 (p < 0.0001). 4. There were characteristic substituent effects of phenolic glucuronidation or sulphation on the 19F-nmr chemical shifts for both F- and CF3-substituted phemols and these substituent effects were a useful aid to metabolite signal assignment. 5. These studies show that nmr spectroscopy provides a rapid and convenient approach to the construction of metabolic databases of simple xenobiotics for the investigation of structure-metabolism relationships.

Animals↗
PubMed1995

1H and 2H NMR spectroscopic studies on the metabolism and biochemical effects of 2-bromoethanamine in the rat.

Male Fischer 344 rats were dosed with 2-bromoethanamine hydrobromide (BEA, N = 6) or [1,2,2,-2H4]-bromoethanamine hydrobromide (BEA-d4, N = 6) at 150 mg/kg i.p. and urine was collected -24 to 0 hr pre-dose and at 0-2 hr, 2-4 hr, 4-8 hr and 8-12 hr post-dose (p.d.). Urine samples were analysed directly using 500 and 600 MHz 1H NMR and 92.1 MHz 2H NMR spectroscopy. The major observed effect of BEA treatment was the induction of transient elevations in urinary glutaric acid (GTA) and adipic acid (ADA) excretion lasting up to 24 hr p.d. Most of the GTA was excreted in the 0-8 hr p.d. with maximal rates of 100-120 microM/hr for each rat occurring between 4 and 8 hr p.d. in animals treated with BEA or BEA-d4. GTA and ADA were shown to be of endogenous origin as there was no detectable incorporation of the 2H label into either compound following treatment of rats with BEA-d4. Following BEA-treatment there was an initial decrease in the levels of urinary citrate, succinate, 2-oxoglutarate and trimethylamine-N-oxide. A subsequent recovery of citrate and succinate was noted following the onset of medullary nephropathy. The abnormal urinary metabolite profiles were similar to that observed in the urine of humans with glutaric aciduria type II (an inborn error of metabolism) caused by a lack of mitochondrial fatty acyl coenzyme A dehydrogenases indicating that BEA or its metabolites have similar metabolic consequences. The BEA metabolite aziridine was detected by 1H and 2H NMR spectroscopy of the urine 8 hr p.d. together with BEA itself and two novel metabolites 2-oxazolidone (OX) and 5-hydroxy-2-oxazolidone (HOX). The formation of OX requires the reaction of BEA with endogenous bicarbonate followed by a cyclisation reaction eliminating HBr. Dosing rats with authentic OX resulted in the excretion of HOX but did not cause glutaric or adipic aciduria indicating that either aziridine or BEA itself was responsible for the presumed defect in mitochondrial metabolism.

Adipates↗
PubMed1995

High resolution NMR spectroscopic studies on the metabolism and futile deacetylation of 4-hydroxyacetanilide (paracetamol) in the rat.

Paracetamol (4-hydroxyacetanilide, acetaminophen) was synthesized with the acetyl group labelled with C2H3 (paracetamol-C2H3), and dosed to rats i.p. at 25 mg/kg (N = 5) and 40 mg/kg (N = 3) body weight. Paracetamol, with a 13CH3 in the acetyl group (paracetamol-13CH3) was also synthesized and dosed to rats i.p. at 40 mg/kg (N = 3). The metabolism and excretion of the 2H-labelled compound was followed in the rat using 600 MHz 1H and 92.1 MHz 2H NMR spectroscopy of urine collected 0-8, 8-24, 24-32 and 32-48 hr post-dosing. The metabolism of paracetamol-13CH3 was also monitored using 600 MHz 1H NMR spectroscopy of urine collected 0-8, 8-24 and 24-48 hr post-dosing. For paracetamol-C2H3 the total recovery of the sulphate, glucuronide and N-acetyl cysteinyl metabolites via the urine accounted for 61.2 +/- 14.1% of the 25 mg/kg dose and 61.4 +/- 8.8% of the 40 mg/kg dose. For paracetamol-13CH3 the recovery was 102.7 +/- 3.7% indicating that the low % urinary recovery with the C2H3-labelled drug is the result of isotope effects on the disposition of paracetamol. In the case of the paracetamol-C2H3, quantitative 1H NMR analysis of urine showed that 13.3 +/- 0.5 and 10.0 +/- 1.2 mole % (25 and 40 mg/kg, respectively) of the urinary paracetamol sulphate recovered following dosing of the deuterium labelled drug had the C2H3 acetyl groups replaced by C1H3 acetyl groups from endogenous sources. In the case of the paracetamol-13CH3 8.9 +/- 0.7 mole % of the sulphate conjugate had also been transacetylated to paracetamol-12CH3. There was no significant difference between the level of futile deacetylation observed for the deuterated and 13C-labelled drug. Overall these data indicate a high level of deacetylation followed by reacetylation (i.e. futile deacetylation) prior to excretion of paracetamol via the nephrotoxic intermediate 4-aminophenol. The level of deacetylation is much higher than has previously been thought which may cast new light on the role of 4-aminophenol in the development of paracetamol induced nephrotoxicity.

Acetaminophen↗
PubMed1995

750 MHz 1H and 1H-13C NMR spectroscopy of human blood plasma.

High-resolution 750 MHz 1H NMR spectra of control human blood plasma have been measured and assigned by the concerted use of a range of spin-echo, two-dimensional J-resolved, and homonuclear and heteronuclear (1H-13C) correlation methods. The increased spectral dispersion and sensitivity at 750 MHz enable the assignment of numerous 1H and 13C resonances from many molecular species that cannot be detected at lower frequencies. This work presents the most comprehensive assignment of the 1H NMR spectra of blood plasma yet achieved and includes the assignment of signals from 43 low M(r) metabolites, including many with complex or strongly coupled spin systems. New assignments are also provided from the 1H and 13C NMR signals from several important macromolecular species in whole blood plasma, i.e., very-low-density, low-density, and high-density lipoproteins, albumin, and alpha 1-acid glycoprotein. The temperature dependence of the one-dimensional and spin-echo 750 MHz 1H NMR spectra of plasma was investigated over the range 292-310 K. The 1H NMR signals from the fatty acyl side chains of the lipoproteins increased substantially with temperature (hence also molecular mobility), with a disproportionate increase from lipids in low-density lipoprotein. Two-dimensional 1H-13C heteronuclear multiple quantum coherence spectroscopy at 292 and 310 K allowed both the direct detection of cholesterol and choline species bound in high-density lipoprotein and the assignment of their signals and confirmed the assignment of most of the lipoprotein resonances.

Adult↗
PubMed1995

Classification of toxin-induced changes in 1H NMR spectra of urine using an artificial neural network.

NMR spectra of urine from rats treated with a range of liver, kidney and testicular toxins at various doses were measured and classified using neural network methods. Toxin-induced changes in the levels of 18 low molecular weight endogenous urinary metabolites were assessed using a simple semi-quantitative scoring system. These scores were used as input to an artificial neural network, the use of which has been explored as a means of predicting the class of toxin. With this limited data set, based only the level of the maximal changes of these 18 metabolites, the network was able to predict the class and hence target organ of the toxins. Renal cortical toxicity was well predicted as was liver toxicity. The few examples of renal medullary toxins in the data set resulted in relatively poor training of the network although correct classification was still possible.

Chemical and Drug Induced Liver Injury↗
PubMed1995

Assignment of the 750 MHz 1H NMR resonances from a mixture of transacylated ester glucuronic acid conjugates with the aid of oversampling and digital filtering during acquisition.

Many drugs containing carboxylic acid functional groups are metabolised in vivo to ester glucuronides (1-O-acyl-beta-D-glucopyranuronates) and, of these, a number show a propensity to undergo internal isomerisation via a transacylation process, causing the carboxylic acid moiety to migrate successively to the 2-, 3- and 4-positions of the glucuronic acid. These products may be responsible, through reactions with plasma proteins, for some of the allergenic side effects in a number of non-steroidal anti-inflammatory drugs. It is important to understand those properties of the drug molecules which facilitate this reaction, and to this end we have studied the transacylation product formation and reaction kinetics in a series of aryl carboxylic acid glucuronides using NMR spectroscopy. However, the resulting 1H NMR spectra are very complex with much resonance overlap, and recourse to spectral simplification processes is necessary. Here, improvement in spectral resolution by oversampling and digital filtering to restrict the detection range of the spectrometer, thus yielding improved digital resolution, is demonstrated. The approach has been applied to the assignment of a mixture of transacylated ester glucuronides of 2-trifluoromethylbenzoic acid through the use of a two-dimensional 1H-1H TOCSY experiment.

Buffers↗
PubMed1995

Prediction of urinary sulphate and glucuronide conjugate excretion for substituted phenols in the rat using quantitative structure-metabolism relationships.

1. The quantitative urinary excretion of the sulphate and glucuronide metabolites of 15 substituted phenols dosed to rat has been determined using high resolution 19F-nmr spectroscopy. 2. The urinary metabolic fate of each of the compounds was related to a series of calculated physicochemical properties for each compound to produce quantitative structure-metabolism relationships (QSMRs). Using these calculated molecular properties it was possible to predict the urinary recovery of xenobiotic material as a percentage of the administered dose, to classify the compounds according to their 'dominant' metabolite pattern and to predict quantitatively the proportions of glucuronide and sulphate conjugates in the urine by the use of multiple linear regression. 3. The quantitative predictions were tested by cross-validation and good prediction of total xenobiotic urinary recovery as a percentage of the administered dose was achieved based on an equation involving the electrophilic superdelocalizability at C4 (para to the hydroxyl function), the smallest principal ellipsoid axis dimension and the heat of formation. The largest moment of inertia and the electrophilic superdelocalizability at C3 were found to be the most significant factors for the prediction of the percentage glucuronide in the urine, and the urinary excretion of sulphate conjugates as a percentage of total urinary recovery was negatively correlated with the glucuronide excretion as little parent compound was excreted.

Animals↗
PubMed1994

Automatic data reduction and pattern recognition methods for analysis of 1H nuclear magnetic resonance spectra of human urine from normal and pathological states.

Multivariate data analysis techniques have been used to compare 600-MHz 1H nuclear magnetic resonance (NMR) spectra of urine obtained from patients with inborn errors of metabolism (IEM) and urine obtained from healthy subjects. These spectra are very complex; each contains many thousands of resonances with a high dynamic range. A consistent method of reducing this wealth of data to manageable proportions is presented as a two-stage process. Computer-based spectral descriptors are automatically generated and then reduced to two-dimensional maps for visualization of clustering. Data-scaling methodology has been developed to achieve complete separation between spectra from control adults and those from adult patients with independently diagnosed IEM. The methods were refined by relating IEM samples to the mean of the control samples and applying supervised learning techniques to identify descriptors contributing to class separation. This approach allowed separation of the various classes of IEM and achieved optimal separation of patients with cystinuria from those with oxalic aciduria; the principal metabolites responsible for this separation were determined as lysine and glyoxalate. The methods developed were then extended by application to the more subtle problem of classifying urine collected from healthy subjects under different physiological conditions (i.e., pre- and post-exercise and in different stages of hydration) where, unlike the IEM case, any underlying biochemical differences were not known at the outset. Fluid-loaded and fluid-deprived samples could be partially separated as well as fluid-deprived and fluid-restored samples. Partial classification of samples on the basis of subject was also observed. Therefore, intersubject differences were liable to obscure the separation by physiological state. However, by relating each sample to a mean of the normal daily urine samples for the same person and applying a form of "range scaling" to exclude data which contributed least to class separation, improved classification of the hydration states resulted, from which it was possible to deduce those biochemical substances which were altered. These novel techniques for the data reduction and classification of NMR spectra make comprehensive use of all of the NMR spectral information and have clear potential to assist in clinical diagnosis.

Adult↗
PubMed1994

Internal temperature calibration for 1H NMR spectroscopy studies of blood plasma and other biofluids.

A method for temperature calibration of human blood plasma and cerebrospinal fluid (CSF) samples inside a high resolution NMR spectrometer is presented. This calibration is based on the temperature dependence of the chemical shift difference between the water signal and that from the H-1 proton of endogenous alpha-glucose or, in some circumstances, beta-glucose. This dependence can be fitted using a second-order polynomial equation and functions for both human blood plasma and human CSF are given. Similar graphs could easily be generated for other fluids. The blood plasma calibration appears to be accurate to +/- 0.9 K in test samples. The use of the blood plasma calibration graph has also been evaluated using the 1H NMR spectra of CSF and shown to overestimate the CSF internal temperature by ca 1.3 K. This approach should have a general applicability to blood plasma and CSF samples from normal and pathological situations or from other species, because there are unlikely to be large changes in ionic strength or pH even in disease states. Knowledge of the exact internal temperature of plasma samples is likely to be of particular importance in the investigation of lipid and lipoprotein interactions because of the significant temperature dependence of lipid and lipoprotein NMR linewidths in such samples.

Body Fluids↗
PubMed1994

Evaluation of liquid chromatography coupled with high-field 1H NMR spectroscopy for drug metabolite detection and characterization: the identification of paracetamol metabolites in urine and bile.

The applicability of coupled reversed-phase high performance liquid chromatography (HPLC)-NMR spectroscopy for the detection and identification of paracetamol (N-(4-hydroxyphenyl)acetamide) and its sulfate, glucuronide and N-acetylcysteinyl metabolites in the unprocessed biological fluids, human urine, rat urine and rat bile, is investigated. Analysis of these samples was performed by gradient HPLC elution and directly coupled 500 MHz 1H NMR spectroscopy detection using a combination of one- and two-dimensional NMR methods in stopped-flow mode. The stopped-flow approach is demonstrated to be an efficient technique for identification of drug metabolites which have, for example, a UV-chromophore. Stopped-flow HPLC analysis with NMR detection is a viable technique and halting the chromatographic process several times during a run has a negligible effect on the separation and NMR characterization. The post-acquisition data processing method of 'quantified maximum entropy' is shown to provide a means of improving the quality of spectra for minor components, thus aiding NMR resonance assignments.

Acetaminophen↗
PubMed1994

High-field deuterium nuclear magnetic resonance spectroscopic monitoring of the pharmacokinetics of selectively deuterated benzoic acid in man.

The stable isotope tracer technique using 13C labeling of substrates followed by NMR spectroscopy of biofluids has been widely used in metabolic investigations, whereas the use of 2H labeling and 2H NMR spectroscopy has been extremely limited. The applicability of the high-field 2H NMR spectroscopy (14.1 T, 92 MHz 2H frequency) in a simple pharmacokinetic problem has now been investigated using selectively deuterated benzoic acid (BA) as a model. [7-13C,2,6-2H2]BA was synthesized for use as a tracer to compare the efficiency and sensitivity of 2H and 13C labeling. The urinary excretion of [7-13C,2,6-2H2]hippuric acid (HA) formed from orally administered [7-13C,2,6-2H2]BA (250 mg) was followed by 92-MHz 2H and 150-MHz 13C NMR spectroscopy (only 10 min accumulation time) following concentration of urine by a factor of 10, using a standard for quantitation. The heights of resonances for 13C7 and 2H2,6 were used to calculate the [7-13C,2,6-2H2]HA concentration. The lower limit of detection using this 2H NMR approach was approximately 60 nmol/ml and was found to be comparable with that of the 13C NMR approach where the quaternary carbon (C7) was labeled. The administered [7-13C,2,6-2H2]BA was found to be quantitatively biotransformed to HA and excreted in urine within 4 h by both NMR approaches. The 2H NMR approach using a high-field NMR spectrometer is potentially useful and practical for pharmacokinetic research on small molecules whose 2H resonances are relatively sharp since the procedures are very simple and convenient.

Benzoates↗
PubMed1994

Studies on the comparative toxicity of S-(1,2-dichlorovinyl)-L-cysteine, S-(1,2-dichlorovinyl)-L-homocysteine and 1,1,2-trichloro-3,3,3-trifluoro-1-propene in the Fischer 344 rat.

The renal tubular toxicity of various halogenated xenobiotics has been attributed to their enzymatic bioactivation to reactive intermediates by S-conjugation. A combination of high resolution proton nuclear magnetic resonance (1H NMR) spectroscopy of urine, renal histopathology and more routinely used clinical chemistry methods has been used to explore the acute toxic and biochemical effects of S-(1,2-dichlorovinyl)-L-cysteine (DCVC), S-(1,2-dichlorovinyl)-L-homocysteine (DCVHC) and 1,1,2-trichloro-3,3,3-trifluoro-1-propene (TCTFP) up to 48 h following their administration to male Fischer 344 (F344) rats. In the absence of gross renal pathology, 1H NMR urinalysis revealed increased excretion of the tricarboxylic acid cycle intermediates citrate and succinate following DCVC administration. In contrast, both DCVHC and TCTFP produced functional defects in the S2 and S3 segments of the proximal tubule that were confirmed histologically. In these cases, 1H NMR urinalysis revealed increased excretion of glucose, L-lactate, acetate and 3-D-hydroxybutyrate (HB) as well as selective amino aciduria (alanine, valine, glutamate and glutamine). The significance of the proximal nephropathies induced by DCVHC and TCTFP is discussed in relation to biochemical observations on other xenobiotics that are toxic by similar mechanisms.

Animals↗
PubMed1994

Application of the one-dimensional TOCSY pulse sequence in 750 MHz 1H-NMR spectroscopy for assignment of endogenous metabolite resonances in biofluids.

The complex 1H-NMR spectrum arising from an intact biofluid has been simplified using a one-dimensional homonuclear polarization transfer experiment (known as TOCSY or HOHAHA). This approach establishes connectivity between sequentially coupled multiplets, and the method is illustrated by the confirmation of the chemical shifts and hence resonance assignment of a number of endogenous metabolites in the 750 MHz 1H-NMR spectrum of seminal fluid. This has allowed the detection and assignment of pyroglutamate and uracil in this fluid for the first time.

Computer Simulation↗
PubMed1994

Ultra high field NMR spectroscopic studies on human seminal fluid, seminal vesicle and prostatic secretions.

Ultra high field 1H-NMR spectroscopic methods have been used to analyse the composition of seminal fluid and its component secretions, prostatic and seminal vesicle fluids from normal human subjects and those with vasal aplasia and non-obstructive infertility. The 1H-NMR spectrum of whole seminal fluid is extremely complex and many resonances are extensively overlapped in single pulse spectra even when measured at 600 or 750 MHz 1H resonance frequency. A combination of 2-D 1H-NMR methods (including J-Resolved and various 1H homonuclear correlation and 1H-13C heteronuclear correlation techniques) were applied at 600 or 750 MHz in order to extensively assign the signals from the organic components of seminal fluid. Prostatic fluid (PF) gives a much less complex metabolite profile than whole seminal fluid and can be completely analysed using 500 MHz 1H-NMR spectroscopy. The 1H-NMR spectra of prostatic fluid are dominated by signals from citrate, spermine and myo-inositol, whereas the spectra of seminal vesicle fluid (SVF) show extensively overlapped signals from complex peptide mixtures together with strong signals for glycerophosphocholine (GPC) and lactate. Whole seminal fluid is a combination of the PF and SVF constituents together with further substances that appear after mixing due to the operation of PF enzymes on SVF, e.g. peptidase activity causes rapid cleavage of peptides to amino acids and GPC is hydrolysed to choline, glycerol and inorganic phosphate. It is also shown that vasal aplasia leads to highly characteristic abnormal metabolite profiles in seminal fluid that can be readily observed in single-pulse 500 and 600 MHz 1H-NMR spectra. Measurement of the molar citrate to choline, or spermine to choline ratios in seminal fluid both show differences of 2 orders of magnitude between vasal aplasia (greater for both ratios) and non-obstructed infertile patients. This work gives an indication of the potential of high field 1H-NMR spectroscopy in the investigation and assessment of the secretory functions of the male genital tract and the evaluation of the infertile male subject.

Amino Acids↗