Highly sensitive liquid chromatography-mass spectrometry method for the quantitative analysis of mometasone furoate in human plasma: Method validation and application to clinical pharmacokinetic studies

We report the development and the validation of a sensitive liquid chromatography-mass spectrometry (LC-MS/MS) method for mometasone furoate (MF) analysis in human plasma. Plasma samples were processed through liquid-liquid extraction and analyzed using LC-MS/MS operating in positive mode using multiple reaction monitoring of transitions m/z 520.9 → 355.0 and m/z 525.8 → 355.0 for MF and the internal standard (IS), respectively. Separation was achieved at 1.0 mL/min on a C18 column using a gradient elution of mobile phase of 0.05% ammonia in water (phase A) and acetonitrile (phase B). The assay range was 0.250-100 pg/mL and proved to be accurate and precise MF. Normalized recoveries were consistent and reproducible with a coefficient of variation (CV%) value of 6.0. The CV (%) of the IS normalized matrix factor was not observed in normal, lipemic, and hemolyzed plasmas. Dilutions of 1:10 were accurately quantified. A cycle of three freeze and thaw and stabilities at room temperature and on the autosampler were demonstrated. In addition, MF in the presence of indacaterol and glycopyrronium was proven to be stable at -70°C for at least 157 days. The present method was successfully applied to quantify MF in patients receiving MF, indacaterol, and glycopyrronium as a fixed-dose combination.

Supported liquid extraction combined with liquid chromatography tandem mass spectrometry for the quantitative analysis of a TLR7 agonist imiquimod LFX453 in plasma at low picograms per milliliter: Method validation and its application to a pharmacokinetic study in minipig

Sample preparation is essential for low-level compound determination. In the present work, supported liquid extraction (SLE) was used as sample preparation for the low-level determination of a new TLR7 agonist imiquimod compound, LFX453. Samples were extracted on ISOLUTE® SLE 96-well plates using tert-butyl-methyl ether followed by evaporation and dry residue reconstitution with 150 μl of a mixture of 0.1% formic acid in acetonitrile-water (50/50, v/v). Samples were eluted using a flow rate of 0.750 ml/min on a C18 column (50 × 2.1 mm, 2.7 μm) with a mobile phase consisting of 0.1% formic acid in water (A) and 0.1% formic acid in acetonitrile (B). Tandem mass spectrometry was used to analyze the samples in positive mode. The method run time was 6.5 min, and the low limit of quantification was 1.00 pg/ml with 0.100 ml of minipig plasma. Intra-run and inter-run precision and accuracy were within the acceptance criteria at four concentration levels over a concentration ranging from 1.00 to 200 pg/ml. There was no matrix effect and recovery, three freeze-thaw cycles and incurred samples reanalysis were validated. The method was successfully applied for measuring LFX453 in minipig plasma after application on minipig skin.

Pharmacokinetics of indacaterol, glycopyrronium and mometasone furoate administered as an inhaled fixed-dose combination in Japanese and Caucasian healthy subjects

BACKGROUND

A once-daily (o.d.) fixed-dose combination of indacaterol acetate (IND), glycopyrronium bromide (GLY), and mometasone furoate (MF) delivered via the Breezhaler® device (IND/GLY/MF) is being developed for treatment of asthma. This study compared steady-state pharmacokinetics of IND, GLY and MF between Japanese and Caucasian male subjects after multiple inhalations of IND/GLY/MF o.d.

METHODS

This was a single-center, open-label, 2-treatment crossover study with a 21-day washout period. Japanese and Caucasian subjects received IND/GLY/MF 150/50/80 μg (inhaled corticosteroid [ICS] medium-dose) or 150/50/160 μg o.d. (ICS high-dose) for 14 days in each period. Pharmacokinetics were characterized up to 24 h post-dose on Days 1 and 14.

RESULTS

In total, 16 Japanese (median age 31 years [range 20-40 years], mean weight 68.3 kg) and 17 Caucasian subjects (median age 27 years [range 21-43 years], mean weight 75.0 kg) were randomized. Geometric mean ratios (Japanese/Caucasian) [90% confidence interval (CI)] for Cmax for IND, GLY and MF at the high ICS dose on Day 14 were 1.31 [1.13, 1.51] 1.38 [1.13, 1.69] and 1.07 [0.969, 1.18], respectively. Geometric mean ratios (Japanese/Caucasian) [90% CI] for AUC0-24h on Day 14 for IND, GLY and MF at the high ICS dose were 1.17 [1.01, 1.35], 1.05 [0.920, 1.20] and 1.15 [1.05, 1.27] respectively. Similar trends were noted for all components for the medium ICS dose treatment. IND/GLY/MF was safe and well tolerated; no AEs suspected to be study drug-related were observed.

CONCLUSION

Pharmacokinetics of IND, GLY and MF (high and medium dose) when delivered as a fixed-dose combination were comparable between Japanese and Caucasian subjects. The IND/GLY/MF combination at the administrated doses was safe and well tolerated in both ethnic groups.

TRIAL REGISTRATION

Japan Registry of Clinical Trial: jRCT2031200227, retrospectively registered on 04, December, 2020.

Pharmacokinetics of indacaterol, glycopyrronium and mometasone furoate following once-daily inhalation as a combination in healthy subjects

Indacaterol (IND), is co-formulated with glycopyrronium (GLY), and mometasone furoate (MF) as a once-daily (o.d.) inhaled fixed-dose combination (IND/GLY/MF) delivered via the Breezhaler® device for maintenance treatment of asthma. We evaluated the steady state plasma pharmacokinetics (PK) of IND, GLY and MF following inhalation of IND/GLY/MF or as monotherapies. This was a randomized, open-label, four-way crossover study. Subjects received IND/GLY/MF 150/50/160 μg (high-dose), IND 150 μg, GLY 50 μg or MF 190 μg (in vitro fine particle mass comparable to 160 μg MF in IND/GLY/MF) via the Breezhaler® device, o.d. for 14 days in each period, with a washout of at least 7 days. PK was characterized on Day 14, up to 24 h post-dose. In total, 36 healthy subjects were randomized. For IND, the geometric mean ratios (90% CI) for AUC0-24h,ss and Cmax,ss were 0.922 (0.878, 0.969) and 1.02 (0.967, 1.08), respectively for the IND/GLY/MF versus IND monotherapy comparison. For GLY, the geometric mean ratios (90% CI) for AUC0-24h,ss and Cmax,ss were 0.986 (0.944, 1.03) and 1.21 (1.09, 1.34), respectively for the IND/GLY/MF versus GLY comparison. For MF, the geometric mean ratios (90% CI) for AUC0-24h,ss and Cmax,ss were 1.16 (1.09, 1.24) and 1.17 (1.09, 1.25), respectively for IND/GLY/MF versus MF comparison. Similar systemic exposure was noted for IND/GLY/MF versus monotherapy for all three mono-components, indicating a lack of PK interaction. Multiple inhaled doses of IND, GLY and MF were safe and well tolerated, when administered alone or in combination. There was no clinically relevant pharmacokinetic interaction between IND, GLY and MF when administered as IND/GLY/MF.

Development and validation of an LC-MS/MS method for the quantitative analysis of the adenosine A2a receptor antagonist NIR178 and its monohydroxy metabolite in human plasma: Application to clinical pharmacokinetics

We report a selective LC-MS/MS method for the simultaneous quantitative determinations of the adenosine A2a receptor antagonist NIR178 (NIR178) and its major metabolite NJI765 in human plasma. Sample preparation steps involved protein precipitation, sample evaporation and reconstitution using a plasma sample volume of 0.1 ml plasma. Separation was achieved in 10 min on an Acquity UPLC BEH C₁₈ 1.7 μm, 2.1 × 50 mm column heated at 60°C with a gradient elution at 0.6 ml/min mobile phase made of water and acetonitrile both acidified with 0.1% formic acid. The detection was performed in positive ion mode and quantification based on multiple reaction monitoring. The linear response range was 1.00-1,000 ng/ml using a 1/x² weighting factor. The intra- and inter-day accuracies (bias %) and intra- and inter-day precisions (CV, %) obtained for NIR178 and NJI765 were within the acceptance criteria. The normalized NIR178 and NJI765 matrix factor calculated from six lots of normal, lipemic and hemolyzed plasmas ranged from 0.97 to 1.05. The normalized recoveries of both NIR178 and NJI765 compared with their internal standards were consistent and reproducible with a CV ≤8.0. This method was successfully applied to support pharmacokinetic studies in adult patients with cancer.

New microfluidic-based sampling procedure for overcoming the hematocrit problem associated with dried blood spot analysis

Hematocrit (Hct) is one of the most critical issues associated with the bioanalytical methods used for dried blood spot (DBS) sample analysis. Because Hct determines the viscosity of blood, it may affect the spreading of blood onto the filter paper. Hence, accurate quantitative data can only be obtained if the size of the paper filter extracted contains a fixed blood volume. We describe for the first time a microfluidic-based sampling procedure to enable accurate blood volume collection on commercially available DBS cards. The system allows the collection of a controlled volume of blood (e.g., 5 or 10 μL) within several seconds. Reproducibility of the sampling volume was examined in vivo on capillary blood by quantifying caffeine and paraxanthine on 5 different extracted DBS spots at two different time points and in vitro with a test compound, Mavoglurant, on 10 different spots at two Hct levels. Entire spots were extracted. In addition, the accuracy and precision (n = 3) data for the Mavoglurant quantitation in blood with Hct levels between 26% and 62% were evaluated. The interspot precision data were below 9.0%, which was equivalent to that of a manually spotted volume with a pipet. No Hct effect was observed in the quantitative results obtained for Hct levels from 26% to 62%. These data indicate that our microfluidic-based sampling procedure is accurate and precise and that the analysis of Mavoglurant is not affected by the Hct values. This provides a simple procedure for DBS sampling with a fixed volume of capillary blood, which could eliminate the recurrent Hct issue linked to DBS sample analysis.

Biodistribution and metabolism studies of lipid nanoparticle-formulated internally [3H]-labeled siRNA in mice

Absorption, distribution, metabolism, and excretion properties of a small interfering RNA (siRNA) formulated in a lipid nanoparticle (LNP) vehicle were determined in male CD-1 mice following a single intravenous administration of LNP-formulated [(3)H]-SSB siRNA, at a target dose of 2.5 mg/kg. Tissue distribution of the [(3)H]-SSB siRNA was determined using quantitative whole-body autoradiography, and the biostability was determined by both liquid chromatography mass spectrometry (LC-MS) with radiodetection and reverse-transcriptase polymerase chain reaction techniques. Furthermore, the pharmacokinetics and distribution of the cationic lipid (one of the main excipients of the LNP vehicle) were investigated by LC-MS and matrix-assisted laser desorption ionization mass spectrometry imaging techniques, respectively. Following i.v. administration of [(3)H]-SSB siRNA in the LNP vehicle, the concentration of parent guide strand could be determined up to 168 hours p.d. (post dose), which was ascribed to the use of the vehicle. This was significantly longer than what was observed after i.v. administration of the unformulated [(3)H]-SSB siRNA, where no intact parent guide strand could be observed 5 minutes post dosing. The disposition of the siRNA was determined by the pharmacokinetics of the formulated LNP vehicle itself. In this study, the radioactivity was widely distributed throughout the body, and the total radioactivity concentration was determined in selected tissues. The highest concentrations of radioactivity were found in the spleen, liver, esophagus, stomach, adrenal, and seminal vesicle wall. In conclusion, the LNP vehicle was found to drive the kinetics and biodistribution of the SSB siRNA. The renal clearance was significantly reduced and its exposure in plasma significantly increased compared with the unformulated [(3)H]-SSB siRNA.

Tetrazole-based deoxyamodiaquines: synthesis, ADME/PK profiling and pharmacological evaluation as potential antimalarial agents

A series of new deoxyamodiaquine-based compounds was synthesized via the modified TMSN3-Ugi multi-component reaction and evaluated in vitro for antiplasmodial activity. The most potent compounds, 6b, 6c and 6j, showed IC50 values in the range of 6-77nM against chloroquine-resistant K1- and W2-strains of Plasmodium falciparum. In vitro ADME characterization of frontrunner compounds 6b and 6c indicates that these two compounds are rapidly metabolized and have a high clearance rate in human and rat liver microsomes. This result correlated well with an in vivo pharmacokinetics study, which showed low bioavailability of 6c in rats. Tentative metabolite identification was determined by LC-MS and suggested metabolic lability of groups attached to the tertiary nitrogen. Preliminary studies on 6b and 6c suggested strong inhibitory activity against the major CYP450 enzymes. In silico docking studies were used to rationalize strong inhibition of CYP3A4 by 6c. Full characterization and biological evaluation of the metabolites is currently underway in our laboratories.

A fast and reliable reversed phase high performance liquid chromatography method for simultaneous determination of selected anti-retroviral and lumefantrine in human plasma

A fast and reliable high performance liquid chromatography (HPLC) method with UV diode array detection for simultaneous quantitative analysis of the anti-retroviral drugs, nevirapine (NVP) and efavirenz (EFV) and the anti-malarial, lumefantrine (LUM) in human plasma has been developed and validated. The sample preparation consisted of a plasma protein precipitation with 0.5% acetic acid acetonitrile solution containing the internal standard halofantrine (HALO) prior the LC-analysis. Chromatographic separation was carried out on a Acclaim Polar Advantage C(16), column (150 mm × 4.6 mm, particle size, 3 μm) using a gradient of mobile phase made of 0.01% TFA in 0.1M ammonium acetate (solvent A) and 0.1% TFA in acetonitrile (solvent B). The separation of NVP, EFV, LUM and HALO was achieved within 17 min at a flow rate of 1.0 mL/min and detections were initially performed at three wavelengths, 275 nm (NVP), 255 nm (EFV), and 300 nm (LUM). The method selectivity was demonstrated in six different human plasma batches. In addition, several concomitant drugs were analyzed under our experimental conditions and none of them co-eluted with EFV, NVP and LUM. This demonstrated that our method is highly selective. Calibration graphs plotted with seven concentrations in duplicate for each compound were linear between the selected ranges with a regression coefficient (R(2)) greater than 0.998. Absolute extraction recovery for NVP, EFV and LUM were 99%, 98.6 and 102%, respectively. Inter- and intra-day coefficients of variation for LUM, EFV and NVP were ≤10%. The lower limits of quantification were 0.125 μg/mL for LUM and 0.250 μg/mL for both EFV and NVP. Intra- and inter-assay relative standard deviation values were found to be less than 15% at the concentrations examined (0.125-10.0 μg/mL for LUM and 0.250-15.0 μg/mL for both EFV and NVP). The present method was successfully implemented in Tanzania and only one wavelength (255 nm) was used to measure samples of patients receiving either NVP or EFV in combination with LUM. The concentration found in human plasma samples for all three compounds were within the calibration range. This makes our method particularly applicable and useful to resource-limited settings.

A small-molecule dengue virus entry inhibitor

The incidence of dengue fever epidemics has increased dramatically over the last few decades. However, no vaccine or antiviral therapies are available. Therefore, the need for safe and effective antiviral drugs has become imperative. The entry of dengue virus into a host cell is mediated by its major envelope (E) protein. The crystal structure of the E protein reveals a hydrophobic pocket that is presumably important for low-pH-mediated membrane fusion. High-throughput docking with this hydrophobic pocket was performed, and hits were evaluated in cell-based assays. Compound 6 was identified as one of the inhibitors and had an average 50% effective concentration of 119 nM against dengue virus serotype 2 in a human cell line. Mechanism-of-action studies demonstrated that compound 6 acts at an early stage during dengue virus infection. It arrests dengue virus in vesicles that colocalize with endocytosed dextran and inhibits NS3 expression. The inhibitors described in this report can serve as molecular probes for the study of the entry of flavivirus into host cells.

Study of bradykinin metabolism by rat lung tissue membranes and rat kidney brush border membranes by HPLC with inductively coupled plasma-mass spectrometry and orthogonal acceleration time-of-flight mass spectrometry

The coupling of the techniques, high-performance liquid chromatography (HPLC), orthogonal acceleration time-of-flight mass spectrometry (OATOF-MS) and inductively coupled plasma mass spectrometry (ICP-MS) provides a very powerful method for identifying and quantifying the products of bradykinin metabolism. In this study, we were able to identify the major metabolites of bradykinin degradation reported in the literature. In addition, a new bradykinin metabolite corresponding to bradykinin 5,9 fragment (BK-(5,9)-fragment) was identified as a product of neutral endopeptidase (NEP) activity. This finding establishes that NEP cleaves bradykinin simultaneously at the positions 4-5 and 7-8. We also demonstrate the equivalent participation of NEP and angiotensin-converting enzyme (ACE) within the rat lung tissue membranes (RLTM) in bradykinin degradation, suggesting its suitability as a model for the assay of dual ACE/NEP inhibitors. On the contrary, in rat kidney brush border membranes (KBBM), ACE is not significantly involved in bradykinin metabolism, with NEP being the major enzyme.

Determination of Vitamin B12 in food products and in premixes by reversed-phase high performance liquid chromatography and immunoaffinity extraction

A new, faster and simple method to quantify Vitamin B12, both in foods and in premixes, by reversed-phase liquid chromatography with UV detection has been developed. Vitamin B12 was extracted from food products with 50 mM sodium acetate buffer pH 4.0 (at 100 degrees C for 35 min) in the presence of sodium cyanide, followed by a purification step on an immunoaffinity column prior to the LC analysis. An enzymatic hydrolysis (pepsin at 37 degrees C and pH 4 for 3 h) prior to the purification step efficiently released the bound Vitamin B12, and thus, allowed obtaining total Vitamin B12 content in food products. Vitamin B12 was monitored by UV at 361 nm after its separation on a reversed-phase narrow-bore column with a gradient of mobile phase made of water/acetonitrile and trifluoroacetic acid (TFA) 0.025%. The specificity of the method was demonstrated by the retention characteristics, UV spectra and by comparing the peak purity with the Vitamin B12 standard. The calibration graphs plotted with six concentrations of Vitamin B12 was linear with a regression coefficient R2 > 0.9997. The repeatability of the method was evaluated at different levels of concentration on six fortified products and the relative standard deviation (RSDr) was below 3.2%. The value of the relative standard deviation of the intermediate precision was below 5.6% (n = 4). The method was successfully applied to several food products and consistent results were obtained in comparison with microbiological assay (MBA). Our data demonstrate that the immunoaffinity columns are highly efficient for the purification of Vitamin B12 and that our HPLC could be used as an alternative method to the microbiological assay for the determination of Vitamin B12 in food products.

Separation of water-soluble vitamins by reversed-phase high performance liquid chromatography with ultra-violet detection: application to polyvitaminated premixes

Nine water-soluble vitamins: [thiamine (B1), ascorbic acid (C), nicotinamide (PP), pyridoxine (B6), calcium pantothenate (B5), folic acid (B9), cyanocobalamin (B12), riboflavin (B2) and biotin (B8)] were separated on a YMC-Pack Pro C18 column (250 mm x 4.6 mm, 5 microm particle size) in a single run with a gradient elution of mobile phase consisting of 0.025% trifluoroacetic acid pH 2.6 (solvent A) and acetonitrile (solvent B). The separation was achieved within 17 min with a flow rate of 0.8 ml min(-1) and the detection was performed at two wavelengths (210 and 275 nm). The calibration graphs plotted with six concentrations of each vitamin were linear with a regression coefficient R2 > 0.995. The method was applied for the quantification of vitamins B1, C, PP, B6, B5, B9 B2 and B8 in polyvitaminated premixes (premixes) used for the fortification of infant nutrition products. The sample preparation involves an aqueous extraction of vitamins and two different samples dilution were used prior the LC-analysis. The specificity of the method was demonstrated by the retention characteristics, UV spectra and by comparing the peak purity with the standard of each vitamin. The repeatability of the method was evaluated at different level of concentrations on 12 premixes and the coefficients of variation (CVr) were below 6.5%. The values of the intermediate precision (CV1) were below 9.6% (n = 6). The concentrations of vitamins found in premixes with our method were comparable to the declared values, since no bias was found between the two sets of results at 95% confidence. The simplicity of the procedure should make it highly desirable for quality control of premixes in the food industry.

Determination of vitamin B5 in human urine by high-performance liquid chromatography coupled with mass spectrometry

In the present work, we have developed a simple and rapid liquid chromatography/mass spectrometry (LC/MS) method for the identification and quantification of vitamin B5 in human urine. Urine was spiked with vitamin B5 internal standard, hopantenic acid (HOPA), and then diluted with the LC mobile phase prior to its analysis by LC/MS. The quantification was performed in single ion monitoring mode. The calibration curve was linear (r2 = 0.999) between 0.25 to 10 microg/mL. With a limit of detection of 0.1 microg/mL the method was sensitive enough to determine low levels of vitamin B5 in urine. The overall quantitative efficiency of the method was evaluated by spiking urine samples with four different concentrations of vitamin B5; the intra-assay coefficient of variation was below 5% and the recoveries were between 96 to 108%. The results of the present study show that the proposed method is selective and sensitive enough for the quantification of vitamin B5 in urine.

Determination of vitamin B5 in a range of fortified food products by reversed-phase liquid chromatography-mass spectrometry with electrospray ionisation

Methods for Vitamin B5 determination in food products remain limited by their low sensitivity and poor selectivity. Here, we have developed a liquid chromatography-mass spectrometry (LC-MS) method for Vitamin B5 determination in wide range of fortified food products. Vitamin B5 was extracted from food samples by heat treatment and analysed by LC-MS in the positive mode using electrospray ionisation (ESI). Vitamin B5 was quantified using hopantenic acid (HOPA) as internal standard after their separation on a C18 narrow-bore column with a gradient of mobile phase made of water/acetonitrile and trifluoroacetic acid (TFA) 0.025%. MS with single ion monitoring mode at mass m/z 220 was used for Vitamin B5 quantification. Calibration curve between 0.5 and 10 microg/ml of Vitamin B5 was linear (r2=0.9993) and the detection limit was determined to be 800 pg. The overall quantitative efficiency of the method was evaluated using Nestle reference sample (infant formula). The intra-assay RSD was 4.8% (n=8), the inter-assay RSD 6.4% (n=4) and the recoveries of the spiked samples were above 95%. Application of the LC-MS method to Vitamin B5 determination in wide range of fortified food products including three US National Institute of Standards and Technology (NIST) reference samples (RM 8435, RM 8415 and SRM 1546) shows consistent results with those obtained by microbiology and recoveries of Vitamin B5 between 93 and 104% for the spiked samples.

Liquid chromatography coupled with inductively coupled plasma mass spectrometry in the pharmaceutical industry: selected examples

Both LC and capillary LC (CapLC) have been successfully interfaced with inductively coupled plasma mass spectrometry (ICP-MS). Gradients of acetonitrile and aqueous based solvents have been employed to separate several compounds of pharmaceutical interest. This paper will describe four application areas in the pharmaceutical industry, and examples will be shown where CapLC, LC and gel electrophoresis via laser ablation have been coupled with ICP-MS. The four areas highlighted in this paper are: (1) the use of derivatisation reactions to "make the invisible visible". Methods involving derivatisations with copper and iron will be described that can be used for the analysis of amines and carboxylic acids by ICP-MS. (2) The profiling of metal ion content (in particular bromine) in biological samples such as human plasma, this study will focus on the metabolism of bromine-labelled peptides (e.g. substance P). (3) The analysis of materials derived from single, solid-phase beads used in combinatorial chemistry, and (4) also discussed will be our findings from investigations into the use of laser ablation ICP-MS on the determination of protein phosphorylation on electrophoresis gel blots.

Simultaneous quantification of Vitamins A, D3 and E in fortified infant formulae by liquid chromatography–mass spectrometry

A novel method for the simultaneous quantification of Vitamins A, D3 and E in fortified infant formulae has been developed using isocratic normal-phase liquid chromatography with positive atmospheric pressure chemical ionization mass spectrometry (LC-APCI-MS). Food products were saponified and the vitamins were extracted by solid-phase extraction (SPE) on a Chromabond XTR cartridge. Quantification of Vitamins D3 and E were performed with Vitamin D2 and 5,7-dimethyltocol (DMT) as internal standards (IS), respectively while no IS was used for Vitamin A. Detection of the vitamins was made in the selected ion monitoring (SIM) mode. MS calibration curves were linear between 0.15 and 12 mg/l for Vitamin A, 5-400 microg/l for Vitamin D3 and 0.25-20 mg/l for Vitamin E with regression coefficient r2 > 0.996 and the limits of detection were below 1.4 ng. The repeatability (CV) obtained on a reference dietetic infant formula was 2.3% for Vitamin A, 2.6% for Vitamin E and 5.9% for Vitamin D3. The between-day variations (CV) over 6 days were in the ranges of 2.4-6.9% for the three vitamins. The mean recoveries from a reference infant formula spiked with all three vitamins ranged from 96 to 105% with a relative standard error less than 9%. The applicability of the method was demonstrated by analyzing a set of infant formula and infant cereals; similar results were obtained with the LC-MS method and reference HPLC methods.

Determination of alpha-tocopherol in infant foods by liquid chromatography combined with atmospheric pressure chemical ionisation mass spectrometry

A novel, sensitive and specific method for the quantification of alpha-tocopherol in two infant foods (milk and cereals) using liquid chromatography on-line with positive atmospheric pressure chemical ionisation mass spectrometry detection (LC/APCI-MS) has been developed. The samples were first saponified in order to eliminate fats and to transform tocopherol esters into free tocopherol, followed up by a liquid-liquid extraction of the analyte in petroleum benzine/diisopropyl ether (75:25, v/v) prior to injection onto the LC system. For the quantification, deuterium-labelled tocopherol was used as internal standard and the samples were monitored in selected ion monitoring (SIM) mode. Calibration curves between 1-40 microg/mL of alpha-tocopherol showed a good linear correlation (r(2) = 0.99994), and the detection limit was determined to be 2.5 ng/mL. The within-day and between-day precision were determined for several dietetic infant formulae and certified reference samples, and found to be below 3.5%. The accuracy determined on a Nestlé reference sample (milk powder) was calculated to be 115.2 +/- 1.2%, which confirms the robustness of the proposed method. This study shows that single quadrupole LC/MS can be applied for the quantification of vitamins in food and the method offers better sensitivity and selectivity than traditional method such as LC-UV. This would simplify the preparation of the food samples and consequently enhance the vitamin analysis throughput in the food area.

Investigation of bradykinin metabolism in human and rat plasma in the presence of the dual ACE/NEP inhibitors GW660511X and omapatrilat

Several studies have suggested that the accumulation of bradykinin, or that of one its metabolites BK1-8, is involved in the occurrence of side effects such as AE associated with the use of various ACEi. In this work a novel approach combining HPLC-UV on-line with oaTOF-MS and ICPMS was applied to investigate in human and rat plasma the metabolism of labelled BK (79/81 Br-Phe5) BrBK in the presence of two new dual ACE/NEP inhibitors (GW660511X and omapatrilat) currently under clinical trial. In human plasma the BrBK half-life values in the absence or in the presence of GW660511X (3.8 microM) or omapatrilat (32 nM) were 38.7 +/- 2.4, 51.2 +/- 4.7 and 114.7 +/- 9.3 min, respectively and BrBK was degraded into BrBK1-8, BrBK1-7, BrBK1-5 and Br-Phe. In the presence of inhibitors, however, the levels of these resultant metabolites were different. Unlike GW660511X, omapatrilat abolished the production of BrBK1-5 and BrBK1-7, suggesting a better ACE inhibition effect over GW660511X as no NEP activity was found. In addition the production of BrBK1-8 was enhanced in the presence of these inhibitors with a greater accumulation being observed with omapatrilat. The production of Br-Phe5 was reduced with GW660511X while no significant change was observed with omapatrilat after 4 h of incubation. In rat plasma the BrBK half-life values in the absence or in the presence of GW660511X (530 nM) or omapatrilat (50 nM) were 9.31 +/- 1.7, 22.06 +/- 3.1 and 25.3 +/- 1.7 min, respectively and BrBK was degraded into BrBK1-8, BrBK1-7, BrBK1-5 and Br-Phe5 plus BrBK2-9, BrBK4-8 and BrBK2-8 metabolites not found in human plasma. GW660511X and omapatrilat reduced the production of BrBK1-5 and BrBK1-7 with more effect being observed with omapatrilat. GW660511X and omapatrilat increased the production of both BrBK1-8 and Br-Phe5 but not that of BrBK4-8 and BrBK2-8. This study shows that the potency of GW660511X in comparison with omapatrilat is more than 100-fold lower in human, but less than 10-fold lower in rat plasma, suggesting that rat may not be a suitable in vivo model for the evaluation of ACE/NEP inhibition in relation to effects in humans.

The determination of protein phosphorylation on electrophoresis gel blots by laser ablation inductively coupled plasma-mass spectrometry

Laser ablation interfaced with inductively coupled plasma-mass spectrometry is described as a new method to determine the presence of phosphorylated proteins on electrophoresis gel blots. The method was applied to the phosphoprotein beta-casein with good detection levels being observed at 16 pmole. Attempts at using the technique to detect beta-casein on electrophoresis gels are also described.

Study of bradykinin metabolism in human and rat plasma by liquid chromatography with inductively coupled plasma mass spectrometry and orthogonal acceleration time-of-flight mass spectrometry

Bradykinin is a small peptide that acts mainly as a hormone by activating specific receptors that confer protection against the development of hypertension. The efficacy of bradykinin is influenced by the activities of various kininases present in plasma and blood. In this study, both human and rat plasma were incubated with a labelled form of bradykinin (at 4 and 12.5 microM), that will be referred to as bromobradykinin. The metabolic fate of bromobradykinin was monitored by liquid chromatography coupled to an orthogonal acceleration time-of-flight mass spectrometer (oaTOF). Quantification measurements of the bromine-containing metabolites were performed on-line, via flow splitting, by inductively coupled plasma mass spectrometry (ICPMS). The data obtained highlighted that the mechanism(s) of bradykinin metabolism in human and rat plasma are different, with the metabolism of bradykinin in rat plasma being much more aggressive than that observed in human plasma. In addition to the known bradykinin metabolites, e.g. [1,5], [1,7] from ACE, [1,8] from carboxypeptidase and [2,9] from aminopeptidase activity, we have identified the presence of new bradykinin metabolites in both human and rat plasma. These have been identified as fragment [5], the amino acid phenylalanine, which was present in both the human and rat plasma and the fragments [2,8] and [4,8] in rat plasma. To our knowledge it is the first time that these fragments have been recorded in human and rat plasma. The occurrence of these new fragments provides evidence for the presence of potentially new enzymes and mechanisms of bradykinin metabolism. The method described here provides a powerful technique for monitoring the activity of the many kininases involved in bradykinin metabolism such as ACE (angiotensin I converting enzyme), carboxypeptidase N and aminopeptidase P. In addition, this procedure could be used as a screening assay for selecting and monitoring the actions of inhibitors of the enzymes implicated in bradykinin metabolism directly in plasma or serum.

Differential isotopic mass splitting as a mass spectrometric tool for identifying protease substrates

A method is described whereby stable isotopic signatures were partially incorporated into both termini of a peptide sequence giving rise to a characteristic cluster of four peaks in the mass spectral analysis. Cleavage of this peptide by a protease between the labeled positions generates two fragments both displaying their own individual signature peaks. The event of protease cleavage of the peptide was monitored by the changes in clusters within the spectrum. We believe that this technique could be used to aid the discovery of new cleavage substrates for proteases. Additionally, the analysis can be automated with dedicated software designed to select and interpret the data since all peaks of interest contain predefined signatures and can be easily distinguished from background noise.

Chemical instability and methods for measurement of cisplatin adducts formed by interactions with cysteine and glutathione

Reactions between cisplatin or its aquated species and L-cysteine (L-cys) or glutathione (GSH) were studied in vitro using liquid chromatography on-line with inductively coupled plasma mass spectrometry (LC-ICPMS) and/or electrospray ionization mass spectrometry (LC-MS) in order to obtain information on the mechanisms occurring in treated patients. Reaction between cisplatin and L-cys yielded initially 4 adducts of which only 2 were stable and detectable after 24 hours incubation; their structures corresponded to bis-platinum cysteinyl adducts. Reaction of cisplatin with GSH proceeded via the formation of at least 11 glutathione-platinum adducts (G1 - G11) which underwent parallel reactions within 24 hours of incubation, probably to form higher molecular weight species. Of the 11 adducts, only 2, G3 and G7, whose structures correspond to [Pt(NH3)2Cl]2(SG) and [Pt(NH3)2OH]2(SG) were still present in the reaction mixture after 24 hours incubation. This study shows that GSH, and to a lesser extent L-cys, incubated with cisplatin in vitro forms unstable and reactive platinum compounds and that LC-ICPMS and LC-MS are 2 complementary techniques suitable for the study of organometallic compounds.

Comparison of the reactivity of oxaliplatin, pt(diaminocyclohexane)Cl2 and pt(diaminocyclohexane1)(OH2)2(2+) with guanosine and L-methionine

The initial rates of reactivity of oxaliplatin, its metabolites Pt(dach)Cl2 and Pt(dach)(OH2)2(2+) with guanosine and L-met in water, NaCl and phosphate were compared. Versus guanosine, the most reactive molecule was Pt(dach)(OH2)2(2+), about 40 fold that of oxaliplatin, the least reactive was Pt(dach)Cl2, Versus L-met, Pt(dach)(OH2)2(2+), was also the most reactive species but only about 2 fold more reactive than Pt(dach)Cl2 and oxaliplatin. Pt(dach)(OH2)2(2+) was approximately 3 fold less reactive versus methionine than guanosine whereas oxaliplatin and Pt(dach)Cl2 were about seven fold more reactive versus methionine than guanosine. Thus, the three platinum compounds oxaliplatin, Pt(dach)Cl2 and Pt(dach)(OH2)2(2+) react with L-met but only the Pt(dach)(OH2)2(2+) has a high reactivity with guanosine. Oxaliplatin, which is stable in water, has to be transformed in the presence of chloride in chloro-derivatives which are aquated to become active particularly versus guanosine. These data demonstrate that oxaliplatin has similarities with cisplatin in terms of chloride versus water coordination and in terms of dependence on chloride concentration for transformations.

Early biotransformations of oxaliplatin after its intravenous administration to cancer patients

This article deals with the fate of oxaliplatin 1 and 3 h after its i.v. administration (130 mg/m(2)) to three patients. Its binding to plasma proteins and penetration into red blood cells were monitored by chromatography on-line with inductively coupled plasma mass spectrometry. Oxaliplatin biotransformations in plasma ultrafiltrate (PUF) and in urine were studied by chromatography coupled to inductively coupled plasma mass spectrometry or to electrospray ionization mass spectrometry. In plasma, four platinum (Pt) compounds were found. The peaks at 200 and 160 kDa corresponding to gamma-globulins contained 40% of the Pt bound; the peak at 60 kDa corresponding to albumin contained 40% of the Pt found. The peak <2 kDa could correspond to oxaliplatin, to its degradation products, or to adducts between Pt compounds and low-molecular-weight species such as glutathione, L-methionine, and L-cysteine. In PUF and urine, oxaliplatin itself, its degradation products, Pt(dach)Cl(2), [Pt(dach)(OH(2))Cl](+), and species that have the same retention times as Pt(dach)(methionine) and [Pt(dach)](2)(glutathione) were found. One hour after infusion, oxaliplatin in PUF and urine represented 12 and 50% of the total Pt, respectively. Three hours after infusion, oxaliplatin, undetectable in PUF, represented 10% of total Pt in urine. Inside red blood cells, two Pt compounds were found. The Pt peak at 60 kDa corresponding to hemoglobin and the peak <2 kDa corresponding to low-molecular species contained, respectively, 60% and 40% of Pt found. This study demonstrates that in the first hours after its infusion, oxaliplatin, in addition to other Pt compounds, is present in plasma and urine and that Pt is bound to albumin, gamma-globulins, and hemoglobin.

Mechanisms of reaction of L-methionine with carboplatin and oxaliplatin in different media: a comparison with cisplatin

The activity of platinum compounds is dependent on nucleophile substitution reactions. In this paper, we study the reactivity of L-met with carboplatin, oxaliplatin and cisplatin by following with HPLC-UV the concentration of L-met and by characterizing the resulting adducts with LC-MS. In the absence of NaCl, in water, the initial rate at which L-met concentration decreases with cisplatin, oxaliplatin and carboplatin is 0.25 +/- 0.007, 0.057 +/- 0.01 and 0.17 +/- 0.02 mM h(-1), respectively. In phosphate buffer this rate is 0.056 +/- 0.009 for cisplatin, 0.019 +/- 0.001 and 0.13 +/- 0.02 for carboplatin and oxaliplatin, respectively. Reactions of L-met with cisplatin occurred via its conversion into monoaqua species in water and into phosphato-derivatives (AP) in phosphate buffer but finally the same methionine-platinum adducts M2 [(NH3)2(met)]Pt, M4 and M5 [(met)2]Pt were characterized. Reaction of carboplatin with L-met occurred via the formation of M0 [(NH3)2(met)(CBDCA)]Pt whose structure is consistent with the direct interaction of L-met with carboplatin. However, the same final products as those found with cisplatin were characterized. The reaction of oxaliplatin with L-met proceeded through a mechanism similar to that of carboplatin to give M7 [(met)(DACH)]Pt. In the presence of NaCl, cisplatin directly reacted with L-met to yield at least five methionine-platinum adducts. The reaction of carboplatin gave the same adducts suggesting its transformation into cisplatin. The reaction of oxaliplatin with L-met occurred via the formation of aquated species A [(OH)(Cl)(DACH)]Pt which readily underwent reaction with L-met to form M6 [(met)(Cl)(DACH)]Pt and M7. This study shows that the reactivity of cisplatin, carboplatin and oxaliplatin is dependent on the media in which they occur. The discrepancy between their reactions with L-met could partly explain their therapeutic differences.