Determination of xanomeline in human plasma by ion-spray tandem mass spectrometry

Identification of Epigallocatechin-3-Gallate (EGCG) from Green Tea Using Mass Spectrometry

In an era where humanity is reinstating its lost hope and expectation on natural products, green tea occupies quite a position for what it has proven to be, in its endeavors for human welfare and health. Epigallocatechin-3-gallate (EGCG) is the key to the vast biological activities of green tea. Green tea is no longer in the backdrop; it has emerged as the most viral, trending bioactive molecule when it comes to health benefits for human beings. This review focuses on the use of various analytical techniques for the analysis of EGCG. That which has been achieved so far, in terms of in vitro, pure component analysis, as well as those spikes in biological fluids and those in vivo in animal and human samples, was surveyed and presented. The use of MS-based techniques for the analysis of EGCG is elaborately reviewed and the need for improvising the applications is explained. The review emphasizes that there is plenty of room to explore matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) applications in this subject area.

Applications of LC-MS in PET radioligand development and metabolic elucidation

Positron emission tomography (PET) is a very sensitive molecular imaging technique that when employed with an appropriate radioligand has the ability to quantititate physiological processes in a non-invasive manner. Since the imaging technique detects all radioactive emissions in the field of view, the presence and biological activity of radiolabeled metabolites must be determined for each radioligand in order to validate the utility of the radiotracer for measuring the desired physiological process. Thus, the identification of metabolic profiles of radiolabeled compounds is an important aspect of design, development, and validation of new radiopharmaceuticals and their applications in drug development and molecular imaging. Metabolite identification for different chemical classes of radiopharmaceuticals allows rational design to minimize the formation and accumulation of metabolites in the target tissue, either through enhanced excretion or minimized metabolism. This review will discuss methods for identifying and quantitating metabolites during the pre-clinical development of radiopharmaceuticals with special emphasis on the application of LC/MS.

Comparison of the pharmacokinetics of different analogs of 11C-labeled TZTP for imaging muscarinic M2 receptors with PET

INTRODUCTION

The only radiotracer available for the selective imaging of muscarinic M2 receptors in vivo is 3-(3-(3-[18F]fluoropropyl)thio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridine) ([18F]FP-TZTP). We have prepared and labeled 3-(3-(3-fluoropropylthio)-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-methylpyridne (FP-TZTP, 3) and two other TZTP derivatives with 11C at the methylpyridine moiety to explore the potential of using 11C-labeled FP-TZTP for positron emission tomography imaging of M2 receptors and to compare the effect of small structural changes on tracer pharmacokinetics (PK) in brain and peripheral organs.

METHODS

11C-radiolabeled FP-TZTP, 3-(3-propylthio)-TZTP (6) and 3,3,3-(3-(3-trifluoropropyl)-TZTP (10) were prepared, and log D, plasma protein binding (PPB), affinity constants, time-activity curves (TACs), area under the curve (AUC) for arterial plasma, distribution volumes (DV) and pharmacological blockade in baboons were compared.

RESULTS

Values for log D, PPB and affinity constants were similar for 3, 6 and 10. The fraction of parent radiotracer in the plasma was higher and the AUC lower for 10 than for 3 and 6. TACs for brain regions were similar for 3 and 6, which showed PK similar to the 18F tracer, while 10 showed slower uptake and little clearance over 90 min. DVs for 3 and 6 were similar to the 18F tracer but higher for 10. Uptake of the three tracers was significantly reduced by coinjection of unlabeled 3 and 6.

CONCLUSION

Small structural variations on the TZTP structure greatly altered the PK in brain and behavior in blood with little change in the log D, PPB or affinity. The study suggests that 11C-radiolabeled 3 will be a suitable alternative to [18F]FP-TZTP for translational studies in humans.

Uptake of Diet Resveratrol into the Human Low-Density Lipoprotein. Identification and Quantification of Resveratrol Metabolites by Liquid Chromatography Coupled with Tandem Mass Spectrometry

In this paper, a sensitive, precise, and selective analytical method has been developed for the identification and quantification of resveratrol metabolites in human low-density lipoprotein (LDL) after moderate consumption of red wine, using high-performance liquid chromatography electrospray in tandem mass spectrometry (LC-ESI-MS/MS). From different extraction procedures tested, solid-phase extraction was selected to minimize matrix effects reaching the highest sensitivity. Standard calibration curves prepared in human LDL for trans-resveratrol were linear over a range of 0.44-438.59 pmol/mL. The accuracy and interassay precision of this LC-MS/MS assay for resveratrol showed a coefficient of variation of <6.0%. The method allows detection and quantification limits for resveratrol in LDL at 0.15 and 0.44 pmol/mL, respectively. Results to date indicate that resveratrol metabolites were incorporated into LDL after a moderate intake of red wine. The metabolites identified in LDL were trans-resveratrol-3-O-glucuronide, cis-resveratrol-3-O-glucuronide, and cis-resveratrol-3-O-glucoside, as well as free trans-resveratrol. To our knowledge, it is the first time that a polyphenol from red wine, specifically resveratrol, has been identified in human LDL after moderate intake of red wine. Furthermore, these findings suggest that these compounds may deliver their antioxidant effect to LDL.

Determination of ragaglitazar, a novel dual acting peroxisome proliferator-activated receptor (PPAR) alpha and -gamma agonist, in human plasma by high-performance liquid chromatography coupled with tandem mass spectrometry

A sensitive and specific LC/MS/MS method has been developed and validated for determination of ragaglitazar (NNC 61-0029 or DRF 2725) in human plasma. After solid-phase extraction (SPEC((R)) PLUS C(8)) of plasma, separation was performed on a Symmetry Shield RP8 column (mobile phase: acetonitrile: 10 mM ammonium acetate, pH 5.6 (40:60 v/v)). Two ranges were validated having LLOQs of either 0.500 or 100 ng/ml and linearity up to either 500 or 50000 ng/ml. The intra-assay precision and accuracy were 1.1% to 15.7% and 85.8% to 118.2% (range 0.500-500 ng/ml) and 2.0% to 8.8% and 92.9% to 104.8% (range 100-50000 ng/ml). The method was applied for determination of ragaglitazar in plasma from phase 1 and 2 clinical studies.

Demonstration of direct bioanalysis of drugs in plasma using nanoelectrospray infusion from a silicon chip coupled with tandem mass spectrometry

Quantitative bioanalysis by direct nanoelectrospray infusion coupled to tandem mass spectrometry has been achieved using an automated liquid sampler integrated with an array of microfabricated electrospray nozzles allowing rapid, serial sample introduction (1 min/ sample). Standard curves prepared in human plasma for verapamil (r2 = 0.999) and its metabolite norverapamil (r2 = 0.998) were linear over a range of 2.5-500 ng/ mL. Based on the observed precision and accuracy, a lower limit of quantitation of 5 ng/mL was assigned for both analytes. Sample preparation consisted of protein precipitation with an organic solvent containing the structural analogue gallopamil as an internal standard. Protein precipitation was selected both to maximize throughput and to test the robustness of direct nanoelectrospray infusion. Aliquots of supernatant (10 pL) were transferred to the back plane of the chip using disposable, conductive pipet tips for direct infusion at a flow rate of 300 nL/min. Electrospray ionization occurred from the etched nozzles (30-microm o.d.) on the front of the chip, initiated by a voltage applied to the liquid through the pipet tip. The chip was positioned near the API sampling orifice of a triple quadrupole mass spectrometer, which was operated in selected reaction monitoring mode. Results are presented that document the complete elimination of system carry-over, attributed to lack of a redundant fluid path. This technology offers potential advantages for MS-based screening applications in drug discovery by reducing the time for methods development and sample analysis.

Narrow-bore high-performance liquid chromatography in combination with ionspray tandem mass spectrometry for the determination of the substance P receptor antagonist ezlopitant and its two active metabolites in plasma

A simple, but highly sensitive and specific, assay was developed for the quantitative determination of ezlopitant and its two active metabolites in human plasma using narrow-bore reversed-phase high-performance liquid chromatography (HPLC) coupled with electrospray tandem mass spectrometry (ES-MS-MS). Ezlopitant, its two pharmacologically active metabolites, an alkene analogue (CJ-12 458) and a benzyl alcohol analogue (CJ-12 764), and their corresponding trideuterated internal standards (I.S.), were extracted from plasma with methyl tert.-butyl ether (MTBE). The dried MTBE extracts were reconstituted and analyzed using a narrow-bore (2.1 mm I.D.) YMC basic HPLC column and a mobile phase of acetonitrile-20 mM ammonium acetate, pH 5 (60:40, v/v). Column effluent was monitored by pneumatically assisted electrospray tandem mass spectrometry. Multiple reaction monitoring (MRM) using the parent to product ions was used to quantify ezlopitant and its two active metabolites. The assay exhibited a linear dynamic range of 0.1-100 ng/ml. Average absolute recoveries from plasma were approximately 71, 80 and 99% for ezlopitant and its two active metabolites CJ-12 485 and CJ-12 764, respectively. The precision (RSD %) and accuracy (Deviation %) values for the method were within +/- 12% and +/- 15%, respectively, for all analytes. Sample analysis times were less than 5 min from one injection to the next. The assay proved to be suitable for pharmacokinetics studies.

Signal suppression in electrospray ionization Fourier transform mass spectrometry of multi-component samples

The high resolution, mass range and sensitivity of Fourier transform mass spectrometry (FTMS) suggest that it could be a valuable tool for the quantitative analysis of biomolecules. To determine the applicability of electrospray ionization combined with FTMS to the quantitation of biomolecules in multi-component samples, mixtures of varying compositions and concentrations of cytochrome c, angiotensin II, insulin and chicken egg white lysozyme were examined. The instrument used has an electrospray source with a hexapole trap to accumulate ions for injection into an ion cyclotron resonance mass analyzer. Linear responses for single component samples of angiotensin II and insulin were in the range 0.031-3 microM and those of both cytochrome c and lysozyme were between 0.031 and 1 microM. In examining various mixtures of the proteins with angiotensin II, it was found that the presence of the large molecules suppresses the signal of the smaller molecules. This is suggested to be a result of ion-ion interactions producing selective ion loss from either the hexapole trap or the ion cyclotron resonance mass analyzer trap. More massive, more highly charged ions can collisionally transfer large amounts of translational energy to smaller, less highly charged ions, ejecting the smaller ions from the trap. Mass discrimination effects resulting from the trapping voltage were also examined. It was found that relative signal intensities of ions of different masses depend on trapping voltage for externally produced ions. The effect is most significant for spectra including masses that differ by 30% or more. This suggests that for quantitation all samples and standards be run at a constant trapping potential.

A simple liquid-liquid extraction with hexane for low-picogram determination of drugs and their metabolites in plasma by high-performance liquid chromatography with positive ion electrospray tandem mass spectrometry

Four sensitive, specific and accurate methods, based on high-performance liquid chromatography (HPLC) with positive ion electrospray tandem mass spectrometry (MS/MS) coupled with liquid-Liquid extraction (LLE), have been developed and validated for the low-picogram determination of two drug candidates and a metabolite (compounds I-III) in human, monkey and rat plasma. In the LLE procedure, hexane or a mixture of hexane and methyl t-butyl ether was used to isolate these compounds from plasma of the different species after basification of each biological sample with sodium carbonate. The reconstituted extracts were then injected into a positive ion electrospray LC/MS/MS system for the quantitative analysis. The lower limit of quantitation of the methods ranged from 20 to 200 pg/mL. The use of hexane for the LLE proved to be simple, rapid and reproducible, and provided very clean extracts with little interference. The inter- and intra-day precision for the four methods was within 9%, and the accuracy was in the range 94-107%. The effect of pH on the isomerization of I (E-isomer) to its Z-isomer (II) showed that the rate of isomerization increased with decrease in pH and that there was no isomerization at pH >/=6.

Determination of the substance P receptor antagonist CP-122,721 in plasma by narrow-bore high-performance liquid chromatography-ionspray tandem mass spectrometry

A simple, highly sensitive and specific LC-MS-MS assay was developed for the determination of CP-122,721 (I) in rat and human plasma. I and a structural analog, CP-129,943 (II, internal standard), were extracted from plasma with methyl tert.-butyl ether (MTBE). The dried MTBE extracts were reconstituted and analyzed using a narrow-bore (2.1 mm I.D.) YMC basic HPLC column and a mobile phase of acetonitrile-20 mM ammonium acetate, pH 5 (50:50, v/v). Column effluents were monitored by ionspray tandem mass spectrometry. Multiple reaction monitoring (MRM) using the parent to product ion combinations of m/z 381-->205 and 395-->219 was used to quantitate I and II, respectively. The assay exhibited a linear dynamic range of 0.2-100 ng/ml. Absolute recoveries from plasma were above 80% for both I and II. The precision and accuracy values for the method were within +/-3 and +/-9%, respectively. Sample analysis times were less than 5 min from one injection to the next. The assay has proved to be applicable to the pharmacokinetic study of I in rats.

Quantitative determination of BMS-186716, a thiol compound, in rat plasma by high-performance liquid chromatography-positive ion electrospray mass spectrometry after hydrolysis of the methyl acrylate adduct by the native esterases

During method development in support of non-clinical studies in animal models, BMS-186716 was found to be extremely unstable in blood and plasma. Stabilization of the compound was achieved by reacting the compound with methyl acrylate (MA) in blood, from which the plasma was then prepared. While the resulting BMS-186716-MA adduct was found to be stable in dog plasma, and hence it was used as the basis for the method developed for analysis of dog plasma samples, the BMS-186716-MA adduct was found to be unstable in rat plasma as it was readily hydrolyzed to BMS-186716-acrylic acid (AA) by native esterases found in rat plasma. Although the finding of the instability of BMS-186716-MA in rat plasma was not the result of prospective planning, we were able to successfully develop a quantitative bioanalytical method using BMS-186716-AA as the analyte instead of the originally planned BMS-186716-MA analyte. The standard and quality-control (QC) samples were prepared by spiking blank plasma with BMS-186716-MA, and then allowing them to stand at room temperature for 1 h to convert BMS-186716-MA to BMS-186716-AA. After adding the internal standard BMS-188035-AA, each sample was acidified with HCl and then extracted with methyl tert.-butyl ether. The reconstituted extract was injected into a HPLC-electrospray ionization mass spectrometric system for detection by positive ion electrospray ionization. A lower limit of quantitation (LLQ) of 5 ng/ml was achieved, using 0.1 ml plasma and a standard curve range of 5-5000 ng/ml.

Quantitative determination of BMS186716, a thiol compound, in dog plasma by high-performance liquid chromatography-positive ion electrospray mass spectrometry after formation of the methyl acrylate adduct

As it is extremely unstable in blood, the thiol compound BMS186716 was stabilized by the addition of methyl acrylate (MA) to blood samples. The blood samples were then kept in ice for 10-15 min for completion of the Michael addition reaction to occur between the thiol group of BMS186716 and MA, after which the plasma was separated by centrifugation under refrigeration. For sample analysis, the standard and quality control samples were prepared by spiking blank plasma with the BMS186716-MA adduct. After addition of the internal standard, BMS 188035-MA, each sample was acidified with HCI and then extracted with methyl tert.-butyl ether. Each reconstituted extract was injected into a high-performance liquid chromatography-positive ion electrospray ionization mass spectrometric system. The electrospray condition was chosen to enhance the [M+NH4]+ signal at the expense of the [M+H]+ signal. Monitoring the [M+NH4]+ signal, a lower limit of quantitation of 2.5 ng/ml was achieved, with 0.5 ml plasma. We have thus shown that a sulfhydryl compound (BMS186716) in blood can successfully be stabilized by reacting it with MA and that the adduct produced is adequately stable in blood and plasma to allow the development of a rugged quantitative bioanalytical method.

Quantitation of SR 27417 in human plasma using electrospray liquid chromatography-tandem mass spectrometry: A study of ion suppression

The effect of coeluting matrix compounds on the quantitation of SR 27417 in human plasma using electrospray liquid chromatography-tandem mass spectrometry has been examined. During the method development stage of this assay, plasma samples spiked with the analyte at 100 pg/mL were extracted using three different procedures: a hexane liquid-liquid extraction, an ethyl acetate back-extraction, and a solid phase extraction. Ion intensity of the analyte was found to be related inversely to the percent ionization of coeluting matrix components as evidenced by full scan spectra. The ethyl acetate back-extraction, which contained the fewest coeluting components, resulted in the highest ion intensity for the analyte. An assay comparison was done by using the liquid-liquid hexane and the ethyl acetate back-extractions for sample preparation. Replicate 1-mL samples (n=5) at 11 concentrations from 5 to 2000 pg/mL were extracted and analyzed. The results for the ethyl acetate back-extracted samples were acceptable from 2000 to 5 pg/mL with accuracy ranging from -11.6 to 2.61% of the nominal concentrations. In contrast, the hexane liquid-liquid method had poor accuracy and precision below 20 pg/mL. The difference is explained by suppression of analyte ion intensity. These results are consistent with the current theory of electrospray ionization.

Determination of BMS-186318 in dog, rat and monkey plasma by liquid chromatography-ionspray mass spectrometry

BMS-186318 is a member of the recently discovered "aminodiol" class of HIV protease inhibitors. A simple but sensitive method was developed for the determination of BMS-186318 in dog plasma and then applied to monkey and rat plasma. The compound was extracted from dog plasma with methyl tert-butyl ether at basic pH. The dried extract was reconstituted in mobile phase and injected into a 150 x 2.1 mm i.d. Zorbax Rx-C18 HPLC column. A portion of the effluent was directed into the LC-ionspray MS system, where the [M+H]+ ion of the secondary amine compound was monitored. The HPLC conditions were chosen in order to achieve a short run time and large sample throughput, with both analyte and internal standard eluting within 1.5 min. The liquid-liquid extraction procedure provided very clean extracts so that sufficient signal-to-noise ratio was obtained with single-stage mass spectrometry instead of the more costly tandem mass spectrometry. The required lower limit of quantitation of 2.5 ng ml-1 was easily achieved. The method has also been validated for BMS-186318 in monkey plasma without modification. The method has been modified for rat plasma. Owing to irreproducibility observed when applying the liquid-liquid extraction method to rat plasma, a solid-phase extraction method was developed. The addition of phenylmethylsulfonyl fluoride was necessary to stabilize BMS-186318 in rat blood and plasma.

Rapid quantitative determination of a collagenase inhibitor and its major metabolite by on-line liquid chromatography with ionspray tandem mass spectrometric detection

A rapid, sensitive and specific analytical method has been developed and validated to quantify the collagenase inhibitor N2-(2(5)-[(hydroxycarbamoyl)methyl)-4-methylvaleryl]-N1, 3-dimethyl-L-valin-amide (I) and its major metabolite (II) from plasma and urine. This method employs an automated solid-phase extraction procedure to isolate the analytes and the internal standard from the biological matrix. Reconstituted extracts were analyzed by HPLC-ionspray MS-MS. Chromatography was performed on a 4.6 mm I.D. reversed-phase guard column. The retention times of the analytes and the internal standard were approximately 1.3 min. The assay has a limit of quantification of 5 ng/ml plasma and a limit of detection of 1 ng/ml, based on 100-micro l plasma aliquots. No sample-drying step was required. The standard curves were linear form 5 to 5000 ng/ml using weighted linear regression analysis (1/y2). The intra- and inter-assay precision were better than + or - 10% with intra- and inter-assay accuracies between 95 and 105%. this new HPLC-MS-MS assay procedure for I and II in plasma and urine has proven to be specific, sensitive, accurate and robust, and is being used routinely for the analysis of I in pre-clinical and clinical trial samples. Up to 200 unknowns may be analyzed each 24 h per analyst.

High-performance liquid chromatographic assay for xanomeline, a specific M-1 agonist, and its metabolite in human plasma

A reversed-phase high-performance liquid chromatographic assay (HPLC) was utilized for monitoring xanomeline (LY246708/NNC 11-0232) and a metabolite, desmethylxanomeline, in human plasma. Xanomeline, desmethylxanomeline and internal standard were extracted from plasm with hexane at basic pH. The organic solvent extract was evaporated to dryness with nitrogen and the dried residue was reconstituted with 0.2 M HCl-methanol (50:50, v/v). A Zorbax CN 150 x 4.6 mm I.D., 5-microns column and mobile phase consisting of 0.5% (5 ml/l) triethylamine (TEA) adjusted to pH 3.0 with concentrated orthophosphoric acid-tetrahydrofuran (THF) (70:30, v/v) produced consistent resolution of analytes from endogenous co-extracted plasma components. Column effluent was monitored at 296 nm/0.008 a.u.f.s. and the assay limit of quantification was 1.5 ng/ml. A linear response of 1.5 to 20 ng/ml was sufficient to monitor plasma drug/metabolite concentrations during clinical trials. HPLC assay validation as well as routine assay quality control (QC) samples indicated assay precision/accuracy was better than +/- 15%.