Identification of endogenous carbonyl steroids in human serum by chemical derivatization, hydrogen/deuterium exchange mass spectrometry and the quantitative structure-retention relationship

Steroids are tetracyclic aliphatic compounds, and most of them contain carbonyl groups. The disordered homeostasis of steroids is closely related to the occurrence and progression of various diseases. Due to high structural similarity, low concentrations in vivo, poor ionization efficiency, and interference from endogenous substances, it is very challenging to comprehensively and unambiguously identify endogenous steroids in biological matrix. Herein, an integrated strategy was developed for the characterization of endogenous steroids in serum based on chemical derivatization, ultra-performance liquid chromatography quadrupole Exactive mass spectrometry (UPLC-Q-Exactive-MS/MS), hydrogen/deuterium (H/D) exchange, and a quantitative structure-retention relationship (QSRR) model. To enhance the mass spectrometry (MS) response of carbonyl steroids, the ketonic carbonyl group was derivatized by Girard T (GT). Firstly, the fragmentation rules of derivatized carbonyl steroid standards by GT were summarized. Then, carbonyl steroids in serum were derivatized by GT and identified based on the fragmentation rules or by comparing retention time and MS/MS spectra with those of standards. H/D exchange MS was utilized to distinguish derivatized steroid isomers for the first time. Finally, a QSRR model was constructed to predict the retention time of the unknown steroid derivatives. With this strategy, 93 carbonyl steroids were identified from human serum, and 30 of them were determined to be dicarbonyl steroids by the charge number of characteristic ions and the number of exchangeable hrdrogen or comparing with standards. The QSRR model built by the machine learning algorithms has an excellent regression correlation, thus the accurate structures of 14 carbonyl steroids were determined, among which three steroids were reported for the first time in human serum. This study provides a new analytical method for the comprehensive and reliable identification of carbonyl steroids in biological matrix.

Trace quantification of GL-V9 and its glucuronide metabolites (5-O-glucuronide GL-V9) in Beagle dog plasma by UPLC-MS/MS and its application to a pharmacokinetic study

GL-V9, a new synthetic flavonoid derived from wogonin, has shown beneficial biological functions. In this study, accurate and sensitive UPLC-MS/MS methods were developed and validated for the quantification of GL-V9 and its glucuronide metabolite (5-O-glucuronide GL-V9) in Beagle dog plasma. The chromatographic separation was performed on a C8 column (ACE Excel 5 C8 50×3.0 mm) using 0.1% formic acid and acetonitrile were used as mobile phase. Mass detection was performed on a triple quadrupole tandem mass spectrometer equipped with an electrospray ionization (ESI) interface operating in positive ion mode. Quantitative analysis was performed in multiple reaction monitoring (MRM) mode with the transitions of m/z 410.2→126.1 for GL-V9, m/z 586.3→410.0 for 5-O-glucuronide GL-V9 and m/z 180.0→110.3 for phenacetin (internal standard), respectively. The calibration curves for GL-V9 and 5-O-glucuronide GL-V9 showed excellent linearity over the concentration range of 0.5-500 ng/mL with correlation coefficient greater than 0.99. The intra- and inter-day accuracies were within 99.86% to 109.20% for GL-V9 and 92.55% to 106.20% for 5-O-glucuronide GL-V9, respectively. The mean recovery was 88.64% ± 2.70% for GL-V9, and 92.31% ± 6.28% for 5-O-glucuronide GL-V9, respectively. The validated method was successfully applied to the pharmacokinetic study in Beagle dogs after oral and intravenous administration. The oral bioavailability of GL-V9 was approximately 2.47%~4.35% in Beagle dogs and reached steady state on the fifth day after repeated dosing.

Simultaneous determination of daidzein, its prodrug and major conjugative metabolites in rat plasma and application in a pharmacokinetic study

The developed method successfully validated that the synthesized prodrug improved the bioavailability of DAN by reducing its phase II metabolites.

Development of an UPLC-MS/MS method coupled with in-source CID for quantitative analysis of PEG-PLA copolymer and its application to a pharmacokinetic study in rats

Poly(ethylene glycol)-block-poly(lactic acid) (PEG-PLA) is a biocompatible and amphiphilic block copolymer composed of a hydrophilic PEG block and a hydrophobic PLA block, which can self-assemble into micelles in water. It is one of the most commonly used biodegradable polymers for drug encapsulation, drug solubilization and drug delivery. Due to the complexity and heterogeneity of PEG-PLA, the precise analysis of this polymer is a great challenge. This study reports an application of an UPLC tandem mass spectrometry coupled with in-source collision induced dissociation (CID) technique for the analysis of a model compound mPEG2000-PDLLA2500-COOH, which could be dissociated in source and generate a series of fragment ions corresponding to its subunits. These surrogate ions including PLA-specific and PEG-specific fragment ions could be further broken into specific product ions in collision cell. Finally, the ion transition at m/z 505.0 → 217.0 was selected for the quantitation of mPEG2000-PDLLA2500-COOH. This assay achieved a lower limit of quantitation (LLOQ) of 0.05 μg/mL with only 30 μL rat plasma. The linear range is 0.05 to 5 μg/mL. Intraday and interday accuracy and precision were within ±12.1%. The method was successfully applied to the pharmacokinetic study of mPEG2000-PDLLA2500-COOH in rats. The results revealed that LC-MS/MS coupled with in-source CID is a sensitive and specific strategy for analysis of PEG-PLA. This method can be potentially extended to the analysis of other pharmaceutical polymer excipients.

Development of a method by UPLC-MS/MS for the quantification of tizoxanide in human plasma and its pharmacokinetic application

BACKGROUND

Nitazoxanide (NTZ) is used for the treatment of gastrointestinal tract colonization by anaerobic bacteria, viruses and other pathogens that represent a major cause of morbidity in Latin America. The aim of the present work was to develop and validate a UPLC-MS/MS method for the selective quantification of tizoxanide (TZN, the major metabolite of NTZ) in human plasma using niclosamide as internal standard; and examine its pharmacokinetic application in healthy volunteers. Nine male subjects received a single oral dose of a NTZ 500-mg tablet under fasting conditions.

RESULTS

The method was linear between 0.1 and 10 µg/ml and capable of separating signals from free-TZN and those delivered by in-source collision-induced dissociation of TZN-glucuronide, quantifying it with accuracy and precision. Mean maximum plasma concentration was 6.79 µg/ml and was reached at 2.4 h post-dose.

CONCLUSION

The method was validated, fulfilling regulatory guidelines. Results suggest low pharmacokinetic variability in the assayed population.