Investigation of two-dimensional high performance liquid chromatography approaches for reversed phase resolution of warfarin and hydroxywarfarin isomers

Bioactivation and reactivity research advances - 2023 year in review

Advances in the field of bioactivation have significantly contributed to our understanding and prediction of drug-induced liver injury (DILI). It has been established that many adverse drug reactions, including DILI, are associated with the formation and reactivity of metabolites. Modern methods allow us to detect and characterize these reactive metabolites in earlier stages of drug development, which helps anticipate and circumvent the potential for DILI. Improved in silico models and experimental techniques that better reflect in vivo environments are enhancing predictive capabilities for DILI risk. Further, studies on the mechanisms of bioactivation, including enzyme interactions and the role of individual genetic differences, have provided valuable insights for drug optimizations. Cumulatively, this progress is continually refining our approaches to drug safety evaluation and personalized medicine.

A Liquid-Liquid Interfacial Strategy for Construction of Electroactive Chiral Covalent-Organic Frameworks with the Aim to Enlarge the Testing Scope of Chiral Electroanalysis

Although electroactive chiral covalent-organic frameworks (CCOFs) are considered an ideal platform for chiral electroanalysis, they are rarely reported due to the difficult selection of suitable precursors. Here, a facile strategy of liquid-liquid interfacial polymerization was carried out to synthesize the target electroactive CCOFs Ph-Py+-(S,S)-DPEA·PF6- and Ph-Py+-(R,R)-DPEA·PF6-. That is, a trivalent Zincke salt (4,4',4″-(benzene-1,3,5-triyl)tris(1-(2,4-dinitrophenyl)pyridin-1-ium)) trichloride (Ph-Py+-NO2) and enantiopure 1,2-diphenylethylenediamine (DPEA) were dissolved in water and chloroform, respectively. The Zincke reaction occurs at the interface, resulting in uniform porosity. As expected, the cyclic voltammetry and differential pulse voltammetry measurements showed that the tripyridinium units of the CCOFs afforded obvious electrochemical responses. When Ph-Py+-(S,S)-DPEA·PF6- was modified onto the surface of a glassy carbon electrode as a chiral sensor, the molecules, which included tryptophan, aspartic acid, serine, tyrosine, glutamic acid, mandelic acid, and malic acid, were enantioselectively recognized in the response of the peak current. Very importantly, the discriminative electrochemical signals were derived from Ph-Py+-(S,S)-DPEA·PF6-. The best peak current ratios between l- and d-enantiomers were in the range of 1.31-2.68. Besides, a good linear relationship between peak currents and enantiomeric excess (ee) values was established, which was successfully harnessed to determine the ee values for unknown samples. In a word, the current work provides new insight and potential of electroactive CCOFs for enantioselective sensing in a broad range.

Separation of chiral and achiral impurities in paroxetine hydrochloride in a single run using supercritical fluid chromatography with a polysaccharide stationary phase

Separating paroxetine hydrochloride and its impurities using conventional reversed-phase liquid chromatography (RPLC) is challenging due to their highly similar structures. In the present study, a rapid, simple, sensitive and environmentally friendly method was developed for the determination of chiral and achiral impurities in raw materials of paroxetine hydrochloride using chiral supercritical fluid chromatography (SFC). The impacts of chiral stationary phases (CSPs), mobile phases, column temperature and back pressure on the retention and separation of analytes were comprehensively evaluated. After method optimization, a satisfying result was obtained on a cellulose tris-(3-chloro-4-methylphenylcarbamate) stationary phase in 4.0 min using 70% CO₂ and 20 mM ammonium acetate in 30% methanol as the mobile phase. Molecular docking was further performed to understand the interactions between the analytes and CSP. The results suggested that hydrogen bonding and π-π interactions were the dominant interactions. The affinity given by the software was in good agreement with the elution order and free energy (△G) values obtained from van't Hoff equations. The results of molecular docking also provide insights into the different retentions of N-methylparoxetine at different temperatures. The results of method validation revealed that the method was sensitive with a limit of detection of approximately 0.05 μg·mL^-1 (corresponding to approximately 0.005% paroxetine hydrochloride in the sample solution). The relative standard deviations (RSDs) of precision and intra-assay precision were all less than 2.0%, and the recoveries of the method were 93.8~105.3% with RSDs less than 3.0%. The chiral and achiral RPLC methods included in the Chinese pharmacopoeia and the SFC method proposed in this study were simultaneously used to determine the impurity content in the raw materials of paroxetine hydrochloride. The results showed that impurities that cannot be detected by the reference method can be accurately quantified using the SFC method. In addition, the SFC method has advantages in terms of throughput, analysis cost and simplicity. This study can provide a reference for further research of impurities in paroxetine hydrochloride and promote the application of chiral SFC in the rapid separation of structurally similar compounds.

Mapping the Separation Landscape in Two-Dimensional Liquid Chromatography: Blueprints for Efficient Analysis and Purification of Pharmaceuticals Enabled by Computer-Assisted Modeling

Recent developments in two-dimensional liquid chromatography (2D-LC) now make separation and analysis of very complex mixtures achievable. Despite being such a powerful chromatographic tool, current 2D-LC technology requires a series of arduous method development activities poorly suited for a fast-paced industrial environment. Recent introductions of new technologies including active solvent modulation and a support for multicolumn 2D-LC are helping to overcome this stigma. However, many chromatography practitioners believe that the lack of a systematic way to effectively optimize 2D-LC separations is a missing link in securing the viability of 2D-LC as a mainstay for industrial applications. In this work, a computer-assisted modeling approach that dramatically simplifies both offline and online 2D-LC method developments is introduced. Our methodology is based on mapping the separation landscape of pharmaceutically relevant mixtures across both first (¹D) and second (²D) dimensions using LC Simulator (ACD/Labs) software. Retention models for ¹D and ²D conditions were built using a minimal number of multifactorial modeling experiments (2 × 2 or 3 × 3 parameters: gradient slope, column temperature, and different column and mobile phase combinations). The approach was first applied to online 2D-LC analysis involving achiral and chiral separations of complex mixtures of enantiomeric species. In these experiments, the retention models proved to be quite accurate for both the ¹D and ²D separations, with retention time differences between experiments and simulations of less than 3.5%. This software-based concept was also demonstrated for offline 2D-LC purification of drug substances.

Combination index of the concentration and in vivo antagonism activity of racemic warfarin and its metabolites to assess individual drug responses

The present study was undertaken to examine whether in vivo vitamin K epoxide reductase complex 1 (VKOR) "actual" antagonism activity, calculated by the concentrations and the reported anticoagulant activities of the R- and S-warfarin enantiomers and their metabolites, correlates with the weekly dose of warfarin. Five patients under palliative care were enrolled in our study and 20 serum samples were analyzed by an enantioselective high-performance liquid chromatography-ultraviolet detection method. In vivo VKOR inhibition activities of S-warfarin, R-warfarin, 7- and 10-hydroxywarfarin were calculated as the ratio of drug or metabolite concentration to the IC₅₀. The mean drug concentrations (± SD) of S- and R-warfarin, 7-hydroxywarfarin and 10-hydroxywarfarin were 334 ± 154 ng/ml, 370 ± 115 ng/ml, 42 ± 15 ng/ml and 80 ± 44 ng/ml, respectively. Then, in vivo VKOR actual antagonism activities of S- and R-warfarin, 7-hydroxywarfarin and 10-hydroxywarfarin were calculated. Good correlation (R² = 0.69-0.72) was obtained between the weekly warfarin dose and the ratios of INR/actual antagonism activity, while poor correlation was observed between the weekly warfarin dose and INR (R² = 0.32) or the activities (R² = 0.17-0.21). Actual antagonism activities along with the INR correlated well with the warfarin dose. This parameter may be useful for predicting or altering warfarin doses, although further verification in a larger study is required.

High throughput analysis enables high throughput experimentation in pharmaceutical process research

High throughput experimentation has become widely used in the discovery and development of new medicines.

Enantioselective multiple heartcut two-dimensional ultra-high-performance liquid chromatography method with a Coreshell chiral stationary phase in the second dimension for analysis of all proteinogenic amino acids in a single run

A multiple heartcut (MHC) 2D-UHPLC method with UV detection has been developed for the enantioselective analysis of complex amino acid mixtures in a single run. The MHC method is based on an achiral gradient RPLC separation with 1.8 μm C18 phase (100 × 2.1 mm ID column) in the first dimension (¹D) and enantioselective isocratic separation on a tert-butylcarbamoylquinine-based 2.7 μm Coreshell particle column (50 × 3 mm ID) in the second dimension (²D). Pre-column derivatization has been performed with Sanger's reagent (2,4-dinitrofluorobenzene) yielding chromogenic 2,4-dinitrophenylated amino acids (DNP-AAs). Heartcuts of 40 μL fractions of the ¹D peaks were sampled into the ²D system via a two-position four-port dual valve connected to two loop decks each equipped with six 40 μL parking loops. Using this setup, 25 amino acids (20 proteinogenic plus allo-Thr, allo-Ile, homoserine (Hse), Orn, β-Ala) have been analyzed enantioselectively in a fully automated manner with a single chiral column within 130 min total run time (¹D and ²D). All ²D separations together took 101.5 min (29 cuts with 3.5 min run time each) and thus the total analysis time was quite efficiently utilized. Faster separations were restricted by some software constraints which did not allow to adjust run times in ²D individually. The practical utility of this enantioselective MHC method is documented by application for the absolute configuration determination of the amino acids in gramicidin and bacitracin. Further optimizations should lead to a generic enantioselective amino acid analyzer for the quality control of synthetic peptides and the structural characterization of non-ribosomal peptides.

Ultrafast Chiral Chromatography as the Second Dimension in Two-Dimensional Liquid Chromatography Experiments

Chromatographic separation and analysis of complex mixtures of closely related species is one of the most challenging tasks in modern pharmaceutical analysis. In recent years, two-dimensional liquid chromatography (2D-LC) has become a valuable tool for improving peak capacity and selectivity. However, the relatively slow speed of chiral separations has limited the use of chiral stationary phases (CSPs) as the second dimension in 2D-LC, especially in the comprehensive mode. Realizing that the recent revolution in the field of ultrafast enantioselective chromatography could now provide significantly faster separations, we herein report an investigation into the use of ultrafast chiral chromatography as a second dimension for 2D chromatographic separations. In this study, excellent selectivity, peak shape, and repeatability were achieved by combining achiral and chiral narrow-bore columns (2.1 mm × 100 mm and 2.1 mm × 150 mm, sub-2 and 3 μm) in the first dimension with 4.6 mm × 30 mm and 4.6 mm × 50 mm columns packed with highly efficient chiral selectors (sub-2 μm fully porous and 2.7 μm fused-core particles) in the second dimension, together with the use of 0.1% phosphoric acid/acetonitrile eluents in both dimensions. Multiple achiral × chiral and chiral × chiral 2D-LC examples (single and multiple heart-cutting, high-resolution sampling, and comprehensive) using ultrafast chiral chromatography in the second dimension are successfully applied to the separation and analysis of complex mixtures of closely related pharmaceuticals and synthetic intermediates, including chiral and achiral drugs and metabolites, constitutional isomers, stereoisomers, and organohalogenated species.

The medicinal chemist's toolbox for late stage functionalization of drug-like molecules

The advent of modern C–H functionalization chemistries has enabled medicinal chemists to consider a synthetic strategy, late stage functionalization (LSF), which utilizes the C–H bonds of drug leads as points of diversification for generating new analogs.

Simultaneous and stereospecific analysis of warfarin oxidative metabolism using 2D LC/Q-TOF

Background: Warfarin is a widely used racemic anticoagulant with narrow therapeutic range and wide interindividual response to treatment. This is due to the extensive and differential clearance of R- and S-warfarin with the involvement of several polymorphic CYP450 enzymes resulting in the formation of several stereoisomeric oxidative metabolites. Results: A stereospecific 2DLC/Q-TOF method was developed for the simultaneous identification and quantitation of hydroxylated warfarin metabolites from a single sample analysis. Using this method metabolites from rat microsomal and plated hepatocyte incubations with R-, S- and (R/S)-warfarin were estimated. Conclusion: Multiheart cutting with high resolution MS and MS/MS analysis is suggested as a viable approach for achiral-chiral separation of metabolites of warfarin and other chiral or prochiral drugs.