Determination of the R- and S-enantiomers of methylone and ethylone in seized drugs by enantioselective liquid chromatography tandem mass spectrometry analysis

Development and validation of a chiral UPLC-MS/MS method for quantifying S-Oxiracetam and R-Oxiracetam in human plasma, urine and feces: Application to a phase-I clinical pharmacokinetic study

A chiral UPLC-MS/MS method was developed and validated to determine oxiracetam enantiomers in human plasma, urine, and feces. The R-Oxiracetam and S-Oxiracetam were quantified using a CHIRALPAK ®AD3 column at 25 ℃, and the resolution was greater than 3.2. The S-Oxiracetam is the eutomer that isresponsible for the treatment of various brain damage. Isocratic elution was conducted at a flow rate of 0.9 mL/min for 6 min using the mixture of methanol and acetonitrile (methanol:acetonitrile, 15:85) containing 0.3‰ formic acid. The methods showed linearity at the range of 0.5-100 µg/mL for each oxiracetam enantiomer. A comprehensive validation process was carried out, covering aspects including linearity, selectivity, carryover, accuracy, precision, interferences, matrix effect, recovery, dilution integrity and stability in matrix and solution. The validated methods were successfully applied to quantifying R-Oxiracetam and S-Oxiracetam in human plasma, urine, and feces of 12 healthy subjects treated with either a single dose of 2 g S-Oxiracetam injection or 4 g Oxiracetam injection in a phase-I clinical trial. There was no significant difference for plasma pharmacokinetic parameters of S-Oxiracetam between the two regimens (P＞0.05). The S-Oxiracetam and Oxiracetam were primarily eliminated through urine in their original form, with cumulative excretion rates of 92.16% and 85.92%, respectively, within 24 h after administration. Enantiomers interconversion was not observed in the plasma, urine, or feces. The results of this study suggest that replacing 4 g Oxiracetam injection with 2 g S-Oxiracetam injection could offer clinical benefits by lowering the dosage and mitigating potential risks, based on the pharmacokinetic characteristics.

Development of enantioselective high-performance liquid chromatography-tandem mass spectrometry method for quantitative determination of methylone and some of its metabolites in oral fluid

In the present study an enantioselective high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the first time for quantitative determination of the recreational drug of abuse methylone and its major metabolites in oral fluid. The simultaneous chemo- and enantioseparation of methylone and its major metabolites was performed on a polysaccharide-based chiral column based on amylose tris(5-chloro-3-methylphenylcarbamate) as chiral selector (Lux i-Amylose-3) with methanol containing 0.4 % (v/v) aqueous ammonium hydroxide as mobile phase. The time required for enantioselective analysis of methylone and its 2 major metabolites was 15 min. This method was fully validated following the Organization of Scientific Area Committees (OSAC) for Forensic Science guidelines. This method was applied for the enantioselective determination of methylone and its metabolites in oral fluid and enantioselectivity in metabolism and pharmacokinetic of the parent compound and metabolites was observed. While the first enantiomer of methylone was found at higher concentration, both metabolites shown greater concentration for the second enantiomer. The results revealed that MET undergoes an enantioselective biotransformation to its metabolites HMMC and MDC, with S-(-)-MET more rapidly metabolized and eliminated from the body.

Binding studies of synthetic cathinones to human serum albumin by high-performance affinity chromatography

The binding affinity to human serum albumin (HSA) of a series of fourteen synthetic cathinones, new psychoactive substances widely abused, was investigated by high-performance affinity chromatography (HPAC). Zonal elution experiments were conducted to measure the retention times of each synthetic cathinone on an HSA column, which enabled the calculation of the percentage of the drug bound. For some synthetic cathinones, enantioselectivity on HSA was found. To gather information on the HSA binding sites and better understand the chiral recognition mechanisms, enantioresolution of selected cathinones was carried out at a milligram scale through liquid chromatography (LC) with carbamate polysaccharide-based columns. This work was followed by zonal displacement chromatography using known competitors with specific binding sites on HSA, namely (S)-ibuprofen and warfarin. Competition was observed between the tested drugs and both competitors (except for pentedrone with warfarin), which is consistent with an allosteric competition involving a non-cooperative binding mechanism.

Development of Levo-Lansoprazole Chiral Molecularly Imprinted Polymer Sensor Based on the Polylysine-Phenylalanine Complex Framework Conformational Separation

The efficacies and toxicities of chiral drug enantiomers are often dissimilar, necessitating chiral recognition methods. Herein, a polylysine-phenylalanine complex framework was used to prepare molecularly imprinted polymers (MIPs) as sensors with enhanced specific recognition capabilities for levo-lansoprazole. The properties of the MIP sensor were investigated using Fourier-transform infrared spectroscopy and electrochemical methods. The optimal sensor performance was achieved by applying self-assembly times of 30.0 and 25.0 min for the complex framework and levo-lansoprazole, respectively, eight electropolymerization cycles with o-phenylenediamine as the functional monomer, an elution time of 5.0 min using an ethanol/acetic acid/H₂O mixture (2/3/8, V/V/V) as the eluent, and a rebound time of 10.0 min. A linear relationship was observed between the sensor response intensity (ΔI) and logarithm of the levo-lansoprazole concentration (l-g C) in the range of 1.0 × 10^-13-3.0 × 10^-11 mol/L. Compared with a conventional MIP sensor, the proposed sensor showed more efficient enantiomeric recognition, with high selectivity and specificity for levo-lansoprazole. The sensor was successfully applied to levo-lansoprazole detection in enteric-coated lansoprazole tablets, thus demonstrating its suitability for practical applications.

Development and validation of a chiral LC-MS/MS method for the separation and quantification of four synthetic cathinones in human whole blood and its application in stability analysis

Synthetic cathinones, a subclass of new psychoactive substances, have gained high popularity on the recreational drugs market over the past years. These drugs typically have a chiral center, so they may exist as two stereoisomers. Therefore the pharmacological, pharmacokinetic or metabolic properties of their enantiomers are expected to differ. However, these drugs are often synthesized and sold as a racemic mixture, and as a consequence, differentiation of their (R)- and (S)- enantiomers is relevant in clinical and forensic toxicology. Information about single enantiomers of synthetic cathinones is relatively scarce due to challenges of their chiral analysis. Hence, a sensitive and reliable liquid chromatography-tandem mass spectrometry method was developed and validated for the chiral separation and quantification of four synthetic cathinones in human whole blood samples. The method was fully validated in terms of linearity, limit of detection, limit of quantification, bias, precision, carryover, interferences, matrix effects, recovery and processed sample stability and successfully applied to evaluate the stability as well as enantioselective degradation of synthetic cathinones enantiomers under various storage conditions. For most of the analytes, significant enantioselective degradation was observed when stored at room temperature or refrigerated, with the E2-enantiomers observed to more rapidly degrade under both conditions. This is the first report concerning the stability and enantioselective degradation of synthetic cathinone enantiomers in whole blood. Moreover, the inversion study demonstrated enantiomeric inversion of R-(-)- and S-(+)-methylenedioxypyrovalerone (MDPV) in human whole blood and methanolic solution.

Synthetic Cathinones: Recent Developments, Enantioselectivity Studies and Enantioseparation Methods

New psychoactive substances represent a public health threat since they are not controlled by international conventions, are easily accessible online and are sold as a legal alternative to illicit drugs. Among them, synthetic cathinones are widely abused due to their stimulant and hallucinogenic effects. To circumvent the law, new derivatives are clandestinely synthesized and, therefore, synthetic cathinones keep emerging on the drug market, with their chemical and toxicological properties still unknown. In this review, a literature assessment about synthetic cathinones is presented focusing on the recent developments, which include more than 50 derivatives since 2014. A summary of their toxicokinetic and toxicodynamic properties are also presented. Furthermore, synthetic cathinones are chiral compounds, meaning that they can exist as two enantiomeric forms which may present different biological and toxicological activities. To analyze the enantiomers, the development of enantiomeric resolution methods for synthetic cathinones is crucial. Many methods have been reported over the years that include mostly chromatographic and electromigration techniques, with liquid chromatography using chiral stationary phases being the technique of choice. This review intended to present an overview of enantioselectivity studies and enantioseparation analysis regarding synthetic cathinones, highlighting the relevance of chirality and current trends.

Original enantioseparation of illicit fentanyls with cellulose-based chiral stationary phases under polar-ionic conditions

Fentanyl analogues used in therapy and a range of highly potent non-pharmaceutical fentanyl derivatives are subject to international control, as the latter are increasingly being synthesized illicitly and sold as 'synthetic heroin', or mixed with heroin. A significant number of hospitalizations and deaths have been reported in the EU and USA following the use of illicitly synthesized fentanyl derivatives. It has been unequivocally demonstrated that the enantiomers of fentanyl derivatives exhibit different pharmaco-toxicological profiles, which makes crucial to avail of suitable analytical methods enabling investigations at a "stereochemical level". Chromatographic methods useful to discriminate the enantioseparation of fentanyls and their derivatives are still missing in the literature. This is the first study in which the enantioseparation of four fentanyl derivatives, that is, (±)-trans-3-methyl norfentanyl, (±)-cis-3-methyl norfentanyl, β-hydroxyfentanyl, and β-hydroxythiofentanyl, has been obtained under polar-ionic conditions. Indeed, the use of ACN-based mobile phases with minor amounts of either 2-propanol or ethanol (plus diethylamine and formic acid as ionic additives) allowed obtaining enantioseparation and enantioresolution factors up to 1.83 and 7.02, respectively. For the study, the two chiral stationary phases cellulose tris(3-chloro-4-methylphenylcarbamate) and cellulose tris(4-chloro-3-methylphenylcarbamate) were used, displaying a remarkably different performance towards the enantioseparation of (±)-cis-3-methyl norfentanyl. Chiral LC analyses with a high-resolution mass spectrometry detector were also carried out in order to confirm the obtained data and demonstrate the suitability and compatibility of the optimized mobile phases with mass spectrometric systems.