phase-I Metabolites Research Articles

Human phase-I metabolism of three synthetic cannabinoids bearing a cumyl moiety and a cyclobutyl methyl or norbornyl methyl tail: Cumyl-CBMEGACLONE, Cumyl-NBMEGACLONE, and Cumyl-NBMINACA.

Synthetic cannabinoid receptor agonists (SCRAs) continue to show high prevalence on the new psychoactive substances drug market. Around 2019-2020, new SCRAs bearing a cumyl moiety emerged: Cumyl-CBMEGACLONE and Cumyl-NBMEGACLONE, carrying a cyclobutyl methyl (CBM) and a norbornyl methyl moiety (NBM) attached to the γ-carbolinone core. These were followed by Cumyl-NBMINACA, the indazole carboxamide analog of Cumyl-NBMEGACLONE. The study aimed at evaluating the human phase-I metabolism of these compounds and at identifying suitable urinary markers to prove their consumption. After enzymatic hydrolysis, 14 authentic urine samples (eight for Cumyl-CBMEGACLONE, four for Cumyl-NBMEGACLONE, and two for Cumyl-NBMINACA) were analyzed by liquid chromatography-quadrupole time-of-flight mass spectrometry. Results were compared with in vitro metabolites generated by pooled human liver microsomes incubation. Fifteen human phase-I metabolites were identified for Cumyl-CBMEGACLONE, nine for Cumyl-NBMEGACLONE, and thirteen for Cumyl-NBMINACA. The main in vivo metabolites were built by monohydroxylation, dihydroxylation, or trihydroxylation. The following urinary biomarkers are suggested for detecting the consumption of the investigated SCRAs: products of monohydroxylation at the CBM and at the core for Cumyl-CBMEGACLONE; two products of monohydroxylation at the norbonyl methyl tail for Cumyl-NBMEGACLONE; and metabolites built by dihydroxylation at the NBM substructure and by an additional hydroxylation at the cumyl moiety for Cumyl-NBMINACA.

Identification of phase-I and phase-II metabolites and the metabolic pathway of the novel synthetic cannabinoid 5F-EDMB-PICA in vitro.

5F-EDMB-PICA is a newly emerged synthetic cannabinoid which has been characterized in relevant literature in recent years. Although phase-I metabolites of 5F-EDMB-PICA have been partly reported, the phase-II metabolism of this synthetic cannabinoid has not been studied yet. In this study, we established a phase-I and phase-II metabolism model in vitro by using pooled human liver microsomes, NADPH regeneration system, and UGT incubation system, with 1mg/ml 5F-EDMB-PICA added and incubated at 37°C for 60min. The metabolites were analyzed by Q Exactive™ Hybrid Quadrupole-Orbitrap™ Mass Spectrometer, via which we discovered and identified 14 phase-I metabolites and 4 phase-II metabolites of 5F-EDMB-PICA, involving pathways such as ester hydrolysis, dehydrogenation, hydrolytic defluorination, hydroxylation, dihydroxylation, glucuronidation, and combinations of the pathways mentioned above. We recommend considering the monohydroxylation metabolites (M9, M10) with higher content and intact ester and 5-fluoropentyl structures as potential biomarkers of 5F-EDMB-PICA.

Identification and characterization of the in-vivo metabolites of the novel soluble epoxide hydrolase inhibitor EC5026 using liquid chromatography quadrupole time of flight mass spectrometry

EC5026 is a novel soluble epoxide hydrolase inhibitor being developed clinically to treat neuropathic pain and inflammation. In the current study, we employed the LC-ESI-Q-TOF-MS/MS technique to identify four in-vivo phase-I metabolites of EC5026 in rat model, out of which three were found to be novel. The identified metabolites include aliphatic hydroxylation, di-hydroxylation, terminal desaturation, and carboxylation. No phase-II metabolites were found. The pharmacokinetic profile of identified metabolites was established after a single oral dose of EC5026 to Wistar rats. The Tmax of the drug and metabolites were found to be in the range of 1–2 hours and 4–12 hours, respectively. The major metabolites M1 and M2 were found to have more than 2-fold (263.87% AUC) and equivalent exposure (96.33% AUC) compared to the parent drug, respectively. Further, the docking study revealed that the mono-hydroxylated and terminally desaturated metabolites possess better binding affinity than the parent drug. Therefore, these metabolites may hold sEH inhibition potential and can be followed through future research.

Development of enantioselective high-performance liquid chromatography-tandem mass spectrometry method for the quantitative determination of 3,4-methylenedioxy-methamphetamine (MDMA) and its phase-1 metabolites in human biological fluids

In the present study enantioselective high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods were developed for the quantitative determination of 3,4-methylenedioxy-methamphetamine (MDMA) and its major phase-1 metabolites 4-hydroxy-3-methoxyamphetamine (HMA), 4-hydroxy-3-methoxymethamphetamine (HMMA) and 3,4-methylenedioxyamphetamine (MDA) in human plasma, sweat, oral fluid (OF) and urine. The simultaneous separation of all these compounds and their respective enantioseparation was accomplished on two polysaccharide-based chiral columns. The Lux AMP column with a proprietary chiral selector enabled baseline separation of the enantiomers of MDMA, HMA and HMMA while MDA enantiomers could not be separated with this column under the experimental conditions used in this study. The Lux i-Amylose-3 column based on amylose tris(5-chloro-3-methylphenylcarbamate) as chiral selector baseline-separated the enantiomers of MDMA, HMMA and MDA while the enantiomers of HMA could not be separated. Thus, the various samples were analyzed by using both columns alternatively in combinations with acetonitrile containing 25% (v/v) 5 mM ammonium bicarbonate buffer at pH 11.0 as mobile phase. Analysis time was less than 4 min with the Lux AMP column and less than 6 min with the Lux i-Amylose-3 column. Both methods were validated and applied to the enantioselective determination of MDMA and its phase-I metabolites in human biological fluids, and enantioselective metabolism of MDMA was confirmed.

Quantitation of 6-chloronicotinic acid and 2-chloro-1,3-thiazole-5-carboxylic acid and their glycine conjugates in human urine to assess neonicotinoid exposure

Neonicotinoids and neonicotinoid-like compounds (NNIs) are widely used insecticides and their ubiquitous occurrence in the environment requires methods for exposure assessment in humans. The majority of the NNIs can be divided into 6-chloropyridinyl- and 2-chlorothiazolyl-containing compounds, suggesting the formation of the group-specific metabolites 6-chloronicotinic acid (6-CNA), 2-chloro-1,3-thiazole-5-carboxylic acid (2-CTA), and their respective glycine derivatives (6-CNA-gly, 2-CTA-gly). Here, we developed and validated an analytical method based on gas chromatography coupled to mass spectrometry (GC-MS/MS) to simultaneously analyze these four metabolites in human urine. As analytical standards for the glycine conjugates were not commercially available, we synthesized 6-CNA-gly, 2-CTA-gly, and their 13C2,15N-labeled analogs for internal standardization and quantitation by stable isotope dilution. We also ensured chromatographic separation of 6-CNA and its isomer 2-CNA. Enzymatic cleavage during sample preparation was proven unnecessary. The limits of quantitation were between 0.1 (6-CNA) and 0.4 μg/L (2-CTA-gly) and the repeatability was satisfactory (coefficient of variation was <19% over the calibration range). We analyzed 38 spot urine samples from the general population and were able to quantify 6-CNA-gly in 58% of the samples (median 0.2 μg/L). In contrast, no 6-CNA could be detected. The results are in line with well-known metabolic pathways specific in humans, that, compared to rodents, favor the formation and excretion of phase–II–metabolites (glycine derivatives) rather than phase-I metabolites (free carboxylic acids). Nevertheless, the exact source of exposure (i.e., the specific NNI) remains elusive in the general population, may even vary quantitatively between different NNIs, and also might be regional specific based on the respective use of individual NNIs. In sum, we developed a robust and sensitive analytical method for the determination of four group-specific NNI metabolites.

Simvastatin: In Vitro Metabolic Profiling of a Potent Competitive HMG-CoA Reductase Inhibitor

Simvastatin (SV) is a semisynthetic derivative of lovastatin (LV), which is biosynthetically produced from the fungus Aspergillus terreus and has a high log p value (log p = 4.39)and thus high hepatic extraction and high efficacy in controlling cholesterol synthesis. The current study was undertaken to investigate the metabolic profile of SV using various mass spectrometry (MS) platforms. Metabolic profiling was studied in in vitro models, rat liver microsomes (RLMs), and isolated perfused rat liver hepatocytes (RLHs) using both ion trap and triple quadruple LC–MS/MS systems. A total of 29 metabolites were identified. Among them, three types of SV-related phase-I metabolites, namely exomethylene simvastatin acid (exomethylene SVA), monohydroxy SVA, and dihydrodiol SVA, were identified as new in RLMs. No phase-II metabolites were identified while incubating with RLHs.

Human phase-I metabolism and prevalence of two synthetic cannabinoids bearing an ethyl ester moiety: 5F-EDMB-PICA and EDMB-PINACA.

Around 2017, with the appearance of 5F-EDMB-PINACA, synthetic cannabinoids (SCs) carrying an ethyl ester moiety at the linked group started spreading on the market of new psychoactive substances (NPS). In 2020 and 2021, the indole analog of 5F-EDMB-PINACA (5F-EDMB-PICA) and the non-fluorinated analog of this compound (EDMB-PINACA) were analytically characterized. Here, we present suitable urinary markers to prove the consumption of these two ethyl analogs. Ten authentic urine samples for each compound were analyzed by liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-qToF-MS). Anticipated phase-I metabolites detected in urine samples were confirmed in vitro by applying a pooled human liver microsomes (pHLM) assay. Prevalence data were obtained from urines collected for abstinence control and submitted to a screening method for SC metabolites. Ten phase-I metabolites of 5F-EDMB-PICA and 18 of EDMB-PINACA were detected by LC-qToF-MS analysis of authentic urine specimens. The main in-vivo metabolites were built by ester hydrolysis, often coupled to further metabolic processes. Investigation of phase-I biotransformation led to the identification of ester hydrolysis, monohydroxylation, and defluorination products as the most suitable urinary biomarkers for 5F-EDMB-PICA. Metabolites formed by ester hydrolysis coupled to ketone formation and by monohydroxylation are suggested for the detection of EDMB-PINACA. From October 1, 2020 to February 1, 2022, among positive urine samples, 5.4% and 10.1% tested positive 5F-EDMB-PICA and EDMB-PINACA, respectively. Due to common metabolites shared among structurally related SCs, the unequivocal detection of their consumption remains challenging for forensic laboratories and requires sensitive methods to monitor multiple metabolites, ideally including highly specific species.

Metabolite Identification of HIV-1 Capsid Modulators PF74 and 11L in Human Liver Microsomes.

PF74 and 11L, as potent modulators of the HIV-1 capsid protein, have been demonstrated to act at both early and late stages in the HIV-1 life cycle. However, their clearance is high in human liver microsomes (HLMs). The main goal of this study was to clarify the metabolism of PF74 and 11L in HLMs, and provide guidance for future structural optimization. To accomplish this, the phase-I metabolites of PF74 and 11L, resulting from in vitro incubation with HLMs, were investigated via ultra-performance liquid chromatography–ultraviolet–high-resolution mass spectrometry (UPLC–UV–HRMS). The results show that 17 phase-I metabolites were putatively annotated for PF74, whereas 16 phase-I metabolites were found for 11L. The main metabolic pathways of PF74 in HLMs were oxidation and demethylation, and the secondary metabolic pathway was hydrolysis; thus, the di-oxidation and demethylation products (M7, M9, M11, and M14) were found to be major metabolites of PF74 in HLMs. In comparison, the main metabolic pathways of 11L in HLMs were oxidation, demethylation, dehydrogenation, and oxidative deamination, with M6′, M11′, M15′, and M16′ as the main metabolites. We suggest that the indole ring and N-methyl group of PF74, and the aniline group, benzene ring R1′, N-methyl, and methoxy group of 11L, were the main metabolic soft spots. Therefore, our research illuminates structural optimization options in seeking improved HIV-1 CA modulators.

Human metabolism of AP-238. A novel synthetic opioid spreading in the shadow of “fentalogues”

The phenomenon of new psychoactive substances is constantly evolving, with novel synthetic opioids (NSO) representing a particular threat given their sometimes extremely high potencies and their potential to produce respiratory depression. As a consequence of recently implemented legal restrictions on fentanyl analogues, a new “legal” generation of opioids, embodied by the class of cinnamylpiperazines, popped up on the illicit drug market. AP-238 was the latest NSO of this series to be notified to the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) and is involved in an increasing number of acute intoxications. Adverse effects associated with the abuse of NSO, their continued evolution, increased popularity and high availability constitute a serious concern and pose an imminent hazard to public health. The identification of specific markers of consumption for these NSO is essential for clinical and forensic casework and represents a new challenge for toxicology laboratories. Referring to this, we investigated the in vivo and in vitro metabolism of AP-238. For tentative identification of the main phase-I metabolites, a pooled human liver microsomes (pHLM) assay was used. Incubation was performed for 2 hours at 37 °C in triplicates, including a blank control (no pHLM) and a zero control (no reference standard). Analyses were carried out using liquid chromatography coupled to time-of-flight mass spectrometry (LC-qToF-MS). Full scan and auto MS/MS data were acquired in one run. In a second run, full scan and broadband collision-induced dissociation (bbCID) data were acquired, checking for characteristic fragment ions (e.g., m/z 117.0699) to detect unexpected metabolites. To compare the relative abundance of the metabolites, a multiple reaction monitoring (MRM) method comprising at least two ion transitions of each metabolite, was applied using liquid chromatography coupled to tandem-mass spectrometry (LC-MS/MS). Chromatographic separation was achieved on a Kinetex® C18 column (100 × 2.1 mm, 2.6 μm). Both instruments were operated in positive ion mode. Anticipated phase-I metabolites detected in the pHLM assay were confirmed in three authentic blood samples collected during postmortem examinations and tested positive for AP-238 in the Institute of Forensic Medicine of Freiburg. In total, ten AP-238 phase-I metabolites were identified by means of LC–qToF–MS in the pHLM assay and confirmed five of these by corresponding signals in the human blood samples. They mainly consisted of products of hydroxylation, oxidation, dealkylation, and combinations of these reactions. A dealkylated/monohydroxylated metabolite was detected with the highest abundance in blood. Suggested biomarkers for AP-238 consumption are generated by monohydroxylation combined with dealkylation (most abundant) and by sole hydroxylation at the cinnamyl substituent, with the latter being highly specific. Although this investigation was carried out with blood samples due to the non-availability of urine, it is likely that these metabolites are suitable markers for urine screening as well. The combination of dealkylation with (multiple) hydroxylation(s) was also observed for further minor metabolites. The exact chemical structures of these metabolites remain unclear and would require isolation and structure elucidation e.g. by nuclear magnetic resonance spectroscopy or synthesis of reference material. However, this does not preclude their use as valid biomarkers. Implementing analytical methods for the detection of NPS metabolites is often crucial to document consumption in clinical and forensic toxicology. In vitro methods like the used pHLM assay proved to be suitable tools for prediction of biomarkers for NSO intake, although they have to be confirmed by authentic samples. If urine is not available, blood can be used for this purpose.

5-Methylmethiopropamine (5-MMPA, mephedrene)–human metabolism and post-mortem investigation of a fatal intoxication

The phenomenon of new psychoactive substances is constantly evolving, with arylalkylamines being one of the largest groups among them. 5-Methylmethiopropamine (5-MMPA, mephedrene), a derivative of methiopropamine (MPA), is available from online vendors selling “research chemicals” and was first seized by German authorities in 2020. No scientific data about its pharmacological effects and its fate in the human body are available so far. Therefore, we investigated the in vivo and in vitro metabolism of 5-MMPA after detection of this compound in a fatal intoxication. For tentative identification of phase-I metabolites 5-MMPA was incubated with pooled human liver microsomes (pHLM). Additionally, an authentic urine sample was worked up using protein precipitation with and without prior glucuronide cleavage. Analyses for metabolite identification were carried out using high resolution LC-ESI(+)-QTOF-MS. Chromatographic separation was achieved on a Kinetex® Biphenyl column (100 × 2.1 mm, 2.6 μm). For the post-mortem investigation of the fatal intoxication, a standard addition approach using automated SPE for sample workup was performed to quantify 5-MMPA in femoral blood with LC-MS/MS. In the pHLM assay three phase-I metabolites were identified, of which only two where confirmed in the available authentic urine sample. In addition, six further phase-I and two phase-II metabolites were detected in the analyzed urine sample. Predominant metabolic reactions were hydroxylation, oxidation, N-dealkylation, glucuronidation and combinations thereof. In urine an oxo-hydroxy metabolite, that was not generated in the pHLM assay, was detected with the highest abundance. The concentration of 5-MMPA in the femoral blood sample was 7.100 ± 600 ng/mL. The in vitro pHLM assay was not suitable to predict the main metabolites of 5-MMPA as confirmed in the available real case sample. The majority of the metabolic reactions, and in particular the oxidation of 5-MMPA, appear to be catalyzed by enzymes that are not present in an active state in the pHLM assay. Analyses of an authentic urine sample suggest oxo-hydroxy-5-MMPA (main metabolite) and N-demethyl-5-MMPA as suitable biomarkers for 5-MMPA consumption. To confirm the exaxt chemical strucuture of these markers, isolation and structure elucidation, e.g. by NMR, or the synthesis of reference compounds would be needed. In the fatal intoxication case, the elevated blood concentration of 5-MMPA was considered likely to have contributed to toxicity/death (equivalent to a Toxicological Significance Score according to Elliott et al. (2017) of 3). This represents the first documented fatal case involving 5-MMPA.

3-Methyl-PCP–in vitro and in vivo metabolism in humans and post-mortem investigation of a fatal intoxication

Arylcyclohexylamine analogs of phencyclidine (PCP) increasingly emerged on the novel psychoactive substance market over the last few years. Recently, 3-Me-PCP appeared on the market and, like many PCP analogs, is considered to be an equally or even more potent dissociative drug as compared to PCP. However, there is a significant lack of scientific data on this compound, as neither fatal nor non-fatal intoxications involving 3-Me-PCP have been reported. Therefore, we investigated the in vivo and in vitro metabolism of 3-Me-PCP and present the findings from a fatal intoxication case involving 3-Me-PCP. For tentative identification of phase-I metabolites, 3-Me-PCP was incubated with pooled human liver microsomes (pHLM). In addition, an authentic urine sample was worked up using protein precipitation with and without prior glucuronide cleavage. Analyses for metabolite identification were carried out using liquid chromatography coupled to time-of-flight mass spectrometry in positive ionization mode (LC-ESI-QTOF-MS). Chromatographic separation was achieved on a Kinetex® Biphenyl column (100 × 2.1 mm, 2.6 μm). For the post-mortem investigation of the fatal intoxication, a standard addition approach using automated SPE for sample workup was performed to quantify 3-Me-PCP in heart blood and urine with LC-MS/MS. 3-Me-PCP was extensively metabolized by hepatic enzymes in the pHLM assay. Altogether, ten in vitro phase-I metabolites of 3-Me-PCP were identified using LC − ESI-QTOF − MS, with hydroxylations, oxidations, and N-dealkylations being the observed reactions. All of these phase-I metabolites could be confirmed in the authentic urine sample. In both experimental settings, the 3-hydroxymethyl-PCP metabolite was detected with the highest abundance, followed by cyclohexyl-hydroxy-3-Me-PCP and the ω-carboxylic acid metabolite formed after ring-opening N-dealkylation at the piperidine moiety. The concentrations of 3-Me-PCP in heart blood and urine of the fatal intoxication case were 510 ± 35 ng/mL and 600 ± 72 ng/mL, respectively. The in vitro pHLM assay was suitable to identify and predict the main metabolites of 3-Me-PCP in the available real case sample. Suggested biomarkers for 3-Me-PCP consumption are 3-hydroxymethyl-PCP, cyclohexyl-hydroxy-3-Me-PCP, and the ω-carboxylic acid metabolite formed after ring-opening N-dealkylation at the piperidine moiety. The chemical structures of the detected metabolites remain tentative until structure elucidation, e.g., by NMR after isolation or the synthesis of reference material was performed. However, this does not preclude their use as valid biomarkers. Furthermore, even in the context of a multidrug intake, the 3-Me-PCP intoxication was confirmed during post-mortem investigations and the determined concentrations of 3-Me-PCP were considered likely to have contributed to toxicity/death (Toxicological Significance Score of 3). This represents the first documented fatal case involving 3-Me-PCP.

Characterization and identification of the metabolites of dihydromethysticin by ultra-high-performance liquid chromatography orbitrap high-resolution mass spectrometry.

Dihydromethysticin, a natural component from Piper methysticum Forst, has been reported to display pharmacological effects in mental disorders and some malignant tumors. However, the metabolism of this component remained unknown. The goal of this work was conducted to discover the metabolic profiles of dihydromethysticin. The in vitro incubation was performed by incubating dihydromethysticin with rat, monkey, and human liver microsomes and hepatocytes. An analytical assay of ultra-high performance liquid chromatography combined with Orbitrap high-resolution mass spectrometry was utilized to detect and identify the metabolites. With high resolution mass spectrometric determination, the accurate mass, elemental composition, and product ions of the metabolites were determined, which enabled structural characterization to become easy. Under the present conditions, four phase-I metabolites, as well as six phase-II metabolites, were detected and their tentative structures were characterized by mass spectra. M4 was found as the most abundant metabolite both in liver microsomes and hepatocytes. Cytochrome P450 1A2, 2C9, and 3A4 contributed to the formation of this metabolite by using human recombinant P450 enzymes. M4 can be oxidized into reactive ortho-quinone intermediate followed by conjugating with glutathione. M4 was also subject to glucuronidation (M1 and M2) and methylation (M5). Demethylenation, oxidation, hydroxylation, glucuronidation, glutathionylation, and methylation were the primary metabolic pathways of dihydromethysticin. This study provides in vitro metabolism data of dihydromethysticin, which is indispensable for understanding the disposition of this compound.

UHPLC-HRMS study of pharmacokinetics of a novel hybrid cholinesterase inhibitor K1234: A comparison between in silico, in vitro and in vivo data

Alzheimer's disease (AD) is one of the most common forms of dementia. Current anti-AD therapeutics exploit the cholinergic hypothesis of its pathophysiology; they aim to inhibit cerebral cholinesterases. K1234 is a novel hybrid molecule derived from Huperzine A and 7-MEOTA-huperzine which shows increased potency in acetylcholinesterase inhibition in vitro compared to the compounds themselves. The study focused on description of the pharmacokinetic behaviour of K1234, blood-brain barrier penetration, identification of the main in vitro and in vivo metabolites. K1234 is relatively non-toxic compound, that is rapidly absorbed after i.p. administration reaching Cmax within minutes, with extensive distribution into tissues and fast metabolism in mice. The dominant metabolic pathway appears to be glucuronidation of the parent molecule and its phase-I metabolites. The passage of K1234 across the blood-brain-barrier in mice appears to be limited, as it reached only approximately one third of the AUC of plasma.

In Vitro Identification of Potential Metabolites of Plinabulin (NPI 2358) in Hepatic Preparations Using Liquid Chromatography-Ion Trap Mass Spectrometry.

Plinabulin (1, NPI2358), a vascular disrupting agent (VDA) molecule, is a synthetic analogue of the natural product phenylahistin (2, NPI 2350), which is isolated from Aspergillus ustus. Evaluation of the in vitro metabolic profile of VDA plinabulin using human liver microsomes (HLMs) and HepaRG Cells Cryopreserved is described. HLMs and HepaRG Cells Cryopreserved were prepared in-house and incubated with plinabulin according to published methodologies. The incubated mixtures were analyzed by liquid chromatography–ion trap mass spectrometry to identify possible metabolic products. The incubated plinabulin (1) revealed the presence of several peaks representing 19 tentative metabolites in HLMs and HepaRG Cells Cryopreserved in the presence of NADPH (nicotinamide adenine dinucleotide phosphate) and in the absence of NADPH-generating system, respectively. However, in NADPH absence, no metabolites and microsomes were generated for 1 in incubated HLMs, indicating a likely involvement of CYP450 enzymes in the metabolism. The metabolite structures, obtained from HLMs and HepaRG Cells Cryopreserved incubations, were elucidated by LC–MS/MS fragmentation study. Seventeen phase-I metabolites were proposed to be the results of isomerization, hydroxylation, hydration, and oxygenation of 1 in HLMs and two isomeric phase-II sulfate conjugate metabolites of 1 in HepaRG Cells Cryopreserved incubation.

Study on the metabolic process of synthetic cannabinoids 4F-MDMB-BINACA and 4F-MDMB-BICA in human liver microsome and zebrafish model via UHPLC-QE Orbitrap MS

In order to address the increasing abuse of synthetic cannabinoids, on July 1, 2021, China listed the whole category of synthetic cannabinoids in the Supplementary Catalog for the Control of Non-medicinal Narcotic Drugs and Psychotropic Substances. Because synthetic cannabinoids metabolize rapidly, techniques are urgently needed to identify the phase I metabolites of new synthetic cannabinoids, as well as the symbol metabolites, which can be used for detection in real cases. In this study, we used pooled human liver microsome (pHLM) and zebrafish combined with ultra-high-performance liquid chromatography (UHPLC) Q Exactive Orbitrap MS to identify the phase Imetabolites of two new synthetic cannabinoids 4F-MDMB-BICA and 4F-MDMB-BINACA in vitro and in vivo, respectively. We studied the toxicokinetics of 4F-MDMB-BICA and 4F-MDMB-BINACA by sampling from a pHLM incubation system at different time points to study the change in metabolites over time. We detected a total of 14 metabolites of 4F-MDMB-BINACA and 16 metabolites of 4F-MDMB-BICA in this study. Metabolites of 4F-MDMB-BICA were detected in vitro for the first time. One metabolite of 4F-MDMB-BINACA, M05, was discovered for the first time. Based on the toxicokinetics results, we recommend three metabolites (M03, M11, M12) of 4F-MDMB-BINACA and three metabolites (M10, M12, M14) of 4F-MDMB-BICA as their symbol metabolites. The results showed that these two structurally similar synthetic cannabinoids 4F-MDMB-BINACA and 4F-MDMB-BICA had similar metabolic processes, as well as similar structures of their main symbol metabolites.

Identification and Characterization of in vitro Metabolites of Belinostat by Rat Liver Microsomes using Ultra Performance Liquid Chromatography Coupled with Tandem Mass Spectrometry

Abstract: Objectives: The objective of the present study is to study the in-vitro metabolites of FDA approved anticancer drug, belinostat which is a histone deacetylase inhibitor. Methods: The metabolites were formed by incubating the drug, belinostat with rat liver microsomes, at 37°C for 24 hr. The newly formed metabolites were identified and characterized with the help of ultra-high performance liquid chromatography which is interlinked with tandem quadrupole time-of-flight mass spectrometry. Results: Two Phase-I metabolites were formed which include a belinostat amide (reductive metabolite) and belinostat acid (deaminated belinostat). We then elucidated the structures of the formed metabolites based on LC-MS/MS data which included accurate masses, the fragmentation of ions and chromatographic retention times. Conclusion: This study describes the detailed in-vitro metabolite profiling of belinostat which will be further helpful to predict the in-vivo metabolism of belinostat in the human body. Enzyme kinetic parameters (Km and Vmax) for both the metabolites were also established using different substrate concentrations. The study will be helpful in determining the safety and efficacy of the drug. This will further help in determining the elimination mechanism of belinostat which in turn will assist in predicting the effectiveness and toxicity of the drug. Key words: Belinostat; Rat Liver Microsomes; Characterization; in-vitro Metabolites; Enzyme Kinetics; LC-MS/MS.

Application of liquid chromatography coupled to data-independent acquisition mass spectrometry for the metabolic profiling of N-ethyl heptedrone

We have investigated the metabolic profile of N-ethyl heptedrone, a new designer synthetic stimulant drug, by using data independent acquisition mass spectrometry. Phase I and phase II metabolism was studied by in vitro models, followed by liquid-chromatography coupled to mass spectrometry, to characterize and pre-select the most diagnostic markers of intake. N-ethyl heptedrone was incubated in the presence of pooled human liver microsomes. The contribution of individual enzymatic isoforms in the formation of the phase I and phase II metabolites was further investigated by using human recombinant cDNA-expressed cytochrome P450 enzymesand uridine 5′-diphospho glucuronosyltransferases.The analytical workflow consisted of liquid-liquid extraction with tert-butyl-methyl-ether at alkaline pH, performed before (to investigate the phase I metabolic profile) and after (to investigate the glucuronidation profile) enzymatic hydrolysis. The separation, identification, and determination of the compounds formed in the in vitro experiments were carried out by using liquid chromatography coupled to either high- or low-resolution mass spectrometry. Data independent acquisition method, namely sequential window acquisition of all theoretical fragment-ion spectra (SWATH®) and product ion scan were selected for high-resolution mass spectrometry, whereas multiple reaction monitoring was used for low-resolution mass spectrometry.Thirteen phase-I metabolites were isolated, formed from reactions being catalyzed mainly by CYP1A2, CYP2C9, CYP2C19 and CYP2D6 and, to a lesser degree, by CYP3A4 and CYP3A5. The phase I biotransformation pathways included hydroxylation in different positions, reduction of the ketone group, carbonylation, N-dealkylation, and combinations of the above. Most of the hydroxylated metabolites underwent conjugation reactions to form the corresponding glucurono-conjugated metabolites. Based on our in vitro observation, the metabolic products resulting from reduction of the keto group, N-dealkylation and hydroxylation of the aliphatic chain appear to be the most diagnostic target analytes to be selected as markers of exposure to N-ethyl heptedrone.

Human metabolism and urinary excretion of seven neonicotinoids and neonicotinoid-like compounds after controlled oral dosages

Few human data on exposure and toxicity are available on neonicotinoids and neonicotinoid-like compounds (NNIs), an important group of insecticides worldwide. Specifically, exposure assessment of humans by biomonitoring remains a challenge due to the lack of appropriate biomarkers. We investigated the human metabolism and metabolite excretion in urine of acetamiprid (ACE), clothianidin (CLO), flupyradifurone (FLUP), imidacloprid (IMI), sulfoxaflor (SULF), thiacloprid (THIAC) and thiamethoxam (THIAM) after single oral dosages at the currently acceptable daily intake levels of the European Food Safety Authority. Consecutive post-dose urine samples were collected up to 48 h. Suspect screening of tentative metabolites was carried out by liquid chromatography–high-resolution mass spectrometry. Screening hits were identified based on their accurate mass, isotope signal masses and ratios, product ion spectra, and excretion kinetics. We found, with the exception of SULF, extensive metabolization of NNIs to specific metabolites which were excreted next to the parent compounds. Overall, 24 metabolites were detected with signal intensities indicative of high metabolic relevance. Phase-I metabolites were predominantly derived by mono-oxidation (such as hydroxy-FLUP, -IMI, and -THIAC) and by oxidative N-desalkylation (such as N-desdifluoroethyl-FLUP and N-desmethyl-ACE, -CLO and -THIAM). IMI-olefin, obtained by dehydration of hydroxylated IMI, was identified as a major metabolite of IMI. SULF was excreted unchanged in urine. Previously reported metabolites of NNIs such as 6-chloronicotinic acid or 2-chlorothiazole-4-carboxylic acid and their glycine derivatives were detected either at low signal intensities or not at all and seem less relevant for human biomonitoring. Our highly controlled approach provides specific insight into the human metabolism of NNIs and suggests suitable biomarkers for future exposure assessment at environmentally relevant exposures.

Metabolic map of the antiviral drug podophyllotoxin provides insights into hepatotoxicity

Podophyllotoxin (POD) is a natural compound with antiviral and anticancer activities. The purpose of the present study was to determine the metabolic map of POD in vitro and in vivo. Mouse and human liver microsomes were employed to identify POD metabolites in vitro and recombinant drug-metabolizing enzymes were used to identify the mono-oxygenase enzymes involved in POD metabolism. All in vitro incubation mixtures and bile samples from mice treated with POD were analysed with ultra-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry. A total of 38metabolites, including six phase-I metabolites and 32 phase-II metabolites, of POD were identified from bile and faeces samples after oral administration, and their structures were elucidated through interpreting MS/MS fragmentation patterns. Nine metabolites, including two phase-I metabolites, five glucuronide conjugates, and two GSH conjugates were detected in both human and mouse liver microsome incubation systems and the generation of all metabolites were NADPH-dependent. The main phase-I enzymes involved in metabolism of POD in vitro include CYP2C9, CYP2C19, CYP3A4, and CYP3A5. POD administration to mice caused hepatic and intestinal toxicity, and the cellular damage was exacerbated when 1-aminobenzotriazole, a broad-spectrum inhibitor of CYPs, was administered with POD, indicating that POD, but not its metabolites, induced hepatic and intestinal toxicities. This study elucidated the metabolic map and provides important reference basis for the safety evaluation and rational for the clinical application of POD.

Metabolism of 4F-MDMB-BICA in zebrafish by liquid chromatography-high resolution mass spectrometry.

In this study, in vivo metabolic studies of the synthetic cannabinoid 4F-MDMB-BICA were investigated using zebrafish models. The metabolites were identified and structurally illustrated by liquid chromatography-high resolution mass spectrometry. Fourteen phase-I metabolites and four phase-II metabolites were generated from zebrafish. The main metabolic pathways of the phase-I metabolism included N-dealkylation, N-dealkylation combined with hydroxylation, amide hydrolysis, oxidative defluorination, oxidative defluorination to butyric acid, acetic acid formation at the indole side chain, hydroxylation, ester hydrolysis followed by hydroxylation, dehydrogenation, dehydrogenation, and N-dealkylation, and oxidative defluorination subsequently combined with dehydrogenation. The main biotransformations of the phase-II metabolism were glucuronidation and sulfation. Two phase-I metabolites (A1 and A11) and four phase-II metabolites (A2, A3, A4, and A12) were reported for the first time. A14, which was confirmed in human biological samples, was detected only in zebrafish samples but not found in human liver microsome incubation study. The current study indicates that the zebrafish model is a promising tool for elucidating the metabolism of NPS in the future.