SFC-MS/MS for orthogonal separation of hydroxylated 17α-methyltestosterone isomers

Because of their performance-enhancing effect, anabolic androgenic steroids (AAS) are often misused in sports. Nearly half of the adverse analytical findings (AAF) in 2022 doping controls are correlated to AAS misuse. Metabolites play a crucial role in the bioanalysis of endogenous and exogenous steroids. Therefore, one important field in antidoping research is the investigation on drug metabolizing and steroidogenic enzymes. The introduction of a hydroxy group is the most common reaction, which is catalyzed by cytochrome P450 (CYP) enzymes in phase-I metabolism. Analysis of AAS metabolites is commonly performed using gas chromatography mass spectrometry (GC-MS) systems. Laborious sample preparation and extended run times compared to liquid chromatography (tandem) mass spectrometry (LC-MS/MS) methods are usually correlated with this type of analysis. On the other hand, liquid chromatography (tandem) mass spectrometry (LC-MS[/MS]) methods have a lower separation efficiency than GC-MS methods. Both techniques lack selectivity for hydroxylated 17α-methyltestosterone metabolites. Therefore, as an orthogonal analytical approach, a supercritical fluid chromatography tandem mass spectrometry method was developed to separate four hydroxy metabolites of 17α-methyltestosterone (2α-/2β-/4-/6β-hydroxy-17α-methyltestosterone). This project aimed to get a more in-depth look at the metabolization and analysis of 17α-methyltestosterone and its hydroxylated metabolites. The developed method revealed lower limits of quantitation between 0.6 and 6 ng/ml at an accuracy of 85–115% using a matrix matched calibration. An in vitro study with human liver microsomes shows 6β-hydroxy-17α-methyltestosterone as main metabolite (15.9%) as well as the metabolite 2β-hydroxy-17α-methyltestosterone (0.5%). The results show that the developed method is sensitive and robust. In addition, the method allows a previously missing discrimination of the hydroxylated metabolites in a short analysis time without prior, complex derivatizations

Syntheses and structural confirmation of stereoisomers and various isotopologues of tetrahydromethyltestosterone

This is an overview of the syntheses and structural conformation of in-house synthesized compounds. These compounds belong to the group of sereoisomers of metabolites of anabolic androgenic steroids and have been used in different studies in our working group

Isotopic tracing of glucose metabolites in human monocytes to assess changes in inflammatory conditions

Differences in metabolic profiles can link to functional changes of immune cells in disease conditions. Here, we detail a protocol for the detection and quantitation of 19 metabolites in one analytical run. We provide the parameters for chromatographic separation and mass spectrometric analysis of isotopically labeled and unlabeled metabolites. We include steps for incubation and sample preparation of PBMCs and monocytes. This protocol overcomes the chromatographic challenges caused by the chelating properties of some metabolites

Sample Preparation Techniques for Growth-Promoting Agents in Various Mammalian Specimen Preceding MS-Analytics

The misuse of growth-promoting drugs such as beta-2 agonists and steroids is a known problem in farming and sports competitions. Prior to the analysis of biological samples via liquid chromatography (LC)–mass spectrometry (MS) or gas chromatography (GC)–MS, sufficient sample preparation is required to reliably identify or determine the residues of drugs. In practice, broad screening methods are often used to save time and analyze as many compounds as possible. This review was conceptualized to analyze the literature from 2018 until October 2023 for sample preparation procedures applied to animal specimens before LC- or GC-MS analysis. The animals were either used in farming or sports. In the present review, solid phase extraction (SPE) was observed as the dominant sample clean-up technique for beta-2 agonists and steroids, followed by protein precipitation. For the extraction of beta-2 agonists, mixed-mode cation exchanger-based SPE phases were preferably applied, while for the steroids, various types of SPE materials were reported. Furthermore, dispersive SPE-based QuEChERs were utilized. Combinatory use of SPE and liquid–liquid extraction (LLE) was observed to cover further drug classes in addition to beta-2 agonists in broader screening methods

Greener and Whiter Analytical Chemistry Using Cyrene as a More Sustainable and Eco-Friendlier Mobile Phase Constituent in Chromatography

Cyrene (dihydrolevoglucosenone) was evaluated for the first time as a potential sustainable mobile phase solvent in reversed-phase chromatography. As a benign biodegradable solvent, Cyrene is an attractive replacement to classical non-green organic chromatographic solvents such as acetonitrile and a modifier, co-eluent to known green solvents such as ethanol. Compared to ethanol, Cyrene is less toxic, non-flammable, biobased, biodegradable, and a cheaper solvent. A fire safety spider chart was generated to compare the properties of Cyrene to ethanol and show its superiority as a greener solvent. Cyrene’s behavior, advantages, and drawbacks in reversed-phase chromatography, including the cut-off value of 350 nm, elution power, selectivity, and effect on the column, were investigated using a model drug mixture of moxifloxacin and metronidazole. A monolithic C18 (100 × 4.6 mm) column was used as a stationary phase. Different ratios of Cyrene: ethanol with an aqueous portion of sodium acetate buffer mobile phases were tested. A mobile phase consisting of Cyrene: ethanol: 0.1 M sodium acetate buffer pH 4.25 (8:13:79, v/v/v) was selected as the most suitable mobile phase system for separating and simultaneously determining metronidazole and moxifloxacin. The greenness and whiteness of the method were evaluated using the qualitative green assessment tool AGREE and the white analytical chemistry assessment tool RGB12. Further potentials of Cyrene as a solvent or modifier in normal phase chromatography, liquid chromatography–mass spectrometry, and supercritical fluid chromatography are discussed

Quality-by-Design Is a Tool for Quality Assurance in the Assessment of Enantioseparation of a Model Active Pharmaceutical Ingredient

The design of experiments (DoE) is one of the quality-by-design tools valued in analytical method development, not only for cost reduction and time effectiveness, but also for enabling analytical method control and understanding via a systematic workflow, leading to analytical methods with built-in quality. This work aimed at using DoE to enhance method understanding for a developed UHPLC enantioseparation of terbutaline (TER), a model chiral drug, and to define quality assurance parameters associated with using chiral mobile phase additives (CMPA). Within a response surface methodology workflow, the effect of different factors on both chiral resolution and retention was screened and optimized using Plackett-Burman and central composite designs, respectively, followed by multivariate mathematical modeling. This study was able to delimit method robustness and elucidate enantiorecognition mechanisms involved in interactions of TER with the chiral modifiers. Among many CMPAs, successful TER enantioresolution was achieved using hydroxypropyl β-cyclodextrin (HP-β-CD) added to the mobile phase as 5.4 mM HP-β-CD in 52.25 mM ammonium acetate. Yet, limited method robustness was observed upon switching between the different tested CMPA, concluding that quality can only be assured with specific minimal pre-run conditioning time with the CMPA, namely 16-column volume (60 min at 0.1 mL/min). For enantiorecognition understanding, computational molecular modeling revealed hydrogen bonding as the main binding interaction, in addition to dipole-dipole inside the CD cavity for the R enantiomer, while the S enantiomer was less interactive

Whiter and Greener RP-HPLC Method for Simultaneous Determination of Dorzolamide, Brinzolamide, and Timolol Using Isopropanol as a Sustainable Organic Solvent in the Mobile Phase

A sustainable reversed-phase chromatographic method has been developed and validated for the simultaneous determination of three active pharmaceutical ingredients, dorzolamide, brinzolamide, and timolol, used to treat glaucoma. The eco-friendly solvent isopropanol has been used as an organic mobile phase constituent. According to the Hansen space green solvent selection tool, isopropanol has a G score of 6.5, comparable to ethanol, which has a G score of 6.6. The mobile phase consists of isopropanol: aqueous sodium acetate buffer (0.1 M, pH 4.25) in the ratio of 10:90 (v/v). The flow rate was maintained at 1 mL/min. Dorzolamide and brinzolamide were detected at 254 nm, and timolol was detected at 295 nm. A high-purity silica with a polymeric C18 modification column (150 × 4.6 mm, 5 µm particle size) was used for this separation. The three compounds were eluted within 8 min. The method was validated according to ICH guidelines. The calibration curves were linear in the range of 20–70 µg/mL, 40–140 µg/mL, and 20–70 µg/mL for dorzolamide, brinzolamide, and timolol, respectively. The LODs were found to be 1.61 µg/mL, 1.60 µg/mL, and 3.16 µg/mL for dorzolamide, brinzolamide, and timolol, respectively. Good accuracy and precision were obtained for the three compounds. The greenness and whiteness of the method were indicated using the AGREE, ChlorTox, and RGB12 tools

Glucuronidation Pathways of 5- and 7-Hydroxypropranolol: Determination of Glucuronide Structures and Enzyme Selectivity

Propranolol, a non-selective beta-blocker medication, has been utilized in the treatment of cardiovascular diseases for several decades. Its hydroxynaphthyl metabolites have been recognized to possess varying degrees of beta-blocker activity due to the unaltered side-chain. This study achieved the successful separation and identification of diastereomeric glucuronic metabolites derived from 4-, 5-, and 7-hydroxypropranolol (4-OHP, 5-OHP, and 7-OHP) in human urine. Subsequently, reaction phenotyping of 5- and 7-hydroxypropranolol by different uridine 5’-diphospho-glucuronosyltransferases (UGTs) was carried out, with a comparison to the glucuronidation of 4-hydroxypropranolol (4-OHP). Among the 19 UGT enzymes examined, UGT1A1, UGT1A3, UGT1A7, UGT1A8, UGT1A9, UGT1A10, UGT2A1, and UGT2A2 were found to be involved in the glucuronidation of 5-OHP. Furthermore, UGT1A6 exhibited glucuronidation activity towards 7-OHP, along with the aforementioned eight UGTs. Results obtained by glucuronidation of corresponding methoxypropranolols and MS/MS analysis of 1,2-dimethylimidazole-4-sulfonyl (DMIS) derivatives of hydroxypropranolol glucuronides suggest that both the aromatic and aliphatic hydroxy groups of the hydroxypropranolols may be glucuronidated in vitro. However, the analysis of human urine samples collected after the administration of propranolol leads us to conclude that aromatic-linked glucuronidation is the preferred pathway under physiological conditions

Mutual Modulation of the Activities of Human CYP2D6 and Four UGTs during the Metabolism of Propranolol

Cytochromes P450 (CYP) and UDP-glucuronosyltransferases (UGT) are two enzyme families that play an important role in drug metabolism, catalyzing either the functionalization or glucuronidation of xenobiotics. However, their mutual interactions are poorly understood. In this study, the functional interactions of human CYP2D6 with four human UGTs (UGT1A7, UGT1A8, UGT1A9, and UGT2A1) were investigated using our previously established co-expression model system in the fission yeast Schizosaccharomyces pombe. The substrate employed was propranolol because it is well metabolized by CYP2D6. Moreover, the CYP2D6 metabolite 4-hydroxypropranolol is a known substrate for the four UGTs included in this study. Co-expression of either UGT1A7, UGT1A8, or UGT1A9 was found to increase the activity of CYP2D6 by a factor of 3.3, 2.1 or 2.8, respectively, for the conversion of propranolol to 4-hydroxypropranolol. In contrast, UGT2A1 co-expression did not change CYP2D6 activity. On the other hand, the activities of all four UGTs were completely suppressed by co-expression of CYP2D6. This data corroborates our previous report that CYP2D6 is involved in functional CYP-UGT interactions and suggest that such interactions can contribute to both adverse drug reactions and changes in drug efficacy