Imitation of phase I oxidative metabolism of anabolic steroids by titanium dioxide photocatalysis

Stochastic dynamic mass spectrometric quantification of steroids in mixture - Part II

This paper deals with quantification of the following steroids in mixture: hydrocortisone (1), deoxycorticosterone (2), progesterone (3) and methyltestosterone (4) by means of mass spectrometry and implementing our innovative stochatic dynamic functional relationship between the analyte concentration in solution and the experimental variable intensity. The mass spectrometric data are correlated independently using chromatography. Chemometric analysis is carried out.

Characterization of lacosamide metabolites by UHPLC–ESI–HRMS method

In this study, the in vitro phase I metabolism of lacosamide was characterized with the use of ultra-high-performance liquid chromatography combined with high-resolution mass spectrometry (quadrupole time-of-flight). The use of two metabolism simulation techniques (photocatalysis and human liver microsomes) allowed the characterization of a polar metabolite of parent compound, not yet described. The experiment with the participation of HLM gave the ability to describe the full liver metabolic pathway of lacosamide. It has been proven that this molecule undergoes deacetylation, demethylation, and during liver tissue metabolism. Photocatalysis with the use of a TiO2 catalyst was proved to be a complementary technique in mimicking in vitro drug metabolism.

Photocatalysis as a Tool for in Vitro Drug Metabolism Simulation: Multivariate Comparison of Twelve Metal Oxides on a Set of Twenty Model Drugs

The constant development in the area of medicinal substances on the market and their subsequent progress in the field of drug analysis has become one of the reasons for the search for alternative, cheaper, and faster methods to determine the metabolism pathways of new molecular entities (NMEs). The simulation of transformation processes using photocatalysis is considered to be one of the promising methods. Although its effectiveness has been proven, the research has so far focused especially on titanium dioxide, while a more accurate comparison of the suitability of different photocatalysts in terms of their use in drug metabolism studies has not been performed. For this purpose, a set of twelve metal oxides was prepared and their photocatalytic efficiency in the direction of drug metabolism mimicking was checked on a model mixture of twenty medicinal substances differing both in chemical structure and pharmacological properties. Incubation with human liver microsomes (HLMs) was used as the reference method. The metabolic profiles obtained with the use of LC-MS analysis were compared using multidimensional chemometric techniques; and the graphic presentation of the results in the form of PCA plot and cluster dendrogram enabled their detailed interpretation and discussion. All tested photocatalysts confirmed their effectiveness. However, the exact outcome of the study indicate advantage of the WO3-assisted photocatalysis over other metal oxides.

Simulation of phase I metabolism reactions of selected calcium channel blockers by human liver microsomes and photochemical methods with the use of Q-TOF LC/MS

The in vitro phase I metabolism of perhexiline and flunarizine, two calcium channel blockers was investigated during this study with the use of human liver microsomes (HLM) method compared with TiO₂, WO₃ and ZnO catalyzed photochemical reaction. In order to determine the structures of metabolites an quadrupole time-of-flight mass spectrometry combined with liquid chromatography (Q-TOF LC/MS) system was used. The obtained high resolution mass spectra enabled to identify thirteen products of metabolism of selected drugs including three not yet described metabolites of perhexiline and two new metabolites of flunarizine. The vast majority of metabolites were confirmed also with the participation of photocatalytic approach of the drug metabolism simulation. The comparison of all metabolic profiles made with the use of computational methods drew attention particularly to TiO₂ and WO₃ catalyzed photochemical reaction as similar to HLM incubation. Additionally, in silico toxicity assessment of the detected transformation products of the analyzed substances was also evaluated.

TiO2 Photocatalyzed Oxidation of Drugs Studied by Laser Ablation Electrospray Ionization Mass Spectrometry

In drug discovery, it is important to identify phase I metabolic modifications as early as possible to screen for inactivation of drugs and/or activation of prodrugs. As the major class of reactions in phase I metabolism is oxidation reactions, oxidation of drugs with TiO2 photocatalysis can be used as a simple non-biological method to initially eliminate (pro)drug candidates with an undesired phase I oxidation metabolism. Analysis of reaction products is commonly achieved with mass spectrometry coupled to chromatography. However, sample throughput can be substantially increased by eliminating pretreatment steps and exploiting the potential of ambient ionization mass spectrometry (MS). Furthermore, online monitoring of reactions in a time-resolved way would identify sequential modification steps. Here, we introduce a novel (time-resolved) TiO2-photocatalysis laser ablation electrospray ionization (LAESI) MS method for the analysis of drug candidates. This method was proven to be compatible with both TiO2-coated glass slides as well as solutions containing suspended TiO2 nanoparticles, and the results were in excellent agreement with studies on biological oxidation of verapamil, buspirone, testosterone, andarine, and ostarine. Finally, a time-resolved LAESI MS setup was developed and initial results for verapamil showed excellent analytical stability for online photocatalyzed oxidation reactions within the set-up up to at least 1 h. Graphical Abstract.

Imitation of phase I metabolism reactions of MAO-A inhibitors by titanium dioxide photocatalysis

The imitation of phase I metabolism of moclobemide and toloxatone, two monoamine oxidase type A (MAO-A) inhibitors, was performed with the use of titanium dioxide photocatalytic process. Ultra high pressure liquid chromatography system coupled with an accurate hybrid ESI-Q-TOF mass spectrometer was used for the evaluation of metabolic profiles, structural elucidation of the identified transformation products and quantitative analysis of the process. Based on high resolution MS and MS/MS data, eleven transformation products were characterized in photocatalytic experiments for moclobemide and seven products for toloxatone. A significant number of these products were found as hepatic metabolites under the incubation of the selected MAO-A inhibitors with human liver microsomes (HLM). What is important, some of these HLM metabolites are not yet described in the literature. It was also found that the multivariate chemometric analysis allowed an effortless characterization of the registered metabolic profiles which can be a useful method for a fast preliminary drug metabolism study. Additionally, principal component analysis (PCA) of the registered TOF (MS) photocatalytic and HLM profiles of moclobemide and toloxatone shows that shorter irradiation time is preferred for photocatalytic metabolism experiments. A heterogeneous photocatalysis with the use of titanium dioxide was found to be a powerful tool for mimicking phase I metabolic reactions, as a fast, sensitive and inexpensive method.

TiO2 Photocatalysis-DESI-MS Rotating Array Platform for High-Throughput Investigation of Oxidation Reactions

We present a new high-throughput platform for studying titanium dioxide (TiO₂) photocatalytic oxidation reactions by performing reactions on a TiO₂-coated surface, followed by direct analysis of oxidation products from the surface by desorption electrospray ionization mass spectrometry (DESI-MS). For this purpose, we coated a round glass wafer with photocatalytically active anatase-phase TiO₂ using atomic layer deposition. Approximately 70 aqueous 1 μL samples can be injected onto the rim of the TiO₂-coated glass wafer, before the entire wafer is exposed to UV irradiation. After evaporation of water, the oxidation products can be directly analyzed from the sample spots by DESI-MS, using a commercial rotating sample platform. The method was shown to provide fast photocatalytic oxidation reactions and analysis with throughput of about four samples per minute. The feasibility of the method was examined for mimicking phase I metabolism reactions of amodiaquine, buspirone and verapamil. Their main photocatalytic reaction products were mostly similar to the products observed earlier in TiO₂ photocatalysis and in in vitro phase I metabolism assays performed using human liver microsomes.

Photolytic and photocatalytic degradation of tandospirone: Determination of kinetics, identification of transformation products and in silico estimation of toxicity

The photolytic and photocatalytic transformation of tandospirone with the use of TiO₂ and H₂O₂ was investigated. A micro-scale method for simultaneous irradiation with simulated full solar spectrum of multiple samples in photostability chamber was proposed. RP-UHPLC-DAD coupled with ESI-Q-TOF mass spectrometer was used for the quantitative and qualitative analysis of the processes. The developed method was fully validated and the kinetic parameters of tandospirone photodegradation were compared. The structures of eighteen photoproducts as well as phototransformation pathways were proposed. Based on the elucidated structures, computational toxicity assessment with the use of various software was performed and most of the photoproducts were found as less or similarly toxic to the parent compound. Nevertheless, several products, including one of the drug main metabolites, were significantly more toxic than the parent drug. The multivariate chemometric method (principal component analysis) was used to compare the toxicity of phototransformation products as well as the toxicity of the assessment methods.

Oxidation of Tyrosine-Phosphopeptides by Titanium Dioxide Photocatalysis

Protein phosphorylation has a key role in cell regulation. Oxidation of proteins, in turn, is related to many diseases and to aging, but the effects of phosphorylation on the oxidation of proteins and peptides have been rarely studied. The aim of this study was to examine the mechanistic effect of phosphorylation on peptide oxidation induced by titanium dioxide photocatalysis. The effect of phosphorylation was compared between nonphosphorylated and tyrosine phosphorylated peptides using electrospray tandem mass spectrometry. We observed that tyrosine was the most preferentially oxidized amino acid, but the oxidation reaction was significantly inhibited by its phosphorylation. The study also shows that titanium dioxide photocatalysis provides a fast and easy method to study oxidation reactions of biomolecules, such as peptides.

Comparison of TiO2 photocatalysis, electrochemically assisted Fenton reaction and direct electrochemistry for simulation of phase I metabolism reactions of drugs

The feasibility of titanium dioxide (TiO2) photocatalysis, electrochemically assisted Fenton reaction (EC-Fenton) and direct electrochemical oxidation (EC) for simulation of phase I metabolism of drugs was studied by comparing the reaction products of buspirone, promazine, testosterone and 7-ethoxycoumarin with phase I metabolites of the same compounds produced in vitro by human liver microsomes (HLM). Reaction products were analysed by UHPLC-MS. TiO2 photocatalysis simulated the in vitro phase I metabolism in HLM more comprehensively than did EC-Fenton or EC. Even though TiO2 photocatalysis, EC-Fenton and EC do not allow comprehensive prediction of phase I metabolism, all three methods produce several important metabolites without the need for demanding purification steps to remove the biological matrix. Importantly, TiO2 photocatalysis produces aliphatic and aromatic hydroxylation products where direct EC fails. Furthermore, TiO2 photocatalysis is an extremely rapid, simple and inexpensive way to generate oxidation products in a clean matrix and the reaction can be simply initiated and quenched by switching the UV lamp on/off.