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

Styryl Group, a Friend or Foe in Medicinal Chemistry

The styryl (Ph-CH=CH-R) group is widely represented in medicinally important compounds, including drugs, clinical candidates, and molecular probes as it positively impacts the lipophilicity, oral absorption, and biological activity. The analysis of matched molecular pairs (styryl vs. phenethyl, phenyl, methyl, H) for the biological activity indicates the superiority aspect of styryl compounds. However, the Michael acceptor site in the styryl group makes it amenable to the nucleophilic attack by biological nucleophiles and transformation to the toxic metabolites. One of the downsides of styryl compounds is isomerization that impacts the molecular conformation and directly affects biological activity. The impact of cis-trans isomerism and isosteric replacements on biological activity is exemplified. We also discuss the styryl group-bearing drugs, clinical candidates, and fluorescent probes. Overall, the present review reveals the utility of the styryl group in medicinal chemistry and drug discovery.

Pharmacokinetics of Flunarizine Hydrochloride After Single Oral Doses in Healthy Subjects: Bioequivalence Study and Food Effects

We designed a study to compare the newly developed 5-mg flunarizine hydrochloride capsules (test) to that of its marketed counterpart (5-mg; reference) among healthy adult Chinese volunteers. We performed an open-label, single-center study that consisted of 2 randomized, crossover trials, including a fasting trial and a fed trial. In each part of the study, the subjects were randomly assigned to either receive the test or reference products (5-mg flunarizine) in a 1:1 ratio. Subjects then received the alternative products, following a 14-day washout period. Concentrations of plasma flunarizine were analyzed using liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters (noncompartmental model) were evaluated using the WinNonlin software. The analysis of variance and Food and Drug Administration bioequivalence statistical criterion of 90% confidence interval for 80% to 125% range (set at P ≤ .05) of geometric means ratios of test: reference product for peak plasma concentration, area under the plasma concentration-time curve (AUC) from time 0 to time t, and AUC from time 0 to infinity were determined. Tolerability was evaluated during the entire study period. Overall, 23 volunteers completed the fasting study, while 40 volunteers completed the fed study. The test formulation was found to be bioequivalent to the marketed formulation, as the 90% confidence interval for the ratio of geometric means of peak plasma concentration (fasting: 87.61%-101.67%; fed: 87.38%-104.06%), AUC from time 0 to time t (fasting: 89.44%-99.92%; fed: 92.65%-98.28%), and AUC from time 0 to infinity (fasting: 95.02%-104.33%; fed: 90.41%-96.96%) were within equivalence limits (80-125%) under both the fasting and fed conditions. When flunarizine was given alongside high-fat meals, time to maximum concentration was delayed ≈3.5 hours compared to fasting conditions. Meantime, high-fat meals increased its exposure by nearly 50%. Furthermore, there were no serious adverse events found among the subjects. This study confirmed that test and reference flunarizine hydrochloride capsules were bioequivalent under fasting and postprandial conditions.

Identification and characterization of citalopram new metabolites with the use of UHPLC-Q-TOF technique: In silico toxicity assessment of the identified transformation products

In this study the metabolite profiling of citalopram with the use of human liver microsomes as well as the complementary photocatalytic method were established. This strategy allowed the detection of five metabolites of citalopram including 3-hydroxycitalopram and 3-oxocitalopram which were found as a new and not previously described metabolites of this drug The photocatalytic simulation of metabolism was carried out using tungsten (VI) oxide nanopowders with the different particle sizes, which allowed to examine the effect of this photocatalyst parameter on the mapping of metabolic processes. The accurate characterization of all observed structures was possible due to the use of ultra-high-pressure liquid chromatography and high-resolution mass spectrometry combined system as a highly useful technique in drug metabolism studies. In order to perform the toxicity prediction of citalopram and its metabolites, the acute toxicity to rodents, as well as genotoxicity, carcinogenicity, developmental toxicity and receptor-mediated toxicity was calculated basing on the in silico tools.

Mimicking of Phase I Metabolism Reactions of Molindone by HLM and Photocatalytic Methods with the Use of UHPLC-MS/MS

Establishing the metabolism pathway of the drug undergoing the hepatic biotransformation pathway is one of the most important aspects in the preclinical discovery process since the presence of toxic or reactive metabolites may result in drug withdrawal from the market. In this study, we present the structural elucidation of six, not described yet, metabolites of an antipsychotic molecule: molindone. The elucidation of metabolites was supported with a novel photocatalytical approach with the use of WO3 and WS2 assisted photochemical reactions. An UHPLC-ESI-Q-TOF combined system was used for the registration of all obtained metabolite profiles as well as to record the high resolution fragmentation spectra of the observed transformation products. As a reference in the in vitro metabolism simulation method, the incubation with human liver microsomes was used. Chemometric comparison of the obtained profiles pointed out the use of the WO3 approach as being more convenient in the field of drug metabolism studies. Moreover, the photocatalysis was used in the direction of the main drug metabolite synthesis in order to further isolation and characterization.