Structure-based mapping of the histone-binding pocket of KDM4D using functionalized tetrazole and pyridine core compounds.

KDM4 histone demethylases became an exciting target for inhibitor development as the evidence linking them directly to tumorigenesis mounts. In this study, we set out to better understand the binding cavity using an X-ray crystallographic approach to provide a detailed landscape of possible interactions within the under-investigated region of KDM4. Our design strategy was based on utilizing known KDM binding motifs, such as nicotinic acid and tetrazolylhydrazides, as core motifs that we decided to enrich with flexible tails to map the distal histone binding site.

Simultaneous quantification of acidic and basic flupirtine metabolites by supercritical fluid chromatography according to European Medicines Agency validation.

Supercritical fluid chromatography (SFC) holds the potential to become an orthogonal method to HPLC/UHPLC in xenobiotic metabolism studies, due to its outstanding capacity to simultaneously separate highly similar (as HPLC) and physicochemically different analytes (problematic using HPLC). Paucity of guideline-conform validation, however, has been a major obstacle to clinical application of SFC, even in cases where biotransformation yields chemically dissimilar metabolites that require more than one HPLC method for comprehensive analysis. Here, a method based on supercritical fluid chromatography coupled to single quadrupole MS detection was developed to simultaneously quantify the divisive analgesic flupirtine and its acidic and basic metabolites, represented by 4-fluorohippuric acid (4-FHA) and the active metabolite D-13223 respectively, using custom-made synthetic internal standards.

The many (inter-)faces of supercritical fluid chromatography: the present and future prospects of online supercritical fluid extraction-supercritical fluid chromatography.

Automated supercritical fluid extraction-supercritical fluid chromatography is an innovative method with low-effort sampling strategies (e.g., dried blood spots) that may make large-scale application faster, cheaper and greener than currently thought possible.

Supercritical fluid extraction (SFE) of ketamine metabolites from dried urine and on-line quantification by supercritical fluid chromatography and single mass detection (on-line SFE-SFC-MS).

On-line solid-phase supercritical fluid extraction (SFE) and chromatography (SFC) coupled to mass spectrometry (MS) has been evaluated for its usefulness with respect to metabolic profiling and pharmacological investigations of ketamine in humans. The aim of this study was to develop and validate a rapid, highly selective and sensitive SFE-SFC-MS method for the quantification of ketamine and its metabolites in miniature amounts in human urine excluding liquid-liquid extraction (LLE). Several conditions were optimized systematically following the requirements of the European Medicines Agency: selectivity, carry-over, calibration curve parameters (LLOQ, range and linearity), within- and between-run accuracy and precision, dilution integrity, matrix effect, and stability.

Ketamine metabolites with antidepressant effects: Fast, economical, and eco-friendly enantioselective separation based on supercritical-fluid chromatography (SFC) and single quadrupole MS detection.

Increasing evidence accumulates that metabolites of the dissociative anesthetic ketamine contribute considerably to the biological effects of this drug and could be developed as next generation antidepressants, especially for acute treatment of patients with therapy-refractory major depression. Analytical methods for the simultaneous determination of the plethora of hydroxylated, dehydrogenated and/or demethylated compounds formed after administration of ketamine hydrochloride are a prerequisite for future clinical investigations and a deeper understanding of the individual role of the isomers of these metabolites. In this study, we present development and validation of a method based on supercritical-fluid chromatography (SFC) coupled to single quadrupole MS detection that allows the separation of ketamine as well as all of its relevant metabolites detected in urine of healthy volunteers.

A stability study of amphotericin B, colistin and tobramycin in a hydrophilic suspension commonly used for selective decontamination of the digestive tract by HPLC and in vitro potency measurements.

Objectives: A suspension for oral use which consists of three non-absorbable antibiotics (amphotericin B, colistin and tobramycin) is often used in clinical practice for the selective decontamination of the digestive tract (SDD) of patients in intensive care. Such a therapy is a preventive tool to minimise the risk of pneumonia and bacteraemia in intubated patients. The administration and the treatment results are controversially discussed.

Quantitative chiral and achiral determination of ketamine and its metabolites by LC-MS/MS in human serum, urine and fecal samples.

Ketamine (KET) is a widely used anesthetic drug which is metabolized by CYP450 enzymes to norketamine (n-KET), dehydronorketamine (DHNK), hydroxynorketamine (HNK) and hydroxyketamine (HK). Ketamine is a chiral compound and S-ketamine is known to be the more potent enantiomer. Here, we present the development and validation of three LC-MS/MS assays; the first for the quantification of racemic KET, n-KET and DHNK in human serum, urine and feces; the second for the separation and quantification of the S- and R-enantiomers of KET, n-KET and DHNK, and the third for separation and quantification of 2S,6S-hydroxynorketamine (2S,6S-HNK) and 2R,6R-hydroxynorketamine (2R,6R-HNK) in serum and urine with the ability to separate and detect 10 additional hydroxylated norketamine metabolites of racemic ketamine.

Substituted tetrazoles as multipurpose screening compounds.

Tetrazoles are small functional heterocycles that are suited to serve simultaneously as aromatic platform for diversity and as functional interaction motif. Furthermore, the tetrazole ring and its deprotonated tetrazolate counterpart are metal ion complexing ligands that possess a rich variety of binding and bridging modes. We recently demonstrated that fragments containing the tetrazole moiety and a metal chelating hydrazide group are well suited to discover selective screening hits with high ligand efficiency for a given protein target.

Purity determination of amphotericin B, colistin sulfate and tobramycin sulfate in a hydrophilic suspension by HPLC.

A suspension comprising of the three antibiotic substances amphotericin B, colistin sulfate and tobramycin sulfate is often used in clinical practice for the selective decontamination of the digestive tract of patients in intensive care. Since no detailed procedures, specifications or stability data are available for manufacturing this suspension, there may be discrepancies regarding formulation and stability of suspensions prepared in different pharmacies. The aim of this work is to develop a standardized formulation and to determine its stability under defined storage conditions.