Stereoselective liquid chromatographic determination of 1′-oxobufuralol and 1′-hydroxybufuralol in rat liver microsomal fraction using hollow-fiber liquid-phase microextraction for sample preparation

Liquid-Phase Microextraction Approaches for Preconcentration and Analysis of Chiral Compounds: A Review on Current Advances

Chirality is a critical issue in pharmaceutics, forensic chemistry, therapeutic drug monitoring, doping control, toxicology, or environmental investigations as enantiomers of a chiral compound can exhibit different activities, i.e., one enantiomer can have the desired effect while the other one can be inactive or even toxic. To monitor enantioselective metabolism or toxicokinetic/toxicodynamic mechanisms in extremely low content in biological or environmental matrices, sample preparation is vital. The present review describes current status of development of liquid-phase microextraction approaches such as hollow fiber liquid-phase microextraction (HF-LPME), electromembrane extraction (EME), dispersive liquid-liquid microextraction (DLLME), and supramolecular solvent-based microextraction (SSME), used for sample preparation of enantiomers/chiral compounds. The advantages and limitations of the above techniques are discussed. Attention is also focused on chiral separation approaches commonly applied to study the stereo-selective metabolism or toxicokinetic/toxicodynamic mechanisms of enantiomers in the biological and environmental samples.

Pharmacokinetics and Differential Regulation of Cytochrome P450 Enzymes in Type 1 Allergic Mice

Type 1 allergic diseases are characterized by elevated production of specific immunoglobulin E (IgE) for each antigen and have become a significant health problem worldwide. This study investigated the effect of IgE-mediated allergy on drug pharmacokinetics. To further understand differential suppression of hepatic cytochrome P450 (P450) activity, we examined the inhibitory effect of nitric oxide (NO), a marker of allergic conditions. Seven days after primary sensitization (PS7) or secondary sensitization (SS7), hepatic CYP1A2, CYP2C, CYP2E1, and CYP3A activities were decreased to 45%-75% of the corresponding control; however, CYP2D activity was not downregulated. PS7 and SS7 did not change the expression levels of five P450 proteins. Disappearance of CYP1A2 and CYP2D substrates from the plasma was not significantly different between allergic mice and control mice. In contrast, the area under the curve of a CYP1A2-mediated metabolite in PS7 and SS7 mice was reduced by 50% of control values. Total clearances of a CYP2E1 substrate in PS7 and SS7 mice were significantly decreased to 70% and 50% respectively, of the control without altering plasma protein binding. Hepatic amounts of CYP1A2 and CYP2E1 substrates were enhanced by allergic induction, being responsible for each downregulated activity. NO scavenger treatment completely improved the downregulated P450 activities. Therefore, our data suggest that the onset of IgE-mediated allergy alters the pharmacokinetics of major P450-metabolic capacity-limited drugs except for CYP2D drugs. NO is highly expected to participate in regulatory mechanisms of the four P450 isoforms.

Enantioselective analysis of ranolazine and desmethyl ranolazine in microsomal medium using dispersive liquid–liquid microextraction and LC–MS/MS

Background: An enantioselective bioanalytical method using dispersive liquid–liquid microextraction (DLLME) and LC–MS/MS was developed for the chiral analysis of ranolazine (RNZ) and one of its metabolites (desmethyl ranolazine [DRNZ]). Results: The analytes were extracted from microsomal medium by DLLME, using chloroform as extractor solvent and acetone as dispersive solvent. The enantiomers of RNZ and DRNZ were analyzed simultaneously for the first time using a Chiralcel OD-H®. Method validation showed recoveries in the order of 55 and 45%, and LLOQ of 25 and 10 ng ml-1 for the enantiomers of RNZ and DRNZ, respectively. Linearity was established in the concentration range of 10 to 1000 and 25 to 2500 ng ml-1 for each DRNZ and RNZ enantiomer, respectively. Conclusion: The unprecedented use of DLLME was demonstrated to be very useful for sample preparation of microsomal matrix. Furthermore, the in vitro metabolism of RNZ was enantioselective.