Chiral discrimination and enantioselective analysis of drugs: an overview

Supercritical fluid extraction: Recent advances and applications

Among the different extraction techniques used at analytical and preparative scale, supercritical fluid extraction (SFE) is one of the most used. This review covers the most recent developments of SFE in different fields, such as food science, natural products, by-product recovery, pharmaceutical and environmental sciences, during the period 2007-2009. The revision is focused on the most recent advances and applications in the different areas; among them, it is remarkable the strong impact of SFE to extract high value compounds from food and natural products but also its increasing importance in areas such as heavy metals recovery, enantiomeric resolution or drug delivery systems.

Beta-cyclodextrin-modified CdSe/ZnS quantum dots for sensing and chiroselective analysis

Beta-cyclodextrin (beta-CD)-functionalized CdSe/ZnS quantum dots (QDs) are used for optical sensing and chiroselective sensing of different substrates using a fluorescence resonance energy transfer (FRET) or an electron transfer (ET) mechanisms. The FRET between the QDs and Rhodamine B incorporated in the beta-CD receptor sites is used for the competitive analysis of adamantanecarboxylic acid and of p-hydroxytoluene. Also, the dye-incorporated beta-CD-modified QDs are used for the chiroselective optical discrimination between D,L-phenylalanine and D,L-tyrosine. The receptor-functionalized QDs are also implemented for the optical detection of p-nitrophenol using an ET quenching route.

Chiral determination of antidepressant drugs and their metabolites in biological samples

The determination of chiral drugs and their metabolites in biological samples is key to gaining a full understanding of enantioselective drug action and disposition, as well as establishing the advantages of using racemate or isolated enantiomers. In this review, methods published in the last 8 years regarding the analysis of chiral antidepressant drugs and their metabolites in biological fluids (e.g., plasma, urine and cerebrospinal fluid) are reviewed. The importance and interest in analyzing the enantiomers of the active compound and its metabolites in biological samples are also discussed.

Comparison of the enantiomers of (+/-)-doxanthrine, a high efficacy full dopamine D(1) receptor agonist, and a reversal of enantioselectivity at D(1) versus alpha(2C) adrenergic receptors

Parkinson's disease is a neurodegenerative condition involving the death of dopaminergic neurons in the substantia nigra. Dopamine D(1) receptor agonists are potential alternative treatments to current therapies that employ L-DOPA, a dopamine precursor. We evaluated the pharmacological profiles of the enantiomers of a novel dopamine D(1) receptor full agonist, doxanthrine (DOX) at D(1) and alpha(2C) adrenergic receptors. (+)-DOX displayed greater potency and intrinsic activity than (-)-DOX in porcine striatal tissue and in a heterologous D(1) receptor expression system. Studies in MCF7 cells, which express an endogenous human dopamine D(1)-like receptor, revealed that (-)-DOX was a weak partial agonist/antagonist that reduced the functional activity of (+)-DOX and dopamine. (-)-DOX had 10-fold greater potency than (+)-DOX at alpha(2C) adrenergic receptors, with an EC50 value of 4 nM. These findings demonstrate a reversed stereoselectivity for the enantiomers of DOX at D(1) and alpha(2C) receptors and have implications for the therapeutic utility of doxanthrine.

Versatile method for chiral recognition by the quartz crystal microbalance: chiral mandelic acid as the detection model

Chiral recognition is considered to be the most important, fundamental basis in the development of separation technology for chiral isomers in the pharmaceutical and biotechnology fields. However, the selective detection of individual enantiomers is still one of the most difficult analytical tasks because of the close similarity of the molecular configurations between chiral isomers. This study presents a versatile vapor-diffused molecular assembly (VDMA) reaction approach for chiral recognition by the quartz crystal microbalance (QCM). Chiral L/D-mandelic acid (MA) was used as the detection model, and L-phenylalanine (L-Phe) was used as the selector. The construction of the L-Phe-modified QCM sensor involved a four-step layer-by-layer assembly procedure. Each modification step was analyzed by cyclic voltammetry, the contact angle, and a resonance frequency measurement. The chiral recognizability of the L-Phe-modified QCM sensor to L-mandelic acid was then examined by resonance frequency measurement using the novel VDMA technique and also investigated by atomic force microscope (AFM) measurements. A chiral discrimination factor of up to approximately 9 between L- and d-MA on the L-Phe-modified QCM sensor was obtained by using this gaseous-phase reaction technique. AFM results also showed obvious selective aggregation of L-MA on the L-Phe-modified surface but no noticeable aggregation of D-MA during the VDMA reaction. Both of the QCM and AFM results confirmed the usefulness of this proposed VDMA technique for the study of chiral recognition. The main advantage of the proposed method is that it offers a universal simple application scheme for the QCM detection of small resonance frequency changes due to chiral molecular recognition by a chiral selector immobilized on the QCM sensor surface.