Enantiomeric bioanalysis of simendan and levosimendan by chiral high-performance liquid chromatography

Efficient preparative separation of 6-(4-aminophenyl)-5-methyl-4, 5-dihydro-3(2H)-pyridazinone enantiomers on polysaccharide-based stationary phases in polar organic solvent chromatography and supercritical fluid chromatography

6-(4-Aminophenyl)-5-methyl-4,5-dihydro-3(2H)-pyridazinone is a key synthetic intermediate for cardiotonic agent levosimendan. Very few studies address the use of chiral stationary phases in chromatography for the enantioseparation of this intermediate. This study presents two efficient preparative methods for the isolation of (R)(-)-6-(4-aminophenyl)-5-methyl-4,5-dihydro-3(2H)-pyridazinone in polar organic solvent chromatography and supercritical fluid chromatography using polysaccharide-based chiral stationary phases and volatile organic mobile phases without additives in isocratic mode. Under optimum conditions, Chiralcel OJ column showed the best performance (α = 1.71, Rs = 5.47) in polar organic solvent chromatography, while Chiralpak AS column exhibited remarkable separations (α = 1.81 and Rs = 6.51) in supercritical fluid chromatography with an opposite enantiomer elution order. Considering the sample solubility, runtime and solvent cost, the preparations were carried out on Chiralcel OJ column and Chiralpak AS column (250 × 20 mm i.d.; 10 µm) in polar organic mode and supercritical fluid chromatography mode with methanol and CO₂ /methanol as mobile phases, respectively. By utilizing the advantages of chromatographic techniques and polysaccharide-based chiral stationary phases, this work provides two methods for the fast and economic preparation of (R)(-)-6-(4-aminophenyl)-5-methyl-4,5-dihydro-3(2H)-pyridazinone, which are suitable for the pharmaceutical industry.

Enatiomeric analysis of simendan by CE with?-CD as chiral selector compared with CMPA-HPLC

The chiral separation of simendan enantiomers using capillary electrophoresis was studied with beta-cyclodextrin (beta-CD) as chiral selector. The influences of the concentration and pH of borate buffer solution, beta-CD concentration and methanol content in the background electrolyte were investigated. These factors were compared with those in an HPLC with beta-CD as chiral mobile phase additive (CMPA-HPLC). The quantification properties of the developed CE method were examined. A baseline separation of simendan enantiomers was achieved in the background electrolyte of 20 mmol/L borate buffer (pH 11.0) containing 12 mmol/L beta-CD-methanol (50:50 in volume ratio). The CE method is comparable with CMPA-HPLC in chiral resolution, although the optimal pH in CE (11.0) is much higher than that (6.0) in CMPA-HPLC. This chiral CE method is applicable to the quantitative ananlysis and enantiomeric excess value determination of L-simendan.

Pharmaceutical and biomedical applications of enantioseparations using liquid chromatographic techniques

The chiral separation methods using liquid chromatographic techniques can be divided into two categories: one is a direct method, which is based on a diastereomer formation on stationary phase or in mobile phase. The other is an indirect method, which is based on a diasteromer formation by reaction with a homochiral reagent. The enantiomer separation on a chiral stationary phases followed by derivatization with an achiral reagent is also dealt with this review article as the indirect method. The pharmaceutical and biomedical applications of enantioseparations using the direct and indirect methods have been considered in this review.

Recent chromatographic and electrophoretic enantioseparations of cardiovascular drugs

The chromatographic and electrophoretic enantiomeric separation and analysis of several clinically used cardiovascular drugs have been reviewed. Several examples of recently reported applications of enantioselective analysis and various cardiovascular agents are presented.

Automated analysis of levosimendan in human plasma by on-line dialysis and liquid chromatography

A fully automated method for quantitation of levosimendan, (R)-(-)-[[4-(1,4,5,6-tetrahydro-4-methyl-6-oxo-3-pyridazinyl) phenyl]hydrazono]propanedinitrile, in human plasma is described. The method involves on-line dialysis of the samples, trace enrichment of the dialysates, and reversed-phase high-performance liquid chromatography with UV detection at 380 nm. An internal standard was used to compensate for variations in the dialysis rate caused by temperature fluctuations. The precision and accuracy of the method were good. The between-day variation (RSD) was 2.7% at a plasma concentration of 15 ng/mL and 1.7% at 450 ng/mL. The limit of quantitation was 5 ng/mL with an RSD of 4.0%. The completion time of the assay was 19 min.