Resolution of racemic metoprolol, propranolol, carvedilol, bisoprolol, salbutamol, and labetalol, commonly used β-blockers, into their enantiomers has been achieved by TLC on silica gel plates impregnated with optically pure L
-Glu and L
-Asp. Acetonitrile-methanol-water-dichloromethane and acetonitrile-methanol-water-glacial acetic acid mobile phases in different proportions enabled successful separation. The spots were detected with iodine vapor. The detection limits were 0.23, 0.1, 0.27, 0.25, 0.2, and 0.2 μg for each enantiomer of metoprolol, propranolol, carvedilol, bisoprolol, salbutamol, and labetalol, respectively.
Authors:Gergely Zachar, Tamás Jakó, István Vincze, Zsolt Wagner, Tamás Tábi, Eszter Bálint, Szilvia Mezey, Éva Szökő, and András Csillag
D-aspartate (D-Asp) modulates adult neural plasticity and embryonic brain development by promoting cell proliferation, survival and differentiation. Here, developmental changes of the excitatory amino acids (EAAs) L-Glu, L-Asp and D-Asp were determined during the first postembryonic days, a time window for early learning, in selected brain regions of domestic chickens after chiral separation and capillary electrophoresis. Extracellular concentration (ECC) of EAAs was measured in microdialysis samples from freely moving chicks. ECC of D-Asp (but not L-EAAs) decreased during the first week of age, with no considerable regional or learning-related variation. ECC of L-Asp and L-Glu (but not of D-Asp) were elevated in the mSt/Ac in response to a rewarding stimulus, suggesting importance of Asp-Glu co-release in synaptic plasticity of basal ganglia. Potassium-evoked release of D-Asp, with a protracted transient, was also demonstrated. D-Asp constitutes greater percentage of total aspartate in the extracellular space than in whole tissue extracts, thus the bulk of D-Asp detected in tissue appears in the extracellular space. Conversely, only a fraction of tissue L-EAAs can be detected in extracellular space. The lack of changes in tissue D-Asp following avoidance learning indicates a tonic, rather than phasic, mechanism in the neuromodulatory action of this amino acid.
Direct resolution of enantiomers of (±)-bupropion (BUP) was achieved by thin-layer chromatography on silica gel plates impregnated with optically pure l-Glu as chiral selector. The solvent system acetonitrile-methanol-dichloromethane-water (5.6:1:2.2:1, v/v) was successful in resolving the enantiomers. Spots were detected by use of iodine vapor. The detection limit was 0.2 μg for each enantiomer of BUP. The effects of concentration of chiral selector, temperature, and pH on enantiomeric resolution were examined. The separation of BUP enantiomers was also investigated by high-performance liquid chromatography (HPLC) on a chlorinated methylated cellulose-based stationary phase. Reversed phase HPLC was successful using binary mixture of aqueous ammonium formate and methanol for separation of enantiomeric pair with detection at 230 nm. The factors influencing HPLC separation were also investigated.
Authors:Tamás Gáll, Gábor Lehoczki, Gyöngyi Gyémánt, Tamás Emri, Zsuzsa M. Szigeti, György Balla, József Balla, and István Pócsi
4.2-Hz shaking frequency. The basic siderophore production medium (pH 7.5) contained 5 g/l L -Asp or Na- L -glutamate monosodium salt monohydrate (Na- L -Glu), 5 g/l L -lysine monohydrochloride ( L -Lys), 2 g/l K 2 HPO 4 , 2 g/l K 2 SO 4 , 1 g