Methods and approaches for determination and enantioseparation of (RS)‐propranolol

Propranolol, a β‐adrenergic receptor antagonist, is a chiral compound that is marketed as a racemate, but only the (S)‐(?)‐enantiomer is responsible for the β‐adrenoceptor blocking activity. Different chromatographic methods have been applied for separation and determination of enantiomers of (RS)‐propranolol. In this article a review is presented on different liquid chromatographic methods used for enantioseparation of (RS)‐propranolol, using both HPLC and TLC. In addition, some aspects of enantioseparation under achiral phases of liquid chromatography have been briefly mentioned.     

Resolution and isolation of enantiomers of (±)‐isoxsuprine using thin silica gel layers impregnated with l‐glutamic acid,comparison of separation of its diastereomers prepared with chiral derivatizing reagents having l‐amino acids as chiral auxiliaries

Thin silica gel layers impregnated with optically pure l ‐glutamic acid were used for direct resolution of enantiomers of (±)‐isoxsuprine in their native form. Three chiral derivatizing reagents, based on DFDNB moiety, were synthesized having l ‐alanine, l ‐valine and S‐benzyl‐l ‐cysteine as chiral auxiliaries. These were used to prepare diastereomers under microwave irradiation and conventional heating. The diastereomers were separated by reversed‐phase high‐performance liquid chromatography on a C₁₈ column with detection at 340 nm using gradient elution with mobile phase containing aqueous trifluoroacetic acid and acetonitrile in different compositions and by thin‐layer chromatography (TLC) on reversed phase (RP) C₁₈ plates. Diastereomers prepared with enantiomerically pure (+)‐isoxsuprine were used as standards for the determination of the elution order of diastereomers of (±)‐isoxsuprine. The elution order in the experimental study of RP‐TLC and RP‐HPLC supported the developed optimized structures of diastereomers based on density functional theory. The limit of detection was 0.1–0.09 µg/mL in TLC while it was in the range of 22–23 pg/mL in HPLC and 11–13 ng/mL in RP‐TLC for each enantiomer. The conditions of derivatization and chromatographic separation were optimized. The method was validated for accuracy, precision, limit of detection and limit of quantification. Copyright © 2014 John Wiley & Sons, Ltd.     

A novel approach for enantioseparation as applied to (RS)‐etodolac from pharmaceutical formulations: LC MS and density functional theory support for confirmation of diastereomers so separated

In the present studies formation of diastereomers of (RS)‐etodolac was confirmed using LC‐MS when [M + H]⁺ or [M]⁺ were recorded for the diastereomers. The lowest energy optimized structures of two diastereomers were drawn, which confirmed the three‐dimensional geometry of the diastereomers. This supports the optimized analytical separation conditions. In addition, separation of diastereomers was successful using a C₁₈ column and a binary mixture of methanol and triethyl ammonium phosphate buffer of pH 4.5 (80:20, v/v) as mobile phase at a flow rate of 1 mL min^?1 and UV detection at 223 nm. The separation method was validated as per International Conference on Harmonization guidelines. (RS)‐Etodolac was isolated from commercial tablets and purified and characterized to be used as racemic standard. Three pairs of diastereomers were synthesized using enantiomerically pure amines, namely, (R)‐(+)‐α‐methyl benzyl amine, (S)‐(?)‐α,4‐dimethylbenzylamine and (R)‐(?)‐1‐cyclohexylethylamine. Derivatization reactions were carried out under conditions of stirring at room temperature (30 °C for 2 h) as well as under microwave irradiation (MWI), and the two types of diastereomers were compared. Reaction conditions for derivatization were optimized with respect to mole ratio of chiral derivatizing agent and (RS)‐etodolac and MWI time. No racemization was observed throughout the study. Copyright © 2015 John Wiley & Sons, Ltd.     

A review of bioanalytical methods for chronic lymphocytic leukemia drugs and metabolites in biological matrices

Quantitation of drugs used for the treatment of chronic lymphocytic leukemia in various biological matrices during both pre-clinical and clinical developments is very important, often in routine therapeutic drug monitoring. The first developed methods for quantitation were traditionally done on LC in combination with either UV or fluorescence detection. However, the emergence of LC with mass spectrometry in tandem in early 1990s has revolutionized the quantitation as it has provided better sensitivity and selectivity within a shorter run time; therefore it has become the choice of method for the analysis of various drugs. In this article, an overview of various bioanalytical methods (HPLC or LC–MS/MS) for the quantification of drugs for the treatment of chronic lymphocytic leukemia, along with applicability of these methods, is given.     

Synergic Synthesis and Characterization of tert-Butyl 4-[(E)-But-1-en-3-yn-1-yl]-3-{[tert-butyl(dimethyl)silyl]oxy}-1H-indole-1-carboxylate

Russian Journal of Organic Chemistry - tert-Butyl 4-[(E)-but-1-en-3-yn-1-yl]-3-{[tert-butyl(dimethyl)silyl]oxy}-1H-indole-1-carboxylate has been synthesized with a good yield and selectivity...     

Luminescence studies of diopside doped with various concentrations of Dysprosium (III)

Research on Chemical Intermediates - Diopside doped with various concentration (0.5, 1.0, 1.5, 2.0 and 2.5 mol%) of Dysprosium were prepared using solid-state reaction technique....     

Isolation of Sesquiterpene Lactones and the Antioxidant and Anticancer Activities of Crude Extracts from Cyanthillium cinereum

Chemistry of Natural Compounds - Three sesquiterpene lactones has been isolated from Cyanthillium cinereum (L.) H. Rob. by bioactivity guided assay and characterized by spectral methods as...     

Photosynthetic,Biochemical and Secondary Metabolite Changes in a Medicinal Plant Chlorophytum borivillianum (Safed musli) against Low and High Doses of UV-B Radiation

Plants are inevitably grown in presence of sunlight, therefore bound to be exposed to natural UV-B radiation. Several studies have already been conducted with UV-B and medicinal plants and only few studies showed dose dependent variation. The present study aims to find out the variations and adaptation in Chlorophytum borivillianum under two different doses of UV-B radiation; ambient + low (3.2 kJm⁻² d⁻¹) and high (7.2 kJm⁻² d⁻¹) UV-B dose, denoted as LD and HD, respectively. Reduction in photosynthetic rate was higher at HD, while plants receiving LD displayed nonsignificant variation. During vegetative and reproductive stage, significant reduction (P ≤ 0.001) in stomatal conductance was obtained when exposed to HD-eUV-B. F_v/F_m showed more reductions in HD-eUV-B (12.6%) followed by LD-eUV-B (7.9%). Low and high doses of UV-B enhanced the anthocyanin content but the increase was significant in HD, indicates epidermal protection strategy by the plants. Under LD-eUV-B, the content of saponin, a major phytochemical constituent was enhanced by 26%. Phytochemical analysis of roots revealed reduction mostly in fatty acid components whereas the steroidal components (stigmasterol and sarsasapogenin) showed enhancement in response to LD. The study suggests the importance of LD-eUV-B in the stimulation of medicinal compounds in C. borivillianum.     

Studies on long lasting optical properties of Eu2+ and Dy3+ doped di-barium magnesium silicate phosphors

Di-bariummagnesium silicate phosphors doped with europiumand dysprosium were prepared under a weak reducing atmosphere. X-ray diffraction pattern of the sample was also done that confirmed the proper preparation of the phosphor. Scanning electron microscope (SEM) images confirmed that the sample has regular surface and uniform grain size distribution. Comparative studies of phosphorescence decay of Ba₂MgSi₂O₇:Eu²⁺, Dy³⁺ phosphors with different concentration of Dy³⁺ were done. The phosphor with 0.5/1.5 mol% of Eu/Dy, exhibited optimum green color afterglow properties. This emission is expected to arise due to transition of Eu²⁺ ions from any of the sublevels of 4f⁶5d¹ configuration to ⁸S_7/2 level of the 4f⁷ configuration. For a suitable trap depth, the trap concentration is expected to be proportional to the concentration of Dy³⁺. These traps are responsible for holding the charge career for a reasonable time, subsequently for increasing the time of afterglow. Hence, optimum Dy³⁺ concentration produces the longer afterglow duration with higher intensity of luminescence signals. Trap depth were also calculated using thermoluminescence glow curve which was indicative of formation of traps suitable for long afterglow.