Determination of streptomycin in a pharmaceutical sample based on its degradation by hydrogen peroxide in the presence of copper(II).

The kinetics of streptomycin degradation by hydrogen peroxide at pH 7.4 was investigated. The reaction was catalyzed by traces of Cu(II) ions, and it was followed spectrophotometrically at 322 nm by applying the initial-rate method. The kinetic parameters of the reaction are reported, and a rate equation is suggested. From the dependence of the relative rate constants on the temperature, the activation energy was calculated to be 57.5 kJ/mol. Based on this reaction, a kinetic method for streptomycin determination is proposed. The calibration graph is linear in the ranges 1.94 - 15.48 microg/cm(3) and 0.15 - 1.94 microg/cm(3). The influence of foreign ions and molecules on the accuracy of the determinations was investigated. The proposed kinetic method has high selectivity and good sensitivity, and enabled to determine streptomycin in pharmaceutical samples.     

High-performance liquid chromatographic determination of glaucine inGlaucium flavum crantz

Summary A method has been developed for the extraction and rapid analysis of D-glaucine inGlaucium flavum Crantz. Simple extraction of the drug with diethyl ether was followed by high-performance liquid chromatography on a μBondapak C₁₈ column using a mixture of acetonitrile, methanol and phosphate buffer as the mobile phase. Data on selectivity, sensitivity and precision demonstrate the reliability of this method.     

Chemical composition and antimicrobial activity of essential oils from Centaurea pannonica and C. jacea

The chemical composition and antimicrobial activity of the essential oils obtained by hydrodistillation from Centaurea pannonica (Heufel) Simonkai and C. jacea L. (Asteraceae), were investigated. The essential oils were analyzed by GC and GC-MS. Forty five and twenty nine compounds were identified in the two oils, respectively. C. pannonica oil was rich in fatty acids (43.7%), with 9-octadecanoic acid (34.0%) and (Z,Z)-9,12-octadecadienoic acid (8.6%) as the major compounds. In contrast, the essential oil of C. jacea was dominated by oxygenated sesquiterpenes (43.2%), among which caryophyllene oxide (23.5%) and spathulenol (8.9%) were the major constituents. However, the oil was also characterized by an important fatty acid fraction (15.5%), with 9-octadecanoic acid (8.9%) and hexadecanoic acid (6.6%) being the main components. The antimicrobial activities of the essential oils were evaluated by the microdilution method against three Gram-positive and three Gram-negative bacteria, and one yeast. Both oils exhibited significant antimicrobial activity, especially against Gram-positive bacteria.     

Use of biopartitioning micellar chromatography and RP-HPLC for the determination of blood–brain barrier penetration of α-adrenergic/imidazoline receptor ligands,and QSPR analysis

For this study, 31 compounds, including 16 imidazoline/α-adrenergic receptor (IRs/α-ARs) ligands and 15 central nervous system (CNS) drugs, were characterized in terms of the retention factors (k) obtained using biopartitioning micellar and classical reversed phase chromatography (log k_BMC and log k_wRP, respectively). Based on the retention factor (log k_wRP) and slope of the linear curve (S) the isocratic parameter (φ₀) was calculated. Obtained retention factors were correlated with experimental log BB values for the group of examined compounds. High correlations were obtained between logarithm of biopartitioning micellar chromatography (BMC) retention factor and effective permeability (r(log k_BMC/log BB): 0.77), while for RP-HPLC system the correlations were lower (r(log k_wRP/log BB): 0.58; r(S/log BB): –0.50; r(φ₀/P_e): 0.61). Based on the log k_BMC retention data and calculated molecular parameters of the examined compounds, quantitative structure–permeability relationship (QSPR) models were developed using partial least squares, stepwise multiple linear regression, support vector machine and artificial neural network methodologies. A high degree of structural diversity of the analysed IRs/α-ARs ligands and CNS drugs provides wide applicability domain of the QSPR models for estimation of blood–brain barrier penetration of the related compounds.     

Influence of selected mobile phase properties on the TLC retention behavior of ziprasidone and its impurities

ABSTRACT

Influence of nine different solvents, either alone or in a mixture, on the retention behavior of ziprasidone and its five impurities were examined by normal-phase thin-layer chromatography. Migration distances of the examined compounds obtained under the examined chromatographic conditions were correlated with calculated mobile phase properties, such as Snyder polarity and Hansen solubility. Linear or second-order polynomial relationships with high correlation coefficients were established between investigated variables. The obtained mathematical functions and statistical results indicated that selected mobile phase properties can be used for the prediction of the retention behavior of ziprasidone and its five impurities.