Biomedical subjects

Danuta Siluk

Publications and source records attributed to Danuta Siluk.

4 recordsLinked to original sources

PubMed2006

Simultaneous determination of buprenorphine, norbuprenorphine and the enantiomers of methadone and its metabolite (EDDP) in human plasma by liquid chromatography/mass spectrometry.

A previously reported enantioselective LC-MS assay for the determination of (R)- and (S)-methadone [Met] and (R)- and (S)-2-ethylidene-1,5-dimethyl-3,3-diphenyl-pyrrolidine [EDDP] (the primary metabolite of Met) has been adapted for use in the simultaneous determination of the plasma concentrations of Met, EDDP, buprenorphine (Bu) and norbuprenorphine (norBu). All of the target compounds were separated within 15 min using an alpha1-acid glycoprotein chiral stationary phase, a mobile phase composed of acetonitrile: ammonium acetate buffer [10 mM, pH 7.0] in a ratio of 18:82 (v/v), a flow rate of 0.9 ml/min at 25 degrees C. Deuterium labeled compounds were used as internal standards [d4-Bu, d3-norBu, (R,S)-d3-Met and (R,S)-d3-EDDP] and linear relationships between peak height ratios and drug concentrations were obtained for Bu and norBu in the range 0.2-12 ng/ml with correlation coefficients greater than 0.999. The relative standard deviations (%R.S.D.) for the intra- and inter-day precision of the method were <4.5% and for accuracy was <4.0%. The method was validated and used to analyze plasma samples obtained from opioid dependent methadone-maintained adults enrolled in a research study.

Buprenorphine↗

PubMed2005

Human red blood cells targeted metabolome analysis of glycolysis cycle metabolites by capillary electrophoresis using an indirect photometric detection method.

A capillary electrophoretic (CE) method with UV indirect spectrophotometric detection for determination of the main compounds of glycolysis in human erythrocytes has been elaborated. Blood samples for electrophoretic analysis were prepared by isolation of erythrocytes, lysis of the cells by heating in double-distilled water and subsequent ultrafiltration with a centrifuge equipped with filter devices: Mr cut off 5000. Using 20 mM 2,6-pyridinedicarboxylic acid (PDC) as a highly UV absorbing carrier electrolyte and 4 mM cetyltrimetylammonium bromide (CTAB), at the resulting pH 12.3, nine of the glycolysis intermediates were separated and characterized. The repeatability and linearity of the method was assessed with percent relative standard deviation (%R.S.D.) for migration time ranging from 0.3 to 1.9% and correlation coefficients of 0.991-0.999 for the studied concentration range. Limits of detection (LOD) for the analyzed metabolites were in the range of 6.25 x 10(-6) to 5.0 x 10(-5) M. The optimized CE method was used to compare metabolome content of red blood cells of 22 healthy volunteers. Mean metabolite concentrations in erythrocytes ranged from 49.6 microM for fructose-6-phosphate (F-6-P) to 3.1 mM for 2,3-diphospho-D-glyceric acid (2,3-DPG). The method can be readily applied in clinical, pathophysiological and epidemiological studies.

2,3-Diphosphoglycerate↗

PubMed2003

Chromatographic retention parameters in medicinal chemistry and molecular pharmacology.

The importance of lipophilicity for pharmacological and toxicological potency of xenobiotics has been recognized for a century. The reference lipophilicity scale is defined by the logarithm of partition coefficient, log P, determined in the l-octanol-water partition system. The tediousness of determinations and limited interlaboratory reproducibility of log P, on one hand, and the observations of linear relationship between log P and chromatographic retention parameters, on the other hand, gave rise to the substitution of the former by the readily available chromatographic data. Since its introduction, the reversed-phase high - performance liquid chromatography (HPLC), which has been viewed in terms of partition of a solute between a polar, aqueous mobile phase and a nonpolar stationary phase appeared especially suitable for lipophilicity (hydrophobicity) determination. The method got wide acceptance and has officially been recommended by the OECD. Fundamental relationships between chromatographic parameters are reviewed from the point of view of convenient and reliable lipophilicity measurements. The advantages and disadvantages of the stationary phase materials, which are presently employed for the determination of lipophilicity as well as those of specific HPLC systems and procedures, are critically reported. The literature on the application of chromatographic and electrochromatographic methods for assessment of lipophilicity of xenobiotics is reviewed. A separate paragraph is devoted to interpretation of retention parameters from HPLC systems comprising biomacromolecules. Role of lipophilicity in drug-biomacromolecule interactions is discussed in terms of quantitative structure-retention relationships (QSRR). Finally, reports are analyzed on systemic information which can be extracted by multivariate methods of data processing, like principal component analysis (PCA), from sets of lipophilicity parameters determined in diverse HPLC systems.

Chemical Phenomena↗

PubMed2002

Lipophilicity and pKa estimates from gradient high-performance liquid chromatography.

The linear-solvent strength (LSS) model of gradient elution has been applied to estimate parameters of lipophilicity and acidity of a series of drugs and model chemicals. Apparent pKa values and log kw values for individual analytes were determined in 2-3 gradient runs. The first experiment (or first two experiments) uses a wide-range organic modifier gradient with pH chosen for suppressed ionization of the analyte. The result of this experiment allows an estimate of contents of organic modifier of the mobile phase (%B) providing the required retention coefficient, k, for the non-ionized analyte. The following experiment is carried out with the latter %B and a pH-gradient of the aqueous component of the eluent that is sufficient to overlap the possible pKa-value of the analyte. The initial pH of the buffer used to make the mobile phase is selected to insure that the analyte is in non-ionized form. The resulting retention time allows an estimate of PKa in a solvent of the selected %B. At the same time, estimates of log kw can also be obtained. The log kw parameter obtained from gradient HPLC by the approach proposed correlated well with the corresponding value obtained by standard procedure of extrapolation of retention data determined in a series of isocratic measurements. Correlation between log kw and the reference parameter of lipophilicity, log P, was very good for a series of test analytes and satisfactory for a structurally diverse series of drugs. The approach supported with specific detection procedures can be recommended for fast screening of lipophilicity of individual components of complex mixtures like those produced by combinatorial chemistry. The values of pKa obtained in a study were found to correlate with the literature pKa data determined in water for a set of aniline derivatives studied. In case of a series of drugs the correlation was less than moderate if the general procedure of pKa determination was applied.

Chromatography, High Pressure Liquid↗