Authors:Huba Kalász, Rafael Doležal, Kornélia Tekes, Kálmán Magyar, Tamás Csermely, and Sándor Hosztafi
Lipophilicity is an important physicochemical characteristic of compounds having potential use in the treatment of humans and animals. Morphine and its semisynthetic derivatives have effects on mu (μ), kappa (κ), and delta (δ) opioid receptors, and their physiological, pharmacological, and therapeutic effects mainly depend on their distribution in the body. The progress in separation techniques has made it possible to use modern methods to determine lipophilic/hydrophilic character of small amounts of organic compounds in just a few minutes. In addition to the classical determination of lipophilicity (shaken-flask method), other experimental methods (such as reversed-phase thin-layer chromatography, distribution-pH profile, etc.) and calculations based on the molecular composition are widely used. The lipophilic character of several morphine derivatives was determined using reversed-phase thin-layer chromatography and also high-performance liquid chromatography (HPLC) method. The results are graphically compared. Lipophilicity (log P) calculation using Pallas 3.8 program was successful only for certain morphine derivatives. Parameters derived from the experimental results of reversed-phase thin-layer chromatography and those of a special HPLC column were well comparable.
Authors:Tamás Csermely, Georg Petroianu, Kamil Kuca, Józsel Fűrész, Ferenc Darvas, Zsolt Gulyás, Rudolf Laufer, and Huba Kalász
Quaternary pyridinium aldoximes have been analyzed by thin-layer chromatography. Their separation was adequate when silica plates were used with a mobile phase with a high water content. As a consequence of their limited migration, reversed-phase TLC was not appropriate for determination of the lipophilicity of quaternary pyridinium aldoximes. Displacement TLC of some quaternary pyridinium aldoximes is, nevertheless, possible using silica as stationary phase with water-acetone-hydrochloric acid mobile phases. Normal-phase TLC with different concentrations of organic modifier gave a series of
values for the pyridinium aldoximes. Approximation of the different plots of
against organic modifier concentration to straight lines afforded
values and the slopes of the lines. The
values and the slopes both serve as indicators of the hydrophilic character of the compounds.