Authors:Huba Kalász, Rafael Doležal, Kornélia Tekes, Kálmán Magyar, Tamás Csermely and Sándor Hosztafi
. Pliska, B. Testa, H. van de Waterbeemd (eds.), Lipophilicity in Drug Action and Toxicology, VCH, Weinheim, 1996, pp. 141–156.
J.Z. Karasova, M. Pohanka, K. Musilek, F. Zemek, K. Kuca , Toxicol. In Vitro
The lipophilicity of twenty new diquinothiazines has been determined by reversed-phase thin-layer chromatography on RP-18 silica plates with acetone-aqueous TRIS (tris(hydroxymethyl) aminomethane) buffer as mobile phase. The
values were linearly dependent on the concentration of acetone. The
values were determined by linear extrapolation to 0% acetone. The experimental lipophilicity log
was determined by use of a calibration plot obtained for six standards. The calculated lipophilicity log
was obtained by use of the software ClogP and compared with experimental log
values. Structure-lipophilicity relationships are discussed on the basis of the log
values and the correlation between
(slope) of the TLC equation.
Lipophilicity is often estimated by thin-layer chromatography (TLC) as a fundamental property related to biological and pharmaceutical activity. In a recent study, we contributed some standardization to the subject by performing a comparative analysis of the different approaches in the field. This part presents an analogous study on silica, the use of which in normal-phase systems seems to be a new trend of recent times. We have compared several approaches of TLC lipophilicity determination: a single TLC run, Soczewiński-Wachtmeister equation coefficients, principal component analysis (PCA) of the retention matrix, and PARAFAC on a three-way array. All techniques were applied to 35 model solutes with simple molecules, using nine concentrations of six modifiers: acetone, dioxane, ethyl acetate, methylethylketone, propan-2-ol, and tetrahydrofuran. Comparative analysis points to several general recommendations. Ethyl acetate seems to give the best correlations with lipophilicity, and the correlations of single retention values, extrapolated values (intercepts), or C0 are satisfactory (around 0.8) to use in normal-phase method in lipophilicity estimation. However, the correlation is quite worse and the normal-phase method should be treated as a method supplementary to the reversed-phase method. Neither PCA nor PARAFAC carried out on the retention matrix improved the correlations.
Authors:Małgorzata Janicka and Dorota Pietras-Ożga
Micellar liquid chromatography (MLC) has been used to study the lipophilicity of eight newly synthesized N-phenyltrichloroacetamide derivatives. Because the lipophilicity of a substance determines its retention and its interactions with micelles, chromatographic data calculated from experimental results — km (log km) — were compared with partition coefficients log P calculated from the molecular structures of the solutes. Micellar mobile phases containing Brij 35 and tetrahydrofuran, alkyl-bonded stationary phases, and two planar chromatography techniques — thin-layer chromatography (TLC) and over-pressured-layer chromatography (OPLC) — were used in the experiments. According to results obtained from the OPLC studies, especially, log km values are excellent descriptors of the lipophilicity of the compounds. Very good linear relationships between log km and log P were obtained by use of this technique (R in the range 0.917–0.987).