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.