Estimation of Lipophilicity of Some Polyoxygenated Steroids by the Means of Normal-Phase Thin-Layer Chromatography

Abstract

Unmodified silica gel in combination with two mobile phases, acetone–n-hexane and acetonitrile–dichloromethane, was used in order to evaluate the capability of normal-phase (NP) chromatography on bare silica gel in estimation of lipophilicity of some polyoxygenated steroids. Soczewinski equation coefficients were employed as a measure of lipophilicity. The R_M⁰ values obtained in NP-systems were correlated with those derived by extrapolation from reversed-phase (RP) systems. In addition, retention data, i.e., lipophilicity parameters determined in NP systems were compared with logP values calculated by use of several commercial computer programs. The results showed that chromatographic parameters R_M⁰, and m obtained in NP system consisted of silica gel as stationary phase and acetone–n-hexane as mobile phase, are acceptable as the measures of lipophilicity of polyoxygenated steroids. The mechanism of retention was discussed.

Keywords:

• calculated lipophilicity
• lipophilicity
• normal-phase chromatography
• polyoxygenated steroids
• silica gel
• structure-retention relationship