Intramolecular distribution of hydrophobicity influences pharmacological activity of propafenone-type MDR modulators

Lipophilicity is one of the major determining physicochemical descriptors for P-glycoprotein (P-gp) inhibitory activity. Recently, Pajeva and Wiese showed that in case of P-gp interaction, lipophilicity may be regarded as space-directed property. In the present study, a series of propafenone-type P-gp inhibitors with systematically varying hydrophobicity distribution within the molecules were synthesised and pharmacologically tested. QSAR studies on the basis of multiple linear regression analysis showed that with increasing lipophilicity of the substituents on the amine moiety, the statistical significance of the indicator variables, denoting the substitution pattern on the central aromatic ring system, also increases. This indicates that the distribution of hydrophobicity within the molecules influences the mode of interaction with P-gp.