Quantitative Analysis of Partition Behavior of Substituted Phenols from Aqueous Phase into Liposomes Made of Lecithin and Various Lipids

The partition coefficient of a series of substituted phenols in lecithin-liposome–water systems, P(L/W), was quantitatively analyzed by use of physicochemical molecular and substituent parameters. The effects on the P(L/W) value of the incorporation of cholesterol and charged lipids such as cardiolipin or stearylamine into the liposomal membranes were examined with the perturbation of the bilayered membrane structure induced by these lipids being taken into account. The partition behavior of phenols was primarily decided by the hydrophobicity, represented in terms of the 1-octanol–water partition coefficient, P(O/W). The partitioned phenols seemed to be in membrane close to the interface. The steric and electronic effects of substituents on the partitioning into liposomes varied significantly depending upon the type of lipids incorporated. The variations in these effects reflect differences in the structure of the interfacial region of the lecithin bilayer modified by the incorporation of various lipids.