Study of the interaction of cholesterol with potentially hypocholesterolemic substances in a monolayer form

The behaviour of mixed monolayers of cholesterol (chol) and stigmastanil phosporylcholine (SPC) at the air–water interface was studied and compared with that of the cholesterol–arachidonic acid (Ara) system in order to examine the molecular interactions between the film components. The structural characteristics of the mixed films was determined from the π–A isotherms recorded on an automated Langmuir-type film balance. The studies confirm that the mixed films are homogeneous and their components exhibit negative deviations from ideality as the result of mutual interactions at the interface. The magnitude of these interactions depends on the surface pressure region, temperature, as well as the system composition. Values of the thermodynamic parameters such as ΔGexc, ΔSexc and ΔHexc provide evidence for the presence of interactions, which are stronger in the chol–SPC system than in the chol–Ara mixed films.