Molecular interactions in lipophilic environments studied by electrochemistry at interfaces between immiscible electrolyte solutions

The description and understanding of absorption and distribution of potential new drug compounds in the organism is of paramount importance for the successful development of new drugs. However, the currently used physical chemical parameters such as oil-water distribution coefficients and ionization constants frequently fall short when it comes to a detailed description of the highly heterogeneous environments of both lipophilic and hydrophilic characters through which the drug compound passes. In this work, a new procedure based on electrochemistry at the interface between immiscible electrolyte solutions for addressing drug compound-ligand interactions in lipophilic environments as well as nonspecific ligand effects on distribution behavior has been developed. An attractive feature of the method is that it can simultaneously provide data for oil-water partition coefficients and ionization constants. The new procedure is demonstrated using five drug compounds with different physical chemical parameters and cholesterol as the oilphase ligand. The use of ligand shift ion partition diagrams in the data presentation allows a quick visualization and comparison of a series of related drug compounds.