Thermodynamic study of new antiepileptic compounds by combining chromatography on the phosphatidylcholine biomimetic stationary phase and differential scanning calorimetry.

Abstract

Liquid chromatography coupled to spectrophotometric detection of new antiepileptic compounds, 1,2,4-triazole-3-thione derivatives, on immobilized artificial membrane phosphatidylcholine is reported. The curves representing the relationship between ln k versus 1/T generated under isocratic conditions by the use of methanol and acetonitrile-containing eluent systems have been constructed in order to determine the thermodynamic parameters: the enthalpies, entropies and the relative free energies. The hydrocarbon chains of analytes significantly influenced the membrane behavior of the whole molecules. Excellent correlations of the theoretical lipophilicity with the experimental thermodynamic descriptors, have confirmed contribution of the hydrophobic interactions in the retention process. However, presence of sulfur or oxygen as heteroatoms at R1 substituents in the 1,2,4-triazole ring appears to be responsible for more pronounced selectivity of these compounds on the phosphatidylcholine stationary phase. Molecular dynamics simulations revealed the selective preferences of the phosphatidylcholine with respect to the compounds with either ether of sulfide moieties. Experimental and theoretical set-ups resulted in corresponding outcomes.