Thermodynamics of partitioning and solvation of ketoprofen in some organic solvent: buffer and liposome systems

Abstract

The ketoprofen (KTP) partitioning thermodynamics was studied in different solvent/buffer systems such as cyclohexane (CH/W), octanol (ROH/W), isopropyl myristate (IPM/W), chloroform (CLF/W); as well as in dimyristoyl phosphatidylcholine (DMPC) and dipalmitoyl phosphatidylcholine (DPPC) liposome systems. In all cases, the rational partition coefficients (K X O/w) were greater than unit; therefore standard transfer free energies were negative in sign indicating a high affinity of KTP for organic media. K X O/w values were approximately eightyfive-fold higher in the ROH/W system regarding the CH/W system, thus indicating a high degree of hydrogen bonding contribution to partitioning. While in the case of IPM/W and CLF/W systems, K X O/w values were approximately only three or four-fold lower than those observed in ROH/W. On the other hand, K X O/w values were approximately seventy-five or one hundred fifty-fold higher in the liposomes compared to ROH/W system indicating a high degree of bilayers immobilization and/or an electrostatic contribution to partitioning. In all cases, standard transfer enthalpies and entropies of KTP from water to organic media were positive in sign indicating some degree of participation of the hydrophobic hydration on the partitioning processes. Finally, by using the reported data for solvation of KTP in water, the associated thermodynamic functions for KTP solvation in all tested organic phases were also calculated.