Equilibrium thermodynamics of the partitioning of non-steroidal anti-inflammatory drugs into human erythrocyte ghost membranes

Abstract

In this work,second derivative spectrophotometry was applied for determining the partition coefficients (Kps) of four non-steroidal anti-inflammatory drugs (NSAIDs; flufenamic, meclofenamic, mefenamic and niflumic acids) into human erythrocyte ghost (HEG) membranes over a temperature range from (283.2 to 313.2)K. The proposed method allowed the evaluation and direct analyses of thermodynamic parameters; enthalpy (ΔHW→M), Gibbs energy (ΔGW→M) and entropy (ΔSW→M) changes of the partitioning of NSAIDs into HEG membranes. The partitioning of NSAIDs between polar aqueous phase and non-polar lipid bilayer HEG membrane phase was exothermic with negative (ΔHW→M) which compensated for the changes in (ΔSW→M). The negative values of (ΔGW→M) revealed that the partitioning of NSAIDs into HEG, owing to their transfer from polar aqueous phase and non-polar HEG phase is spontaneous. The enthalpy–entropy correlation analysis resulted in a good linearity that suggests an identical partitioning enthalpy–entropy driven compensation mechanism for the studied NSAIDs.