Interaction of Melatonin with Zwitterionic Model Lipid Membranes

Abstract

Melatonin is a key hormone secreted by the pineal gland in the brain. It interacts strongly with cell membranes and plays a protective role in several diseases such as Alzheimer's disease, cardiovascular diseases, and cancer. Hence, studies on the interaction of melatonin with lipid bilayer membranes have gained importance. In this regard, the present study aims to analyze the influence of different concentrations (0 to 15 mol%) of melatonin on the thermal and structural properties of zwitterionic stearoyl-2-oleoyl-sn-glycero-3-phosphocholine (SOPC) lipid bilayer model systems by using Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). The DSC results have shown that melatonin interacts with the membrane in a concentration-dependent fashion, induces patch formation, and alters the phase behaviour by reducing the main phase transition temperature. FTIR data has shown that increasing the melatonin concentration caused a reduction in the wavenumber of C=O and PO$$_{2}^-$$ antisymmetric stretching vibrations corresponding to the ester carbonyl and phosphate groups of SOPC lipids. This indicates the possibility of strong hydrogen bonding of melatonin with the SOPC lipids and nearby water molecules in the environment, suggesting its preferential location near lipid heads at the interfacial region. These results help to understand the organization and interactions of melatonin with membranes and provide insights to develop safe melatonin-based formulations for pharmaceutical applications.