Influence of melatonin on the structural and thermal properties of SOPC lipid membranes

Melatonin, a hormone secreted by the pineal gland in the brain, plays a key role in the regulation of sleep-wake cycles. Due to its antioxidant and free radical scavenging properties, it has shown promising protective effects against cancer, and neurodegenerative disorders. Studies pertaining to the use of melatonin and its biophysical effects on cell membranes are important for their biomedical implications. The main goal of our study is to investigate the effect of melatonin on the thermal and structural properties of 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine (SOPC) phospholipid membranes using sensitive techniques such as Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC). For this purpose, SOPC lipid bilayer membranes were prepared with different melatonin concentrations (10–50 mol%). DSC results have indicated that melatonin strongly interacts with the membrane lipids in a concentration-dependent fashion to form domains and alters the phase behavior by reducing the main phase transition temperature, lipid order, and increasing membrane fluidity. FTIR data have shown that increasing the melatonin concentration caused a reduction in the wavenumber of CO and PO2− antisymmetric stretching vibrations, indicating the possibility of strong hydrogen bonding between melatonin and the SOPC lipid with the nearby water molecules in the environment, suggesting its preferential location near lipid head groups at the interfacial region. Understanding the organization of melatonin in membranes and its influence on membrane properties is important to gain thorough knowledge and to develop safe melatonin-based formulations for therapeutic applications.