Oleuropein aglycone in lipid bilayer membranes. A molecular dynamics study

Olive oil has been recognized to possess many therapeutic applications. Its beneficial effects arise from many causes, but one of them lies on the presence of oleuropein aglycone (OA). OA presents a plethora of pharmacological beneficial properties. Although there is a great research going on the effect of polyphenols and their derivatives on different aspects of health, much less knowledge is available of the molecular basis of their beneficial effects. Due to the prominent hydrophobic character of OA and its high phospholipid/water partition coefficient, some of its possible effects on biological systems might be related to its capacity to interact with and locate into the membrane. In this work we have aimed to locate the molecule of OA in two membrane model systems, i.e., POPC/Chol and POPC/POPG/Chol. OA locates in between the hydrocarbon acyl chains of the phospholipids but its specific location and molecular interactions differ depending on the lipid system. OA is nearer to the membrane surface in the POPC/Chol system but it is located at a deeper position in the POPC/POPG/Chol system. Furthermore, OA seems to interact stronger with POPG than with POPC, implying the existence of specific interactions with negatively-charged phospholipids. Some of the biological effects of OA could be due to its preferential location in the membrane depending on the membrane lipid composition as well as the existence of specific interactions with specific phospholipids.