Inclusion of Terpenoid Plant Extracts in Lipid Bilayers Investigated by Molecular Dynamics Simulations

The plant Perilla frutescens is widely employed in Asian medicine. The active components of Perilla include cyclic terpenes, which have a diverse range of antimicrobial, anticancer, sedative, and anti-inflammatory properties, hinting at a membrane-mediated mechanism of action. We have used molecular dynamics (MD) simulations and isothermal titration calorimetry (ITC) to investigate the interaction of four terpenes with model lipid bilayers. The ITC and MD data are mostly in accordance. The terpenes partition into membranes, pack along the lipid tails, and alter bilayer structure and dynamics. Three of the four molecules could cross the bilayer. The carboxylate-group-containing terpene modifies headgroup repulsion and increases the area per lipid by more than 10%, in a manner reminiscent of membrane-thinning peptides and solvents such as DMSO. Our results support the possibility that at least some medicinal properties of volatile Perilla extracts might arise from interactions with the lipid bilayer component of biological membranes.