Anionic Form of Usnic Acid Promotes Lamellar to Nonlamellar Transition in DPPC and DOPC Membranes

Usnic acid is a secondary metabolite found in several species of lichens, organisms resulting from the symbiosis between fungi and algae. This compound has been extensively studied because of its pharmacological properties. Despite its potential medicinal importance, it exhibits a high degree of toxicity. The confinement of the usnic acid within liposomes has been investigated as a possibility to reduce its toxicity. In this work, we characterize the interaction of usnic acid in its neutral and anionic states (usniate) with DPPC and DOPC by means of molecular dynamics simulations. A lamellar to nonlamellar transition is observed for both membranes upon contact with usniate within 100 ns time scale. The transition suggests the formation of a liposome-like structure encapsulating the metabolyte. Furthermore, such process occurs at a significantly shorter time frame for DOPC.