Preparation of liposomes containing oleanolic acid via micelle-to-vesicle transition

Micelle-to-vesicle transition method was used to make liposomes containing oleanolic acid. First, the solubilization of potassium salt of oleanolic acid at basic condition by micelle formation was confirmed. Using the soluble state of oleanolic acid at basic condition, liposomes containing oleanolic acid was prepared by adjusting pH. After making homogeneous aqueous mixture of potassium salt of oleanolic acid and lecithin in basic condition, the solution was neutralized to produce the lecithin-based liposomes that contain oleanolic acid inside the lipid bilayers. The optimal loading of oleanolic acid to lecithin (about 25 mole%) was found to exist to produce liposomal suspension of small size without homogenization step. Electron microscopy and dynamic light scattering studies showed that the narrowly distributed, reconstituted oleanolic acid-containing liposomes were prepared without severe mechanical treatment.