Oleanolic acid and ursolic acid stabilize liposomal membranes

Area of Science:

• Biochemistry
• Membrane Biophysics
• Pharmacology

Background:

• Liposomal membranes are crucial in drug delivery and biological systems.
• Understanding how natural compounds interact with lipid bilayers is essential for their therapeutic applications.
• Oleanolic acid (OA) and ursolic acid (UA) are natural compounds with potential biological activities.

Purpose of the Study:

• To investigate the effects of oleanolic acid (OA) and ursolic acid (UA) on the fluidity and stability of dipalmitoyl phosphatidylcholine (DPPC) liposomal membranes.
• To compare the effects of OA and UA with cholesterol on liposomal membrane properties.

Main Methods:

• Liposomes composed of DPPC were prepared.
• Fluorescence polarization using 1,6-diphenyl-1,3,5-hexatriene (DPH) was employed to measure membrane fluidity.
• Calcein leakage assay was used to assess membrane stability.
• Experiments were conducted on both crystalline and liquid-crystalline liposomal membranes.

Main Results:

• OA and UA demonstrated a moderate fluidity-modulating effect on liquid-crystalline DPPC membranes.
• Both OA and UA exhibited a strong condensing effect on both crystalline and liquid-crystalline DPPC membranes.
• The observed effects of OA and UA were comparable to those of cholesterol.

Conclusions:

• Oleanolic acid and ursolic acid possess significant membrane fluidity-modulating and condensing properties.
• These biophysical effects suggest potential mechanisms for the biological functions of OA and UA.
• The findings provide insights into the interaction of these triterpenoids with lipid bilayers.