Binary phase behavior of cholesteryl oleate with cholesteryl linoleate

Area of Science:

• Lipid chemistry
• Materials science
• Crystallography

Background:

• Existing literature shows disagreement regarding the solid-state co-solubility of cholesteryl linoleate and cholesteryl oleate.
• Understanding the phase behavior of these unsaturated esters is crucial for various applications, including lipid formulation and biological studies.

Purpose of the Study:

• To accurately redetermine the phase diagram for binary combinations of cholesteryl linoleate and cholesteryl oleate.
• To clarify the solid-state co-solubility and phase relationships of these two important lipids.

Main Methods:

• X-ray diffraction analysis was employed to investigate the solid-state structures.
• Phase diagram determination was conducted for binary mixtures of cholesteryl linoleate and cholesteryl oleate.

Main Results:

• X-ray data confirmed that cholesteryl linoleate and cholesteryl oleate fractionate in the solid state.
• The redetermined phase diagram indicates a peritectic relationship between these two compounds.
• Complete miscibility was observed in the mesophases, with evidence for metastable intermediate solids, but previously reported crystal polymorphism was not found.
• Oleate-rich samples showed phase separation of crystalline cholesteryl oleate at room temperature.

Conclusions:

• The study resolves previous disagreements by establishing a clear phase diagram for cholesteryl linoleate and cholesteryl oleate, characterized by fractionation and a peritectic relationship.
• The observed phase separation in oleate-rich samples may have implications for the immobilization of lipids within fatty lesions.
• The findings contribute to a better understanding of lipid behavior in binary systems.