Binary phase behavior of cholesteryl oleate with cholesteryl linoleate.

Because disagreement about the co-solubility of cholesteryl linoleate and cholesteryl oleate in the solid state is evident in the literature, the phase diagram for binary combinations of these two unsaturated esters is redetermined. X-ray data demonstrate that the two components fractionate and the phase diagram indicates that a peritectic relationship exists between these compounds. As reported previously, the two esters are fully miscible in the two mesophases. Evidence is also seen for metastable intermediate solids but the crystal polymorphism reported earlier for both lipids has not been found. It is also found that oleate-rich binary samples equilibrated at room temperature undergo a phase separation of crystalline cholesteryl oleate which may have some implications for the immobilization of these lipids in fatty lesions.