DSC, X-ray and NMR properties of cholesterol—cholestanol—dihydrate crystals

The melting point, X-ray diffraction and longitudinal relaxation time ( T 1) of cholesterol—cholestanol—dihydrate crystals (CC2W) were studied in an effort to produce new experimental data related to atherosclerotic plaques. The crystals were precipitated from ethanolic solutions at several cholesterol: cholestanol (CS:CN) ratios. The melting point of CC2W crystals obtained at the CS:CN ratio 75:25, 50:50, 25:75 was 122–124° C. The X-ray patterns recorded from these crystals of the same CN: CS ratios showed two additional diffraction peaks, as compared to those of CN and CS patterns. On the other hand, the values of T 1 relaxation time measured by proton magnetic resonance were different for every CS: CN ratio for the various solution compositions. This latter method seems to be more precise for the detection of the presence of coprecipitated components in the CC2W mixed crystals than X-ray or thermal analysis. The results suggest that CN and CS do not have to be present in equimolar quantities in order for CC2W crystals to be formed. The presence of CC2W in the blood may have significance in the nucleation of cholesterol crystals in atherosclerotic plaques.