Preparation and Spectroscopic Characterization of Ternary Inclusion Complexes of Ascorbyl Palmitate and Urea with γ-Cyclodextrin

A three-component inclusion complex of ascorbyl palmitate (ASCP), urea (UR), and gamma-cyclodextrin (gamma CD) with a molar ratio of 1/12 has been prepared for the first time using the evaporation method (EVP method) and the grinding and mixing method (GM method). Also, we investigated changes in the physicochemical properties of the three-component complexes. The powder X-ray diffraction (PXRD) measurements showed ASCP, UR, and gamma CD characteristic peaks in the physical mixture (PM) (AU (ASCP/UR = 1/12)/gamma CD = 1/2). In GM(AU (ASCP/UR = 1/12)/gamma CD = 1/1), new diffraction peaks were observed around 2 theta = 7.5 degrees and 16.6 degrees, while characteristic peaks derived from EVP (ASCP/UR = 1/12) were observed at 2 theta = 23.4 degrees and 24.9 degrees. On the other hand, new diffraction peaks at 2 theta = 7.4 degrees and 16.6 degrees were observed in GM (1/2). In the differential scanning calorimeter (DSC) measurement, an endothermic peak at around 83 degrees C was observed in the GM (1/1) sample, which is thought to originate from the phase transition of urea from the hexagonal to the tetragonal form. An endothermic peak around 113.9 degrees C was also observed for EVP (ASCP/UR = 1/12). However, no characteristic phase transition-derived peak or EVP (ASCP/UR = 1/12)-derived endothermic peak was observed in GM (1/2). Near infrared (NIR) spectroscopy of GM (1/2) showed no shift in the peak derived from the CH group of ASCP. The peaks derived from the NH group of UR shifted to the high and low wavenumber sides at 5032 cm(-1) and 5108 cm(-1) in EVP (ASCP/UR = 1/12). The peak derived from the OH group of gamma CD shifted, and the peak derived from the OH group of ASCP broadened at GM (1/2). These results suggest that AU (ASCP/UR = 1/12)/gamma CD prepared by the mixed grinding method formed inclusion complexes at the molar ratio (1/2).

Automated summary

A three-component inclusion complex of ascorbyl palmitate (ASCP), urea (UR), and gamma-cyclodextrin (gamma CD) with a molar ratio of 1/12 has been prepared using the evaporation method and the grinding and mixing method. The physical and chemical properties of the complexes were investigated, and it was found that the grinding and mixing method induced new diffraction peaks and phase transition of urea. The complex formed by the grinding and mixing method at a molar ratio of 1/2 showed inclusion complexes of gamma CD.