Study on complexation of ascorbic acid derivatives with γ-cyclodextrin

The aim of this study was to assess the physicochemical properties of a solid dispersion of L-ascorbyl 6-palmitate (ASCP) as poorly water soluble and γ-cyclodextrin (γCD) prepared by co-precipitation or co-grinding by using powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (solution state 1H-NMR and solid state 13C-NMR), and solubility test. Physical assessments and measurements indicated that a co-precipitate of ASCP and γCD resulted in inclusion complex formation at a molar ratio of 1:3 and that a ground mixture of ASCP and γCD resulted in inclusion complex formation at a molar ratio of 1:2. A solubility test revealed that the co-precipitate and ground mixture had improved solubility compared to ASCP alone. The co-precipitate had greater solubility than the ground mixture. This result is presumably due to molecular interaction occurring as result of the differences in the molar ratios and differences in the structure of complexes for ASCP and γCD in a solid state.