Synthesis and Characterization of βCD-Mel Complex

To synthesize the βCD–Mel complex, the saturated solutions method was employed [13 (link),14 (link),15 (link),17 (link),82 (link),83 (link)]. In total, 0.2025 g of Mel were dissolved in ethanol and then added to a solution of βCD (0.7530 g dissolved in water) at 4 °C with gentle and constant stirring, allowing the temperature to rise slowly up to room temperature. The new solution was kept motionless under a hood for one week until the evaporation of the solvents. Finally, small crystals precipitated at the bottom of the crystallizer were extracted and washed with a 50% v/v solution (ethanol/water) at 4 °C and vacuum filtered for one hour in a kitasate with a Büchner funnel equipped with a double layer of filter paper, to remove the excesses of cyclodextrin, drug or solvents that moisten the complex. The crystals were then pulverized and dried in a vacuum line to remove the water or ethanol, which may remain occluded in the powder, then stored in amber vials with a Teflon seal. The new βCD–Mel complex was characterized by powder X-ray diffraction (PXRD), NMR of one (¹H) and two (ROESY) dimensions, UV-vis spectroscopy for calculating the loading capacity, degree of solubilization, complexation efficiency, and association constant. The complex was also used for a permeability study called PAMPA (parallel artificial membrane permeability assay).