Preparation and physicochemical characterization of inclusion complexes derived from phytosterols and β-cyclodextrin

Phytosterols (PS), that is vegetable sterols, are compounds widely recognized for lowering the absorption of cholesterol and decreasing cancer risk, with βsitosterol, stigmasterol and campesterol being the most abundant. As PS is poorly soluble in aqueous solutions, many approaches have been proposed to increase their solubility and bioavailability. β-cyclodextrin (β-CD) could be used to increase PS aqueous solubility because of its capacity to entrap a variety of hydrophobic guest molecules in its cavity. In this work, the formation of β-CD/PS inclusion complexes was confirmed by Differential Scanning Calorimetry (DSC), Electrospray Ionization-High Resolution Mass Spectrometry (ESIHRMS) and Fourier Transform Infrared Spectroscopy (FT-IR), while structural characteristics were determined by one- and two-dimensional Nuclear Magnetic Resonance (NMR) techniques. Results confirmed 1:1 binding stoichiometry, which suggests the total inclusion of rings and chains of the different PS. The hypothesis of folding of the lateral chains into the cavity may be supported by the multiple correlations observed in the Nuclear Overhauser Effect Spectroscopy (NOESY) and rotatingframe Nuclear Overhauser Effect Spectroscopy (ROESY) spectra.