Experimental and Computational Study on the Inclusion Complexes of β-Cyclodextrin with Selected Food Phenolic Compounds

A number of phenolic compounds, including caffeic acid, trans-ferulic acid and p-coumaric acid that are commonly found in food products are beneficial for human health. Cyclodextrins can form inclusion complexes with various organic compounds in which the physiochemical properties of the included organic molecules are changed. In this study, three phenolic compounds with β-cyclodextrin as inclusion complexes were studied. The complexes were characterized by various analytical methods, including NMR-, FT-IR spectroscopy, mass spectrometry, differential scanning calorimetry and scanning electron microscopy. Results showed that the phenolic compounds used in this study were able to form inclusion complexes in the hydrophobic cavity of β-cyclodextrin by non-covalent bonds. Their physicochemical properties were changed due to the complex formation. In addition, a computational study was performed to find factors that were responsible for binding forces between flavors and β-cyclodextrin. The quantum-mechanical calculations supported the results obtained from experimental studies. Thus, DH_f for the complex of p-coumaric acid and b-cyclodextrin has been found as -11.72 kcal/mol, which was about 3 kcal/mol more stable than for inclusion complexes of other flavors. A HOMO-LUMO gap for the complex of p-coumaric acid and b-cyclodextrin had the largest value (8.19 eV) in comparison to other complexes, which was an indication of higher stability complex.