Combined computational and experimental study on the inclusion complexes of beta-cyclodextrin with selected food phenolic compounds

摘要

Phenolic compounds, such as 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, inclusion complexes of three phenolic compounds with beta-cyclodextrin were investigated. The complexes were characterized by various analytical methods, including nuclear magnetic resonance (NMR) spectroscopy, Fourier IR (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 beta-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 beta-cyclodextrin. The quantum-mechanical calculations supported the results obtained from experimental studies. Thus, Delta H-f for the complex of p-coumaric acid and beta-cyclodextrin has been found as -11.72kcal/mol, which was about 3kcal/mol more stable than for inclusion complexes of other flavors. Energies of frontier orbitals (higher occupied molecular orbital (HOMO) and lower unoccupied molecular orbital (LUMO)) were analyzed, and it was found that H-L gap for the complex of p-coumaric acid and beta-cyclodextrin had the largest value (8.19eV) in comparison to other complexes, which confirmed the experimental findings of the most stabile complex.