Inclusion reactions of β-cyclodextrin and its derivatives with cinnamaldehyde in Cinnamomum loureirii essential oil

The inclusion reactions of β-cyclodextrin (β-CD), heptakis (2,6-di-O-methyl)-β-CD (DM-β-CD), and mono[2-O-(2-hydroxy-propyl)]-β-CD (HP-β-CD) with cinnamaldehyde (CA) in Cinnamomum loureirii essential oil were investigated using spectrofluorimetry. The results revealed that the best inclusion time was 30 min and the neutral pH conditions were more advantageous to the process. The stoichiometry of β-CD including CA complex was 1:1 (molar ratio). The inclusion constants decreased with the increase of temperature, and the inclusion abilities of β-CD were according to the following order: β-CD > DM-β-CD > HP-β-CD. At the same time, the inclusion constants and the thermodynamic parameters such as ΔG, ΔH, and ΔS were determined in the ranges of 25–55 °C. The thermodynamic measurements showed that the inclusion process was an exothermic and enthalpy-driven process accompanied with a negative entropic contribution. Molecular modeling was performed by molecular mechanics using MM2 in CS Chem 3D, determined by model calculation performance parameter, and the result was identical with the ultimate result of the thermodynamic measurements.