Study of formation constant, thermodynamics and β-ionone release characteristic of β-ionone-hydroxypropyl-β-cyclodextrin inclusion complex

Abstract

β-Ionone has a characteristic violet-like odor and is an important flavor and fragrance ingredient used in food and perfumery. Furthermore, it has the ability to selectively kill tumor cells and is a promising anticancer agent. In order to improve its solubility, stability and long-release characteristics, β-ionone was encapsulated in hydroxypropyl-β-cyclodextrin (HP-β-CD) to form inclusion complex. The formation constants (K) and thermodynamics were explored by ultraviolet–visible (UV/V) absorption method. The values of K obtained at 35 °C, 45 °C and 55 °C were 29.6 × 103 l/mol, 8.4 × 103 l/mol and 4.9 × 103 l/mol, respectively. Gibbs free energy changes (ΔG) for the interactions of β-ionone and HP-β-CD at 35 °C, 45 °C and 55 °C were − 26.4 kJ/mol, − 23.9 kJ/mol and − 23.6 kJ/mol, respectively. Enthalpy change (ΔH) and entropy change (ΔS) were − 1.1 kJ/mol and − 2.3 J/(K mol), respectively. The solid β-ionone-HP-β-CD inclusion complex was characterized by FTIR and thermogravity analysis (TGA). The FTIR results confirmed that β-ionone was successfully encapsulated in HP-β-CD and that encapsulation of β-ionone did not change the frame of HP-β-CD. The TGA results showed that the release of most of the β-ionone from β-ionone-HP-β-CD inclusion complex mainly occurred in the temperature range of 210–320 °C. A relative larger release rate appeared at 240 °C and the beginning stage of HP-β-CD decomposition. It also revealed that the thermal stability of β-ionone was improved by the encapsulation technology.