Inclusion complexes of eucalyptus essential oil with β-cyclodextrin: preparation, characterization and controlled release

In this study, eucalyptus essential oil (EEO) was encapsulated into β-cyclodextrin (β-CD) by saturated aqueous solution method. The success of EEO encapsulation was confirmed by laser light scatting, scanning electron microscopy, Fourier transform infrared spectroscopy, differential scanning calorimeter and thermogravimetric analysis. Releasing characteristics experiments were carried out at various temperatures, relative humidity (RH), storage time and high temperature stability test. Release kinetics of EEO from the inclusion complexes was investigated by zero-order kinetics, first-order kinetics and Avrami’s equation. The result showed that the release model of EEO from inclusion complexes fitted better for Avrami’s equation. Kinetics analysis based on the Avrami’s equation revealed that the release of EEO was accelerated with the increases of RH and temperature. For storage time treatment, the volatilization of EEO was significantly inhibited after encapsulation. High temperature stability test further revealed that EEO was protected after having been encapsulated into β-CD. For all treatments, the release parameter n was between 0.5 and 1.0, which presenting a diffusion-limited and first-order mode. These results indicated that encapsulation enhanced the stability and prolonged the acting time of EEO, and the release rate of EEO can also be passively controlled by the ambient temperature, humidity and storage time.