Background: Essential oils are poor aqueous solubility and high volatility compounds. The encapsulation of
essential oils with cyclodextrins (CDs) can protect them from the adverse environmental conditions and improve their
stability. Therefore, increasing the functional capabilities of essential oils when they were used as additives in
pharmaceutical and food systems. Additionally, the release of active compounds is an important issue. However, there were
few studies about the effect of different CDs on the release of drugs after encapsulation. Therefore, the information on the
study of release models is considerably limited.
Objective: This study aimed to (i) characterize the physico-chemical properties and release behavior of myrcene
encapsulated in the four different shell matrices of α-CD, β-CD, γ-CD and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD),
which were selected from the perspective of stability, and (ii) determine the release mechanism of myrcene in inclusion
Methods: ICs of myrcene and four CDs were prepared by freeze-drying. The physico-chemical properties of ICs were fully
characterized by laser diffraction particle size analyzer, scanning electron microscope (SEM), Fourier-transform infrared
spectroscopy (FT-IR) and differential scanning calorimeter (DSC). The release behaviors of ICs at 50, 60, 70 and 80 °C
were determined and described by zero-order or first-order kinetics with the Henderson-Pabis, Peppas, Avrami and Page
mathematical models. Moreover, the possible binding modes of ICs were identified with molecular modelling technique.
Results: Firstly, the structure of particle size distribution (PSD), FT-IR, DSC and SEM showed that (i) CDs could
effectively encapsulate the myrcene molecules, and (ii) the release kinetics were well simulated by Avrami and Page
models. Secondly, the release rates of the ICs experienced unsteady state in the early stage, and gradually became almost
constants period after 20 hours. Except that the release of myrcene in γ-CD/myrcene belonged to the first-order kinetic, the
release models of the remaining three ICs belonged to diffusion mode. Thirdly, the calculated binding energies of the
optimized structures for α-CD/myrcene, β-CD/myrcene, γ-CD/myrcene, and HP-β-CD/myrcene ICs were −4.28, −3.82, −4.04, and −3.72 kcal/mol, respectively. Finally, the encapsulation of myrcene with α-CD and β-CD was preferable
according to the stability and release characteristics.
Conclusion: The encapsulation of myrcene was profoundly affected by the type of CDs, and the stability could be improved
by complexation with suitable CDs. The binding behavior between guest and CD molecules, and the release profile of the
guest molecules could be effectively explained by the kinetics parameters and molecular modelling. This study can provide
an effective basis and guide for screening suitable shell matrices.