Background: Essential oils are poor aqueous solubility and high volatility compounds. The
encapsulation of essential oils with Cyclodextrins (CDs) can protect them from 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 Complexes (ICs).
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 zeroorder
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 an 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.