[Difference in inclusion behavior of β-cyclodextrin and hydroxypropyl-β-cyclodextrin with menthol]

Area of Science:

• Pharmacology
• Materials Science
• Traditional Chinese Medicine

Background:

• Volatile oils are crucial in traditional Chinese medicine but suffer from instability and complex compositions.
• Cyclodextrin inclusion complexation is a common technique to enhance the stability and preparation of volatile oils.
• β-cyclodextrin (β-CD) is widely used, but research on selecting optimal inclusion materials for volatile oils is limited.

Purpose of the Study:

• To compare the inclusion efficiency of β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) for volatile oil components.
• To investigate the inclusion behavior of menthol, a model compound from mint volatile oil, with β-CD and HP-β-CD.
• To provide a foundation for selecting appropriate cyclodextrins for volatile oil inclusion complexes.

Main Methods:

• Menthol was used as a model drug for inclusion studies with β-CD and HP-β-CD.
• Phase solubility diagrams were constructed to evaluate inclusion behavior and determine inclusion equilibrium constants (K).
• Spectroscopic (IR) and thermal analysis (DSC, TG) techniques were employed to confirm the formation of inclusion complexes.

Main Results:

• HP-β-CD demonstrated a linear increase in menthol solubility with concentration (AL-type diagram, K=3188.62 L•mol⁻¹).
• β-CD showed a linear increase in menthol solubility up to 12.5 mmol•L⁻¹ (K=818.73 L•mol⁻¹), followed by negative deviation (AN-type diagram).
• The study confirmed distinct inclusion behaviors between β-CD and HP-β-CD.

Conclusions:

• HP-β-CD exhibits significantly higher efficacy in forming inclusion complexes with menthol compared to β-CD.
• The findings highlight the importance of selecting appropriate cyclodextrin derivatives for optimizing volatile oil stability.
• This research provides critical data for the development of stable and effective traditional Chinese medicine formulations.