Hydroxypropyl-β-cyclodextrin inclusion complex improves the percutaneous therapeutic effect of eugenol on psoriasis mice.

The insolubility and volatility of eugenol (EG) limit its clinical application. In this study, cyclodextrin (CD) was used to encapsulate EG and hydroxypropyl-β-cyclodextrin (HP-β-CD) with lower binding energy was selected by comparison. The preparation process optimization and characterization showed that the EG-HP-β-CD inclusion complex could be successfully prepared. More importantly, inclusion complex can significantly increase the solubility and stability of EG. In addition, in vitro release and transdermal studies, inclusion complex gel release curve conformed to the Higuchi equation, and the cumulative release rate reached 80 % at 24 h, which provided good sustained release properties. Notably, inclusion complex gel increased EG skin retention by reducing the transdermal permeation rate and cumulative permeation amount. It was verified in the mouse psoriasis model that the inclusion complex gel group had better efficacy. By comparison, the epidermal thickness and inflammatory infiltration of inclusion complex group were improved, which was closely related to drug skin retention. The anti-inflammatory effect was revealed by regulating the expression of IL-17 A, IL-1β, IL-6, IL-23, and TNF-α, participating in JAK1/STAT3 pathway. The results provide a new idea and theoretical basis for the formulation design of volatile oil transdermal therapy for psoriasis.