Permeation of Hydroxypropyl-Beta-Cyclodextrin and Its Inclusion Complex Through Mouse Small Intestine Determined by Spectrophotometry

Background: Cyclodextrins (CDs) are commonly used host molecules of inclusion complex. However, due to the lack of a sensitive determination method, the absorption process of CDs remains unclear. Objective: In this study, an oleuropein (OL) inclusion complex employing hydroxylpropyl-betacyclodextrin (HP-beta-CD) as host molecules was prepared and the formation of inclusion complex was ascertained by FT-IR and DSC. Spectrophotometry was established for the determination of HP-beta-CD, based on the fact that the absorbance of phenolphthalein (PP) decreased in the presence of HP-beta-CD. Methods: The assay conditions were optimized to augment the method sensitivity. Molecular docking was employed to verify the strong interaction between PP and HP-beta-CD. The permeation process of free HP-beta-CD, HP-beta-CD of OL inclusion complex, free OL, and OL in the inclusion complex, was examined using an in vitro mouse small intestine model. Results: Though HP-beta-CD possessed a hydrophilic outside shell, it could permeate through the mouse small intestine quickly with a cumulative permeating amount of over 90% in 2 h. Free HPbeta- CD, the host molecule HP-beta-CD, and guest molecule OL of the inclusion complex exhibited consistent permeating profiles across the mouse small intestine. Conclusion: The approach for the determination of HP-beta-CD was accurate and precise (%RSD=2.98).