Host-guest interaction of 13-cyclodextrin with isomeric ursolicacid and oleanolic acid＂ physicochemical characterization andmolecular modeling study

摘要

Ursolic acid （UA） and oleanolic acid （OA） are insoluble drugs. The objective of this study was to encapsulate theminto β-cyclodextrin （13-CD） and compare the solubility and intermolecular force of β-CD with the two isomerictriterpenic acids. The host-guest interaction was explored in liquid and solid state by ultraviolet-visible absorption, 1 HNMR, phase solubility analysis, and differential scanning calorimetry, X-ray powder diffractometry, and molecularmodeling studies. Both experimental and theoretical studies revealed that β-CD formed 1：1 water soluble inclusioncomplexes and the complexation process was naturally favorable. In addition, the overall results suggested that ring Ewith a carboxyl group of the drug was encapsulated into the hydrophobic CD nanocavity. Therefore, a clear differentinclusion behavior was observed, and UA exhibited better affinity to β-CD compared with OA in various media dueto little steric interference, which was beneficial to form stable inclusion complex with β-CD and increase its watersolubility effectively.