The selectivity of encapsulation of leflunomide and teriflunomide by native alpha-, beta- and gamma-cyclodextrins was investigated through H-1 NMR and molecular modeling. Thermodynamic analysis revealed the main driving forces involved in the binding. For alpha-cyclodextrin, the partial encapsulation was obtained while deep penetration was characterized for the other two cyclodextrins, where the remaining polar fragment of the molecule is located outside the macrocyclic cavity. The interactions via hydrogen bonding are responsible for high negative enthalpy and entropy changes accompanying the complexation of cyclodextrins with teriflunomide. These results were in agreement with the molecular modeling calculations, which provide a clearer picture of the involved interactions at the atomic level.
