Preparation and study on the inclusion complexes of two tanshinone compounds with beta-cyclodextrin

Solid inclusion complexes of two tanshinones (Tans): tanshinone IIA (Tan IIA), tanshinone I (Tan I) with beta-cyclodextrin (beta-CD) were synthesized by coprecipitation method. The solid inclusion complexes were characterized by using several analytical techniques: (1)H NMR spectra, IR spectra and thermal analysis. Stoichiometry of the inclusion complexes of Tans with beta-CD or HP-beta-CD is 1:1 which was investigated in solution. The formation constants of the complexes were determined by UV spectrophotometry. For same kind of CD, the stability was in the order: Tan IIA > Tan I; for same guest, the stability was in the order: HP-beta-CD > beta-CD. The effect of temperature on the inclusion interaction was examined and the thermodynamic parameters of inclusion process, Delta G, Delta H, Delta S were determined as well. The experimental results indicate that the inclusion process was an exothermic and enthalpy-driven process accompanied with a negative entropic contribution. The inclusion interaction between CD and Tans satisfied the law of enthalpy-entropy compensation.