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

Solid inclusion complexes of two tanshinones (Tans): tanshinone IIA (Tan IIA), tanshinone I (Tan I) with β-cyclodextrin (β-CD) were synthesized by coprecipitation method. The solid inclusion complexes were characterized by using several analytical techniques: 1H NMR spectra, IR spectra and thermal analysis. Stoichiometry of the inclusion complexes of Tans with β-CD or HP-β-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-β-CD > β-CD. The effect of temperature on the inclusion interaction was examined and the thermodynamic parameters of inclusion process, ΔG, ΔH, ΔS 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.