Improvement of dissolution characteristics of psoralen by cyclodextrins complexation

Psoralen was found to form an inclusion complex with beta-cyclodextrin (beta CD), heptakis(2,6-di-O-methyl)-beta-cyclodextrin (DM beta CD) and hepatakis(2,3,6-tri-O-methyl)-beta-cyclodextrin (TM beta CD). Phase solubility studies revealed the formation of a 1:1 molar complexes. The stability constant were 663 M-1 for beta CD, 603 M-1 for DM beta CD and 69.6 M-1 for TM beta CD. The formation of complexes in the solid state was confirmed by spectroscopic analyses, X-ray diffractometry and differential thermal data. The solubility and dissolution rate of the complexed forms were improved, particularly for the DM beta CD complex. The strength of binding of psoralen to DNA was not influenced by complexation with cyclodextrins.