Improvement of dissolution characteristics of psoralen by cyclodextrins complexation.

Psoralen was found to form an inclusion complex with β-cyclodextrin (βCD), heptakis(2,6-di-O-methyl)-β-cyclodextrin (DMβCD) and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TMβCD). Phase solubility studies revealed the formation of a 1:1 molar complexes. The stability constant were 663 M-1 for βCD, 603 M-1 for DMβCD and 69,6 M-1 for TMβCD. 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 DMβCD complex. The strength of binding of psoralen to DNA was not influenced by complexation with cyclodextrins.