Studies on aqueous solubility of 3,3′-diindolylmethane derivatives using cyclodextrin inclusion complexes

The supramolecular interaction of 3,3′-diindolylmethane (DIM) and its derivatives with α-, β-, and γ-cyclodextrins (CDs) has been investigated to improve their aqueous solubility. A series of complexes of α-, β-, and γ-CDs with DIMs were prepared and their inclusion complexation behavior in solution phase assessed by fluorescence, UV–visible spectroscopy and circular dichroism. Circular dichroism spectra revealed that incorporation of DIMs in the chiral environment of the CDs affecting their electric transitions leading to the development of induced circular dichroism bands in the near UV region. A linear increase of aqueous solubility of DIMs in presence of CDs was observed from their phase–solubility diagrams indicating the formation of soluble inclusion complexes. According to the continuous variation method a 1:1 stoichiometry has been proposed for DIM cyclodextrins complexes.