Inclusion complexation of 2-hydroxypropyl-beta-cyclodextrin with biologically active compounds 2-hydroxybenzaldehyde isonicotinoylhydrazone and 2-hydroxy-3-methoxybenzaldehyde isonicotinoylhydrazone in buffer pH 7.4 solution and in solid state have been investigated. The solubility of compounds at different concentrations 2-hydroxypropyl-beta-cyclodextrin was studied by phase solubility method. The profile displayed a typical A(L)-type, indicating the formation of 1:1 stoichiometric inclusion complex. Solution state complexation in buffer was validated by ultra violet absorption. Stoichiometry of complex was confirmed by Job's method. The water solubility of compounds studied was significantly increased through complexation with 2-hydroxypropyl-beta-cyclodextrin. Complexation stability constants and thermodynamic parameters have been calculated. It has been concluded that inclusion complexation is an exothermal and enthalpy-determined process. The solid state inclusion complex was prepared by the ball-milling method and characterized by differential scanning calorimetry, Fourier-transform infrared spectroscopy and X-ray powder diffraction. The dissolution rate of the active pharmaceutical ingredient of the supramolecular complexes were obtained. (C) 2016 Elsevier B.V. All rights reserved.