Cyclodextrin-based drug stabilizing system

UV spectroscopy study of para-aminosalicylic acid behaviour in the presence of β-cyclodextrin and without it in buffer solutions was realized. Influence of duration of contact, acidity of solution, temperature, and content of reagents in the binary solutions on the complex formation between β-cyclodextrin and para-aminosalicylic acid was examined. The stability constants of the supramolecular complexes formed at pH = 1.00 and pH = 6.86 were calculated by the Ketelar equation at various temperatures. It was found that the inclusion interaction of β-cyclodextrin with protonated type of para-aminosalicylic acid is superior to that for its anionic one. From the temperature dependence of stability constants the thermodynamic parameters involved in the complex formation (ΔG, ΔH, ΔS) were calculated. It was proved that complex formation between β-cyclodextrin and para-aminosalicylic acid is spontaneous process accompanied by the release of heat and decrease of entropy. To characterize the solid product of para-aminosalicylic acid inclusion into the cavity of β-cyclodextrin supramolecular complex with a 1:1 mole ratio of components have been prepared by kneading method and studied by IR spectroscopy and X-ray diffraction.