Thermal studies on mixtures of aminosalicylic acids with cyclodextrins

The thermal behaviour of the aminosalicylic acids is compared with the behaviour of their 1:1 molar ratio physical and kneaded mixtures with each of three different cyclodextrins (b-, hydroxypropyl-b-, and g-cyclodextrin), using differential scanning calorimetry and thermogravimetry coupled with evolved gas analysis by Fourier transform infrared spectroscopy. X-ray powder diffraction and infrared spectroscopy provided complementary information. Comparison of the effects of the different cyclodextrins on the behaviour of the individual aminosalicylic acid isomers shows that hydroxypropyl-b-cyclodextrin has the greatest interaction with 3-aminosalicylic acid and 5-aminosalicylic acid, followed by g-cyclodextrin, while b-cyclodextrin generally shows the least interaction. For 4-aminosalicylic acid, the effect of g-cyclodextrin seems to be more marked than for 3-aminosalicylic acid and 5-aminosalicylic acid. This revised version was published online in July 2006 with corrections to the Cover Date.