Structural and Thermal Characterization of Cyclodextrin - Suprofen Complexes

Abstract

Suprofen, α-methyl-4-(2-thienylcarbonyl)benzeneacetic acid, a non-steroidal anti-inflammatory drug (NSAID), forms an inclusion complex with β-cyclodextrin of formula (β-cyclodextrin)2·(suprofen)·20H2O 1 and with TRIMEB (a permethylated β-cyclodextrin) of formula (β-cyclodextrin)·(suprofen)·0H2O 2. These species were investigated by thermal analysis techniques (HSM, TGA, DSC), powder X-ray diffraction (PXRD), and single-crystal X-ray diffraction at 173 K. Thermal analysis of 1 revealed dehydration followed by decomposition at 311.0°C, and only melting at 161.0°C for 2. The host-to-drug stoichiometric ratio was determined by UV spectrophotometry, and found to be 2:1 for 1 and 1:1 for 2. Single-crystal X-ray methods revealed that 1 crystallizes in the orthorhombic space group C2221, with a 19.0409(1), b 24.1949(2), c 32.4707(2) Å, and Z 4 formula units. Complex 2 crystallizes in the orthorhombic space group P212121, with a 15.389(1), b 21.051(1), c 27.027(2) Å, and Z 4 formula units. The (S)-enantiomer of suprofen was preferentially included in both characterized crystals.