Thermal characterization, polymorphism, and stability evaluation of Se-NSAID derivatives with potent anticancer activity

Stability, thermal characterization, and identification of possible polymorphism are relevant in the development of novel therapeutic drugs. In this context, thirty new nonsteroidal anti-inflammatory drug (NSAID) derivatives containing selenium (Se) as selenoesters or diacyl diselenides with demonstrated anticancer activity were thermally characterized in order to establish thermal stability criteria and detect possible polymorphic forms. Compounds were analyzed by a combination of thermogravimetry, differential scanning calorimetry, and X-ray diffraction techniques, and five different calorimetric behaviors were identified. Two compounds based on naproxen (I.3d and I.3e) and an indomethacin-containing derivative (II.2) presented two crystalline forms. The stability under acid, alkaline and oxidative conditions of selected polymorphs was also assessed using high-performance liquid chromatography. In addition, the cytotoxic activity of Se-NSAID crystalline polymorphs was studied in several cancer cell lines in vitro. Remarkably, no significant differences were found among the polymorphic forms tested, thus proving that these compounds are thermally qualified for further drug development.