abstract
The processes of production in chemical-related industries often rely on the use of volatile organic solvents, normally generating large amounts of hazardous wastes. During the past decades, major efforts have been done to transform chemical processes included in the principles of Green Chemistry, Sustainability and, more recently, Circular Economy. This thesis intends to work on two important challenges of pharmaceutical industry, namely the valorization of pharmaceutical wastes and the separation of enantiomers resorting on the application of alternative solvents, in particular, ionic liquids (ILs) and deep eutectic solvents (DES). Motivated by circular economy and searching for a new strategy to the currently proposed (i.e., incineration), novel aproaches to valorize wastes of domestic origin (unspent and/or outdated medicines) are proposed. Since circa 90 % of the active ingredients in an outdated medicine are still in their active form, in this work, the recovery of valuable active drugs from pharmaceutical wastes using IL-mediated extraction processes is proposed. The processes of extraction and separation of drugs from pharmaceutical wastes require an initial step of solid-liquid extraction, which was designed in this work by the use of different ILs, well-recognized by their solvency power of ILs for a large plethora of compounds/biomolecules. The separation stage of the extracted active ingredients was also investigated by the application of IL-based aqueous biphasic systems (ABS) or IL-based three-phase partitioning (TPP). In the end, the isolation of the active ingredients was accomplished by the addition of anti-solvents properly selected. The wide applicability of the proposed ABS-based technology was evidenced by the recovery of several model active pharmaceutical ingredients (three non-steroidal anti-inflammatory drugs and one antidepressant). The challenge of dealing with racemic mixtures and the differentiated biological activities that enantiomers generally present is investigated in this thesis. The most common two approaches to obtain pure enantiomers are the asymmetric synthesis and the separation of racemates. Although being considered the most powerful approach, the asymmetric synthesis is limited by the high costs and complexity of the processes. In turn, the separation of racemates is more flexible, cheaper and simpler. Under this scenario, it is here proposed the use of ABS composed of chiral ILs (CILs) as an alternative to enantioseparation. Two groups of CILs, i.e., those bearing chiral cations and those containing chiral anions were synthesized and applied to enantioseparation. After the characterization of the ABS phase diagrams (CIL + salt, CIL + polymer) it was possible to evaluate their enantioselectivity on the separation of racemic mandelic acid, here used as model racemic compound. In a second approach, deep eutectic solvents (DES) were envisaged as potential chiral solvents by the study of chirality impact on the solid-liquid equilibrium diagram.
authors
Francisca A. e Silva
our authors
Ana Francisca Osório de Almeida Coelho e Silva
Junior Researchersupervisors
João A. P. Coutinho, Sónia P. M. Ventura