Green synthesis of choline-based ionic liquids and utilization in the extraction of biomolecules from Limnospira platensis microalgae

The search for new classes of solvents to improve chemical reactions and processes, aiming for a better impact on the planet's environment, and on the health and safety of all living beings, is constant. Such new class includes choline chloride (ChCl)-based ionic liquids that can efficiently replace imidazole-based ionic liquids (ILs) due to their non-toxic, biocompatible nature, accessibility, and cost-effective properties. In this context, the synthesis of choline-based ionic liquids (ILs) was investigated through the reaction of choline hydroxide with different acids. The work aimed to evaluate the influence of the anion on the properties of the ionic liquid and the toxicity of synthesized ILs in Artemia salina and in the efficiency of extraction of biomolecules from Spirulina (Limnospira platensis). The FTIR and NMR analyses confirmed the synthesis of the ILs. The size of the anion chain influenced the physical and chemical properties of the ILs, in which the IL synthesized using citrate anion (anion with the longest chain) showed the highest viscosity. The (2-hydroxyethyl)-trimethylammonium hydroxide ionic liquid was not toxic to A. salina at 1000 mu g mL-1. Besides that, the ionic liquids (2-hydroxyethyl)-trimethylammonium bisulfate, (2-hydroxyethyl)-trimethylammonium acetate and (2-hydroxyethyl)-trimethylammonium citrate were practically non-toxic. The (2-hydroxyethyl)-trimethylammonium citrate was more efficient in extraction of phycocyanin and allophycocyanin among other evaluated ILs, obtaining 164.6 mg L-1 and 200.69 mg L-1, respectively, and also in the removal of chlorophyll. Thus, the simple preparation of choline-based ILs, at different physicochemical properties, and the low toxicity of these molecules are advantages to their application in green processes.