Solubility of pharmaceutical compounds in ionic liquids

• Solubilities of N-acetyl-l-cysteine (antioxidant), coumarin, and 4-hydroxycoumarin (anticoagulants) in ionic liquids.
• Applicability of common ionic liquids with a good environmental impact is envisaged.
• Appropriate solvents for the drug manufacturing.
• Sustainable solubilities of pharma compounds in ILs for pharmaceutical industry.
• The competitive solvents for pharmaceutical industry were discovered.

The solubility of N-acetyl-l-cysteine, coumarin and 4-hydroxycoumarin in alternative solvents was studied in this work. The solid–liquid equilibrium (SLE) measurements have been performed using a dynamic (synthetic) method. Melting points and enthalpies of fusion of the pharmaceutical compounds were acquired using a differential scanning calorimetry (DSC). The solubility of N-acetyl-l-cysteine and 4-hydroxycoumarin in trifluoromethanesulfonate ionic liquids was found to be significantly higher than in the studied bis(trifluoromethylsulfonyl)amide ionic liquids while coumarin exhibited the opposite behaviour.The solid–liquid phase equilibria were described using the six different correlation equations which revealed a good description with an acceptable standard deviation temperature range.Moreover, the solubility data were used to calculate the 1-octanol/water partition coefficients of the studied drugs. Coumarin has a high partition coefficient, which is considered to be favourable for a rapid absorption of compounds once they are in an aqueous solution. N-acetyl-l-cysteine showed opposite results for the system with 1-octanol/water.