Solubility of luteolin in several imidazole-based ionic liquids and extraction from peanut shells using selected ionic liquid as solvent

• The solubility of luteolin in several ionic liquids (ILs) was investigated.
• [C4mim]NO3 showed considerably higher dissolution ability of luteolin.
• Luteolin was successfully extracted from peanut shells using [C4mim]NO3.
• The extraction conditions of luteolin from peanut shells were optimized by RSM.

Several hydrophilic and hydrophobic 1-alkyl-3-methylimidazole ionic liquids (ILs) were screened for their dissolution ability of luteolin to determine the IL suitable for extraction of luteolin from peanut shells. The experimental data indicated that hydrophilic 1-butyl-3-methyl-imidazolium nitrate ([C4mim]NO3) shows considerably higher dissolution ability of luteolin than commonly used organic solvents and other ILs investigated, which can be used as an efficient substitute of organic solvent for extraction of luteolin. The extraction of luteolin from peanut shells was performed using [C4mim]NO3 aqueous solution as solvent, and extraction conditions were analyzed and optimized by response surface methodology (RSM) with central composite design (CCD). Extraction temperature has significant effect on the yield of luteolin, followed by [C4mim]NO3 concentration. Under the optimal conditions namely liquid–solid ratio of 7.6 mL g−1, temperature of 100 °C and [C4mim]NO3 aqueous solution of 49%, determined by RSM, the yield of luteolin was 79.8 ± 1.48%, which was close to the 78.4% predicted by RSM.