Extraction of Luteolin from Peanut Shells by A Hydrophilic Ionic Liquid‐based Microwave‐assisted Method

Abstract An ionic liquid‐based microwave‐assisted extraction method was developed to extract luteolin from peanut shells effectively. A series of hydrophilic 1‐alkyl‐3‐methylimidazolium ionic liquids with different anions (Br − , Cl − and BF 4 − ) and different cations ([C 2 mim] + , [C 4 mim] + , [C 8 mim] + and [C 10 mim] + ) were screened, and [C 10 mim]Br was found to be the optimal extraction solvent. The reason is that when the cations are the same, the hydrogen bonding between Br − and the phenolic hydroxyl group on luteolin is the strongest; when the anions are the same, the carbon chain growth enhances the van der Waals force between the ionic liquid and the luteolin. The concentration of ionic liquid, extraction temperature, liquid‐solid ratio and extraction time were optimized by both single factor experiments and response surface methodology. Under the optimized conditions of [C 10 mim]Br concentration 1.00 mol/L, extraction temperature 85 °C, liquid‐solid ratio 11.63:1 mL/g, extraction time 12 min, the extraction yield of luteolin reached 80.36±0.67%. In addition, compared with conventional solvents, [C 10 mim]Br showed an excellent extraction yield to extracting luteolin from peanut shells .