Extraction of quercetin from nothopanax scutellarium leaves via ionic liquid-based microwave-assisted extraction

Introduction: Nothopanax scutellarium leaves have been used in Indonesian traditional medicine to treat several diseases. Previous studies used conventional extraction methods with large volumes of organic solvents, long extraction times, and low levels of quercetin content. This study was aimed to identify the optimal solvent among different ionic liquids that has the highest quercetin content. Methods: Ionic liquids including 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium hydrogen sulfate, and 1-hexyl-3-methylimidazolium bromide, for extracting quercetin from N. scutellarium leaves using microwave-assisted extraction under the following conditions: ratio, 1:10; operation time, 10 min; and power, 10 W. Then, quercetin was fractionated using ethyl acetate and separated using 0.01 mol/L sodium bocarbonate, dipotassium phosphate or sodium cloride. The total flavonoid content was determined using a UV-Vis spectrophotometer, and quercetin content was determined using HPLC. Results: Extraction with 1-butyl-3-methylimidazolium chloride using NaCl as the separation salt was associated with the highest total flavonoid (360.57 mg/g) content among the ILs, whereas 1-butyl-3-methylimidazolium tetrafluoroborate combined with sodium chloride generated the highest quercetin content (26.13 mg/g). Conclusion: 1-butyl-3-methylimidazolium tetrafluoroborate is the optimal solvent for extracting quercetin from N. scutellarium leaves.