Application of imidazole-based ionic liquids in microwave-assisted extraction of trans-resveratrol from Gnetum Gnemon L. seeds

Objective: This study aimed to compare the efficiency of three imidazole-based ionic liquids (ILs) in the microwave-assisted extraction (MAE) of trans-resveratrol from Gnetum gnemon seeds. Methods: Trans-resveratrol was quantitatively extracted using 1-hexyl-3-methylimidazolium bromide ([hmim]Br), 1-butyl-3-methylimidazolium chloride ([bmim]Cl), and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF₄) in a microwave oven. Extraction parameters, including solvent concentration, liquid-solid ratio, and extraction time, were optimized using response surface methodology on the basis of the Box-Behnken design. A reverse-phase high-performance liquid chromatography method was used to determine resveratrol content with acetonitrile: water (75:25 v/v) as the mobile phase. The total phenolic content was determined by the Folin-Ciocalteu method. Results: Under optimal conditions, the resveratrol content when extraction was performed using [hmim]Br, [bmim]Cl, and [bmim]BF₄ was 0.068, 0.059, and 0.038 mg/g dry weight, respectively, and total phenolic content was 0.647, 1.736, and 1.436 mg gallic acid equivalent/g, respectively.