Examination of 1-methylimidazole series ionic liquids in the extraction of flavonoids from Chamaecyparis obtuse leaves using a response surface methodology

Ionic liquids (ILs) are a new type of reagent that has accelerated research in extraction technology. On the other hand, few studies have systematically applied 1-methylimidazole ([MIM]) series ILs to the extraction of bioactive compounds from plants. In this study, [MIM] series ILs were used to extract four bioactive flavonoids, such as dihydrokaempferol, quercitrin, amentoflavone and myricetin, from Chamaecyparis obtuse (CO) leaves. First, a screen of the extraction method and solvent revealed the [MIM] series ILs to be suitable as additives in methanol in Soxhlet extraction. Second, an examination of a range of cations and anions of [MIM] series ILs for extraction revealed 1-decyl-3-methylimidazolium bromide ([DMIM][Br]) to be the best selection as an additive in methanol for the Soxhlet extraction of flavonoids from (CO) leaves. Finally, some factors of extraction, such as temperature, time and amount of samples, were examined systematically using a response surface methodology (RSM). Based on the above optimization, 2.41, 3.47, 0.76 and 3.15 mg/g of dihydrokaempferol, quercitrin, amentoflavone and myricetin, respectively, were extracted from 15 g of CO leaves by 2.5 mg mL−1 of [DMIM][Br] as additives in 200 mL of methanol in Soxhlet extraction at 200 °C for 8 h. This study highlights the potential of [MIM] series ILs as promising reagents for the extraction of bioactive compounds from plants.