Evaluation of alcohol-based deep eutectic solvent in extraction and determination of flavonoids with response surface methodology optimization

Deep eutectic solvents (DESs) are emerging rapidly as a new type of green solvent instead of an ionic liquid (IL), and are typically formed by mixing choline chloride with hydrogen bond donors. Few studies have applied DESs to the extraction and determination of bioactive compounds. Therefore, in the present study, DESs were used to extract flavonoids (myricetin and amentoflavone), which are well known and widely used antioxidants, to extend their applications. A range of alcohol-based DESs with different alcohols to choline chloride (ChCl) mixing ratios were used for extraction using several extraction methods. Other factors, such as temperature, time, water addition and solid/liquid ratio, were examined systematically using a response surface methodology (RSM). A total of 0.031 and 0.518 mg g−1 of myricetin and amentoflavone were extracted under the optimized conditions: 35 vol% of water in ChCl/1,4-butanediol (1/5) at 70.0 °C for 40.0 min and a solid/liquid ratio of 1/1 (g 10 mL−1). Good linearity was obtained from 0.1 × 10−3 to 0.1 mg mL−1 (r2 > 0.999). The excellent properties of DESs highlight their potential as promising green solvents for the extraction and determination of a range of bioactive compounds or drugs.