Extraction of Seleno-Amino Acids from Cardamine Hupingshanensis by Ultrasonic Assisted Deep Eutectic Solvents Extraction

In this work, deep eutectic solvent (DES) combined with ultrasonic-assisted extraction was proposed to extract free seleno-amino acids from Cardamine hupingshanensis. The contents of seleno-amino acids in the extract were determined by high-performance liquid chromatography with a fluorescence detector (HPLC-FLD). Response surface design was used to optimize the extraction conditions such as ultrasonic time, ultrasonic temperature, and liquid-solid ratio. The results showed that DES prepared by choline chloride and ethylene glycol had the highest extraction efficiency of seleno-amino acids. The main free seleno-amino acids in Cardamine hupingshanensis were selenocystine (SeCys2) and selenomethylcysteine (SeMeCys). The optimal extraction conditions were as follows: liquid-solid ratio of 50 mL·g–1; extraction temperature of 40 °C; and extraction time of 45 min. Under the optimal extraction conditions, the SeCys2 and SeMeCys contents were 356 μg·g–1 and 147 μg·g–1, respectively. This study shows that DES has great potential in extraction and separation.