Effects of ionic liquids and pulsed electric fields on the extraction of antioxidants from green asparagus roots

Asparagus officinalis root (AR) contains valuable bioactive compounds that have beneficial health properties. The aim of this study was to optimize the extraction of polyphenols and flavonoids in green AR using two novel technologies; pulsed electric field (PEF) and ionic liquids (IL). Further, the antioxidant activity of the obtained extracts was determined. The total polyphenol content, total flavonoid content (TFC), and antioxidant activity (2,2-diphenyl-1-picrylhydrazyl, oxygen radical absorbance capacity and Ferric reducing/antioxidant power assays) were determined. The PEF conditions (PEF strength of 1.6 kV/cm, frequency of 200 Hz and pulse width of 20 mu s) resulted in a higher extraction yield as compared to conventional solvent extraction, but had lower antioxidant activities. The optimal conditions for IL extraction were by using 0.5% 1-butyl-3-methylimidazolium chloride at a solid: liquid (S:L) ratio of 1:10 for four min. The IL extraction resulted in a total of 122 mg RE/ mL TFC which was 70 to 80 folds more than the TFC obtained by PEF. The IL extracts had higher TFC and antioxidant activity than PEF, but the safety of the ILs need further research.