Ionic liquid based ultrasonic assisted extraction of isoflavones from Iris tectorum Maxim and subsequently separation and purification by high-speed counter-current chromatography

Abstract: We developed an ionic liquid based ultrasonic assisted extraction (ILUAE) method for the extraction of the three isoflavones, namely tectoridin, iristectorin B and iristectorin A from Iris tectorum Maxim of the Iridaceae family. Three kinds of 1-alkyl-3-methylimidazolium ionic liquids with different alkyl chain and anion were investigated. The results indicated that ionic liquids (ILs) showed remarkable effects on the extraction yield of isoflavones. In addition, the ILUAE, including several ultrasonic parameters, such as the concentration, extraction time and solvent to solid ratio have been optimized. Under these optimal conditions (e.g., with 30min extraction time and the solvent to solid ratio of 30ml/g), this approach gained the highest extraction yields of tectoridin (37.45mg/g), iristectorin B (2.88mg/g) and iristectorin A (5.28mg/g). Meanwhile, tectoridin, iristectorin B and iristectorin A in the ILUAE extract were separated and purified successfully through the high-speed counter-current chromatography (HSCCC) with a two-phase solvent system consisting of n-butanol–water (1:1, v/v). The additional advantage of this approach is that 60.21mg tectoridin, 4.33mg iristectorin B and 8.24mg iristectorin A with more than 95.0% purities have been obtained from 400mg ILUAE extract of I. tectorum within 5h and one-step elution under the most optimized conditions (e.g., a flow rate of 2.0ml/min, 900rpm and the wavelengh of 280nm). The obtained fractions were successfully analyzed by HPLC and identified by 1H-NMR and 13C-NMR. [Copyright &y& Elsevier]