Microwave-assisted aqueous two-phase extraction of isoflavonoids from Dalbergia odorifera T. Chen leaves

An efficient microwave-assisted aqueous two-phase extraction (MA-ATPE) technique was developed to simultaneously extract and enrich genistein and biochanin A from Dalbergia odorifera T. Chen leaves. Three salts were investigated, and dipotassium hydrogen phosphate was selected to form aqueous two-phase system (ATPS). Box-Behnken Design combined with response surface methodology was applied to optimize the operating parameters of MA-ATPE. The optimal conditions were as follows: salt concentration 20%, absolute alcohol concentration 25%, extraction temperature 45.5 degrees C, extraction time 10 min and irradiation power 300 W. Under the optimized condition, the extraction yields of genistein and biochanin A reached 1.034 mg/g DM and 2.023 mg/g DM, respectively. Compared with microwave assisted extraction (MAE) and heat reflux extraction (HRE), the contents of genistein and biochanin A in the extracts reached 12.966 mg/g extract and 25.526 mg/g extract, which were 2.48- and 2.30-fold to that of MAE, 2.64- and 2.80-fold to that of HRE. Furthermore, the antioxidant activities of extracts from MA-ATPE, MAE and HRE were 0.342, 0.389, 0.411 mg/mL (IC50), according to the DPPH radical-scavenging assay. Moreover, the phase-forming salt can be recyclable. In conclusion, MA-ATPE was an efficient, eco-friendly and economical technique, which represented an excellent alternative for the extraction of bioactive compounds from plant. (C) 2013 Elsevier B.V. All rights reserved.