Simple and efficient approach for enrichment of major isoflavonoids from Astragalus membranaceus with macroporous resins and their nephroprotective activities

Abstract

Isoflavonoids are abundant in Astragalus membranaceus and exhibit multiple pharmacological activities, including nephroprotective activity. In the present study, a simple, green and effective method for the simultaneous enrichment of four major bioactive isoflavonoids from A. membranaceus with macroporous resin was established. Among ten widely used macroporous resins, AB-8 resin exhibited the highest adsorption capacity and desorption ratio in static tests. The static equilibrium adsorption data fit to the Langmuir isotherm, and the adsorption kinetics followed the pseudo-second order model. Dynamic adsorption and desorption experiments were performed to optimize the separation parameters. After only one cycle of treatment with a stepwise elution on AB-8 resin, the contents of calycosin-7-O-β-d-glucoside (CAG), ononin (ONO), calycosin (CAL) and formononetin (FOR) in the final product were 7.71-, 10.64-, 10.50- and 9.49-fold increased with recovery yields of 70.89, 83.14, 85.01 and 74.62%, respectively. Furthermore, the target isoflavonoid-enriched product exhibited better nephroprotective activity than the crude extract, and both the purity of the isoflavonoids and their bioactivities were significantly enhanced after enrichment with macroporous resin. The developed method is a promising foundation for the scaled-up preparation of bioactive isoflavonoids for their wide use in the pharmaceutical industry.