Development of microwave assisted extraction for the simultaneous determination of isoflavonoids and saponins in Radix Astragali by high performance liquid chromatography

A microwave assisted extraction (MAE) procedure was first developed for the simultaneous determination of isoflavonoids and astragalosides in Radix Astragali (RA). MAE showed the highest extraction efficiency when compared to Soxhlet, reflux, and ultrasonic extraction. It was found that flavonoid glycoside malonates were converted into their related glycosides during the prolonged conventional extraction, thus affecting the reproducibility. However, the conversion was inhibited when using MAE. After being optimized in terms of solvents, microwave power, and irradiation time, MAE was used for the simultaneous determination of isoflavonoids and astragalosides in RA with HPLC-UV-evaporative light scattering detection (ELSD). Our results indicated that extraction by MAE was more effective than by other conventional techniques. Moreover, the MAE method followed by HPLC-UV-ELSD determination was a simple, rapid, and reliable method for the quality assessment of RA.