Identification and Determination of Flavonoids in Astragali Radix by High Performance Liquid Chromatography Coupled with DAD and ESI-MS Detection

A method for the analysis of flavonoids in Astragali Radix by high-performance liquid chromatography (HPLC) combined with photodiode-array detection (DAD) and an electrospray ionization (ESI) - mass spectrometry (MS) was developed. After the samples were extracted with ethanol, the optimum separation conditions for these analytes were achieved using a gradient elution system and a 2.0 x 150 mm Shimadzu VP-ODS column. Eight flavonoids were identified to exist in Astragali Radix based on their characteristic UV data and mass spectra. The concentrations of three major components in this herb-ononin, calycosin and formononetin-were determined by LC/ESI-MS in positive selective ion monitoring (SIM) mode. The calibration curves were linear in the range of 0.9 similar to 180.0 mu g.mL(-1) for ononin, 1.8 similar to 360.0 mu g.mL(-1) for calycosin and 1.4 similar to 280 mu g.mL(-1) for formononetin, respectively. The limits of quantification (LOQ) and detection (LOD) were 0.9 mu g.mL(-1) and 0.2 mu g.mL(-1) for ononin, 1.8 mu g.mL(-1) and 0.5 mu g.mL(-1) for calycosin, 1.4 mu g.mL(-1) and 0.5 mu g.mL(-1) for formononetin, respectively. The standard recoveries were between 95.4 similar to 104.7%. The developed method was proven to be useful for the quantitative and qualitative analysis of flavonoid constituents in various resources of Astragali Radix.