Determination of seventeen main flavonoids and saponins in the medicinal plant Huang-qi (Radix Astragali) by HPLC-DAD-ELSD

A simple, rapid, and reliable method, namely high-performance liquid chromatography coupled with diode array and evaporative light scattering detectors (HPLC-AD-ELSD), was developed to simultaneously determine twelve major flavonoids and five main saponins in different parts of the medicinal plant Huang-qi (Radix Astragali). The DAD wavelength was set at 280 nm for the UV detection of flavonoids, while the drift tube temperature was set at 105 degrees C and the nebulizing gas flow rate at 2.7 L/min for ELSD detection of saponins. The method was fully validated with respect to linearity (r(2) > 0.998), sensitivity, precision, and accuracy (recovery rate between 93.3 and 104.2%). The analytical results of different parts of the medicinal plant Huang-qi revealed that the levels of total flavonoids or saponins in individual parts can vary considerably and the concentration of each compound in different parts is also significantly different. The aerial parts (stems and leaves) contain even higher total contents of flavonoids (although of different kinds) than the commonly used roots of the plants. In addition, the concentration of total flavonoids and saponins in the extract of the fibrous roots was surprisingly highest among all parts of Astragalus species. All of these findings provide clear evidence and scientific support for utilization of different parts of the medicinal plant Huang-qi and also for reduction in waste of plant resources.