Quantitative Evaluation of Twelve Major Components of Sulfur-Fumigated Astragali Radix with Different Durations by UPLC-MS

In this study, an improved UPLC-MS (Ultra-high performance liquid chromatography-tandem mass spectrometry) method for simultaneously quantifying twelve major components belonging to two chemical types was developed and validated, and was applied to quantitatively compare the quality of sulfur-fumigated Astragali Radix of different durations and of the fresh reference sample. The results showed that the contents of triterpenes astragaloside III and astragaloside IV decreased moderately, while the flavonoids calycosin, formononetin, and 7,2'-dihydroxy-3',4'-dimethoxyisoflavane decreased significantly. The corresponding flavonoid glycosides increased accordingly, which indicated the occurrence of chemical transformation of flavonoids and glycosides in the process of sulfur-fumigation. These transformations were further confirmed by the synthesis of flavonoid glycosides under simulated sulfur-fumigation circumstances. Furthermore, the sulfur-fumigated duration varied in proportion with the contents of compounds 7, 11, and 12. These results suggest that the established method was precise, accurate and sensitive enough for the global quality evaluation of sulfur-fumigated Astragali Radix. Further, sulfur-fumigation not only changes the proportions of bioactive components, but also causes chemical transformation in Astragali Radix.