Characterization of novel astragaloside malonates from Radix Astragali by HPLC with ESI quadrupole TOF MS.

A structurally identified new compound named malonylastragaloside I was isolated and obtained from Radix Astragali. This novel compound was found to be unstable especially under high temperature and pH value. Using sonication extraction, addition of formic acid, and an efficient medium pressure ODS C(18) column chromatography method, a high yield of 40 mg of this compound was obtained from 150 g of powdered crude herbal medicine. Malonylastragaloside I was structurally characterized by NMR and ESI quadrupole TOF MS. With the strategy of target precursor ions scan, a total of 22 astragalosides including 8 astragaloside malonates were screened and characterized from the methanolic extract of Radix Astragali by HPLC-Q-TOF/MS. The eight astragaloside malonates were found in both Astragalus membranaceus var. mongholicus and A. membranaceus. The results provided a real profile of various triterpene saponins in Radix Astragali. It is a first report regarding isolation and characterization of astragaloside malonates in Astragalus species.