High performance liquid chromatography coupled to electrospray ionization and quadrupole time-of-flight-mass spectrometry as a powerful analytical strategy for systematic analysis and improved characterization of the major bioactive constituents from Radix Dipsaci.

Radix Dipsaci (RD), the dried root of Dipsacus asper, is commonly used as a traditional Chinese medicine for the treatment of bone diseases and functions in strengthening bone and healing bone fractures. Nevertheless, the high polarity, non chromophores and low abundance of multiple compounds in this plant bring difficulty for their isolation and structural determination by traditional chromatographic and spectroscopic techniques, which hindered the use of RD in clinical practice and retarded the process of RD modernization. In this work, a sensitive and rapid high-performance liquid chromatography coupled with electrospray time-of-flight-mass spectrometry (HPLC-ESI-QTOF-MS/MS) was employed to rapidly separate and identify the multiple minor constituents in RD. Separation was performed an Agilent poroshell 120 EC-C18 column (2.1mm×100mm, i.d., 2.7μm) with 0.1% formic acid aqueous solution and acetonitrile as the mobile phase under gradient conditions. As a result, 36 major constituents including dipsacus saponins, iridoid glycosides and caffeoyl quinic acid derivatives were identified or tentatively characterized from the RD, 11 of which had not been previously reported to the best of our knowledge. In conclusion, the HPLC-ESI-QTOF-MS/MS is feasible and credible technique to separate and identify the constituents in complex matrices of traditional Chinese medicines.