Structural characterization and identification of oleanane‐type triterpene saponins in Glycyrrhiza uralensis Fischer by rapid‐resolution liquid chromatography coupled with time‐of‐flight mass spectrometry

Abstract

Oleanane-type triterpene saponins (OTS) are major active ingredients in Glycyrrhiza uralensis. In this work, a rapid-resolution liquid chromatography with time-of-flight mass spectrometry (RRLC/TOF-MS) method has been developed to characterize and identify OTS from G. uralensis. The major diagnostic ions and fragmentation pathways from thirteen OTS have been characterized for the first time. At a low fragmentor voltage of 120 V in positive ion mode, the precursor ion [M + H](+) or/and [M + Na](+) was obtained for accurate determination of molecular formula. When the fragmentor voltage was increased to 425 V, abundant characteristic fragment ions were observed for structural characterization. Neutral losses of sugar moieties, such as glucuronic acid (GlcA, 176 Da), glucose (Glc, 162 Da) and rhamnose (Rha, 146 Da), were commonly observed in the MS spectra for prediction of the sugar number and sequences. Other typical losses included AcOH (60 Da), CH(2)O (30 Da), 2 × H(2)O (2 × 18 Da) and HCOOH (46 Da) from [Aglycone + H-H(2)O](+) (named [B](+)), corresponding to the presence of a C(22)-acetyl group, C(24)-hydroxyl group, C(22)-hydroxyl group or C(30)-carboxyl group on the aglycone moiety, respectively. In particular, characteristic ring cleavages of the aglycone moieties on A- and B-rings were observed. Based on the fragmentation patterns of reference compounds, nineteen OTS have been identified in an extract of G. uralensis, thirteen of which were unambiguously identified and the other six were tentatively assigned.

Chemical profiling and quantification of Gua-Lou-Gui-Zhi decoction by high performance liquid chromatography/quadrupole-time-of-flight mass spectrometry and ultra-performance liquid chromatography/triple quadrupole mass spectrometry

“…Triterpene saponins were recognized as the major active ingredients in Glycyrrhizae Radix [41]. In this work, a total of 20 triterpene saponins were identified and showed similar MS/MS behaviors.…”

“…In this work, a total of 20 triterpene saponins were identified and showed similar MS/MS behaviors. In the negative ion mode, all saponin compounds [28,29,36,41].…”

Fragmentation investigation of seven arylnaphthalide lignans using liquid chromatography/tandem quadrupole time‐of‐flight mass spectrometry

“…-was formed by the loss of a carboxyl and a methyl group, both of these product ions had a similar abundance. Loss of a carboxyl group from the lactone ring formed a product ion at m/z 334 [C 20 -was generated by the loss of ÁCHO from the A ring. Successive or simultaneous losses of methyl and CO from the product ion at m/z 350 [C 20 -.…”

“…Loss of a carboxyl group from the lactone ring formed a product ion at m/z 334 [C 20 -was generated by the loss of ÁCHO from the A ring. Successive or simultaneous losses of methyl and CO from the product ion at m/z 350 [C 20 -. The prevalent fragmentation pattern for compound 3 was the loss of methyl from the 7-methoxy group on the A ring.…”

“…The remaining QTOFMS parameters, including the voltages of the transfer optics, ion focus, quadrupole lens, TOF, and detector, were automatically optimized by the instrument autotuning procedure. Before the starting of analysis, mass calibration was performed daily using a mixture of four reference compounds provided by the manufacturer, providing [ [20] In addition to the mass measurements, the theoretical isotope distribution for each elemental composition was compared with the experimental results. A scoring algorithm was used to generate an i-FIT ™ value for each possible elemental composition where a lower i-FIT ™ value indicated a better match to the experimental result.…”