A rapid resolution liquid chromatography coupled with quadruple-time-of-flight mass spectrometry (RRLC-Q-TOF-MS) method was developed for analysis of chemical transformation of 20(
S)-protopanaxatriol (PPT)-type ginsenosides R
e, R
g2, and R
f in acidic conditions. The transformation products were identified by comparing the retention time of the standard compounds, the accurate mass measurement, and the fragment ions obtained from RRLC-Q-TOF-tandem mass spectrometry (MS/MS) analyses. The specific product ions of aglycone PPT (
m/
z 475), C-24- and C-25-hydrated PPT (
m/
z 493), and 螖20(21) or 螖20(22) dehydration PPT (
m/
z 457) by MS/MS were discussed for structural characterization. Experiments demonstrated that chemical transformation mechanisms of 20(
S)-PPT-type ginsenosides in acidic conditions include hydrolysis of saccharide substitution, 螖20(21) or 螖20(22) dehydration, and hydration addition reactions at C-24 and C-25. The chemical transformation pathway for 20(
S)-PPT-type ginsenosides was summarized. The developed RRLC-Q-TOF-MS method was also applied for comparative analysis of 20(
S)-PPT ginsenoside and related chemical transformation products in ginseng products.
Keywords:
RRLC-Q-TOF-MS; ginsenoside; chemical transformation; Panax ginseng