Comprehensively qualitative and quantitative analysis of ginsenosides in Panax notoginseng leaves by online two-dimensional liquid chromatography coupled to hybrid linear ion trap Orbitrap mass spectrometry with deeply optimized dilution and modulation system

Abstract

Panax notoginseng leaves (PNL) was considered as a potential medicinal part with abundant protopanaxdiol type ginsenosides. In this study, an integrated system was developed for simultaneously qualitative and quantitative analysis of ginsenosides in PNL using online comprehensive two-dimensional hydrophilic interaction chromatography and reversed-phase liquid chromatography coupled to a hybrid linear ion trap-Orbitrap mass spectrometry (online HILIC × RP-ESI/HRMS/MSn). The system was configured based on the combination of a XBridge amide column (150 mm × 2.1 mm, 2.5 μm) and Accucore phenyl-hexyl (50 mm × 4.6 mm, 2.6 μm) for the first and second dimensions, respectively. An additional water phase was introduced to dilute the eluent from the first dimension to decrease its elution strength in the second dimension. The online dilution, modulation interface and the second-dimension gradient program were deeply optimized to reduce possible sample loss and improve system resolution. Under the optimal conditions, a total of 226 ginsenosides were unambiguously identified or tentatively characterized by aid of high-resolution accurate mass and MSn fragment data in both negative and positive ion modes, and 93 of them were discovered as potentially new ginsenosides in PNL. Besides, the validated online HILIC × RP-LTQ-MS method was applied to determine 24 ginsenosides directly on 2D-EIC contour plots in nine batches of PNL samples. The powerful separation capability acquired by the developed online HILIC × RP system affords not only reliable structural information for identification, but also accurate quantitation. This combined system can also be used to characterize and quantify bioactive ingredients in the samples with complex matrices.