Expeditious discrimination of four species of the Panax genus using direct infusion-MS/MS combined with multivariate statistical analysis

A practical approach based on direct infusion-MS/MS (DI-MS/MS) was demonstrated for metabolomic classification of four species in the Panax genus. The species Panax ginseng, Panax notoginseng, Panax quinquefolius and Panax vietnamensis were analyzed to develop an efficient tool for authenticating ginseng. Four target ions (m/z 783.5, 945.5, 1107.5 and 1149.2) were selected from LC-MS screening results for DI-MS/MS analysis. The target ions served as classifiers of the four species. As a targeted analysis, DI-MS/MS provided the structural identities of the target ions, clear spectral data and high sensitivity in a shorter time than routine LC-MS analysis. Principal component analysis and partial least squares-discriminant analysis of the DI-MS/MS fingerprinting revealed distinct grouping of the data. The results were validated by cross-validation and a permutation test to examine the utility of the statistical models. The spectral intensities of each species were compared with one another using box plots, which allowed straightforward authentication of the Panax species. The proposed method showed improved efficiency over other current methods for discrimination of large quantities of plant material. Additionally, to the best of our knowledge, this is the first study in which DI-MS/MS has been used to classify plant samples.