Liquid Chromatography Tandem Mass Spectrometry Combined with Fourier Transform Mid-Infrared Spectroscopy and Chemometrics for Comparative Analysis of Raw and Processed Gentiana rigescens

Herbal medicines have been shown to change chemical constituents upon different processing approaches, which might lead to different pharmacological activities and therapeutic effects. In this study, raw and processed Gentiana rigescens (wine-, vinegar-, and salt water-processed) were extracted and profiled by ultra-fast liquid chromatography tandem mass spectrometry (UFLC–MS/MS) and Fourier transform mid-infrared spectroscopy (FT-MIR). Hierarchical cluster analysis (HCA) based on FT-MIR revealed potential relationships between raw and processed samples, while the processed sample displayed chemical variation. Partial least-squares discriminate analysis (PLS-DA) was used for screening the marker metabolites. The results indicated that UFLC–UV-MS/MS and FT-MIR fingerprints with chemometrics could effectively evaluate the quality of G. rigescens under different processed approaches. Eight compounds were selected as potential marker metabolites for contributing to the most effective classification of raw and processed samples. In addition, these potential marker metabolites were tentatively identified by matching mass information with the fragmentation patterns of the published literature or standard compounds. These results revealed that UFLC–UV-MS/MS and FT-MIR methods coupled with chemometrics could provide an effective platform for monitoring quality variations of G. rigescens under different processed approaches.