In traditional Chinese medicine practice, drying method is an essential factor to influence the components of Chinese medicinal herbs. In this study, an ultra-performance liquid chromatography quadrupole time-of-flight tandem mass spectrometry (UPLC-QTOF-MS/MS)-based approach was used to compare the content of chemical compounds of mountain cultivated ginseng that had been natural air dried (LX-P) and vacuum freeze-dried (LX-L). Multivariate statistical analysis such as principal component analysis (PCA) and supervised orthogonal partial least squared discrimination analysis (OPLS-DA) were used to select the influential components of different samples. There were 41 ginsenosides unambiguously identified and tentatively assigned in both LX-L and LX-P. The results showed that the characteristic components in LX-P were ginsenoside Rb1, ginsenoside Rc, ginsenoside Rg6, dendrolasin, and ginsenoside Rb2. The characteristic components in LX-L were malonyl-ginsenoside Re, malonyl-ginsenoside Rb1, malonyl-ginsenoside Rc, malonyl-ginsenoside Rb1 isomer, malonyl-ginsenoside Rb2, malonyl-ginsenoside Rb3, malonyl-ginsenoside Rd isomer, gypenoside XVII, and notoginsenoside Fe. This is the first time that the differences between LX-L and LX-P have been observed systematically at the chemistry level. It was indicated that vacuum freeze-drying method can improve the content of malonyl-ginsensides in mountain cultivated ginseng.
Keywords: OPLS-DA; PCA; UPLC-QTOF-MS/MS; mountain cultivated ginseng (MCG); vacuum freeze-drying.