Metabolite Fingerprinting for Identification of Panax ginseng Metabolites Using Internal Extractive Electrospray Ionization Mass Spectrometry

Abstract

Ginseng, a kind of functional food and medicine with high nutritional value, contains various pharmacological metabolites that influence human metabolic functions. Therefore, it is very important to analyze the composition and metabolites of ginseng. However, the analysis of active metabolites in ginseng samples usually involves various experimental steps, such as extraction, chromatographic separation, and characterization, which may be time-consuming and laborious. In this study, an internal extractive electrospray ionization mass spectrometry (iEESI-MS) method was developed to analyze active metabolites in ginseng samples with sequential sampling and no pretreatment. A total of 44 metabolites, with 32 ginsenosides, 6 sugars, and 6 organic acids, were identified in the ginseng samples. The orthogonal partial least-squares discriminant analysis (OPLS-DA) score plot showed a clear separation of ginseng samples from different origins, indicating that metabolic changes occurred under different growing conditions. This study demonstrated that different cultivation conditions of ginseng can be successfully discriminated when using iEESI-MS-based metabolite fingerprints, which provide an alternative solution for the quality identification of plant drugs.

Keywords: ginseng; internal extractive electrospray ionization mass spectrometry; metabolite fingerprinting; metabolites; sequential sampling.

Figure 1

The apparatus diagram of the iEESI-MS.

Figure 2

The fingerprint data of methanol (0.5 mM ammonium chloride) extracted from three samples detected using iEESI-MS: (a) fingerprint data of the ginseng under forest sample, (b) fingerprint data of the Panax quinquefolium (Canada) sample, and (c) fingerprint data of the Panax quinquefolium (Jilin) sample.

Figure 3

The fingerprint spectra of different solvents for the detection of ginseng under forest samples detected with iEESI-MS. (a,c,e,g) in the left column correspond to the fingerprint spectra of the ginseng under forest samples under 0.5 mM ammonium chloride in methanol, 0.1% formic acid in water/ethanol (v:v = 1:1), 10 mM ammonium acetate in acetonitrile/methanol (v:v = 1:1), and 0.1% formic acid in acetonitrile/ethanol (v:v = 1:1) solvents, respectively; (b,d,f,h) in the right column correspond to the fingerprint spectra of the ginseng under forest samples extracted sequentially in 0.5 mM ammonium chloride in methanol, 0.1% formic acid in water/ethanol (v:v = 1:1), 10 mM ammonium acetate in acetonitrile/methanol (v:v = 1:1), and 0.1% formic acid in acetonitrile/ethanol (v:v = 1:1) solvents, respectively.

Figure 4

Tandem MS analysis of characteristic ions of the active components in the ginseng under forest and two Panax quinquefolium samples detected with iEESI-MS: (a) MS² spectrum of m/z 117→, (b) MS² spectrum of m/z 133→, (c) MS² spectrum of m/z 179→, (d) MS² spectrum of m/z 191→, (e) MS² spectrum of m/z 503→, and (f) MS² spectrum of m/z 215→.

Figure 5

Tandem MS analysis of typical ginsenosides in ginseng under forest and two Panax quinquefolium samples detected with iEESI-MS: (a) MS² spectrum of m/z 637→, (b) MS² spectrum of m/z 783→, (c) MS² spectrum of m/z 793→, (d) MS² spectrum of m/z 799→, (e) MS² spectrum of m/z 945→, (f) MS² spectrum of m/z 1077→, (g) MS² spectrum of m/z 1107→, and (h) MS² spectrum of m/z 1149→.

Figure 6

Scatter plot of OPLS-DA scores of two Panax quinquefolius samples detected using sequential iEESI-MS: (a) score scatter plot of the 2D OPLS-DA model, (b) score scatter plot of the 3D OPLS-DA model, and (c) bar plot with the OPLS-DA model of the VIP.