Identification of Nutritional Ingredients and Medicinal Components of Pueraria lobata and Its Varieties Using UPLC-MS/MS-Based Metabolomics

Abstract

Pueraria lobata and its variety P. lobata var. thomsonii are both traditional Chinese medicines that have high nutritional and medical value; whereas another variety, P. lobata var. montana has low nutritional and medicinal value and can cause ecological disasters. The material basis of different nutritional and medicinal values, which are caused by metabolite differences among these varieties, remains to be further clarified. Here, we performed ultra performance liquid chromatography-tandem mass spectrometry based widely targeted metabolome analysis on Pueraria lobata, P. lobata var. thomsonii, and P. lobata var. montana. Among them, a total of 614 metabolites were identified, and distinguished from each other using orthogonal partial least squares discriminant analysis. Our results suggest that the nutritional differences between P. lobata and its varieties can be explained by variations in the abundance of amino acids, nucleotides, saccharides, and lipids; differences in flavonoids, isoflavones, phenolic acids, organic acids, and coumarins contents caused the differences in the medicinal quality of P. lobata and its varieties. Additionally, the key metabolites responsible for the classification of the three Pueraria varieties were identified. This study provides new insights into the underlying metabolic causes of nutritional and medicinal variation in P. lobata and its varieties.

Keywords: Pueraria lobata; UPLC-MS/MS; metabolite profiling; primary metabolites; secondary metabolites.

Figure 1

Phenotype of P. lobata and its two varieties. (A) One-year-old root tuber of P. lobata (a,b), P. lobata var. thomsonii (c,d), and P. lobata var. montana (e,f). Scale bar = 1 cm. (B) Cluster analysis of metabolites from root tuber samples of P. lobata, P. lobata var. thomsonii, and P. lobata var. montana. The color indicates the level of accumulation of each metabolite, from low (green) to high (red). The Z-score represents the deviation from the mean by standard deviation units.

Figure 2

Differential root tuber metabolites among P. lobata, P. lobata var. thomsonii, and P. lobata var. montana. PCA of metabolites identified from P. lobata, P. lobata var. thomsonii, and P. lobata var. montana. Equal volumes of P. lobata, P. lobata var. thomsonii, and P. lobata var. montana root tuber samples were mixed for use as a quality control (QC).

Figure 3

OPLS-DA of metabolites identified among P. lobata, P. lobata var. thomsonii, and P. lobata var. montana (a–c). OPLS-DA model plots for the comparison group P. lobata versus P. lobata var. thomsonii, P. lobata versus P. lobata var. montana, and P. lobata var. thomsonii versus P. lobata var. montana, respectively.

Figure 4

Heatmap of metabolites from root tuber samples of the HNMV group and the LNMV group. The color indicates the level of accumulation of each metabolite, from low (green) to high (red).

Figure 5

Differentially accumulating metabolites between P. lobata and P. lobata var. thomsonii. (A) Volcano plot of the 595 metabolites identified. Differential metabolites were defined as metabolites with a fold change of ≥2 or ≤0.5 in P. lobata compared to P. lobata var. thomsonii. A threshold of VIP ≥ 1.0 was used to separate differential metabolites from unchanged metabolites. (B) Cluster analysis of the differential metabolites identified between P. lobata and P. lobata var. thomsonii.