Analysis of Differentiated Chemical Components between Zijuan Purple Tea and Yunkang Green Tea by UHPLC-Orbitrap-MS/MS Combined with Chemometrics

Abstract

Zijuan tea (Camellia sinensis var. assamica cv. Zijuan) is a unique purple tea. Recently, purple tea has drawn much attention for its special flavor and health benefits. However, the characteristic compounds of purple tea compared with green tea have not been reported yet. The present study employed a non-targeted metabolomics approach based on ultra-high performance liquid chromatography (UHPLC)-Orbitrap-tandem mass spectrometry (MS/MS) for comprehensive analysis of characteristic metabolites between Zijuan purple tea (ZJT) and Yunkang green tea (YKT). Partial least squares-discriminant analysis (PLS-DA) indicated that there are significant differences in chemical profiles between ZJT and YKT. A total of 66 major differential metabolites included catechins, proanthocyanins, flavonol and flavone glycosides, phenolic acids, amino acids and alkaloids were identified in ZJT. Among them, anthocyanins are the most characteristic metabolites. Nine glycosides of anthocyanins and six glycosides of proanthocyanins were found to be significantly higher in ZJT than that in YKT. Subsequently, pathway analysis revealed that ZJT might generate anthocyanins and proanthocyanins through the flavonol and flavone glycosides. Furthermore, quantitative analysis showed absolutely higher concentrations of total anthocyanins in ZJT, which correlated with the metabolomics results. This study presented the comprehensive chemical profiling and the characterized metabolites of ZJT. These results also provided chemical evidence for potential health functions of ZJT.

Keywords: UHPLC–Orbitrap–MS/MS; Yunkang green tea; Zijuan purple tea; anthocyanins; characteristic chemical compounds; metabolite profiling; proanthocyanins.

Figure 1

Multivariate statistical analysis of the differences in metabolites between Zijuan purple tea (ZJT) and Yunkang green tea (YKT). (A) Principal component analysis (PCA)-X score in positive ion mode (R²X = 0.73; Q² = 0.47); (B) partial least squares-discriminant analysis (PLS-DA) score in positive ion mode (R²X = 0.519; R²Y = 0.996; Q² = 0.972); (C) PLS-DA model validation in positive ion mode (R² = 0.818; Q² = −0.0476); (D) PCA-X score in negative ion mode (R²X = 0.638; Q² = 0.506); (E) PLS-DA score in negative ion mode (R²X = 0.656; R²Y = 0.999; Q² = 0.991); (F) PLS-DA model validation in negative ion mode (R² = 0.626; Q² = −0.226).

Figure 2

Heat map representing metabolites levels in ZJT and YKT. Red and blue boxes represent values that were higher and lower than the mean value, respectively.

Figure 3

Concentration of anthocyanin in ZJT and YKT (mg/g) (n = 3, mean ± standard error of the mean (SEM)), ### p < 0.001, compared to ZJT.

Figure 4

Pathway analysis of ZJT and YKT. The y-axis (−log (p-value)) and x-axis represents the significance of the pathway and pathway impact between ZJT and YKT, respectively.

Figure 5

Metabolic pathways of flavone and flavonol biosynthesis and amino acid biosynthesis in ZJT and YKT. Red (LgFC > 0) and blue (LgFC < 0) boxes represent values that were higher and lower than the mean value, respectively.