Non-targeted Metabolomic Analysis Reveals the Difference in Metabolite Composition between De’ang Sour Tea and Ripe Pu’er Tea

The difference in metabolite composition between De’ang sour tea and ripe Pu’er tea both made from the Yunnan Daye tea cultivar was investigated by non-targeted metabolomics based on ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC/QTOF-MS). The results showed that there was a big difference in metabolite composition between De’ang sour tea and ripe Pu-erh tea. Principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) could clearly distinguish the two kinds of tea according to their metabolite composition. A total of 268 significantly differential metabolites belonging to 21 classes were detected between them, accounting for all metabolites of 63.81% of the total metabolites, including 49 amino acids, 39 fatty acids, 36 nucleotides, 29 organic acids, and 18 sugars. The differential metabolites ergothiine, 3-dimethoxyphenylacetic acid, 3-hydroxymandelic acid, acetylcholine chloride, 2-hydroxy-4-methylvaleric acid, misoglitol, L-proline, 4-dioxyheptanoic acid, propanediol, proanthocyanidin B₂, N-acetylglycine may have important contributions to the formation of the taste quality of the two kinds of tea. Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway analysis showed that there were significant differences in the metabolism levels of amino acids and nucleotides in De’ang sour tea and Pu’er tea, and that the pathways related to amino acid metabolism and nucleotide metabolism had an important impact on the taste and quality of both kinds of tea.