Chemical Diversity of Fuzhuan Brick Teas from Hunan and Shaanxi

This study aimed to explore the diversity of metabolites and compare the metabolite profiles of Fuzhuan brick teas from Hunan and Shaanxi, to find out the difference in chemical components between fresh tea leaves and Fuzhuan brick tea and to identify the metabolites from fungi in Fuzhuan brick tea. Metabolomic studies on fresh tea leaf samples, Hunan and Shaanxi Fuzhuan brick teas and fungi from them were performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and molecular networks of characteristic metabolites. The results showed no significant difference between Hunan and Shaanxi samples in the diversity or profile of metabolites. However, the diversity of metabolites significantly increased as fresh tea leaves were processed into Fuzhuan brick tea, with a decrease in the contents of flavan-3-ols, alkaloids, most amino acids and their derivatives being observed, as well as an increase in the contents of lysophosphatidylcholines (LPCs) and fatty acids, which was accompanied by the appearance of a rich variety of fungal metabolites. Among them, the typical ones included isopentenyl cyclic dipeptides, isopentenyl benzaldehydes, whose existence enriched the diversity of metabolites in Fuzhuan brick tea.