Abstract: This study aimed to explore the metabolites characteristics of white tea and the mechanism for the formation of metabolites during processing. White tea, green tea, oolong tea and black tea were processed from one bud with two or three leaves from the tea cultivars Fuyun 6 and Huangdan. The abundance of all metabolites in fresh tea leaves and tea was determined by using ultra-high performance liquid chromatography coupled to quadrupole time of flight mass spectrometry (UPLC-Q-TOF MS). Metabolites that differed between white tea and other types of tea were selected and identified. A total of 152 and 148 differential metabolites were determined for Fuyun 6 and Huangdan, respectively. Among them, 33 metabolites were identified as major compounds in tea, including catechins and its derivatives, anthocyanidins, hydrolysable tannins, flavonols or flavone glycosides, phenolic acids and theaflavins. The results of principle component analysis showed that white tea was between oolong tea and black tea in terms of first principle component whereas it was clearly separated from other types of tea in terms of second principle component. The loading plot showed that the characteristic metabolites of white tea that made it discint from other tea types were flavonol or flavone glycosides, gallated catechin and catechin derivates. The abumdances of most of the identified flavonols or flavone glycosides in white tea were significantly higher than those of other types of tea. The abundances of catechins and anthocyanidins were significantly lower than in white tea than in green tea and approximated to black tea, especially non-gallated catechins. The abundances of theaflavin and theaflavin-3-gallate were significantly higher in white tea than in green tea while no significant differences in the abunadance of theaflavin-3’-gallate or theaflavin-3,3’-gallate were seen between white tea and green tea. Interestingly, the abundance of 8-C-ascorbyl-EGCG, an EGCG derivate, was significantly higher than in white tea than in other types of tea.

Key words: ultra-high performance liquid chromatography coupled to quadrupole time of flight mass spectrometry, non-target metabolomics, tea processing, different tea types, white tea