Identification of key metabolites based on non-targeted metabolomics and chemometrics analyses provides insights into bitterness in Kucha [Camellia kucha (Chang et Wang) Chang]

Camellia kucha (Chang et Wang) Chang is a special tea in China, which is extremely bitter but beneficial for human health. However, there are no systematic studies on Kucha metabolites, especially those associated with bitterness. In this study, a non-targeted metabolomics approach based on UHPLC-LTQ-Orbitrap-MS was applied to comprehensively profile the characteristic metabolites of two Kucha cultivars by comparison with three common tea cultivars. A total of 90 differential metabolites were identified. Among them, eight key metabolites (theacrine, 2,4-dimethyl-1H-indole, EGCG, dihydrokaempferol, panasenoside, 3-cresotinic acid, 3-methylglutaconic acid, and L-histidine) were more abundant in Kucha than in the controls, most of which were positively correlated with bitterness. Furthermore, quantitative analysis of some important catechins and alkaloids by HPLC implied absolutely higher concentrations of EGCG and theacrine in Kucha, which was similar to the metabolomics results. These results will be contribute to future research on the bitter and nutritional properties of Kucha.