National Research Center of Engineering Technology for Utilization of Botanical Functional Ingredients, Changsha 410128, China; Key Laboratory of Education Ministry for Tea Science, Hunan Agricultural University, Changsha 410128, China; Collaborative Innovation Center of Utilization of Functional Ingredients from Botanicals, Changsha 410128, China; Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, Changsha 410128, China. Electronic address: [Email]
The metabolites of green tea influence its quality and physiological characteristics. Therefore, to further increase the utilization of green tea leaves, it is imperative to understand the distribution and variation of their secondary metabolites with respect to different harvesting times. This study compared the metabolomes of young leaves of 'Anji Baicha' between early spring tea and late spring tea in positive and negative ESI modes using UPLC-ESI-Q-TOF/MS. Potential biomarkers were selected by principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) of chemometrics methods. Results showed that the metabolic profiles of young leaves in early and late spring tea were significantly different. The metabolite-related pathways associated with these differences included those involved in biosynthesis of flavonoids, phenylpropanoids, flavone and flavonol, phenylalanine, tyrosine, and tryptophan. In early spring tea leaves, concentrations of amino acids (l-glutamine and l-tryptophan), (S)-(-)-limonene, most of the catechins, and flavonol/flavone glycosides were found to be significantly increased, while proanthocyanidins (proanthocyanidin A1, prodelphinidin A1, and prodelphinidin A2 3'-gallate) concentrations were significantly decreased. As a result of the metabolomics analysis of young leaves of green tea plants with respect to different harvesting time, information regarding physiological characteristics and optimal harvesting time was obtained.