Abstract
Wuyi Rock tea, well-recognized for rich flavor and long-lasting fragrance, is a premium subcategory of oolong tea mainly produced in Wuyi Mountain and nearby regions of China. The quality of tea is mainly determined by the chemical constituents in the tea leaves. However, this remains underexplored for Wuyi Rock tea cultivars. In this study, we investigated the leaf metabolite profiles of 14 major Wuyi Rock tea cultivars grown in the same producing region using UPLC-QTOF MS and UPLC-QqQ MS with data processing via principal component analysis and cluster analysis. Relative quantitation of 49 major metabolites including flavan-3-ols, proanthocyanidins, flavonol glycosides, flavone glycosides, flavonone glycosides, phenolic acid derivatives, hydrolysable tannins, alkaloids and amino acids revealed clear variations between tea cultivars. In particular, catechins, kaempferol and quercetin derivatives were key metabolites responsible for cultivar discrimination. Information on the varietal differences in the levels of bioactive/functional metabolites, such as methylated catechins, flavonol glycosides and theanine, offers valuable insights to further explore the nutritional values and sensory qualities of Wuyi Rock tea. It also provides potential markers for tea plant fingerprinting and cultivar identification.
Highlights
Oolong tea is a partially-fermented tea manufactured in southeast China, mainly in Fujian and Guangdong
(XYMX), ‘Jinfenghuang’ (JFH), ‘Aijiaowulong’ (AJWL), ‘Guazijin’ (GZJ) and ‘Jinsuoshi’ (JSS) (Figure 1), non-targeted analysis based on UPLC-QTOF MS was performed to profile tea leaves
All tea plants of Camellia sinensis used in the current study were grown at the same tea germplasm garden and under the same cultivation practice, which was managed by the Wuyi
Summary
Oolong tea is a partially-fermented tea manufactured in southeast China, mainly in Fujian and Guangdong. Non-targeted metabolomics approach based on UPLC-QTOF MS, GC-TOF MS or NMR is a powerful technique capable of detecting a high number of endogenous metabolites simultaneously [10] It has been widely applied in tea research to study impacts of environmental factors on tea metabolites [11,12,13], characterize dynamic changes during tea manufacture [14,15] and discover key compounds for tea type discrimination [16,17]. Data processing by principal component analysis (PCA), partial least squared discriminant analysis (PLS-DA) and hierarchical cluster analysis revealed differences as well as commonalities between the leaf phytochemical compositions among cultivars It offered a comprehensive view for leaf metabolomes of Wuyi Rock tea cultivars in general and provided basis for future characterizations of nutritional values, sensory qualities and biological properties of Wuyi Rock tea
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