Abstract:

To elucidate the influence of various drying methods on the metabolite profiling of fresh tea leaves, Camellia sinensis var. sinensis ‘Xiaoye 1’, C. sinensis var. sinensis ‘Rougui’ and C. sinensis var. assamica ‘Hainandaye 1’ were employed as research subjects. The study findings provided a scientific basis for selecting appropriate drying methods in tea metabolite analysis. Utilizing a non-targeted metabolomics approach facilitated by ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS), the metabolites in tea samples subjected to vacuum freeze-drying and oven-drying were both qualitatively and quantitatively assessed. Subsequent analysis revealed disparities in their relative content. In both positive and negative ion detection modes, 3327 distinct metabolite ion peaks were identified, encompassing categories such as polyphenols, alkaloids, amino acids and their derivatives, carboxylic acids and their derivatives, aromatic compounds, sugars, glycosides, and others. Notably, the drying method employed significantly affected the metabolite content determination. For Camellia sinensis var. sinensis ‘Xiaoye 1’ and C. sinensis var. assamica ‘Hainandaye 1’, the vacuum freeze-drying method yielded results more consistent with fresh leaves, whereas for Camellia sinensis var. sinensis ‘Rougui’, oven-drying proved to be more similar. Further analysis revealed that the contents of flavonoids, amino acids and their derivatives, and aromatic substances remained relatively stable across different drying conditions. The contents of flavonoids, amino acids and their derivatives, and aromatic compounds were relatively stable under different drying conditions. Other polyphenols, alkaloids, sugars and glycosides, carboxylic acids and their derivatives were significantly affected by drying methods. The study clarified the basis for the selection of tea metabolomics drying methods. It was suggested that oven-drying should be preferred for large quantities of samples, vacuum freeze-drying should be preferred for accurate quantification, and flexible selection should be made according to the characteristics of target metabolites and varieties.

Key words: tea, non-targeted metabolomics, ultra-high performance liquid chromatography-mass spectrometry, oven-drying, vacuum freeze-drying, metabolite stability, UHPLCMS