Evaluation of astringent taste of green tea through mass spectrometry-based targeted metabolic profiling of polyphenols

The contributions of many polyphenols other than catechins and flavonols to the astringency of tea are often neglected. Here, the contributions of polyphenols were assessed through targeted metabolic profiling using liquid chromatography-mass spectrometry. A total of 86 polyphenols were identified from 47 green tea samples with varying astringency scores, of which 76 compounds were relatively quantified. A correlation matrix analysis revealed that monohydroxyflavonol and acyl derivatives of polyphenols, except for galloylated catechins, had negative correlations with the other polyphenols. Principal component analysis revealed a distinct separation of monohydroxyflavonol and acyl derivatives of polyphenols from the other polyphenols. The results suggest metabolic differences in terms of hydroxylation, glycosylation, acylation, and condensation reactions of polyphenols between the different tea samples, particularly between the samples obtained in spring and autumn. The correlation analysis showed that metabolic fluxes toward the aforementioned four reactions of polyphenols played unique roles in the astringency of tea infusions.