Monitoring of pickled tea during processing: From LC-MS based metabolomics analysis to inhibitory activities on α-amylase and α-glycosidase

Abstract

Different from post-fermented teas, pickled tea is a unique processed tea of fresh leaves of Camellia sinensis var. assamica under anaerobic fermentation. It is mainly consumed in ethnic minority areas in southwest China. The chemical characteristics of pickled tea during processing were studied by mass spectrometry-based metabolomics and quantitative determination. Metabolomics results showed that a total of 44 marker compounds, including flavan-3-ols, organic acids, glycosides, and flavonoids were identified in pickled tea during fermentation. Thereinto, galloylated catechins were mainly degraded or oxidated into the corresponding nongalloylated catechins and theaflavins. Caffeine and theobromine slightly varied, while organic acids markedly varied during the whole processing. In addition, butanedioic, lactic, and gallic acid were found as the main organic acids in pickled tea and their contents were 220 ± 9, 177 ± 21, and 172 ± 6 μg/g, respectively. The inhibitory effects of pickled tea samples on α-amylase and α-glucosidase were also investigated and subsequently analyzed with respect to chemical-biological activities correlation. The results showed that glycosides and most organic acids were key α-amylase inhibitors, while catechins and flavonoids were key α-glucosidase inhibitors. The present study aimed to comprehensively explore the chemical variation of pickled tea during processing, and key inhibitors of α-glucosidase and α-amylase.