An emerging strategy for evaluating the grades of Keemun black tea by combinatory liquid chromatography-Orbitrap mass spectrometry-based untargeted metabolomics and inhibition effects on α-glucosidase and α-amylase. (25th April 2018)

• Record Type: Journal Article
• Authors: Guo, Xuemei; Long, Piaopiao; Meng, Qilu; Ho, Chi-Tang; Zhang, Liang
• Is Part Of: Food chemistry. Volume 246(2018)
• Page Start: 74
• Page End: 81
• Publication Date: 2018-04-25
• Subjects: Black tea -- Grade -- Theasinensin -- Metabolomics -- Theaflavins -- α-Glucosidase -- LC–MS; Food -- Analysis -- Periodicals; Food -- Composition -- Periodicals; 664
• DOI: 10.1016/j.foodchem.2017.10.148
• Languages: English
• ISSNs: 0308-8146

Abstract

Highlights: Theaflavins and catechins' levels did not correlated to black tea grades. Untargeted metabolomics classified Keemun black teas into two groups. Theasinensin A is an important grade-related bioactive marker compound. Metabolomics in combination with activities provide a strategy for tea research. Abstract: Quantitative analysis and untargeted liquid chromatography mass spectrum (LC–MS) based metabolomics of different grades of Keemun black tea (KBT) were conducted. Quantitative analysis did not show tight correlation between tea grades and contents of polyphenols, but untargeted metabolomics analysis revealed that high-grades KBT were distinguished from the low-grades. S -plot and Variable Importance (VIP) analysis gave 28 marker compounds responsible for the discrimination of different grades of KBT. The inhibitory effects of KBT on α-amylase and α-glucosidase were positively correlated to tea grades, and the correlation coefficient between each marker compound and inhibitory rate were calculated. Thirteen compounds were positively related to the anti-glycemic activity, and theasinensin A, afzelechin gallate and kaempferol-glucoside were confirmed as grade-related bioactive marker compounds by chemical and bioassay in effective fractions. This study suggested that combinatory metabolomics and bioactivities assay provided a new strategy for the classification of tea grades.