Characterization of thrombin inhibitors in tea through ultra high performance liquid chromatography-mass spectrometry combined with multivariate statistical analysis

In this study, thrombin inhibitors in tea were characterized by combining thrombin inhibition assay of tea extracts with ultra high performance liquid chromatography–mass spectrometry based multivariate statistical analysis. The inhibitory activity on thrombin for ten tea samples were tested in vitro. Then, upon collecting and processing liquid chromatography-mass spectrometry data, combined with the results of activity assays, principal component analysis, and orthogonal partial least squares discriminant analysis were applied to predict discriminate differential markers. Six of twelve predicted marker compounds were tentatively identified. Among them, epigallocatechin 3- O -gallate, epicatechin gallate, epigallocatechin and gallocatechin 3- O -gallate showed good inhibitory activity on thrombin with IC 50 values of 5.033, 6.573, 6.704 and 6.842 mM, respectively. Moreover, molecular docking results indicated that these four active compounds could insert into the catalytic activity pocket of thrombin and the residue GLU192 may be their binding site.