Efficient isolation of catechins from green tea and characterization of interaction property of catechins with proteins by HPLC–UV/DAD combined with ultrafiltration

Abstract

The aim of this study was to ascertain systematically interaction properties of active compounds in green tea extract (GTE) and involved proteins in the path of drugs delivery by high performance liquid chromatography–UV/DAD combined with ultrafiltration. GTE prepared by 50% methanol was separated successfully into fourteen components under optimized chromatographic conditions. Binding degrees of (−)-catechin (C), (−)-epigallocatechin gallate (EGCG), caffeine, and (−)-epicatechin gallate (ECG) in GTE with human plasma protein, rat plasma protein, human serum albumin (HSA), pancreas membrane protein (PMP), and rat pancreas cell membrane (PCM) were determined, respectively. The binding degrees of C, EGCG, ECG, and caffeine were above 80% of the total plasma (human or rat), and the binding degrees of four components were still above 65% at 0.6 mM HSA solution. The binding degrees of C, EGCG, and ECG with PMP were 36.9, 37.4, and 39.2%, and the binding degrees of EGCG and ECG to PCM were 78.8 and 91.5%, respectively. These results showed that there were high binding degrees between these components and transportation proteins in plasma, and receptor proteins on cell membrane. Compared with C and caffeine, EGCG and ECG had always higher binding degrees with different proteins, which meant EGCG and ECG were true active components. Based on these results, we suggest that the inhibition of the pathogenesis of some diseases by green tea should be associated with the high binding degrees of catechins to target receptors.