Abstract

Cercis chinensis Bunge is a valuable industrial crop with extensive medicinal and biological activities. To develop efficient tyrosinase inhibitors, condensed tannins were isolated from Cercis chinensis Bunge flowers. Thiolysis high-performance liquid chromatography–electrospray ionization mass spectrometry and electrospray ionization full mass spectrometry analyses revealed that the primary components in condensed tannins were prodelphinidins with gallic catechin/epigallocatechin (GC/EGC) as a structural unit with a small number of procyanidins and high level of galloylation. Enzyme kinetic analysis revealed that Cercis chinensis Bunge flower condensed tannins (CBCT) exhibited strong tyrosinase (TYR) monophenolase and diphenolase inhibitory activities, and their IC50 values were 38.9 and 15.3 μg/mL, respectively. CBCT belongs to a reversible mixed-type inhibitor of diphenolase. The UV spectroscopy and fluorescence quenching assays showed that CBCT inhibited the activity of TYR by binding to the two copper ion active centers of TYR and masking tryptophan activity. The TYR formed stable hydrogen bonds with GC/EGC through residues Lys70, Thr324, and Glu340 through molecular simulations. In addition, CBCT exhibited strong antioxidant and antibacterial properties, and could efficiently preserve fresh-cut lotus roots. Therefore, CBCT is a non-toxic natural product with antioxidant, anti-tyrosinase, and antibacterial properties and has the potential to be developed as a new type of fruit and vegetable preservative.