Abstract:To investigate the inhibitory effect of dietary flavan-3-ol polyphenolic compounds on tau protein aggregation,this study first employed a recombinant expression system in Escherichia coli to produce tau352 protein and obtained high-purity protein through purification.Molecular docking was used to rapidly screen flavan-3-ol polyphenolic compounds exhibiting strong binding affinity with tau protein.Then,validation was performed on the interaction between flavan-3-ol polyphenolic compounds and tau protein,as well as their inhibitory effect on tau aggregation.As for the results,sodium dodecyl sulfate-polyacrylamide gel electrophoresis（SDS-PAGE）revealed the molecular weight of tau352 protein to be approximately 48 kDa.A tau K18 structural domain model was constructed via homology modelling.Molecular docking was employed to screen 10 compounds with high binding potential from 99 polyphenols,with epigallocatechin gallate（EGCG）exhibiting the highest docking score（138.54）.Further,EGCG,（-）-epigallocatechin（EGC）,and proanthocyanidins were selected for in vitro validation.According to fluorescence quenching,EGCG exhibited the strongest binding affinity to tau352 protein,with a binding constant of 1.14×105 L/mol.Circular dichroism（CD）spectroscopy indicated that EGCG altered the secondary structure of tau protein,reducing β-sheet formation.Fluorescence kinetic assays demonstrated that all polyphenols inhibited heparin-induced tau352 protein aggregation,with EGCG exhibiting the highest inhibition rate and a median inhibition concentration（IC50）of 20.46 μmol/L.These findings demonstrated that flavan-3-ol polyphenols could modulate tau protein secondary structure and inhibit tau protein aggregation,providing experimental evidence for the potential of natural products in intervening in neurodegenerative diseases.