Chirality-dependent interaction between zein and dihydromyricetin isomers: binding mechanism and gastrointestinal behaviour

Stereoisomerism, referring to the existence of molecules as chiral forms with distinct three-dimensional configurations, plays a crucial role in determining how bioactive compounds interact with food proteins. This study investigated the effects of dihydromyricetin (DMY) stereochemistry, including ( 2R, 3R )-, ( 2S, 3S )-, and racemic (rac)- forms, on its binding with zein and the subsequent release during simulated digestion. Zein-DMY complexes were prepared and analysed using fluorescence spectroscopy, molecular dynamics simulation, and an in vitro gastrointestinal model. Results showed that all zein-DMY complexes exhibited smaller particle size and higher zeta potential than original zein ( p  < 0.05). Fluorescence quenching analysis suggested that zein-( 2R, 3R )-DMY complex had higher quenching constants (3.2 × 10 4  L·mol −1 ) and binding constants (3.2 × 10 4  L·mol −1 ) than the zein-( 2S, 3S ) and zein-(rac)-DMY complexes. Molecular dynamics simulations further confirmed this preferential binding, showing a lower average root-mean-square deviation (RMSD, 0.26 nm) and a more negative binding energy (−38.2 kcal/mol) of zein-( 2R, 3R )-DMY interaction compared to zein-( 2S, 3S )-DMY interaction. In vitro digestion results revealed that zein-( 2R, 3R )-DMY complex had the lowest cumulative release of DMY in the intestinal phase. The digestive products of the zein-DMY complexes, particularly zein-( 2R, 3R )-DMY, exhibited significantly enhanced antioxidant potency compared to pure DMY ( p  < 0.05). In conclusion, the chiral configuration of DMY is the main factor determining its interaction with zein and its digestive release behaviour, providing valuable insights for designing stable, protein-based delivery systems in functional food applications.