Revealing the interaction mechanism between cyanidin-3-O-glucoside and potato starch through setting different...

This study elucidated the interaction mechanisms between potato starch (PS) and cyanidin-3-O-glucoside (C3G) through solvent perturbations (various salts, D₂O, and ethanol), combining experimental characterization with molecular dynamics (MD) simulations. The electrostatic interaction was identified as the dominant driving force, as evidenced by a marked reduction in PS-C3G interactions in the presence of salt and ethanol. Specifically, binding affinity decreased by approximately 90 % in 0.1 M NaCl, and a concentration-dependent weakening effect was observed in ethanol, with the binding ratio declining to 23.60 % at 90 % (v/v) ethanol. Conversely, D₂O caused negligible change in binding parameters, excluding hydrogen bonding as a primary mechanism. These binding trends were consistently supported by particle size, confocal laser scanning microscope (CLSM) and scanning electron microscope (SEM) observations, showing reduced particle size, fluorescence intensity and surface attachments of PS-C3G in ionic and ethanol environments compared to aqueous and D₂O environments. At the atomic level, MD simulations showed increased solvent-accessible surface area (SASA) and root-mean-square deviation (RMSD) of starch chains and decreased electrostatic forces in salt solvents, demonstrating that salt ions weaken the PS-C3G interaction by shielding electrostatic attractions, whereas ethanol addition progressively decreased conformational stability, with energy calculations confirming gradual interaction weakening. This multi-scale analysis demonstrates that the PS-C3G interaction is predominantly governed by electrostatic interaction, with hydrogen bonding playing a secondary role. The study establishes a novel perspective on solvent perturbation as a powerful strategy for elucidating complex interaction mechanisms in the starch-polyphenols system.