Cyanidin-3-O-galactoside attenuates Aβ aggregation and disintegrates preformed amyloid fibril

• Cy3Gal inhibits Aβ fibrillogenesis. • Cy3Gal disassembles preformed Aβ fibril. • Hydrophobic clumping and charge redistribution drive the interaction. • Preferential binding of Cy3Gal to monomeric Aβ shifts the equilibrium. Amyloid-β (Aβ) fibril accumulation in the brain is a key feature of Alzheimer’s disease and a major therapeutic target. While the antibody aducanumab is currently the only approved agent for Aβ fibril elimination, no small-molecule alternative is available. Cyanidin-3- O -galactoside (Cy3Gal), a natural anthocyanin, has shown therapeutic potential, but its mechanism remains unclear. We evaluated Cy3Gal’s anti-amyloid effects using Thioflavin T (ThT) fluorescence assays and transmission electron microscopy (TEM) to assess its ability to slow down Aβ fibrillogenesis and disassemble existing fibrils. Molecular dynamics (MD) simulations were conducted to visualize the disassembly process, while microscale thermophoresis (MST) assessed Cy3Gal’s binding to monomeric and oligomeric Aβ. In vivo effects were tested using Caenorhabditis elegans CL2006 expressing human Aβ. Cy3Gal significantly attenuated Aβ aggregation and disassembled preformed fibrils, as confirmed by ThT reduction and TEM imaging. MD simulations revealed that Cy3Gal disrupts the fibril’s hydrophobic core and asparagine/glutamine ladder via electrostatic and hydrophobic interactions and MST data indicated a higher affinity for monomeric Aβ. Cy3Gal administration also alleviated Aβ-induced paralysis in C. elegans . Cy3Gal exhibits dual activity in both attenuating Aβ fibrillogenesis and promoting fibril disassembly. Its mechanism involves structural disruption driven by flavylium–residue interactions and preferential monomer binding. These findings highlight Cy3Gal as a promising natural small-molecule candidate for Alzheimer’s therapy.