Hypothesis 1: Rutin suppresses tau aggregation by binding exposed beta-sheet nucleation motifs in MAPT repeat domains, especially PHF6-like steric zipper surfaces, and stabilizing a less aggregation-prone monomer ensemble. The flavonol core could provide pi-stacking against aromatic residues while the glycoside hydroxyl network reduces dehydration at early oligomer interfaces. Test: recombinant K18/K19 tau seeding, HDX-MS footprinting, and cryo-EM of fibrils assembled with rutin.
Hypothesis 2: Rutin acts upstream of aggregation by chelating redox-active metals and dampening oxidative cross-linking that accelerates tau oligomer nucleation. In this model the key readout is not just fewer fibrils, but reduced dityrosine-rich oligomer species and lower ROS-amplified phosphorylation/fragmentation pressure on tau. Test: compare copper- or iron-driven tau aggregation, dityrosine immunoreactivity, and tau seeding activity in neuronal lysates.
Hypothesis 3: Rutin shifts proteostasis rather than tau chemistry directly, increasing chaperone-assisted clearance and autophagic disposal of misfolded tau species. This would predict stronger effects in intact neurons than in cell-free assays and synergy with HSP70 or lysosome-activating interventions. Test: measure LC3 flux, SQSTM1 turnover, tau half-life, and seeded aggregate burden after rutin exposure.