Baicalein inhibits amyloid beta42 aggregation through disruption of the Asp23-Lys28 salt bridge

The aggregation of amyloid beta-42 (Aβ42) into β-sheet-rich fibrillar structures is a critical pathogenic feature of Alzheimer's disease (AD). Baicalein (BCN), a natural flavonoid, has been shown to inhibit aggregation in amyloidogenic proteins, including human islet amyloid polypeptide (hIAPP), which shares structural similarities with Aβ42. This study investigates the inhibitory and disaggregation effects of BCN on Aβ42 using biophysical assays and atomistic molecular dynamics (AT-MD) simulations. Thioflavin-T (ThT) fluorescence, circular dichroism (CD) spectroscopy, and fluorescence microscopy reveal that BCN significantly reduces fibril formation and induces disaggregation of preformed Aβ42 fibrils in a concentration-dependent manner. Dynamic light scattering (DLS) analysis further confirms that BCN stabilizes Aβ42 in its monomeric form, preventing the formation of larger aggregates. AT-MD simulations show that BCN interacts with the aggregation-prone region of Aβ42, specifically disrupting the Asp23-Lys28 salt bridge, which is crucial for β-sheet formation. The simulations also reveal that BCN promotes the formation of α-helical structures, reducing β-sheet content and hindering aggregation. Secondary structure analysis via DSSP plots confirms that BCN shifts Aβ42 towards less aggregation-prone conformational states. These results highlight BCN's dual function in inhibiting both the formation and disaggregation of Aβ42 fibrils. This study provides mechanistic insights into BCN's therapeutic potential for amyloid-related diseases, suggesting that it can effectively target the β-sheet spine structures common to multiple amyloidogenic proteins, offering a promising approach for mitigating AD progression.