Inhibition of amyloid fibril formation and cytotoxicity by a chemical analog of Curcumin as a stable inhibitor.

Clinical application of curcumin for Alzheimer's disease treatment is severely limited with regard to its poor bioavailability, high rate of metabolism, and instability under neutral condition. In the current study, we designed three compounds in which the diketone moiety of curcumin was replaced by cyclohexanone. In these compounds, the linker length of the molecules was optimal; and substitution of dioxolane for hydroxyl groups on compound 3 should prevent metabolic inactivation. The inhibitory effect of the compounds was investigated against hen egg white lysozyme (HEWL) fibrillation using AFM (atomic force microscope), ThT (thioflavin T) and MTT assay. We found that all three compounds were able to inhibit HEWL aggregation in a dose-dependent manner and inhibit the cytotoxic activity of aggregated HEWL. Docking results demonstrated that the compounds could bind into lysozyme and occupy the whole active site groove. In conclusion, we present chemical analogs of curcumin with various modifications in the spacer and the phenolic rings as improved inhibitors of amyloid aggregation.