N-Benzyl, N-phenethyl and N-benzyloxybenzamide derivatives inhibit amyloid-beta (Aβ42) aggregation and mitigate Aβ42-induced neurotoxicity

A library of N-benzylbenzamide, N-phenethylbenzamide and N-benzyloxybenzamide derivatives were designed, synthesized and evaluated as amyloid beta (Aβ42) aggregation inhibitors. These compounds were designed by replacing the α,β-unsaturated linker region of chalcone with an amide bioisostere. The Aβ42 aggregation inhibition properties of these 27 benzamide derivatives were evaluated by the thioflavin T (ThT)-based fluorescence aggregation kinetics assay, transmission electron microscopy (TEM) studies, Aβ42-induced cytotoxicity assay in mouse hippocampal neuronal HT22 cell lines, fluorescence live cell imaging, and computational modelling studies using a pentamer model of Aβ42. These studies led to the identification of N-benzylbenzamides 3a and 3f, N-phenethylbenzamide 5a and N-benzyloxybenzamide 7a as promising compounds that were able to exhibit anti-aggregation properties in the ThT-based fluorescence experiments, TEM studies and more significantly were able to rescue the hippocampal neuronal HT22 cells from Aβ42-induced cytotoxicity (91–96% cell viability at 25 µM). These results demonstrate the usefulness of these benzamide-based templates in the design and development of novel small molecules as chemical tools and therapeutics to study and treat Alzheimer’s disease.