Allium roseum L. extract inhibits amyloid beta aggregation and toxicity involved in Alzheimer’s disease

Allium roseum is an important medicinal and aromatic plant, specific to the North African flora and a rich source of important nutrients and bioactive molecules including flavonoids and organosulfur compounds whose biological activities and pharmacological properties are well known. In the present study, the inhibition of amyloid beta protein toxicity by the ethanolic extract of this plant is investigated for the first time. Preliminary biochemical analyses identified kæmpferol and luteolin-7-o-glucoside as the more abundant phenolic compounds. The effects of A. roseum extract (ARE) on aggregation and aggregate cytotoxicity of amyloid beta-42 (Aβ(42)), whose brain aggregates are a hallmark of Alzheimer’s disease, were investigated by biophysical (ThT assay, Dynamic light scattering and transmission electron microscopy) and cellular assays (cytotoxicity, aggregate immunolocalization, ROS measurement and intracellular Ca(2+) imaging). The biophysical data suggest that ARE affects the structure of the Aβ(42) peptide, inhibits its polymerization, and interferes with the path of fibrillogenesis. The data with cultured cells shows that ARE reduces Aß(42) aggregate toxicity by inhibiting aggregate binding to the cell membrane and by decreasing both oxidative stress and intracellular Ca(2+). Accordingly, ARE could act as a neuroprotective factor against Aβ aggregate toxicity in Alzheimer’s disease.