In a triple transgenic AD (3xTg-AD) mouse model, 3-month treatment with quercetin decreased extracellular β-amyloidosis and ameliorated microglial and astroglial activation in the brain, as evidenced by decreased levels of Aβ1-40, Aβ1-42, and BACE1-mediated cleavage of APP. This evidence concerns the gene BACE1 and Alzheimer disease.