Phenylpropanoids, flavonoids, terpenoids, alkaloids, and their derivatives have been shown to improve the pathological changes of AD by acting on multiple targets, such as inhibiting acetylcholinesterase, reducing tau and amyloid aggregation, reducing neuroinflammation, reducing Aβ1-42-induced neurotoxicity, and inhibiting β-site amyloid precursor protein cleaving enzyme 1 (BACE-1). The gene discussed is BACE1; the disease is Alzheimer disease.