ACHE and early-onset autosomal dominant Alzheimer disease: Notably, the enhanced potency of the neuroprotective property in β-carboline molecules can be related to the structural activity relationship, that is, the addition of alkoxy groups to alkyl chains, especially in 6,12-dimethoxy-3-ethyl-β-carboline (22), which facilitates the suppression of acetylcholinesterase (AChE) activity, therefore preventing the risk of Alzheimer’s disease [20].