The development of drugs to treat Alzheimer disease has focused on strategies that enhance central cholinergic function. Some herbal plants, which have fewer adverse effects and are less expensive than other medications, are attractive drug candidates for a variety of diseases. In this study we tested the ability of extracts from~ 100 plants to inhibit the enzyme acetylcholinesterase. Among the plants, Levisticum officinale, Berberis integerrima, and Rheum ribes inhibited the enzyme. We identified the active inhibitory compounds of these plants using thin-layer chromatography (TLC) bioautography. Our results suggest that alkaloid and terpenoid compounds are primarily responsible for the inhibitory activity of these plants. More research is needed to detect all of the compounds and chemical structures that make up these plants.