Huperzine A is an alkaloid originally isolated from Qiang Ceng Ta, a traditional Chinese preparation made from the whole plant of the club moss Huperzia serrata. It is a reversible inhibitor of acetylcholinesterase (AChE), and it has attracted research attention since its anticholinesterase activity was described by Chinese scientists. Preclinical research covers the structural biology of its binding to AChE, cholinesterase selectivity, rodent memory models, neuronal and glial cell culture and rodent models of Alzheimer's disease.