Huperzine A, a compound extracted from the Chinese club moss Huperzia serrata, is used in China and other countries as a treatment to support memory and cognitive function, particularly in Alzheimer's disease. Its primary mechanism of action is as a reversible acetylcholinesterase inhibitor, which means it helps prevent the breakdown of acetylcholine—a neurotransmitter important for memory and learning—thereby increasing its availability in the brain. This is similar to the mechanism of several approved Alzheimer's medications, such as donepezil and rivastigmine.

Several clinical trials, mostly small and predominantly conducted in China, have suggested that huperzine A may improve cognitive function and daily living activities in people with Alzheimer’s disease. A 2013 Cochrane review concluded that huperzine A appears to have beneficial effects on cognitive function, global clinical status, and activities of daily living, but emphasized the need for larger, well-designed studies with longer follow-up to confirm these findings. The quality of the evidence is limited due to methodological weaknesses in many studies, including small sample sizes, short duration, and potential publication bias.

Overall, while there is scientific rationale and some clinical evidence supporting huperzine A's use for Alzheimer's disease, the evidence is not as robust or conclusive as for standard pharmaceutical treatments. Further high-quality research is required to establish its efficacy and safety profile.