Huperzine-A is a plant alkaloid derived from the Chinese club moss plant, Huperzia serrata, which is a member of the Lycopodium species. In China, huperzine extract has been used for centuries for various treatments such as swelling, fever and blood disorders.

During the past few years, Huperzine A, one of the chemicals in Chinese club moss, has been studied extensively for its potential in treating dementias such as Alzheimer's disease. Dementia is an increasing deficiency in thought processes caused by brain damage or disease. Like the prescription drugs currently available for individuals with Alzheimer's, Huperzine A, temporarily blocks an enzyme known as acetylcholinesterase, which is concentrated in the brain, spinal cord, and red blood cells. This enzyme, also called cholinesterase, breaks down one of the body's neurotransmitters, acetylcholine. Neurotransmitters are chemicals that carry messages from nerve cells to other cells. Acetylcholine plays a role in learning, remembering, and thinking; and decreased amounts of it are associated with conditions involving the loss of mental functioning.

By reducing the activity of acetylcholinesterase, Huperzine A may help to reduce the breakdown of acetylcholine, keeping more of it in the blood. Frequently called a "cholinergic" effect, the increase in acetylcholine may help preserve or even restore memory. Several studies of memory-impaired animals and humans have shown that taking Huperzine A may help to relieve dementia. Additionally, in a small study of teenagers, Huperzine A appeared to enhance general mental functioning when it was taken consistently for as little as one month. However, more research is needed before Huperzine A can be recommended for either dementia or general memory improvement.