Huperzine A is a nootropoic chemical that is used to improve memory and combat Alzheimer's Disease. The substance comes from the huperzia serrata plant, which is a type of low-lying moss commonly found throughout Asia. This naturally-occurring substance is an alkaloid, which means that its nitrogen atoms have a basic potentiometric hydrogen ion concentration (pH).
This plant was first used in Chinese herbal medicine to treat fevers and blood disorders. It has been used as such an alternative treatment for many years, but it was not until 1948 that the active compound, huperzine A, was isolated. In both China and the United States, this substance is sold as an over-the-counter supplement for memory enhancement and Alzheimer's improvement.
Almost all medical trials of huperzine A have been carried out in China, but researchers in the United States have recently begun to take an interest in it. The National Institute on Aging (NIA), a U.S. agency, is conducting a multi-stage study to determine how effective the substance is in enhancing cognitive function. Studies done in China in 1991 and 1995 — both using placebos and double-blind, randomized methods — found that huperzine A was effective in treating both Alzheimer's and other memory-degenerating conditions. Subsequent Chinese studies showed less promising effects, but a 2008 review of clinical trials conducted in that country found that, overall, huperzine A does have some beneficial effects.
One of the main chemical functions of huperzine A is as an acetylcholinesterase (AChE) inhibitor. Acetylcholinesterase is a brain enzyme that breaks down the neurotransmitter acetylcholine (ACh), which is responsible for a large amount of synaptic functioning and neuronal arousal in the central nervous system (CNS). One molecule of AChE is able to degrade the function of approximately 25,000 acetylcholine molecules, making it extremely potent. Inhibitors of this enzyme were often used as nerve gas agents, as an excess of acetylcholine in the body will lead to muscle paralysis and death by asphyxiation.
Individuals with Alzheimer's often have a lack of acetylcholine as well as depressed cognitive functioning. This is because acetylcholine plays a role in neuronal stimulation, memory, and learning, in addition to simple arousal functions. Low levels of AChE can free up acetylcholine and allow more neuron activity.
Huperzine is an extremely effective AChE inhibitor, and only 100 to 200 micrograms (mg) need to be ingested per day for it to be effective. In healthy individuals, huperzine A typically produces mild feelings of alertness. Possible, but rare, side effects of this drug include skin hives, diarrhea, and insomnia.