Huperzia Serrata and Huperzine A: From Chinese Folk Medicine to Supplement

What it is

Huperzia serrata is a club moss used in Chinese herbal medicine. Huperzine A is a compound first isolated from it. [1] The purified compound is sold in the United States as a dietary supplement to promote cognitive function. [2] Prescribed Alzheimer's medicines such as donepezil, galantamine and rivastigmine work by the same mechanism, so huperzine A is a plant-derived compound that became both a research drug and a supplement. [2]

Traditional use

A review of the club moss subfamily says about 20 species have traditionally been used for conditions such as dementia, rheumatism and traumatic injury, and that identifying the right plant is a recurring problem that creates confusion in the literature. [1] Memorial Sloan Kettering says Huperzia serrata is used in traditional Chinese formulas for blood circulation and pain, while huperzine A was developed in Asia for Alzheimer's disease and vascular dementia. [2] A plant identification problem matters for buyers too: the label may not tell you which species is in a product.

How it is proposed to work

Huperzine A is described as selectively inhibiting acetylcholinesterase, an enzyme that breaks down a brain chemical involved in memory. [2] That is a proposed mechanism; a mechanism does not prove a benefit.

What trials found

Alzheimer's disease: insufficient evidence.

• A Cochrane review of six trials (454 patients) reported better scores than placebo on several scales, with mild adverse events. But it noted the methodological quality of most trials was not high, and concluded only one study was of adequate quality and size, so there is inadequate evidence to make any recommendation about its use. [3]
• A larger US trial (210 people with mild to moderate Alzheimer's) found the lower dose did not change the main cognitive score at 16 weeks, and changes in global impression, behavior and daily living were not significant. A higher dose showed an improvement at one earlier time point but not clearly at 16 weeks. [4]
• A review of over-the-counter memory supplements described results for huperzine A as mixed. [5]

Memory in healthy people: Proper evidence not found in the sources we read. For this see nootropics and memory supplements.

Why trial quality matters: the Cochrane authors named the low quality of most included trials as the main limit on what can be concluded, and asked for rigorous, large trials. [3]

Memory changes: what to do

New or worsening forgetfulness deserves a proper assessment, because many causes are treatable. See memory changes: when to get help and mild cognitive impairment and dementia. Other drugs with traditional origins are covered in arsenic trioxide, huperzine and other drugs with traditional origins.