Huperzine A

Adverse effects

Huperzine A may present with mild cholinergic side effects such as nausea, vomiting, and diarrhea. Slight muscle twitching and slurred speech might also occur, as well as hypersalivation and sweating. The use of huperzine A during pregnancy and lactation is not recommended due to the lack of sufficient safety data.

Pharmacology

Huperzine A is a potent, highly specific, reversible acetylcholinesterase inhibitor, with IC50 binding affinity of ~82 nM. It is also a weak NMDA receptor antagonist, with IC50 of ~65,000–82,000 nM (65–82 μM); due to this relatively low affinity, huperzine A is unlikely to produce significant NMDA receptor blockade at clinically relevant concentrations in humans. Huperzine A readily crosses the blood–brain barrier and demonstrates central nervous system activity at therapeutic doses as low as 100 μg in humans.

Acetylcholinesterase is an enzyme that catalyzes the breakdown of choline-based neurotransmitters, particularly acetylcholine (ACh), which plays a critical role in memory, learning, and behavior. The structure of the complex of huperzine A with acetylcholinesterase has been determined by X-ray crystallography (PDB code: 1VOT; see the 3D structure).

Drug interactions

Huperzine A may have additive effects if taken with drugs causing bradycardia, such as beta-blockers, which may decrease heart rate. Theoretically, there may be possible additive cholinergic effects if huperzine A is taken with other acetylcholinesterase inhibitors or cholinergic agents.

Safety

Huperzine A, in spite of the possible cholinergic side effects, seems to have a wide margin of safety. Toxicology studies show huperzine A to be non-toxic even when administered at 50–100 times the human therapeutic dose. The extract is active for 6 hours at a dose of 2 μg/kg with no remarkable side effects.

Synthesis

Two scalable and efficient total syntheses of huperzine A have been reported.

History

In 1989, a research study found that the chemical structure of the alkaloid selagine reported in 1960 from a study of Lycopodium slago L. (analyzed using 60-MHz NMR) was identical to that of Huperzine A.

Research

Effects

Huperzine A has been investigated as a possible treatment for diseases characterized by neurodegeneration such as Alzheimer's disease, and there is some evidence from small-scale studies that it can benefit cognitive functioning, global clinical status, and ability to engage in activities of daily living (ADLs) among individuals with the disease. In a 2016 systematic review of systematic reviews, huperzine A was associated with a standardized mean difference of 1.48 (95% CI, 0.95–2.02) compared to placebo on measures of ADL among people with dementia, but the evidence was very low-quality and uncertain. In a 2022 umbrella review, huperzine A was associated with broad benefits to dementia patients' cognitive functioning, but the degree of heterogeneity in measurements and outcomes of the reviewed studies indicated publication bias toward huperzine A benefit.

Use in organophosphate poisoning

Huperzine A might be useful in the treatment of organophosphate nerve agent poisoning by preventing damage to the central nervous system caused by such agents.

Use as Oneirogen

Huperzine A may be used as a (very weak) Oneriogen.

References

References

1. (2007). "Pharmacokinetics of huperzine A following oral administration to human volunteers". European Journal of Drug Metabolism and Pharmacokinetics.
2. (1986). "The structures of huperzine A and B, two new alkaloids exhibiting marked anticholinesterase activity". Canadian Journal of Chemistry.
3. "Huperzines and analogs.".
4. (2014). "Huperzimine, a novel Lycopodium alkaloid from Huperzia serrata.". Canadian Journal of Chemistry.
5. (September 2010). "Huperzine alkaloids from Australasian and southeast Asian Huperzia". Pharmaceutical Biology.
6. (2013). "Huperzine A for Alzheimer's disease: a systematic review and meta-analysis of randomized clinical trials". PLOS ONE.
7. (April 2008). "Huperzine A for Alzheimer's disease". The Cochrane Database of Systematic Reviews.
8. "Huperzine A". Natural Standard.
9. (January 2006). "Progress in studies of huperzine A, a natural cholinesterase inhibitor from Chinese herbal medicine". Acta Pharmacologica Sinica.
10. (2004). "Herbs and Nutrients for the Mind: A Guide to Natural Brain Enhancers". Greenwood Publishing Group.
11. (April 2009). "Efficacy and safety of natural acetylcholinesterase inhibitor huperzine A in the treatment of Alzheimer's disease: an updated meta-analysis". Journal of Neural Transmission.
12. (1999). "Huperzine A: A novel acetylcholinesterase inhibitor". Drugs of the Future.
13. (2012). "The pharmacology and therapeutic potential of (-)-huperzine A". Journal of Experimental Pharmacology.
14. (September 2008). "[+]-Huperzine A treatment protects against N-methyl-D-aspartate-induced seizure/status epilepticus in rats". Chemico-Biological Interactions.
15. (1998). "Huperzine A--an interesting anticholinesterase compound from the Chinese herbal medicine". Acta Medica.
16. (January 1997). "Structure of acetylcholinesterase complexed with the nootropic alkaloid, (-)-huperzine A". Nature Structural Biology.
17. (March 2000). "Huperzine A". American Journal of Health-System Pharmacy.
18. (April 2025). "Old Chinese herbal medicine used for fever yields possible new Alzheimer disease therapy". JAMA.
19. (May 2002). "Review of the value of huperzine as pretreatment of organophosphate poisoning". Neurotoxicology.
20. (2011). "A robust and scalable synthesis of the potent neuroprotective agent (−)-huperzine A". Chemical Science.
21. (2012). "Development of a Large-Scale Synthetic Route to Manufacture (−)-Huperzine A". Organic Process Research & Development.
22. (October 1989). "Alkaloids of ''Lycopodium selago''. On the identity of selagine with huperzine A and the structure of a related alkaloid.". Canadian Journal of Chemistry.
23. (January 1960). "The structure of selagine.". Tetrahedron Letters.
24. (June 2003). "The psychopharmacology of huperzine A: an alkaloid with cognitive enhancing and neuroprotective properties of interest in the treatment of Alzheimer's disease". Pharmacology, Biochemistry, and Behavior.
25. (March 2000). "Huperzine A, a potential therapeutic agent for treatment of Alzheimer's disease". Current Medicinal Chemistry.
26. (April 2016). "Interventions to delay functional decline in people with dementia: a systematic review of systematic reviews". BMJ Open.
27. (2022-02-01). "The Efficacy and Safety of Alzheimer's Disease Therapies: An Updated Umbrella Review". Journal of Alzheimer's Disease.
28. (May 2002). "Review of the value of huperzine as pretreatment of organophosphate poisoning". Neurotoxicology.
29. (March 2005). "[Advances on study of organophosphate poisoning prevented by Huperzine A]". Wei Sheng Yan Jiu = Journal of Hygiene Research.