Huperzine A
Natural Alkaloid Enhances Memory and Cognitive Ability
Huperzine A is a sesquiterpene alkaloid with the molecular formula C15 H18 N2 O, and a molecular mass of 242.32 grams/mole. Huperzine A is found in several related species of the lycopodiaceae family but to date it is most often extracted from Huperizia serrata (toothed clubmoss). Huperzine content in H. serrata varies with plant part, harvesting methods, and growth location but dried leaves average about 0.012 percent of the alkaloid. H. serrata materials contain over 55 other complex alkaloids like lycodine, lycopodine, and tohogenol.
Huperizia
H. serrata is a small terrestrial club moss that grows among rocks and the base of trees in tropical and temperate regions of Asia and the Pacific. It has been incorporated in traditional Chinese Medicine (TCM) for hundreds of years internally and topically in the treatment of blood loss, blood disorders, dementia, fever, hemorrhoids, inflammation, irregular menses, memory management, pneumonia, physical injury, edema, and vomiting blood.
Huperzine A and Cognitive Function
Huperzine A from H. serrata has gained popularity due to its ability to support cognitive function and is used in China to manage conditions like Alzheimer's disease and vascular dementia. This is primarily due to its temporary acetylcholine esterase inhibiting effect. Acetylcholine is a neurotransmitter which delivers messages between brain cells. After messages are sent, nerve cells break down this neurotransmitter using an enzyme called acetylcholine esterase. Often in conditions of cognitive dysfunction like Alzheimer's disease there is a lack of acetylcholine so one of the strategies for management is the inhibition of the enzyme that breaks it down. Several pharmacological medications like donezepil, galantamine, and rivastigmine work this way. Huperzine A appears to have additional neuroprotective, nerve-growth promoting, and N-methyl D-aspartate (NMDA) receptor antagonist properties which further substantiate its use in cognitive support.
Huperzine A has been substantiated for the clinical management of:
- Alzheimer's disease
- Dementia from multiple infarctions
- Memory deficit associated with traumatic brain injury
- Cognitive deficits associated with schizophrenia
- Myasthenia gravis
Dosage
Traditional ingested doses of the H. serrata herb involve 1.5 – 20 g/day of dried leaves, usually in a water tea infusion. Ground fresh or dry plant material is used topically for acute injuries. Therapeutic dosage of extracted Huperzine A range from 50 – 400 micrograms/day. Anecdotal backing indicates 50 micrograms/day for general cognitive support while substantiated research indicates 200 micrograms a day for management of more serious conditions like Alzheimer's disease. Huperzine A is also administered intramuscularly at 200-400 micrograms per day in the treatment of myasthemia gravis.
Absorption & Elimination
When ingested, huperzine A is rapidly absorbed and distributed throughout the human body, including the blood brain barrier. It reaches maximum dose level after about 80 minutes and has a half-life of about 4.5 hours. This time length makes it ideal for two and three times a day dosages. Huperzine A is eliminated at a moderate, linear rate by the liver.
Toxicity & Adverse Effects
While there is little documentation regarding adverse reactions, several Chinese monographs warn against overdosing and describe it as potentially toxic. In mice, the dose lethal for half of rodents studied (LD50) was 5.2 mg/kg by mouth.
Adverse reactions associated with H. serrata include:
- Dizziness
- Blurred vision
- Sweating
- Hypotension
- Shortness of Breath
Huperzine A is considered a prescription medication in China and should not be taken by children, pregnant or nursing women, and those with severe liver or kidney disease.
Supplementary References
Alan P. ; Tueckmantel Kozikowski and Kozikowski, Alan P.; Tueckmantel, Werner, “Chemistry, Pharmacology, and Clinical Efficacy of the Chinese Nootropic Agent Huperzine A,” Accounts of Chemical Research 32, no. 8 (1999): 641–650, doi:10.1021/ar9800892.
Desilets, J. J. Gickas, and K. C. Dunican, “Role of Huperzine A in the Treatment of Alzheimer's Disease,” The Annals of Pharmacotherapy 43, no. 3 (2009): 514.
Hemendinger et al., “Huperzine a provides neuroprotection against several cell death inducers using in vitro model systems of motor neuron cell death,” Neurotoxicity Research 13, no. 1 (2008): 49-61.
Tang Bai and Bai, D. L.; Tang, X. C.; He, X. C., “Huperzine A, a potential therapeutic agent for treatment of Alzheimer's disease,” Current Medicinal Chemistry 7, no. 3 (2000): 355–374.
Huperizia serrata
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