Acetylcholinesterase inhibitor and NMDA receptor antagonist
REVIEW Huperzine A is an optically active sesquiterpene alkaloid isolated from the Chinese herb Huperzia serrata. In the US, huperzine A is sold as a dietary supplement for memory support. The botanical has been used in China for centuries for the treatment of swelling, fever and blood disorders. Clinical trials in China have shown it to be effective in improving cognitive performance in patients with Alzheimer's disease and enhancing memory in adolescents complaining of memory inadequacy. Huperzine A is also an acetylcholinesterase inhibitor and NMDA receptor antagonist. Huperzine A preferentially inhibits tetrameric AChE (G4 form) and the structure of the complex of huperzine A with acetylcholinesterase has been determined by X-ray crystallography. This mode of action and structural data has brought Huperzine Ato the forefront as a possible treatment for diseases characterized by neurodegeneration - particularly Alzheimer's disease. Huperzine A is also a NMDA receptor antagonist which may either reduce or increase glutamate induced damage in brain and increase nerve growth factor levels in rats.
Clinical trials in China have shown that huperzine A is comparably effective to similar drugs on the market, and may even be safer in terms of side effects. The National Institute on Aging has completed a Phase II clinical trial to evaluate the safety and efficacy of huperzine A in the treatment of Alzheimer's disease in a randomized controlled trial of its effect on cognitive function. In 2008, the National Institute on Aging conducted the first controlled trial outside of China evaluating the efficacy and toxicity of huperzine A to improve cognitive function in patients with AD. In this multi-center, double-blind, placebo-controlled Phase II trial, 210 participants with mild to moderate AD received either 200 mcg of huperzine A, 400 mcg of huperzine A, or placebo twice daily for 16 weeks. While no statistical difference in cognitive scores was noted in patients in the lower dose huperzine A group compared to placebo, the higher dose (400 mcg) of huperzine A led to improved cognition and activities of daily living. However, no significant changes were noted in any of the three groups in overall change in disease or in psychiatric ratings according to the AD Assessment Scale-Cognitive (ADAS-Cog) scale. Huperzine A was safe and well tolerated in the study
(-)-Huperzine A also possesses the ability to protect cells against hydrogen peroxide, β-amyloid protein, glutamate, ischemia and staurosporine-induced cytotoxicity and apoptosis. These protective effects are related to its ability to attenuate oxidative stress, regulate the expression of apoptotic proteins Bcl-2, Bax, P53, and caspase-3, protect mitochondria, upregulate nerve growth factor and its receptors, and interfere with amyloid precursor protein metabolism.'
Kozikowski, Alan P; Tueckmantel, Werner (1999). Chemistry, Pharmacology, and Clinical Efficacy of the Chinese Nootropic Agent Huperzine A, Accounts of Chemical Research 32 (8): 641-650.
'Wang BS, Wang H, Wei ZH, Song YY, Zhang L, Chen HZ. Efficacy and safety of natural acetylcholinesterase inhibitor huperzine A in the treatment of Alzheimer''s disease: an updated meta-analysis. J Neural Transm. 2009 Apr;116(4):457-65.'
Sun QQ, Xu SS, Pan JL, Guo HM, Cao WQ. Huperzine-A capsules enhance memory and learning performance in 34 pairs of matched adolescent students. Zhongguo Yao Li Xue Bao. 1999 Jul;20(7):601-3.
Coleman BR, Ratcliffe RH, Oguntayo SA, Shi X, Doctor BP, Gordon RK, Nambiar MP [+]-Huperzine A treatment protects against N-methyl-D-aspartate-induced seizure/status epilepticus in rats. Chem Biol Interact. 2008 Sep 25;175(1-3):387-95.