Huperzine A is an alkaloid naturally occurring in pure huperzine and in varying amounts from other huperzine species. Huperzine A has been studied as a treatment for neurological conditions such as Alzheimer's disease, but a meta-analysis of these studies concluded that they were of poor methodological quality and the results should be interpreted with caution. Huperzine inhibits the breakdown of the neurotransmitter acetylcholine by the enzyme acetylcholinesterase. It is commonly sold over-the-counter as a dietary supplement and is marketed as a cognitive enhancer to improve memory and concentration. Huperzine A is extracted from the huperzine spike plant. Huperzine A is a reversible inhibitor of acetylcholinesterase and NMDA receptors that cross the blood-brain barrier. Acetylcholinesterase is the enzyme that catalyzes the breakdown of acetylcholine at synapses and some neurotransmitters that perform the same function. A complex of huperzine A with radiolabeled acetylcholine crystals has been determined at 10 . Huperzine A has been studied for several years as a potential treatment for diseases characterized by neurodegeneration, particularly Alzheimer's disease. A 2013 meta-analysis found that this compound may be effective in improving cognitive function, medical status, and activities of daily living in individuals with Alzheimer's disease. However, due to the poor size and quality of the clinical trials reviewed, it is not recommended for use as a treatment for Alzheimer's disease unless further high-quality studies confirm its beneficial effects. Huperzine A is also marketed as a dietary supplement with claims of improving memory and mental function. Huperzine A may cause mild cholinergic side effects such as nausea, vomiting, and diarrhea. It is not recommended for use during pregnancy and lactation due to a lack of adequate safety data. Huperzine A may have additive effects if taken with medications that cause bradycardia, such as beta-blockers, which may reduce heart rate. In theory, there may be potential additive cholinergic effects if taken with other acetylcholinesterase inhibitors or cholinergic agents. Two scalable and efficient macro recipes from Huberzin A.