Huperzine A is a selective acetylcholinesterase inhibitor and seems to have non-cholinergic effects as well. However, how it works is not fully understood. Acetylcholine is broken down by acetylcholinesterase. Therefore, inhibiting this enzyme should increase levels of acetylcholine. Most acetylcholinesterase activity seems to be associated with the amyloid core of senile plaques, which are in increased numbers in people with Alzheimer’s disease. Huperzine A has antioxidant and neuroprotective properties. It counteracts glutamate-induced toxicity, possibly by interacting with NMDA receptors.