Chinese club moss, Lycopodium serrata (a.k.a. Huperzia serrata) has received a lot of attention in the last few years as a source of the compound Huperzine A. This phytonutrient, traditionally used for memory enhancement and as a tonic for "old age" in Chinese medicine, seems to work as a potent inhibitor of acetylcholinesterase, an enzyme that breaks down the neurotransmitter acetylcholine. This transmitter is essential in a variety of processes, participating in nerve signaling throughout the brain and also between the nerves and muscles. Huperzine seems to be more effective than many other, more toxic, pharmaceuticals used as Ach inhibitors (like tacrine, e.g. Cheng 1998).
Some of the most interesting research focuses on the club moss's benefits in treating myasthenia gravis ("severe muscle tiredness", literally), a disease in which the levels of acetylcholine in the neuromuscular junction drop. Another area of focus recently involves the treatment of Alzheimer's disease, a more common and well-known condition that also may involve decreased levels of acetylcholine in the brain (amongst other things). An impressively large clinical trial, started in April 2006 in hospitals all across the country, focuses on this plant's ability to treat Alzheimer's disease. The results are due in December. Stay tuned.