Chinese Club Moss (Huperzia serrata) supplies Huperzine A, a compound that slows the breakdown of acetylcholine, a brain chemical tied to learning and memory.
Users often take it in the morning or early afternoon to protect nighttime sleep while sharpening daytime focus.
This supplement can interfere with drugs prescribed for Alzheimer's, glaucoma, or other nervous system conditions. Anyone with asthma, a heart condition, or who is pregnant or nursing should exercise caution.