(-)-Huperzine A-d₄ hydrochloride is deuterated labeled (-)-Huperzine A (HY-17387). (-)-Huperzine A (Huperzine A) is an alkaloid isolated from Huperzia serrata, with neuroprotective activity. (-)-Huperzine A is a potent, highly specific, reversible and blood-brain barrier penetrant inhibitor of acetylcholinesterase (AChE), with an IC₅₀ of 82 nM. (-)-Huperzine A also is non-competitive antagonist of N-methyl-D-aspartate glutamate (NMDA) receptor. (-)-Huperzine A is developed for the research of neurodegenerative diseases, including Alzheimer’s disease^{[1][2][3][4][5]}.