Lycopodium alkaloids from Huperzia serrata

Five new Lycopodium alkaloids, huperzine Y1 (1), huperzine Y2 (2), huperzine Y3 (3), (+)-huperzine Z (4a) and (-)-huperzine Z (4b) as well as ten known alkaloids (5-14) were isolated from Huperzia serrata. The structures of the new compounds were established using extensive spectroscopic (1D and 2D NMR, IR, and HRESIMS) and calculated electronic circular dichroism (ECD) methods. Compounds 4a and 4b were a pair of enantiomers successfully separated by chiral HPLC resolution. Compounds 2 and 3 indicated inhibitory activities against acetylcholinesterase with IC₅₀ value of 57.1 ± 1.6 and 32.7 ± 1.0 μΜ, respectively. However, no compound showed inhibitory effect on butyrocholinesterase at the concentration of 100 μΜ.