A new Lycopodium alkaloid together with a phenolic glyco-side-arbutin, were isolated from the whole plant of Huperzia serrata. The new compound was assigned the trivial name of huperzine I. The structures of these two compounds were determined on the basis of spectral evidence. A new Lycopodium alkaloid together with a phenolic glyco-side-arbutin, were isolated from the whole plant of Huperzia serrata. The new compound was assigned the trivial name of huperzine I. The structures of these two compounds were determined on the basis of spectral evidence .