Cholinesterase inhibition by huperzine B

The anti-cholinesterase effect of huperzine B, a new alkaloid isolated from Chinese herb Huperzia serrata(1), was examined in vitro. Erythrocyte membrane of rat and caudate nuclei of pig were used as source of acetylcholinesterase (AChE). Rat serum and human serum were chosen as source of butyrocholinesterase (BuChE). The pl50 (negative logarithm of molar concentration causing 50% inhibition of ChE) of huperzine B towards erythrocyte, caudate nuclei, rat serum and human serum were 6.1, 6.2, 3.9 and 2.8, respectively. Huperzine B exerted a more potent inhibitory effect on AChE than that of BuChE. The order of anti-AChE activity were： huperzine A>physostigmine>neostiginine> huperzine B>galanthamine. Huperzine B is a mixed and reversible inhibitor of AChE.