Inhibition of Acetylcholinesterase Activity by some Isoquinoline Alkaloids*,**

Abstract
The effects of quaternary protoberberine and benzophenanthridine alkaloids on acetylcholinesterase (ACHE, EC 3.1.1.7) activity in vitro and on isolated rat duodenum and guinea pig ileum tissue preparations have been studied. The ACHE inhibitory activity of quaternary alkaloids depends on the cationpseudobase equilibrium of the studied alkaloids in solution. The relationship between pKR+ values and the biological activity is described. The influence of surfactants on pseudobase formation of benzo-phenanthridine alkaloids has been discussed.