Abstract
Acetylcholinesterase plays a crucial role in the metabolism of neurotransmitter, acetylcholine. Inhibition of
Torpedo californica acetylcholinesterase by triterpenoidal alkaloids buxamine-B (
1) and buxamine-C (
2) has been studied by enzyme kinetics and molecular docking experiments. Buxamine-C (
2) has been found to be 20-fold potent than buxamine-B (
1) (
K
i
=
5.5 and 110
μM, respectively). The ligand docking experiments predicted that the cyclopentanophenanthrene skeleton of both inhibitors properly fits into the aromatic gorge of the enzyme. The C-3 and C-20 amino groups of both alkaloids mimic the well-known bis-quaternary ammonium inhibitors such as decamethonium and interact with Trp84 and Trp279 residues of the enzyme, respectively. The C-3 amino group in buxamine-C (
2) appears to be better positioned at the bottom of the aromatic gorge and thus seems to be crucial for the inhibitory activity of such inhibitors.