Synthesis,biochemical evaluation,and molecular modeling of organophosphate-coumarin hybrids as potent and selective butyrylcholinesterase inhibitors

A small library of new organophosphorylated warfarins and 3-benzylcoumarins were synthesized and evaluated for in vitro cholinesterase inhibition by Ellman’s method. Most of the compounds were found to be selective for butyrylcholinesterase (BChE) over acetylcholinesterase (AChE), with IC₅₀ values ranging from 0.363 μM to 53.0 μM determined after 15 s of enzyme exposure. Comparison of the most potent compound, 3b with its constitutional isomer 2b revealed the high importance of phosphate positioning. Reversed selectivity and a 100-fold reduction in anti-BChE activity was observed when the organophosphate was attached to the benzyl instead of the coumarin. Docking calculations suggest that 3b binds initially as a transition state mimic with near-optimal phosphate orientation relative to S198 and occupation of the oxyanion hole prior to phosphorylation. These results might inspire the design of a new type of non-neuropathic and irreversible coumarin-based inhibitor against BChE.