Metaproterenol, Isoproterenol, and Their Bisdimethylcarbamate Derivatives as Human Cholinesterase Inhibitors

Metaproterenol and isoproterenol are bronchodilators that provide a structural basis for many other bronchodilators currently in use. One of these structurally related bronchodilators is terbutaline; it is administered as a prodrug, bambuterol, and is metabolized (bioconverted) into terbutaline by butyrylcholinesterase (BChE). The metabolism rate can be affected by BChE gene polymorphism in the human population and BChE stereoselectivity. The aim of our study was to investigate inhibition of human BChE and acetylcholinesterase (AChE) with metaproterenol, isoproterenol, and newly synthesized racemic bisdimethylcarbamate derivatives of metaproterenol (metacarb) and isoproterenol (isocarb) and their (R)-enantiomers to see if their bioconversion is affected by BChE inhibition in the same way as that for bambuterol. Metacarb and isocarb proved to be selective BChE inhibitors, as they progressively inhibited AChE 960 to 80 times more slowly than BChE(UU). All studied cholinesterases displayed poor affinity for metaproterenol and isoproterenol, yet BChE(UU) had an affinity about five times higher than that of AChE.