Quinolizidinyl derivatives of bi- and tricyclic systems as potent inhibitors of acetyl- and butyrylcholinesterase with potential in Alzheimer's disease

► Quinolizidinyl derivatives of bi- and tricyclic systems potently inhibit AChE and/or BChE. ► The thioxanthene derivative 15 inhibits preferentially BChE (IC50 = 0.15 μM, SI = 47). ► The acridine derivative 43 is a balanced AChE/BChE inhibitor (IC50 = 0.22 and 0.69 μM respectively). ► The 6-hydroxy coumarine derivative 46 inhibits preferentially AChE (IC50 = 0.35 μM, SI = 15). ► Remarkably periciazine 3 potently inhibits BChE (IC50 = 0.23 μM), many fold more than the common anti-psychotics.