Alzheimer's disease (AD) presents an increasingly alarming health-care problem as the leading form of dementia in modern society. AD is a complex disease and the underlying cause is not defined. Decades of research have resulted in three main hypotheses, i.e. cholinergic, amyloid and tau hypothesis. There are currently only four drugs approved for the treatment of symptoms of AD. Research shows increased activity of butyrylcholinesterase (BChE) during the later stages of AD, while the activity of acetylcholinesterase (AChE) is decreased. Altogether, BChE represents a potential target for the management of AD.
Within the Master's thesis, analogues of potent BChE inhibitor discovered by ligand-based screening program LiSiCA were designed, synthesized and evaluated. Six out of seven designed analogues were successfully synthesized alongside with the hit compound. Compounds were characterized by methods of nuclear magnetic resonance (NMR), infrared spectroscopy (IR) and high resolution mass spectrometry (HRMS). Purity of synthesized compounds was determined using high performance liquid chromatography (HPLC). Median inhibitory concentration (IC50) for human butyrylcholinesterase (hBChE) and human acetylcholinesterase (hAChE) was determined using the method of Ellman. Comparing IC50 values, we were able to determine the structure activity relationships and selectivity of analogues in comparison to hit compound. Replacement of piperidine with smaller pyrrolidine or larger azepane resulted in diminished inhibitory potency on hBChE. Cis 3-(4-fluorostyryl)piperidine analogue 25 (IC50 = 44.2 ±4.0 nM) was the only compound that showed more potent inhibition over the hit compound (IC50 = 99.8 ±8.7 nM). In collaboration with the group of crystallographers from France, crystal structure of analogue 25 in the active site of hBChE was resolved, which provided the structural rationel for nanomolar inhibition of hBChE.