Acetylcholinesterase and butyrylcholinesterase inhibitory activities of khellactone coumarin derivatives isolated from Peucedanum japonicum Thurnberg.

Cholinesterase (ChE) and monoamine oxidase (MAO) inhibitors have been attracted as candidate treatments for Alzheimer's disease (AD). Fifteen khellactone-type coumarins from the roots of Peucedanum japonicum Thunberg were tested for acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and MAO inhibitory activities. Compound 3'-angeloyl-4'-(2-methylbutyryl)khellactone (PJ13) most potently inhibited AChE (IC50 = 9.28 µM), followed by 3'-isovaleryl-4'-(2-methylbutyroyl)khellactone (PJ15) (IC50 = 10.0 μM). Compound senecioyl-4'-angeloyl-khellactone (PJ5) most potently inhibited BChE (IC50 = 7.22 μM) and had the highest selectivity index (> 5.54), followed by 3'-senecioyl-4'-(2-methylbutyryl)khellactone (PJ10) and 3',4'-disenecioylkhellactone (PJ4) (IC50 = 10.2 and 10.7 μM, respectively). Compounds PJ13, PJ15, and PJ5 showed reversible and mixed-types of inhibition with Ki values of 5.98, 10.4 (for AChE), and 4.16 µM (for BChE), respectively. However, all 15 compounds weakly inhibited MAO-A and MAO-B. Molecular docking simulation revealed that PJ13 had a higher binding affinity (- 9.3 kcal/mol) with AChE than PJ15 (- 7.8 kcal/mol) or PJ5 (- 5.4 kcal/mol), due to the formation of a hydrogen bond with Tyr121 (distance: 2.52 A). On the other hand, the binding affinity of PJ5 (- 10.0 kcal/mol) with BChE was higher than for PJ13 (- 7.7 kcal/mol) or PJ15 (- 8.1 kcal/mol), due to the formation of a hydrogen bond with Ser198 (distance: 2.05 A). These results suggest that PJ13 and PJ5 are potential reversible selective inhibitors of AChE and BChE, respectively, for the treatment of AD.