Exploring Basic Tail Modifications of Coumarin-Based Dual Acetylcholinesterase-Monoamine Oxidase B Inhibitors: Identification of Water-Soluble, Brain-Permeant Neuroprotective Multitarget Agents

Abstract

Aiming at modulating two key enzymatic targets for Alzheimer's disease (AD), i.e., acetylcholinesterase (AChE) and monoamine oxidase B (MAO B), a series of multitarget ligands was properly designed by linking the 3,4-dimethylcoumarin scaffold to 1,3- and 1,4-substituted piperidine moieties, thus modulating the basicity to improve the hydrophilic/lipophilic balance. After in vitro enzymatic inhibition assays, multipotent inhibitors showing potencies in the nanomolar and in the low micromolar range for hMAO B and eeAChE, respectively, were prioritized and evaluated in human SH-SY5Y cell-based models for their cytotoxicity and neuroprotective effect against oxidative toxins (H2O2, rotenone, and oligomycin-A). The present study led to the identification of a promising multitarget hit compound (5b) exhibiting high hMAO B inhibitory activity (IC50 = 30 nM) and good MAO B/A selectivity (selectivity index, SI = 94) along with a micromolar eeAChE inhibition (IC50 = 1.03 μM). Moreover, 5b behaves as a water-soluble, brain-permeant neuroprotective agent against oxidative insults without interacting with P-gp efflux system.

Structure–property relationship study of the HPLC enantioselective retention of neuroprotective 7‐[(1‐alkylpiperidin‐3‐yl)methoxy]coumarin derivatives on an amylose‐based chiral stationary phase

“…A number of already reported and newly synthesized racemic compounds ( rac ‐ 1–16 ) were screened on two amylose‐based CSPs (Figure ) used in normal polar mode (MeOH and ACN, or their combination, as the mobile phases) to optimize the experimental conditions for a good performance in terms of enantioselectivity ( α ) and resolution ( R S ). A number of achiral 1‐piperidin‐4‐yl derivatives ( 17–25 , Supporting Information) were also screened to highlight the physicochemical properties mainly modulating retention on the amylose‐based CSP.…”

“…To place the above trends on quantitative basis, we assessed lipophilicity of the investigated SAs. The piperidinylcoumarin derivatives are bases with pK a values ranging from 9.5 to 10 for the N-alkyl derivatives (1 and 2) to 8.3-8.9 for the N-benzyl derivatives (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16). The pK a value of the N-benzyl compound 3 was determined through 1 H NMR spectroscopy [26] and found to be 8.02 (Supporting Information).…”

“…Starting materials, reagents, catalysts, analytical grade solvents, and HPLC grade solvents were purchased from Sigma–Aldrich (Milan, Italy). Synthesis and analytical data of compounds 1 , 3–5 , 9 , 10 , 13 , 14 , and 16 have been previously reported . Compounds 2 , 6–8 , 11 , 12 , and 15 , and related intermediates, were synthesized in this study, following similar procedures with slight modifications (Supporting Information).…”

“…The enantiomers were isolated by semipreparative column ; [α] 20 D = −18.5° ( c 0.13, MeOH) and −33.5° ( c 0.08, MeOH) for the first eluted enantiomers of 3 and 4 , respectively.…”

“…Within a long‐standing research program aimed at developing new multitarget small molecules for the treatment of neurological multifactorial disorders, including Alzheimer's disease [–13], we recently reported a wide series of 1‐benzyl‐piperidin‐3‐yl and piperidin‐4‐yl derivatives of 7‐hydroxy‐3,4‐dimethyl‐coumarin . These compounds are potent inhibitors of monoamine oxidase B (MAO B) and acetylcholinesterase (AChE) with good selectivity over the two respective isoforms (MAO A and butyrylcholinesterase).…”