Investigating alkyl nitrates as nitric oxide releasing precursors of multitarget acetylcholinesterase-monoamine oxidase B inhibitors

Herein we envisaged the possibility of exploiting alkyl nitrates as precursors of alcohol-bearing dual inhibitors targeting acetylcholinesterase (AChE) and monoamine oxidase B (MAO B), key enzymes in neurodegenerative syndromes such as Alzheimer's disease (AD), through biotransformation unmasking an alcoholic function upon nitric oxide (NO) release. The cooperation to neuroprotection of low fluxes of NO and target enzymes’ inhibition by the alcohol metabolites might return a multitargeting effect. The in vitro screening towards ChEs and MAOs of a collection of 21 primary alcohols disclosed a subset of dual inhibitors, among which three diverse chemotypes were selected to study the corresponding nitrates. Nitrate 14 proved to be a brain permeant, potent AChE-MAO B inhibitor by itself. Moreover, it protected human SH-SY5Y lines against rotenone and hydrogen peroxide with a poor inherent cytotoxicity and showed a slow conversion profile to its alcohol metabolite 9d that still behaved as bimodal and neuroprotective molecule

First-in-Class Isonipecotamide-Based Thrombin and Cholinesterase Dual Inhibitors with Potential for Alzheimer Disease

Recently, the direct thrombin (thr) inhibitor dabigatran has proven to be beneficial in animal models of Alzheimer’s disease (AD). Aiming at discovering novel multimodal agents addressing thr and AD-related targets, a selection of previously and newly synthesized potent thr and factor Xa (fXa) inhibitors were virtually screened by the Multi-fingerprint Similarity Searching aLgorithm (MuSSeL) web server. The N-phenyl-1-(pyridin-4-yl)piperidine-4-carboxamide derivative 1, which has already been experimentally shown to inhibit thr with a Ki value of 6 nM, has been flagged by a new, upcoming release of MuSSeL as a binder of cholinesterase (ChE) isoforms (acetyl- and butyrylcholinesterase, AChE and BChE), as well as thr, fXa, and other enzymes and receptors. Interestingly, the inhibition potency of 1 was predicted by the MuSSeL platform to fall within the low-to-submicromolar range and this was confirmed by experimental Ki values, which were found equal to 0.058 and 6.95 μM for eeAChE and eqBChE, respectively. Thirty analogs of 1 were then assayed as inhibitors of thr, fXa, AChE, and BChE to increase our knowledge of their structure-activity relationships, while the molecular determinants responsible for the multiple activities towards the target enzymes were rationally investigated by molecular cross-docking screening

4-Hydroxycoumarins as Michael donors in asymmetric routes to polycyclic coumarins (microreview)

Different [3,4]-fused polycyclic 2H-chromen-2-ones can be prepared in a stereoselective fashion starting from 4-hydroxycoumarins as nucleophilic synthones. Herein we report a brief overview of the most recent methods including Pd-catalyzed [3+3] annulation processes, organocatalytic one-pot and domino Michael addition/cyclization, tandem conjugate addition/hydroxyalkylation, and organocascade catalytic reaction

Chasing ChEs-MAO B Multi-Targeting 4-Aminomethyl-7-Benzyloxy-2H-Chromen-2-ones

A series of 4-aminomethyl-7-benzyloxy-2H-chromen-2-ones was investigated with the aim of identifying multiple inhibitors of cholinesterases (acetyl- and butyryl-, AChE and BChE) and monoamine oxidase B (MAO B) as potential anti-Alzheimer molecules. Starting from a previously reported potent MAO B inhibitor (3), we studied single-point modifications at the benzyloxy or at the basic moiety. The in vitro screening highlighted triple-acting compounds (6, 8, 9, 16, 20) showing nanomolar and selective MAO B inhibition along with IC50 against ChEs at the low micromolar level. Enzyme kinetics analysis toward AChE and docking simulations on the target enzymes were run in order to get insight into the mechanism of action and plausible binding modes. © 2019 by the authors

1,2,3,4-Tetrahydroisoquinoline/2H-chromen-2-one conjugates as nanomolar P-glycoprotein inhibitors: Molecular determinants for affinity and selectivity over multidrug resistance associated protein 1

A series of coniugates bearing a 1,2,3,4-tetrahydroisoquinoline motif linked to substituted 7-hydroxy-2H-chromen-2-ones was synthesized and assayed through calcein-AM test in Madin-Darby Canine Kidney (MDCK) cells overexpressing P-glycoprotein (P-gp) and closely related multidrug resistance associated protein 1 (MRP1) to probe the interference with efflux mechanisms mediated by P-gp and MRP1, respectively. A number of substituents at C3 and C4 of coumarin nucleus along with differently sized and shaped spacers was enrolled to investigate the effects of focused structural modifications over affinity and selectivity. Linker length and flexibility played a key role in enhancing P-gp affinity as proved by the most potent P-gp modulator (3h, IC50 = 70 nM). A phenyl ring within the spacer (3k, 3l, 3o) and bulkier groups (Br in 3r, Ph in 3u) at coumarin C3 led to derivatives showing nanomolar activity (160 nM < IC50 < 280 nM) along with outstanding selectivity over MRP1 (SI > 350). Molecular docking calculations carried out on a human MDR1 homology model structure contributed to gain insights into the ligands’ binding modes. Some compounds (3d, 3h, 3l, 3r, 3t, 3u) reversed MDR thereby restoring doxorubicin cytotoxicity when co-administered with the drug into MDCK-MDR1 cells

A twenty-year journey exploring coumarin-based derivatives as bioactive molecules

The coumarin core (i.e., 1-benzopyran-2 (2H)-one) is a structural motif highly recurrent in both natural products and bioactive molecules. Indeed, depending on the substituents and branching positions around the byciclic core, coumarin-containing compounds have shown diverse pharmacological activities, ranging from anticoagulant activities to anti-inflammatory, antimicrobial, anti-HIV and antitumor effects. In this survey, we have reported the main scientific results of the 20-years investigation on the coumarin core, exploited by the research group headed by Prof. Angelo Carotti (Bari, Italy) either as a scaffold or a pharmacophore moiety in designing novel biologically active small molecules

Natural Scaffolds with Multi-Target Activity for the Potential Treatment of Alzheimer’s Disease

A few symptomatic drugs are currently available for Alzheimer’s Disease (AD) therapy, but these molecules are only able to temporary improve the cognitive capacity of the patients if administered in the first stages of the pathology. Recently, important advances have been achieved about the knowledge of this complex condition, which is now considered a multi-factorial disease. Researchers are, thus, more oriented toward the preparation of molecules being able to contemporaneously act on different pathological features. To date, the inhibition of acetylcholinesterase (AChE) and of β-amyloid (Aβ) aggregation as well as the antioxidant activity and the removal and/or redistribution of metal ions at the level of the nervous system are the most common investigated targets for the treatment of AD. Since many natural compounds show multiple biological properties, a series of secondary metabolites of plants or fungi with suitable structural characteristics have been selected and assayed in order to evaluate their potential role in the preparation of multi-target agents. Out of six compounds evaluated, 1 showed the best activity as an antioxidant (EC50 = 2.6 ± 0.2 µmol/µmol of DPPH) while compound 2 proved to be effective in the inhibition of AChE (IC50 = 6.86 ± 0.67 µM) and Aβ1–40 aggregation (IC50 = 74 ± 1 µM). Furthermore, compound 6 inhibited BChE (IC50 = 1.75 ± 0.59 µM) with a good selectivity toward AChE (IC50 = 86.0 ± 15.0 µM). Moreover, preliminary tests on metal chelation suggested a possible interaction between compounds 1, 3 and 4 and copper (II). Molecules with the best multi-target profiles will be used as starting hit compounds to appropriately address future studies of Structure-Activity Relationships (SARs)

Evaluation of water‐soluble Mannich base prodrugs of 2,3,4,5‐tetrahydroazepino[4,3‐b]indol‐1(6H)‐one as multitarget‐directed agents for Alzheimer’s disease

Aiming at addressing the poor aqueous solubility in in vivo assays of the recently disclosed 6-phenethyl-2,3,4,5- tetrahydroazepino[4,3-b]indol-1(6H)-one (1), human butyrylcholinesterase inhibitor (hBChE, IC5013 nM) and protective agent in NMDA-induced neurotoxicity, different Mannich base derivatives were studied. The N-(4- methylpiperazin-1-yl)methyl derivative 2c showed a 50-fold increase of solubility in pH 7.4 buffered solution, high stability in serum and pH 7.4 (half-life > 24 h) and rapid (< 3 min) conversion to 1 at acidic pH. Albeit less active than 1, 2c retained moderate hBChE inhibition (IC50 3.35 M) and a significant protective effect against NMDA-induced neurotoxicity at 0.1 M. Moreover, 2c resulted a weaker serum albumin binder than 1, a blood-brain barrier permeant, and exerted negligible cytotoxicity on HepG2 cells. These findings suggest that 2c could be a water-soluble prodrug candidate of 1 for oral administration or a slow-release injectable derivative in in vivo AD models

Design, synthesis and biological evaluation of light-driven on-off multitarget AChE and MAO-B inhibitors

Neurodegenerative diseases are multifactorial disorders characterized by protein misfolding, oxidative stress, and neuroinflammation, finally resulting in neuronal loss and cognitive dysfunctions. Nowadays, an attractive strategy to improve the classical treatments is the development of multitarget-directed molecules able to synergistically interact with different enzymes and/or receptors. In addition, an interesting tool to refine personalized therapies may arise from the use of bioactive species able to modify their activity as a result of light irradiation. To this aim, we designed and synthesized a small library of cinnamic acid-inspired isomeric compounds with light modulated activity able to inhibit acetylcholinesterase (AChE) and monoamine oxidase B (MAO-B), with remarkable selectivity over butyrylcholinesterase (BChE) and MAO-A, which have been investigated as the enzyme targets related to Alzheimer's disease (AD). The inhibitory activities were evaluated for the pure E-diastereomers and the E/Z-diastereomer mixtures, obtained upon UV irradiation. Molecular docking studies were carried out to rationalize the differences in the inhibition potency of the E and Z diastereomers of the best performing analogue 1c. Our preliminary findings may open-up the way for developing innovative multitarget photo-switch drugs against neurodegenerative diseases