Novel (coumarin-3-yl)carbamates as selective MAO-B inhibitors: synthesis, in vitro and in vivo assays, theoretical evaluation of ADME properties and docking study

Recent advances in the natural product analogues for the treatment of neurodegenerative diseases

Neurodegenerative diseases (NDs) represent a hallmark of numerous incapacitating and untreatable conditions, the incidence of which is escalating swiftly, exemplified by Alzheimer's disease and Parkinson's disease. There is an urgent necessity to create pharmaceuticals that exhibit high efficacy and minimal toxicity in order to address these debilitating diseases. The structural complexity and diversity of natural products confer upon them a broad spectrum of biological activities, thereby significantly contributing to the history of drug discovery. Nevertheless, natural products present challenges in drug discovery, including time-consuming separation processes, low content, low bioavailability, and other related issues. To address these challenges, numerous analogs of natural products have been synthesized. This methodology enables the rapid synthesis of analogs of natural products with the potential to serve as lead compounds for drug development, thereby paving the way for the discovery of novel pharmaceuticals. This paper provides a summary of 127 synthetic analogues featuring various natural product structures, including flavonoids, alkaloids, coumarins, phenylpropanoids, terpenoids, polyphenols, and amides. The compounds are categorized based on their efficacy in treating various diseases. Furthermore, this article delves into the structure-activity relationship (SAR) of certain analogues, offering a thorough point of reference for the systematic development of pharmaceuticals aimed at addressing neurodegenerative conditions.

Potent, selective and reversible hMAO-B inhibition by benzalphthalides: Synthesis, enzymatic and cellular evaluations and virtual docking and predictive studies

Monoaminooxidases (MAOs) are important targets for drugs used in the treatment of neurological and psychiatric disorders and particularly on Parkinson's Disease (PD). Compounds containing a trans-stilbenoid skeleton have demonstrated good selective and reversible MAO-B inhibition. Here, twenty-two (Z)-3-benzylidenephthalides (benzalphthalides, BPHs) displaying a trans-stilbenoid skeleton have been synthesised and evaluated as inhibitors of the MAO-A and MAO-B isoforms. Some BPHs have selectively inhibited MAO-B, with IC50 values ranging from sub-nM to μM. The most potent compound with IC50 = 0.6 nM was the 3',4'-dichloro-BPH 16, which showed highly selective and reversible MAO-B inhibitory activity. Furthermore, the most selective BPHs displayed a significant protection against the apoptosis, and mitochondrial toxic effects induced by 6-hydroxydopamine (6OHDA) on SH-SY5Y cells, used as a cellular model of PD. The results of virtual binding studies on the most potent compounds docked in MAO-B and MAO-A were in agreement with the potencies and selectivity indexes found experimentally. Additionally, related to toxicity risks, drug-likeness and ADME properties, the predictions found for the most relevant BPHs in this research were within those ranges established for drug candidates.

Recent Advancements and SAR Studies of Synthetic Coumarins as MAO-B Inhibitors: An Updated Review

BACKGROUND

The oxidative deamination of a wide range of endogenous and exogenous amines is catalyzed by a family of enzymes known as monoamine oxidases (MAOs), which are reliant on flavin-adenine dinucleotides. Numerous neurological conditions, such as Parkinson's disease (PD) and Alzheimer's disease (AD), are significantly correlated with changes in the amounts of biogenic amines in the brain caused by MAO. Hydrogen peroxide, reactive oxygen species, and ammonia, among other toxic consequences of this oxidative breakdown, can harm brain cells' mitochondria and cause oxidative damage.

OBJECTIVE

The prime objective of this review article was to highlight and conclude the recent advancements in structure-activity relationships of synthetic derivatives of coumarins for MAO-B inhibition, published in the last five years' research articles.

METHODS

The literature (between 2019 and 2023) was searched from platforms like Science Direct, Google Scholar, PubMed, etc. After going through the literature, we have found a number of coumarin derivatives being synthesized by researchers for the inhibition of MAO-B for the management of diseases associated with the enzyme such as Alzheimer's Disease and Parkinson's Disease. The effect of these coumarin derivatives on the enzyme depends on the substitutions associated with the structure. The structure-activity relationships of the synthetic coumarin derivatives that are popular nowadays have been described and summarized in the current study.

RESULTS

The results revealed the updated review on SAR studies of synthetic coumarins as MAO-B inhibitors, specifically for Alzheimer's Disease and Parkinson's Disease. The patents reported on coumarin derivatives as MAO-B inhibitors were also highlighted.

CONCLUSION

Recently, coumarins, a large class of chemicals with both natural and synthetic sources, have drawn a lot of attention because of the vast range of biological actions they have that are linked to neurological problems. Numerous studies have demonstrated that chemically produced and naturally occurring coumarin analogs both exhibited strong MAO-B inhibitory action. Coumarins bind to MAO-B reversibly thereby preventing the breakdown of neurotransmitters like dopamine leading to the inhibition of the enzyme A number of MAO-B blockers have been proven to be efficient therapies for treating neurological diseases like Alzheimer's Disease and Parkinson's Disease. To combat these illnesses, there is still an urgent need to find effective treatment compounds.

A Comprehensive Review of the Docking Studies of Chalcone for the Development of Selective MAO-B Inhibitors

Monoamine oxidase B is a crucial therapeutic target for neurodegenerative disorders like Alzheimer's and Parkinson's since they assist in disintegrating neurotransmitters such as dopamine in the brain. Pursuing efficacious monoamine oxidase B inhibitors is a hot topic, as contemporary therapeutic interventions have many shortcomings. Currently available FDA-approved monoamine oxidase inhibitors like safinamide, selegiline and rasagiline also have a variety of side effects like depression and insomnia. In the quest for a potent monoamine oxidase B inhibitor, sizeable, diverse chemical entities have been uncovered, including chalcones. Chalcone is a renowned structural framework that has been intensively explored for its monoamine oxidase B inhibitory activity.The structural resemblance of chalcone (1,3-diphenyl-2-propen-1-one) based compounds and 1,4-diphenyl- 2-butene, a recognized MAO-B inhibitor, accounts for their MAO-B inhibitory activity. Therefore, multiple revisions to the chalcone scaffold have been attempted by the researchers to scrutinize the implications of substitutions onthe molecule's potency. In this work, we outline the docking investigation results of various chalcone analogues with monoamine oxidase B available in the literature until now to understand the interaction modes and influence of substituents. Here we focused on the interactions between reported chalcone derivatives and the active site of monoamine oxidase B and the influence of substitutions on those interactions. Detailed images illustrating the interactions and impact of the substituents or structural modifications on these interactions were used to support the docking results.

N-(coumarin-3-yl)cinnamamide Promotes Immunomodulatory, Neuroprotective, and Lung Function-Preserving Effects during Severe Malaria

Plasmodium berghei ANKA (PbA) infection in mice resembles several aspects of severe malaria in humans, such as cerebral malaria and acute respiratory distress syndrome. Herein, the effects of N-(coumarin-3-yl)cinnamamide (M220) against severe experimental malaria have been investigated. Treatment with M220 proved to protect cognitive abilities and lung function in PbA-infected mice, observed by an object recognition test and spirometry, respectively. In addition, treated mice demonstrated decreased levels of brain and lung inflammation. The production and accumulation of microglia, and immune cells that produce the inflammatory cytokines TNF and IFN-γ, decreased, while the production of the anti-inflammatory cytokine IL-10 by innate and adaptive immune cells was enhanced. Treatment with M220 promotes immunomodulatory, neuroprotective, and lung function-preserving effects during experimental severe malaria. Therefore, it may be an interesting therapeutic candidate to treat severe malaria effects.

Monoamine oxidase B inhibitors based on natural privileged scaffolds: A review of systematically structural modification

Monoamine oxidase is a flavin enzyme that catalyzes the oxidation of monoamine neurotransmitters in the brain. Various toxic by-products, aldehydes and hydrogen peroxide produced during the catalytic process, can cause oxidative stress and neuronal cell death. Overexpression of MAO-B and insufficient dopamine concentration are recognized as pathological factors in neurodegenerative diseases (NDs) including Parkinson's disease (PD) and Alzheimer's disease (AD). Therefore, the inhibition of MAO-B is an attractive target for the treatment of NDs. Despite significant efforts, few selective and reversible MAO-B inhibitors have been clinically approved. Natural products have emerged as valuable sources of lead compounds in drug discovery. Compounds such as chromone, coumarin, chalcone, caffeine, and aurone, present in natural structures, are considered as privileged scaffolds in the synthesis of MAO-B inhibitors. In this review, we summarized the structure-activity relationship (SAR) of MAO-B inhibitors based on the naturally privileged scaffolds over the past 20 years. Additionally, we proposed a balanced discussion on the advantages and limitations of natural scaffold-based MAO-B inhibitors with providing a future perspective in drug development.

8-Amide and 8-carbamate substitution patterns as modulators of 7-hydroxy-4-methylcoumarin's antidepressant profile: Synthesis, biological evaluation and docking studies

Psychiatric and neurological disorders affect millions of people worldwide. Currently available treatments may help to improve symptoms, but they cannot cure the diseases. Therefore, there is an urgent need for potent and safe therapeutic solutions. 8-Amide and 8-carbamatecoumarins were synthetized and evaluated as human monoamine oxidase A and B (hMAO-A and hMAO-B) inhibitors. Comparison between both scaffolds has been established, and we hypothesized that the introduction of different substituents can modulate hMAO activity and selectivity. N-(7-Hydroxy-4-methylcoumarin-8-yl)-4-methylbenzamide (9) and ethyl N-(7-hydroxy-4-methylcoumarin-8-yl)carbamate (20) proved to be the most active and selective hMAO-A inhibitors (IC₅₀ = 15.0 nM and IC₅₀ = 22.0 nM, respectively), being compound 9 an irreversible hMAO-A inhibitor twenty-four times more active in vitro than moclobemide, a drug used in the treatment of depression and anxiety. Based on PAMPA assay results, both compounds proved to be good candidates to cross the blood-brain barrier. In addition, these compounds showed non-significant cytotoxicity on neuronal viability assays. Also, the best compound proved to have a t_1/2 of 6.84 min, an intrinsic clearance of 195.63 μL min^-1 mg^-1 protein, and to be chemically stable at pH 3.0, 7.4 and 10.0. Docking studies were performed to better understand the binding affinities and selectivity profiles for both hMAO isoforms. Finally, theoretical drug-like properties calculations corroborate the potential of both scaffolds on the search for new therapeutic solutions for psychiatric disorders as depression.

Computational Chemistry and Molecular Modeling of Reversible MAO Inhibitors

Proper elucidation of drug-target interaction is one of the most significant steps at the early stages of the drug development research. Computer-aided drug design tools have substantial contribution to this stage. In this chapter, we specifically concentrate on the computational methods widely used to develop reversible inhibitors for monoamine oxidase (MAO) isozymes. In this context, current computational techniques in identifying the best drug candidates showing high potency are discussed. The protocols of structure-based drug design methodologies, namely, molecular docking, in silico screening, and molecular dynamics simulations, are presented. Employing case studies of safinamide binding to MAO B, we demonstrate how to use AutoDock 4.2.6 and NAMD software packages.

Monoamine oxidase inhibitors: A concise review with special emphasis on structure activity relationship studies

Monoamine oxidase enzyme is necessary for the management of brain functions. It oxidatively metabolizes monoamines and produces ammonia, aldehyde and hydrogen peroxide as by-products. Excessive production of by-products of monoamine metabolism generates free radicals which cause cellular apoptosis and several neurodegenerative disorders for example Alzheimer's disease, Parkinson's disease, depression and autism. The inhibition of MAOs is an attractive target for the treatment of neurological disorders. Clinically approved MAO inhibitors for example selegiline, rasagiline, clorgyline, pargyline etc. are irreversible in nature and cause some adverse effects while recently studied reversible MAO inhibitors are devoid of harmful effects of old monoamine oxidase inhibitors. In this review article we have listed various synthesized molecules containing different moieties like coumarin, chalcone, thiazole, thiourea, caffeine, pyrazole, chromone etc. along with their activity, mode of action, structure activity relationship and molecular docking studies.

Coumarin-Resveratrol-Inspired Hybrids as Monoamine Oxidase B Inhibitors: 3-Phenylcoumarin versus trans-6-Styrylcoumarin

Monoamine oxidases (MAOs) are attractive targets in drug design. The inhibition of one of the isoforms (A or B) is responsible for modulating the levels of different neurotransmitters in the central nervous system, as well as the production of reactive oxygen species. Molecules that act selectively on one of the MAO isoforms have been studied deeply, and coumarin has been described as a promising scaffold. In the current manuscript we describe a comparative study between 3-phenylcoumarin (endo coumarin-resveratrol-inspired hybrid) and trans-6-styrylcoumarin (exo coumarin-resveratrol-inspired hybrid). Crystallographic structures of both compounds were obtained and analyzed. 3D-QSAR models, in particular CoMFA and CoMSIA, docking simulations and molecular dynamics simulations have been performed to support and better understand the interaction of these molecules with both MAO isoforms. Both molecules proved to inhibit MAO-B, with trans-6-styrylcoumarin being 107 times more active than 3-phenylcoumarin, and 267 times more active than trans-resveratrol.

Natural Coumarins: Exploring the Pharmacological Complexity and Underlying Molecular Mechanisms

Coumarins belong to the benzopyrone family commonly found in many medicinal plants. Natural coumarins demonstrated a wide spectrum of pharmacological activities, including anti-inflammatory, anticoagulant, anticancer, antibacterial, antimalarial, casein kinase-2 (CK2) inhibitory, antifungal, antiviral, Alzheimer's disease inhibition, neuroprotective, anticonvulsant, phytoalexins, ulcerogenic, and antihypertensive. There are very few studies on the bioavailability of coumarins; therefore, further investigations are necessitated to study the bioavailability of different coumarins which already showed good biological activities in previous studies. On the evidence of varied pharmacological properties, the present work presents an overall review of the derivation, availability, and biological capacities of coumarins with further consideration of the essential mode of their therapeutic actions. In conclusion, a wide variety of coumarins are available, and their pharmacological activities are of current interest thanks to their synthetic accessibility and riches in medicinal plants. Coumarins perform the valuable function as therapeutic agents in a range of medical fields.

Curcumin-Coumarin Hybrid Analogues as Multitarget Agents in Neurodegenerative Disorders

Neurodegenerative diseases have a complex nature which highlights the need for multitarget ligands to address the complementary pathways involved in these diseases. Over the last decade, many innovative curcumin-based compounds have been designed and synthesized, searching for new derivatives having anti-amyloidogenic, inhibitory of tau formation, as well as anti-neuroinflammation, antioxidative, and AChE inhibitory activities. Regarding our experience studying 3-substituted coumarins with interesting properties for neurodegenerative diseases, our aim was to synthesize a new series of curcumin–coumarin hybrid analogues and evaluate their activity. Most of the 3-(7-phenyl-3,5-dioxohepta-1,6-dien-1-yl)coumarin derivatives 11–18 resulted in moderated inhibitors of hMAO isoforms and AChE and BuChE activity. Some of them are also capable of scavenger the free radical DPPH. Furthermore, compounds 14 and 16 showed neuroprotective activity against H₂O₂ in SH-SY5Y cell line. Nanoparticles formulation of these derivatives improved this property increasing the neuroprotective activity to the nanomolar range. Results suggest that by modulating the substitution pattern on both coumarin moiety and phenyl ring, ChE and MAO-targeted derivatives or derivatives with activity in cell-based phenotypic assays can be obtained.

Deciphering the detailed structure-activity relationship of coumarins as Monoamine oxidase enzyme inhibitors-An updated review

In the last few years, Monoamine oxidase (MAO) have emerged as a target for the treatment of many neurodegenerative diseases including anxiety, depression, Alzheimer's, and Parkinson's diseases. The MAO inhibitors especially selective and reversible inhibitors of either of the isoenzymes (MAO-A & MAO-B) have been given more attention as both the form have different therapeutic properties and hence can be used for different neurological disorders. The lack of selective and reversible inhibitors available for both the enzymes and severity of the neuronal disorder in society have opened a new door to the researchers to carry out large and dedicated researches in this field. Among the several classes of the molecule as the inhibitors, coumarins hold a rank as a potent scaffold with its ease of synthesis, high therapeutic potential, and reversibility in inhibiting MAOs. The current review is an update of the research in the field that covers the works during the last six years (2014-2020) with a major focus on the SAR of the coumarin derivatives including synthetic, natural, and hybrids of coumarins with FDA-approved drugs.

Gamma-decanolactone: Preliminary evaluation as potential antiparkinsonian drug

Treatment of Parkinson's disease (PD) includes the use of monoamine oxidase-B (MAO-B) inhibitor drugs. In this work we have evaluated the possible gamma-decanolactone (GD) effect in vitro to inhibit the A and B isoforms of human monoamine oxidase (hMAO) enzyme and their citotoxicity in human hepatoma cell line (HepG2). Also, binding studies to A₁, A_2A A_2B and A₃ adenosine receptors were performed. A docking study of gamma-decanolactone has been carried out with the molecular targets of MAO-A and MAO-B isoforms. The physicochemical properties and ability to cross physiological barriers, as the blood brain barrier (BBB), was elucidated by computational studies. The in vivo assays, the rota-rod test, body temperature assessment and open field test were performed in reserpinized mice (1.5 mg/kg, i.p.; 18:00 before) to evaluate the effect of gamma-decanolactone (300 mg/kg), alone or associated with Levodopa plus Benserazide (LD + BZ, 100:25 mg/kg, i.p.). Gamma-decanolactone inhibited preferentially the MAO-B in a reversible manner, with an inhibitory concentration of 50% (IC₅₀) 55.95 ± 9.06 μM. It was shown to be a safe drug since only at the highest concentration decreased the viability of HepG2 cells. It also does not bind to adenosine receptors investigated in this study. The molecular docking study show that the gamma-decanolactone ligand adopts a relatively compact conformation in the active site of hMAO-B, while we note an extended conformation of gamma-decanolactone ligand in the hMAO-A isoform. The physicochemical properties obtained, and the theoretical models utilized for the evaluation of ability to cross the BBB, predict a good gamma-decanolactone bioavailability and access to the central nervous system (CNS). In the in vivo studies, gamma-decanolactone partially reversed the ataxia of the reserpinized mice at 01:00 h and 01:30 h post-administration. Concomitant treatment of gamma-decanolactone with LD + BZ, at 01:30 h showed a potentiation of the reversibility of ataxia and facilitated the reversal of hypothermia caused by reserpine for all measured times (P <0.01 vs vehicle), except at 24:00 h, but not reversed the hypokinesia in the open field test. In summary, the results herein obtained and in conjunction with previous studies, suggest that gamma-decanolactone could be a drug with potential utility as antiparkinsonian drug.

Design, synthesis, and evaluation of 1, 4-benzodioxan-substituted chalcones as selective and reversible inhibitors of human monoamine oxidase B

The inhibition of monoamine oxidase B (MAO-B) could be an effective approach for the treatment of various neurological disorders. In this study, a series of 1, 4-benzodioxan-substituted chalcone derivatives were designed, synthesised and evaluated for their inhibitory activity against human MAO-B (hMAO-B). The majority of these compounds showed inhibitory activity and high selectivity. The most potent compound, (E)-1-(3-bromo-4-fluorophenyl)-3-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)prop-2-en-1-one (22), exhibited an IC₅₀ of 0.026 µM with a selectivity index greater than 1538. Kinetics and reversibility studies confirmed that the representative active compounds acted as competitive and reversible inhibitors of hMAO-B. The enzyme-inhibitor interactions were investigated by molecular docking studies and the rationale was provided. As these potent hMAO-B inhibitors exhibited low neurotoxicity and possessed promising drug-like properties, we believe that these active compounds could be further investigated as potential drug candidates for future in vivo studies.

Identification of 7,8-dihydroxy-3-phenylcoumarin as a reversible monoamine oxidase enzyme inhibitor

We herein report the biological evaluation of 3-arylcoumarin derivatives (3a-l) as potential human monoamine oxidase-A and -B (hMAO-A and hMAO-B) inhibitors. The result indicated that 7,8-dihydroxy-3-(4-nitrophenyl)coumarin (3j) was most effective against MAO-A (inhibition concentration [IC₅₀ ] = 6.46 ± 0.02 µM) and MAO-B (IC₅₀  = 3.8 ± 0.3 µM) enzymes than other synthesized compounds and reference compounds (pargyline and moclobemide). Furthermore, compound (3j) showed (a) nonselectivity against hMAO enzymes, (b) reversible hMAO enzymes inhibition, and (c) neuroprotection against H₂ O₂ -treated human neuroblastoma (N2a) cells. Finally, a molecular modeling study revealed that the hMAO enzymes inhibitory activity of the compound (3j) may be due to the orientation where the nitro (NO₂ ) group lies deep into the receptor and the phenyl ring directed toward flavin adenosine dinucleotide via hydrogen bond interaction, and possible π-π interaction with various important residues. Thus, the results of the present study demonstrate that compound (3j) can be considered as a promising scaffold for the development of hMAO-A and hMAO-B inhibitors.

Novel coumarin-pyridazine hybrids as selective MAO-B inhibitors for the Parkinson's disease therapy

The 3-pyridazinylcoumarin scaffold was previously reported as an efficient core for the discovery of reversible and selective inhibitors of MAO-B, a validated drug target for PD therapy which also plays an important role in the AD progress. Looking for its structural optimization, novel compounds of hybrid structure coumarin-pyridazine, differing in polarizability and lipophilicity properties, were synthesized and tested against the two MAO isoforms, MAO-A and MAO-B (compounds 17a-f and 18a-f). All the designed compounds selectively inhibited the MAO-B isoenzyme, exhibiting many of them IC₅₀ values ranging from sub-micromolar to nanomolar grade and lacking neuronal toxicity. The 7-bromo-3-(6-bromopyridazin-3-yl)coumarin (18c), the most potent compound of these series (IC₅₀ = 60 nM), was subjected to further in vivo studies in a reserpine-induced mouse PD model. The obtained results suggest a promising potential for 18c as antiparkinsonian agent. Molecular modeling studies also provided valuable information about the enzyme-drug interactions and the potential pharmacokinetic profile of the novel compounds.

7-Amidocoumarins as Multitarget Agents against Neurodegenerative Diseases: Substitution Pattern Modulation

This study explores the potential of 7-amidocoumarins as multitarget agents against Parkinson's and Alzheimer's diseases, by modulating the substitution patterns within the scaffold. Sixteen compounds were synthesized via 7-amino-4-methylcoumarin acylation, and in vitro evaluation of the molecules against hMAO-A, hMAO-B, hAChE, hBuChE and hBACE1 was performed. Five compounds turned out to be potent and selective hMAO-B inhibitors in the nanomolar range, six displayed inhibitory activity of hMAO-A in the low micromolar range, one showed hAChE inhibitory activity and another one hBACE1 inhibitory activity. MAO-B reversibility profile of 7-(4'-chlorobenzamido)-4-methylcoumarin (10) was investigated, with this compound being a reversible inhibitor. Neurotoxicity on motor cortex neurons and neuroprotection against H₂ O₂ were also studied, corroborating the safety profile of these molecules. Finally, theoretical ADME properties were also calculated, showing these molecules as good candidates for the optimization of a lead compound. Results suggest that by modulating the substitution pattern at position 7 of the scaffold, selective or multitarget molecules can be achieved.

Recent advances in dopaminergic strategies for the treatment of Parkinson's disease

Parkinson's disease (PD) is the second most common progressive neurodegenerative disease worldwide. However, there is no available therapy reversing the neurodegenerative process of PD. Based on the loss of dopamine or dopaminergic dysfunction in PD patients, most of the current therapies focus on symptomatic relief to improve patient quality of life. As dopamine replacement treatment remains the most effective symptomatic pharmacotherapy for PD, herein we provide an overview of the current pharmacotherapies, summarize the clinical development status of novel dopaminergic agents, and highlight the challenge and opportunity of emerging preclinical dopaminergic approaches aimed at managing the features and progression of PD.

Coumarin analogue 3-methyl-7H-furo[3,2-g] chromen-7-one as a possible antiparkinsonian agent

Introduction:

Parkinson’s disease is the second most common neurodegenerative disease. Monoamine oxidase B inhibitors are used in the treatment of this disease concomitantly with levodopa or as monotherapy. Several substituted coumarins have shown activity as inhibitors of monoamine oxidase B.

Objective:

To evaluate the possible antiparkinsonian effects of the coumarin analogue FCS005 (3-methyl-7H-furo[3,2-g]chromen-7-one) in mouse models, as well as its inhibitory activity towards monoamine oxidases (MAO) and its antioxidant activity.

Materials and methods:

FCS005 was synthesized and the reversal of hypokinesia was evaluated in the reserpine and levodopa models. Moreover, in the haloperidol model, its anticataleptic effects were evaluated. Additionally, the monoamine oxidase inhibitory activity and antioxidant activity of FCS005 were evaluated using in vitro and ex vivo studies, respectively.

Results:

FCS005 (100 mg/kg) caused the reversal of hypokinesia in the reserpine and levodopa models. This furocoumarin also presented anti-cataleptic effects at the same dose. Besides, it showed selective inhibitory activity towards the MAO-B isoform and antioxidant activity.

Conclusion:

These results attribute interesting properties to the compound FCS005. It is important to continue research on this molecule considering that it could be a potential antiparkinsonian agent.

Molecular docking studies of coumarin hybrids as potential acetylcholinesterase, butyrylcholinesterase, monoamine oxidase A/B and β-amyloid inhibitors for Alzheimer's disease

Coumarins are the phytochemicals, which belong to the family of benzopyrone, that display interesting pharmacological properties. Several natural, synthetic and semisynthetic coumarin derivatives have been discovered in decades for their applicability as lead structures as drugs. Coumarin based conjugates have been described as potential AChE, BuChE, MAO and β-amyloid inhibitors. Therefore, the objective of this review is to focus on the construction of these pharmacologically important coumarin analogues with anti-Alzheimer’s activities, highlight their docking studies and structure–activity relationships based on their substitution pattern with respect to the selected positions on the chromen ring by emphasising on the research reports conducted in between year 1968 to 2017.

Coumarin: A Natural, Privileged and Versatile Scaffold for Bioactive Compounds

Many naturally occurring substances, traditionally used in popular medicines around the world, contain the coumarin moiety. Coumarin represents a privileged scaffold for medicinal chemists, because of its peculiar physicochemical features, and the versatile and easy synthetic transformation into a large variety of functionalized coumarins. As a consequence, a huge number of coumarin derivatives have been designed, synthesized, and tested to address many pharmacological targets in a selective way, e.g., selective enzyme inhibitors, and more recently, a number of selected targets (multitarget ligands) involved in multifactorial diseases, such as Alzheimer's and Parkinson's diseases. In this review an overview of the most recent synthetic pathways leading to mono- and polyfunctionalized coumarins will be presented, along with the main biological pathways of their biosynthesis and metabolic transformations. The many existing and recent reviews in the field prompted us to make some drastic selections, and therefore, the review is focused on monoamine oxidase, cholinesterase, and aromatase inhibitors, and on multitarget coumarins acting on selected targets of neurodegenerative diseases.

Synthesis and structure-activity relationship study of novel 3-heteroarylcoumarins based on pyridazine scaffold as selective MAO-B inhibitors

Compounds of hybrid structure pyridazine-coumarin were discovered as potent, selective and reversible inhibitors of monoamine oxidase B (MAO-B). These compounds were synthesized in good yield following a multistep approach based on Knoevenagel reaction and using as key intermediate pyridazinone 16, which was obtained from maleic anhydride and furan. Compounds 9b and 9d are the most active compounds of these series, with IC₅₀ values in the sub-micromolar range, and lack of cytotoxic effects. Theoretical calculation of ADME properties also suggested a good pharmacokinetic profile for both compounds. Docking simulations provided insights into enzyme inhibitor interactions and allowed us to rationalize the observed structure-activity relationships (SARs).

Computational Drug Target Screening through Protein Interaction Profiles

The development of computational methods to discover novel drug-target interactions on a large scale is of great interest. We propose a new method for virtual screening based on protein interaction profile similarity to discover new targets for molecules, including existing drugs. We calculated Target Interaction Profile Fingerprints (TIPFs) based on ChEMBL database to evaluate drug similarity and generated new putative compound-target candidates from the non-intersecting targets in each pair of compounds. A set of drugs was further studied in monoamine oxidase B (MAO-B) and cyclooxygenase-1 (COX-1) enzyme through molecular docking and experimental assays. The drug ethoxzolamide and the natural compound piperlongumine, present in Piper longum L, showed hMAO-B activity with IC₅₀ values of 25 and 65 μM respectively. Five candidates, including lapatinib, SB-202190, RO-316233, GW786460X and indirubin-3′-monoxime were tested against human COX-1. Compounds SB-202190 and RO-316233 showed a IC₅₀ in hCOX-1 of 24 and 25 μM respectively (similar range as potent inhibitors such as diclofenac and indomethacin in the same experimental conditions). Lapatinib and indirubin-3′-monoxime showed moderate hCOX-1 activity (19.5% and 28% of enzyme inhibition at 25 μM respectively). Our modeling constitutes a multi-target predictor for large scale virtual screening with potential in lead discovery, repositioning and drug safety.

Multifunction of Chrysin in Parkinson's Model: Anti-Neuronal Apoptosis, Neuroprotection via Activation of MEF2D, and Inhibition of Monoamine Oxidase-B

Chrysin, a flavonoid compound existing in several plants, is applied as a dietary supplement because of its beneficial effects on general human health and alleviation of neurological disorders. However, mechanisms underlying neuroprotection of chrysin has not been fully elucidated, and the effects of chrysin on the Parkinson's disease (PD) model in vivo have not been investigated. It is here shown that chrysin protects primary granular neurons against 1-methyl-4-phenylpyridinium ion insult via antiapoptosis by reversing the dysregulated expression of Bcl-2, Bax, and caspase 3. The mechanisms also involved activating transcriptional factor myocyte enhancer factor 2D (MEF2D) via regulation of AKT-GSK3β signaling. In this in vivo model of PD, chrysin rescued the dopaminergic neurons loss and alleviated the decrease in dopamine level induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in mice. Moreover, chrysin markedly inhibited monoamine oxidase-B activity in vitro and in vivo. In conclusion, chrysin exerts beneficial effects to PD, possibly through multitarget mechanisms including antineuronal apoptosis, activation of the AKT-GSK3β/MEF2D pathway, and inhibition of the MAO-B activity.

Propargylamine as functional moiety in the design of multifunctional drugs for neurodegenerative disorders: MAO inhibition and beyond

Much progress has been made in designing analogues that can potentially confer neuroprotection against debilitating neurodegenerative disorders, yet the multifactorial pathogenesis of this cluster of diseases remains a stumbling block for the successful design of an 'ultimate' drug. However, with the growing popularity of the "one drug, multiple targets" paradigm, many researchers have successfully synthesized and evaluated drug-like molecules incorporating a propargylamine function that shows potential to serve as multifunctional drugs or multitarget-directed ligands. It is the aim of this review to highlight the reported activities of these propargylamine derivatives and their prospect to serve as drug candidates for the treatment of neurodegenerative disorders.

Recent developments on the structure–activity relationship studies of MAO inhibitors and their role in different neurological disorders

Development of MAO inhibitors as effective drug candidates for the management and/or treatment of different neurological disorders.

3-Amidocoumarins as Potential Multifunctional Agents against Neurodegenerative Diseases

Monoamine oxidase (MAO) generates reactive oxygen species (ROS), which cause neuronal cell death, causing neurodegeneration. Agents that are able to concurrently inhibit MAO and scavenge free radicals represent promising multifunctional neuroprotective agents that could be used to delay or slow the progression of neurodegenerative diseases. In this work, variously substituted 3-amidocoumarins are described that exert neuroprotection in vitro against hydrogen peroxide in rat cortical neurons, as well as antioxidant activity in a 1,1-diphenyl-2-picrylhydrazyl (DPPH⋅) radical scavenging assay. Selective and reversible inhibitors of the MAO-B isoform were identified. Interestingly, in the case of the 3-benzamidocoumarins, substitution at position 4 with a hydroxy group abolishes MAO-B activity, but the compounds remain active in the neuroprotection model. Further evaluation of 3-heteroarylamide derivatives indicates that it is the nature of the heterocycle that determines the neuroprotective effects. Evaluation in a parallel artificial membrane permeability assay (PAMPA) highlighted the need to further improve the blood-brain barrier permeability of this compound class. However, the compounds described herein adhere to Lipinski's rule of five, suggesting that this novel scaffold has desirable properties for the development of potential drug candidates.

New Frontiers in Selective Human MAO-B Inhibitors

Accumulating evidence shows a relationship between the human MAO-B (hMAO-B) enzyme and neuropsychiatric/degenerative disorder, personality traits, type II alcoholism, borderline personality disorders, aggressiveness and violence in crime, obsessive-compulsive disorder, depression, suicide, schizophrenia, anorexia nervosa, migraine, dementia, and PD. Thus, MAO-B represents an attractive target for the treatment of a number of human diseases. The discovery, development, and therapeutic use of drugs that inhibit MAO-B are major challenges for future therapy. Various compounds and drugs that selectively target this isoform have been discovered recently. These agents are synthetic compounds or natural products and their analogues, including chalcones, pyrazoles, chromones, coumarins, xanthines, isatin derivatives, thiazolidindiones, (thiazol-2-yl)hydrazones, and analogues of marketed drugs. Despite considerable efforts in understanding the binding interaction with specific substrates or inhibitors, structural information available for the rational design of new hMAO-B inhibitors remains unsatisfactory. Therefore, the quest for novel, potent, and selective hMAO-B inhibitors remains of high interest.

Synthesis, pharmacological study and docking calculations of new benzo[f]coumarin derivatives as dual inhibitors of enzymatic systems involved in neurodegenerative diseases

Background: Due to the complex etiology of neurodegenerative diseases, there is growing interest in multitarget drugs. In this study we synthesized and evaluated a new series of compounds, with benzo[f]coumarin structure, as potential inhibitors of MAO-A, MAO-B, AChE and BuChE. Results: In vitro studies show that most of the studied compounds inhibited the activity of MAO-B in the nano- to micro-molar range. 3-(3´-methoxyphenyl)benzo[f]coumarin is the most active compound with an IC50 value against MAO-B of 2.44 nM. Most of the derivatives exhibited an important selectivity profile against the MAO-B isoform. Some of them also acted as in vitro inhibitors of BuChE, with 3-(2´-hydroxyphenyl)benzo[f]coumarin being the most active with an IC50 value of 1.13 µM. In addition, a theoretical study of the physicochemical properties of the new compounds, as well as a docking study in both MAO isoforms, were carried out. Important structure–activity relationships were obtained. Conclusion: Important preliminary structure–activity relationships were concluded from the experimental results. These results encourage us to further explore the potential of this chemical family as potential drug candidates for the treatment of Alzheimer‘s disease.