Selected C7-substituted chromone derivatives as monoamine oxidase inhibitors

Benzodioxane Carboxamide Derivatives As Novel Monoamine Oxidase B Inhibitors with Antineuroinflammatory Activity

In this study, a series of N-phenyl-2,3-dihydrobenzo[b][1,4]dioxine-6-carboxamide derivatives were designed, synthesized, and evaluated for their inhibitory activities against human MAO-B (hMAO-B). The structure-activity relationship (SAR) was investigated and summarized. Compound 1l (N-(3,4-dichlorophenyl)-2,3-dihydrobenzo[b][1,4]dioxine-6-carboxamide) showed the most potent inhibitory activity with an IC50 value of 0.0083 μM and the selectivity index (IC50 (hMAO-A)/IC50 (hMAO-B)) was >4819. Kinetics and reversibility studies confirmed that compound 1l acted as a competitive and reversible inhibitor of hMAO-B. Molecular docking studies revealed the enzyme-inhibitor interactions, and the rationale was provided. Additionally, compound 1l could effectively inhibit the release of NO, TNF-α, and IL-1β in both LPS- and Aβ1-42-stimulated BV2 cells and attenuate the cytotoxicity induced by Aβ1-42. Since compound 1l exhibited low neurotoxicity, we believe that the hit compound with dual activities of inhibiting MAO-B and antineuroinflammation could be further investigated as a novel potential lead for future studies in vivo.

Discovery of novel 2-(4-(benzyloxy)-5-(hydroxyl) phenyl) benzothiazole derivatives as multifunctional MAO-B inhibitors for the treatment of Parkinson's disease

To discover novel multifunctional agents for the treatment of Parkinson's disease, a series of 2-(4-(benzyloxy)-5-(hydroxyl) phenyl) benzothiazole derivatives was designed, synthesized and evaluated. The results revealed that representative compound 3h possessed potent and selective MAO-B inhibitory activity (IC₅₀ = 0.062 µM), and its inhibitory mode was competitive and reversible. Additionally, 3h also displayed excellent anti-oxidative effect (ORAC = 2.27 Trolox equivalent), significant metal chelating ability and appropriate BBB permeability. Moreover, 3h exhibited good neuroprotective effect and anti-neuroinflammtory ability. These results indicated that compound 3h was a promising candidate for further development against PD.

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.

Field and atom-based 3D-QSAR models of chromone (1-benzopyran-4-one) derivatives as MAO inhibitors

Monoamine oxidases (MAOs) are flavo-enzymes that aid in the oxidative deamination of neurotransmitters like dopamine, serotonin, and epinephrine. MAO inhibitors are antidepressants that work by preventing the breakdown of brain neurotransmitters and regulating mood. MAO inhibitors that use the chromone (1-benzopyran-4-one) structure have been found to be quite effective in studies. The current study involves the creation of pharmacophore models, 3-D QSAR, virtual screening, and docking investigations, all of which are evaluated using various criteria. The investigation included 39 ligands that emerged pharmacophore AHRRR_1, as the best pharmacophore model with a survival score of 5.6485. The 3D QSAR investigation revealed a significant model with the values of R2 = 0.9064 and Q2 = 0.8239. Docking study revealed that compound 18 had the highest docking (-10.402 kcal/mol) score in the series and showed interactions with the essential amino acid TYR398 required for MAO inhibitory activity. ZINC compounds were screened using the created pharmacophore model, which was followed up with a virtual screening study. The ZINC compounds with the best XP docking scores are ZINC03113255, ZINC07777127, ZINC05166353 and ZINC09341502 (with docking scores -10.021, -9.486, -8.031 and -7.792 kcal/mol, respectively). ZINC03113255, which showed the best score, has binding interactions with amino acid residues, TYR326, TYR398 and LYS296 of monoamine oxidase B. The ADME analysis demonstrated the compound's drug-like characteristics. The findings of this study may be used in the development of chromone compounds that target the MAO inhibitor.Communicated by Ramaswamy H. Sarma.

Introduction of benzyloxy pharmacophore into aryl/heteroaryl chalcone motifs as a new class of monoamine oxidase B inhibitors

The inhibitory action of fifteen benzyloxy ortho/para-substituted chalcones (B1-B15) was evaluated against human monoamine oxidases (hMAOs). All the molecules inhibited hMAO-B isoform more potently than hMAO-A. Furthermore, the majority of the molecules showed strong inhibitory actions against hMAO-B at 10 μM level with residual activities of less than 50%. Compound B10 has an IC₅₀ value of 0.067 μM, making it the most potent inhibitor of hMAO-B, trailed by compound B15 (IC₅₀ = 0.12 μM). The thiophene substituent (B10) in the A-ring exhibited the strongest hMAO-B inhibition structurally, however, increased residue synthesis did not result in a rise in hMAO-B inhibition. In contrast, the benzyl group at the para position of the B-ring displayed more hMAO-B inhibition than the other positions. Compounds B10 and B15 had relatively high selectivity index (SI) values for hMAO-B (504.791 and 287.600, respectively). K_i values of B10 and B15 were 0.030 ± 0.001 and 0.033 ± 0.001 μM, respectively. The reversibility study showed that B10 and B15 were reversible inhibitors of hMAO-B. PAMPA assay manifested that the benzyloxy chalcones (B10 and B15) had a significant permeability and CNS bioavailability with Pe value higher than 4.0 × 10^-6 cm/s. Both compounds were stabilized in protein-ligand complexes by the π-π stacking, which enabled them to bind to the hMAO-B enzyme's active site incredibly effectively. The hMAO-B was stabilized by B10- and B15-hMAO-B complexes, with binding energies of - 74.57 and - 87.72 kcal/mol, respectively. Using a genetic algorithm and multiple linear regression, the QSAR model was created. Based on the best 2D and 3D descriptor-based QSAR model, the following statistics were displayed: R² = 0.9125, Q²_loo = 0.8347. These findings imply that B10 and B15 are effective, selective, and reversible hMAO-B inhibitors.

Design, Synthesis, and Biological Evaluation of Novel Chromanone Derivatives as Multifunctional Agents for the Treatment of Alzheimer's Disease

Based on a multitarget strategy, a series of novel chromanone-1-benzyl-1,2,3,6-tetrahydropyridin hybrids were identified for the potential treatment of Alzheimer's disease (AD). Biological evaluation demonstrated that these hybrids exhibited significant inhibitory activities toward acetylcholinesterase (AChE) and monoamine oxidase B (MAO-B). The optimal compound C10 possessed excellent dual AChE/MAO-B inhibition both in terms of potency and equilibrium (AChE: IC₅₀ = 0.58 ± 0.05 μM; MAO-B: IC₅₀ = 0.41 ± 0.04 μM). Further molecular modeling and kinetic investigations revealed that compound C10 was a dual-binding inhibitor bound to both the catalytic anionic site and peripheral anionic site of AChE. In addition, compound C10 exhibited low neurotoxicity and potently inhibited AChE enzymatic activity. Furthermore, compound C10 more effectively protected against mitochondrial dysfunction and oxidation than donepezil, strongly inhibited AChE-induced amyloid aggregation, and moderately reduced glutaraldehyde-induced phosphorylation of tau protein in SH-SY5Y cells. Moreover, compound C10 displayed largely enhanced improvements in cognitive behaviors and spatial memory in a scopolamine-induced AD mice model with better efficacy than donepezil. Overall, the multifunctional profiles of compound C10 suggest that it deserves further investigation as a promising lead for the prospective treatment of AD.

Design and Synthesis of (Z)-5-(Substituted benzylidene)-3-cyclohexyl-2-thioxothiazolidin-4-one Analogues as Anti-Tyrosinase and Antioxidant Compounds: In Vitro and In Silico Insights

Many compounds containing the β-phenyl-α,β-unsaturated carbonyl (PUSC) scaffold, including cinnamamide derivatives, have been shown to inhibit tyrosinase potently in vitro and in vivo. Structural changes to cinnamamide derivatives were produced by adding a dithionate functional group to provide eight (Z)-5-(substituted benzylidene)-3-cyclohexyl-2-thioxothiazolidin-4-one analogs with high log p values for skin. These analogs were synthesized using a two-step reaction, and their stereochemistry was confirmed using the ³J_C4-Hβ values of C4 measured in proton-coupled ¹³C mode. Analogs 2 (IC₅₀ = 5.21 ± 0.86 µM) and 3 (IC₅₀ = 1.03 ± 0.14 µM) more potently inhibited mushroom tyrosinase than kojic acid (IC₅₀ = 25.26 ± 1.10 µM). Docking results showed 2 binds strongly to the active site of tyrosinase, while 3 binds strongly to an allosteric site. Kinetic studies using l-tyrosine as substrate indicated 2 and 3 competitively and non-competitively inhibit tyrosinase, respectively, which was supported by our docking results. In B16F10 cells, 3 significantly and concentration-dependently reduced α–MSH plus IBMX induced increases in cellular tyrosinase activity and melanin production and the similarity between these inhibitory patterns implied that the anti-melanogenic effect of 3 might be due to its tyrosinase-inhibitory ability. In addition, 2 and 3 exhibited strong antioxidant effects; for example, they reduced ROS and ONOO^– levels and exhibited radical scavenging activities, suggesting that these effects might underlie their anti-melanogenic effects. Furthermore, 3 suppressed the expressions of melanogenesis-associated proteins and genes in B16F10 cells. These results suggest (Z)-5-(substituted benzylidene)-3-cyclohexyl-2-thioxothiazolidin-4-one analogs offer a means of producing novel anti-melanogenesis agents.

5-Demethoxy-10'-ethoxyexotimarin F, a New Coumarin with MAO-B Inhibitory Potential from Murraya exotica L

Rutaceae plants are known for being a rich source of coumarins. Preliminary molecular docking showed that there was no significant difference for coumarins in Clausena and Murraya, both of which had high scoring values and showed good potential inhibitory activity to the MAO-B enzyme. Overall, 32 coumarins were isolated from Murraya exotica L., including a new coumarin 5-demethoxy-10′-ethoxyexotimarin F (1). Their structures were elucidated on the basis of a comprehensive analysis of 1D and 2D NMR and HRMS spectroscopic data, and the absolute configurations were assigned via a comparison of the specific rotations and the ECD exciton coupling method. The potential of new coumarin (1) as a selective inhibitor of MAO-B was initially evaluated through molecular docking and pharmacophore studies. Compound (1) showed selectivity for the MAO-B isoenzyme and inhibitory activity in the sub-micromolar range with an IC50 value of 153.25 ± 1.58 nM (MAO-B selectivity index > 172).

Revealing the role of the benzyloxy pharmacophore in the design of a new class of monoamine oxidase-B inhibitors

The conceptual layout of monoamine oxidase (MAO) inhibitors has been modified to explore their potential biological application in the case of neurological disorders for the time being. The current review article is an effort to display the summation of innovative conceptual prospects of MAO inhibitors and their intriguing chemistry and bioactivity. Based on this scenario, we emphasize the pivotal role of the benzyloxy moiety attached to scaffolds like oxadiazolones, indolalkylamines, safinamide, caffeine, benzofurans, α-tetralones, β-nitrostyrene, benzoquinones, coumarins, indoles, chromones, and chromanone analogs, while acting as an MAO inhibitor.

Synchronous Fluorescence Determination of Al3+ Using 3-Hydroxy-2-(4-Methoxy Phenyl)-4H-Chromen-4-One as a Fluorescent Probe

A simple synchronous fluorescent chemosensor 3-hydroxy-2-(4-methoxyphenyl)-4H-chromen-4-one (3-HC) has been synthesized for the selective analysis of Al³⁺. On the addition of Al³⁺, 3-HC displayed a redshift with a change in wavelength of emission maximum from 436 to 465 nm along with enhancement in fluorescence intensity, which formed the basis for its sensitive detection. Under optimized conditions, 3-HC was applied for the determination of Al³⁺ in the concentration range of 1 × 10^-7-1 × 10^-6 M. The limit of detection (LOD) and limit of quantification (LOQ) values were found out to be 1.69 × 10^-8 and 5.07 × 10^-8 M respectively. Further, the developed method was applied for the analysis of Al³⁺ in real water samples (tap water, bottled water, and tube well water) which showed good recovery values in the range of 95-99.7% with RSD less than 4%.

New Aspects of Monoamine Oxidase B Inhibitors: The Key Role of Halogens to Open the Golden Door

A large plethora of drugs and promising lead compounds contain halogens in their structures. The introduction of such moieties strongly modulates their physical-chemical features as well as pharmacokinetic and pharmacodynamic profile. The most important outcome was shown to be the ability of these halogens to favourably influence the drug-target interaction and energetic stability within the active site by the establishment of halogen bonds. This review attempted to demonstrate the key role exerted by these versatile moieties when correctly located in an organic scaffold to display Monoamine Oxidase (MAO) inhibition and selectivity towards the B isoform of this important enzyme. Human MAOs are well-recognized as therapeutic targets for mood disorders and neurodegenerative diseases and medicinal chemists were prompted to discover the structural requirements crucial to discriminate the slight differences between the active sits of the two isoforms (MAO-A and MAOB). The analysis of the structure-activity relationships of the most important scaffolds (hydrazothiazoles, coumarins, chromones, chalcones, pyrazolines) and the impact of halogen (F, Cl, Br and I) insertion on this biological activity and isozyme selectivity have been reported being a source of inspiration for the medicinal chemists.

Design and synthesis of novel 3,4-dihydrocoumarins as potent and selective monoamine oxidase-B inhibitors with the neuroprotection against Parkinson's disease

The monoamine oxidase-B (MAO-B) inhibitors with neuroprotective effects are better for Parkinson's disease (PD) treatment, due to the complicated pathogenesis of PD. To develop new hMAO-B inhibitors with neuroprotection, a novel series of 3,4-dihydrocoumarins was designed as selective and reversible hMAO-B inhibitors to treat PD. Most compounds showed potent and selective inhibition for hMAO-B over hMAO-A with IC₅₀ values ranging from nanomolar to sub-nanomolar. Among them, compound 4d was the most potent hMAO-B inhibitor (IC₅₀ = 0.37 nM) being about 20783-fold more active than iproniazid, and exhibited the highest selectivity for hMAO-B (SI > 270,270). Kinetic studies revealed that compound 4d was a reversible and competitive inhibitor of hMAO-B. Neuroprotective studies indicated that compound 4d could protect PC12 cells from the damage induced by 6-OHDA and rotenone. Besides, compound 4d did not exhibit acute toxicity at a dose up to 2500 mg/kg (po), and could cross the BBB in parallel artificial membrane permeability assay. More importantly, compound 4d was able to significantly prevent the motor deficits in the MPTP-induced PD model. These results indicate that compound 4d is an effective and promising candidate against PD.

Chromone and donepezil hybrids as new multipotent cholinesterase and monoamine oxidase inhibitors for the potential treatment of Alzheimer's disease

A series of chromone and donepezil hybrids were designed, synthesized, and evaluated as multipotent cholinesterase (ChE) and monoamine oxidase (MAO) inhibitors for the potential therapy of Alzheimer's disease (AD). In vitro studies showed that the great majority of these compounds exhibited potent inhibitory activity toward BuChE and AChE and clearly selective inhibition for hMAO-B. In particular, compound 5c presented the most balanced potential for ChE inhibition (BuChE: IC₅₀ = 5.24 μM; AChE: IC₅₀ = 0.37 μM) and hMAO-B selectivity (IC₅₀ = 0.272 μM, SI = 247). Molecular modeling and kinetic studies suggested that 5c was a mixed-type inhibitor, binding simultaneously to peripheral and active sites of AChE. It was also a competitive inhibitor, which occupied the substrate and entrance cavities of MAO-B. Moreover, compound 5c could penetrate the blood-brain barrier (BBB) and showed low toxicity to rat pheochromocytoma (PC12) cells. Altogether, these results indicated that compound 5c might be a hopeful multitarget drug candidate with possible impact on Alzheimer's disease therapy.

Chromenones as Multineurotargeting Inhibitors of Human Enzymes

The complex nature of multifactorial diseases, such as Morbus Alzheimer, has produced a strong need to design multitarget-directed ligands to address the involved complementary pathways. We performed a purposive structural modification of a tetratarget small-molecule, that is contilisant, and generated a combinatorial library of 28 substituted chromen-4-ones. The compounds comprise a basic moiety which is linker-connected to the 6-position of the heterocyclic chromenone core. The syntheses were accomplished by Mitsunobu- or Williamson-type ether formations. The resulting library members were evaluated at a panel of seven human enzymes, all of which being involved in the pathophysiology of neurodegeneration. A concomitant inhibition of human acetylcholinesterase and human monoamine oxidase B, with IC₅₀ values of 5.58 and 7.20 μM, respectively, was achieved with the dual-target 6-(4-(piperidin-1-yl)butoxy)-4H-chromen-4-one (7).

A review on flavonoid-based scaffolds as multi-target-directed ligands (MTDLs) for Alzheimer's disease

Alzheimer's disease (AD), the most common form of dementia, is a multifactorial neurodegenerative disease. The target enzymes inhibition including cholinesterase, beta-secretase, monoamine oxidase and inhibition of amyloid-β aggregation as well as oxidative stress and metal chelation play an important role in the pathogenesis of AD. Chroman-4-one scaffold with benzo-γ-pyrone network is a privileged structure in organic synthesis and drug design. A large number of research has been carried out on modified naturally occurring chromanone scaffolds and/or synthesized new analogues, to obtain effective drugs for AD management. The present review summarizes aspects related to the multi-target-directed ligands (MTDLs) strategy in enzyme targets modulation performed with natural and synthesized chroman-4-one-based structures to look at their potential in the management of multifactorial Alzheimer's disease.

Synthesis and pharmacological evaluation of novel chromone derivatives as balanced multifunctional agents against Alzheimer's disease

In a continuing effort to develop multitargeted compounds as potential treatment agents against Alzheimer's disease (AD), a series of chromone derivatives were designed, synthesized and evaluated. In vitro assay indicated that most of the target compounds have both MAOs inhibition activities, antioxidant activity and biometal chelating ability. Especially, compound s19 exhibits good inhibitory potency for inhibition of MAOs (IC₅₀ value of 5.12μM for hMAO-A and 0.816μM for hMAO-B), moderate inhibition of Aβ aggregation (75.1% at 20μM), metal chelation, control of ROS generation and antioxidant activity (ORAC=3.62). In addition, s19 could reduce PC12 cells death induced by oxidative stress and penetrate the blood-brain barrier (BBB). Taken together, these results suggested that s19 might be a promising multitargeted compound for AD treatment.

The Benzopyrone Biochanin-A as a reversible, competitive, and selective monoamine oxidase B inhibitor

Background

Monoamine oxidase-B (MAO-B) inhibitors are widely used in the treatment of Parkinson’s disease. They increase vital monoamine neurotransmitters in the brain. However, there is a need for safer natural reversible MAO inhibitors with MAO-B selectivity. Our previous studies showed that Psoralea corylifolia seeds (PCS) extract contains compounds that inhibit monoamine oxidase-B.

Methods

In this study, six of PCS constituents sharing a benzopyrone structure were investigated. The compounds Biochanin-A (BIO-A), isopsoralen, 6-prenylnaringenin, neobavaisoflavone, psoralen, and psoralidin, were tested for their ability to inhibit recombinant human MAO-A and B (hMAO-A and hMAO-B) isozymes. The ability of these compounds to inhibit MAO-A and MAO-B were compared to that of PCS ethanolic extract (PCSEE) using spectrophotometric assays and confirmed by luminescence assays. The highly potent and selective MAO-B inhibitor, BIO-A, was further investigated for both isozymes reversibility and enzyme kinetics. Molecular docking studies were used to predict the bioactive conformation and molecular interactions of BIO-A with both isozymes.

Results

The data obtained indicate that benzopyrones inhibited hMAO-A and hMAO-B with different degrees as confirmed with the luminescence assay. BIO-A inhibited hMAO-B with high potency and selectivity in the present study (IC₅₀ = 0.003 μg/mL) and showing 38-fold more selectivity than PCSEE (hMAO-B IC₅₀ = 3.03 μg/mL, 17-fold selectivity) without affecting hydrogen peroxide. Furthermore, BIO-A reversibly and competitively inhibited both hMAOs with significantly lower inhibitory constant (K_i) in hMAO-B (3.8 nM) than hMAO-A (99.3 nM). Our docking studies indicated that the H-bonds and hydrophobic interactions at the human MAO-A and MAO-B active sites contributed to the reversibility and selectivity of BIO-A.

Conclusions

The data obtained indicate that BIO-A is a potent, reversible and selective MAO-B inhibitor and may be recommended for further investigation in its possible use in the therapeutic management of Parkinson’s and Alzheimer’s diseases.

Synthesis and evaluation of small molecules bearing a benzyloxy substituent as novel and potent monoamine oxidase inhibitors

A new series of small molecules bearing a benzyloxy substituent have been designed, synthesized and evaluated for hMAO inhibitory activity in vitro. Most of the compounds were potent and selective MAO-B inhibitors, and were weak inhibitors of MAO-A. In particular, compounds 9e (IC₅₀ = 0.35 μM) and 10e (IC₅₀ = 0.19 μM) were the most potent MAO-B inhibitors, and exhibited the highest selectivity for MAO-B (9e, SI > 285.7-fold and 10e, SI = 146.8-fold). In addition, the structure-activity relationships for MAO-B inhibition indicated that electron-withdrawing groups in the open small molecules were more suitable for MAO-B inhibition, and substitutions at the benzyloxy of the open small molecules, particularly with the halogen substituted benzyloxy, were more favorable for MAO-B inhibition. Molecular docking studies have been done to explain the potent MAO-B inhibition of the open small molecules. Furthermore, the representative compounds 9e and 10e showed low neurotoxicity in SH-SY5Y cells in vitro. So the small molecules bearing the benzyloxy substituent could be used to develop promising drug candidates for the therapy of neurodegenerative diseases.

Aurone Mannich base derivatives as promising multifunctional agents with acetylcholinesterase inhibition, anti-β-amyloid aggragation and neuroprotective properties for the treatment of Alzheimer's disease

A series of aurone Mannich base derivatives were designed, synthesized and evaluated as multifunctional agents for the treatment of Alzheimer's disease. In vitro assays demonstrated that most of the derivatives were selective AChE inhibitors with good multifunctional properties. Among them, compound 7d exhibited outstanding inhibitory activity for RatAChE, EeAChE and HuAChE (IC₅₀ = 0.00878 ± 0.0002 μM, 0.0212 ± 0.006 μM and 0.0371 ± 0.004 μM, respectively). Moreover, 7d displayed high antioxidant activity and could confer significant neuroprotective effect against H₂O₂-induced PC-12 cell injury. In addition, 7d also showed biometal chelating abilities, good self- and Cu²⁺-induced Aβ_1-42 aggregation inhibitory potency and high BBB permeability. These multifunctional properties highlight 7d as promising candidate for further studies directed to the development of novel drugs against AD.

Synthesis and pharmacological evaluation of donepezil-based agents as new cholinesterase/monoamine oxidase inhibitors for the potential application against Alzheimer's disease

In a continuing effort to develop multitargeted compounds as potential treatment agents against Alzheimer's disease (AD), a series of donepezil-like compounds were designed, synthesized and evaluated. In vitro studies showed that most of the designed compounds displayed potent inhibitory activities toward AChE, BuChE, MAO-B and MAO-A. Among them, w18 was a promising agent with balanced activities, which exhibited a moderate cholinesterase inhibition (IC₅₀, 0.220 μM for eeAChE; 1.23 μM for eqBuChE; 0.454 μM for hAChE) and an acceptable inhibitory activity against monoamine oxidases (IC₅₀, 3.14 μM for MAO-B; 13.4 μM for MAO-A). Moreover, w18 could also be a metal-chelator, and able to cross the blood-brain barrier with low cell toxicity on PC12 cells. Taken together, these results suggested that w18 might be a promising multitargeted compound for AD treatment.

Synthesis and evaluation of 4-hydroxyl aurone derivatives as multifunctional agents for the treatment of Alzheimer's disease

A series of 4-hydroxyl aurone derivatives were designed synthesized and evaluated as potential multifunctional agents for the treatment of Alzheimer's disease. The results demonstrated that most of the derivatives exhibited good multifunctional properties. Among them, compound 14e displayed good inhibitory activities of self- and Cu(2+)-induced Aβ1-42 aggregation with 99.2% and 84.0% at 25μM, respectively, and high antioxidant activity with a value 1.90-fold of Trolox. In addition, 14e also showed remarkable inhibitory activities of both monoamine oxidase A and B with IC50 values of 0.271μM and 0.393μM, respectively. However the 6-methoxyl aurones 15a-c revealed excellent selectivity toward MAO-B. Furthermore, the representative compounds 14e and 15b displayed good metal-chelating abilities and blood-brain barrier (BBB) permeabilities in vitro.

Evaluation of the Isoflavone Genistein as Reversible Human Monoamine Oxidase-A and -B Inhibitor

Monoamine oxidases inhibitors (MAOIs) are effective therapeutic drugs for managing Parkinson's disease (PD) and depression. However, their irreversibility may lead to rare but serious side effects. As finding safer and reversible MAOIs is our target, we characterized the recombinant human (h) MAO-A and MAO-B inhibition potentials of two common natural isoflavones, genistein (GST) and daidzein (DZ) using luminescence assay. The results obtained showed that DZ exhibits partial to no inhibition of the isozymes examined while GST inhibited hMAO-B (IC₅₀ of 6.81 μM), and its hMAO-A inhibition was more potent than the standard deprenyl. Furthermore, the reversibility, mode of inhibition kinetics, and tyramine oxidation of GST were examined. GST was a time-independent reversible and competitive hMAO-A and hMAO-B inhibitor with a lower K_i of hMAO-B (1.45 μM) than hMAO-A (4.31 μM). GST also inhibited hMAO-B tyramine oxidation and hydrogen peroxide production more than hMAO-A. Docking studies conducted indicated that the GST reversibility and hMAO-B selectivity of inhibition may relate to C5-OH effects on its orientation and its interactions with the threonine 201 residue of the active site. It was concluded from this study that the natural product GST has competitive and reversible MAOs inhibitions and may be recommended for further investigations as a useful therapeutic agent for Parkinson's disease.

Evaluation of the Inhibitory Effects of Bavachinin and Bavachin on Human Monoamine Oxidases A and B

Monoamine oxidase B inhibitors (MAO-BIs) are used in the early management of Parkinson's disease (PD). Long-term suspected side effects of MAO-B classical inhibitors established the need for safer alternative therapeutic agents. In our study, the flavanone bavachinin (BNN) and its analog bavachin (BVN) found in the seeds of Psoralea corylifolia L. ethanolic extract (PCSEE) were investigated for their human MAO-A and MAO-B (hMAO-A and hMAO-B) inhibition. Both PCSEE and BNN effectively reduced hMAO-B activity more than hMAO-A while BVN had activating effects. BNN showed selective hMAO-B inhibition (IC₅₀ ~ 8.82 μM) more than hMAO-A (IC₅₀2009;~ 189.28 μM). BNN in the crude extract was determined by HPLC, also validated by TLC showing a yield of 0.21% PCSEE dry weight. BNN competitively inhibited hMAO-A and hMAO-B, with a lower hMAO-B K_i than hMAO-A K_i by 10.33-fold, and reduced hMAO-B K_m/V_max efficiency ratio to be comparable to the standard selegiline. Molecular docking examination of BNN and BVN predicted an indirect role of BNN C7-methoxy group for its higher affinity, selectivity, and reversibility as an MAO-BI. These findings suggest that BNN, which is known to be a potent PPAR-γ agonist, is a selective and competitive hMAO-B inhibitor and could be used in the management of PD.

Synthesis and Preliminary Biological Evaluation of 1,3,5-Triazine Amino Acid Derivatives to Study Their MAO Inhibitors

Three series of 4,6-dimethoxy-, 4,6-dipiperidino- and 4,6-dimorpholino-1,3,5-triazin-2-yl) amino acid derivatives were synthesized and characterized. A preliminary study for their monoamine oxidase inhibitory activity showed that compounds 7, 18, and 25 had MAO-A inhibition activity comparable to that of the standard clorgyline, with apparently more selective inhibitory activity toward MAO-A than MAO-B and no significant acute toxicity.

Multi-target tacrine-coumarin hybrids: cholinesterase and monoamine oxidase B inhibition properties against Alzheimer's disease

A series of novel tacrine-coumarin hybrids were designed, synthesized and evaluated as multi-target agents against Alzheimer's disease. The biological assays indicated that most of compounds displayed potent inhibitory activity toward AChE and BuChE, and clearly selective inhibition for MAO-B. Among these compounds, 14c exhibited strong inhibitory activity for AChE (IC50 values of 33.63 nM for eeAChE and 16.11 nM for hAChE) and BuChE (IC50 values of 80.72 nM for eqBuChE and 112.72 nM for hBuChE), and the highest inhibitory activity against hMAO-B (IC50 value of 0.24 μM). Kinetic and molecular modeling studies revealed that 14c was a mixed-type inhibitor, binding simultaneously to catalytic, peripheral and mid-gorge sites of AChE. It was also a competitive inhibitor, which covered the substrate and entrance cavities of MAO-B. Moreover, 14c could penetrate the CNS and show low cell toxicity. Overall, these results suggested that 14c might be an excellent multi-target agent for AD treatment.

Chromanones: selective and reversible monoamine oxidase B inhibitors with nanomolar potency

Compound 4f was a potent and selective inhibitor for hMAO-B.

Multifunctional 3-Schiff base-4-hydroxycoumarin derivatives with monoamine oxidase inhibition, anti-β-amyloid aggregation, metal chelation, antioxidant and neuroprotection properties against Alzheimer's disease

These 3-Schiff base-4-hydroxycoumarin derivatives were multifunctional agents with monoamine oxidase inhibition, anti-β-amyloid aggregation, metal chelation, antioxidant and neuroprotection properties against Alzheimer's disease.

Acetophenone derivatives: novel and potent small molecule inhibitors of monoamine oxidase B

Compounds 1j and 2e were both potent and selective MAO-B inhibitors.