MAOIs Research Articles

70-year history of studying the effectiveness of therapy of patients with depression with antidepressants - irreversible nonselective monoamine oxidase inhibitors

The history of studying the effectiveness of therapy of patients with depression by irreversible non-selective monoamine oxidase inhibitors (MAOIs) is analyzed and systematized. Authors describe the stages of the appearance of the first data on the effectiveness of treatment by the first representatives (the 50s of the XX century), the targeted study of the effectiveness of the use of numerous «new» representatives and the emergence of disagreements in assessing the power of therapy (the end of the 50s-60s of the XX century), continuing to study the effectiveness of treatment by representatives who remained in clinical practice, and establishing its clinical predictors (80s-90s of the XX century), the appearance of the first data on the effectiveness of therapy for «atypical depression» (1959-1960) and further development of this issue (80s-90s of the XX century). The stage of formation and development of the idea of the effectiveness of treatment for resistant depression (late 70s-90s of the XX century) is characterized. Separately, the history of studying the effectiveness of application in the USSR and Russia (late 50s- 90s of the XX century) is outlined. The current state of the issue of assessing the effectiveness of therapy (the end of the 90s of the XX century - 2022) is shown.

Evolution of ideas about the risk of tyramine syndrome developing during therapy with irreversible non-selective monoamine oxidase inhibitors (to the 70th anniversary of the first use of this group of antidepressants)

We describe the history of studying of the problem of tyramine syndrome during the treatment with antidepressants, irreversible non-selective monoamine oxidase inhibitors. Data on clinical observations are presented. Early hypotheses of pathogenesis are considered. The period of discovery of the relationship between increased blood pressure and the use of foods containing tyramine is outlined. The transformation of terminology is demonstrated. The events associated with the restriction of the use of therapy are characterized. The formation of the opinion about the exaggeration of the risk of developing tyramine syndrome is analyzed. Data on the involvement in the discussion of the problem of tyramine syndrome of society as a whole are given.

Monoamine Oxidase Inhibitors Prevent Glucose-Dependent Energy Production, Proliferation and Migration of Bladder Carcinoma Cells.

Bladder cancer is the 10th most common cancer in the world and has a high risk of recurrence and metastasis. In order to sustain high energetic needs, cancer cells undergo complex metabolic adaptations, such as a switch toward aerobic glycolysis, that can be exploited therapeutically. Reactive oxygen species (ROS) act as key regulators of cancer metabolic reprogramming and tumorigenesis, but the sources of ROS remain unidentified. Monoamine oxidases (MAOs) are mitochondrial enzymes that generate H2O2 during the breakdown of catecholamines and serotonin. These enzymes are particularly important in neurological disorders, but recently, a new link between MAOs and cancer has been uncovered, involving their production of ROS. At present, the putative role of MAOs in bladder cancer has never been evaluated. We observed that human urothelial tumor explants and the bladder cancer cell line AY27 expressed both MAO-A and MAO-B isoforms. Selective inhibition of MAO-A or MAO-B limited mitochondrial ROS accumulation, cell cycle progression and proliferation of bladder cancer cells, while only MAO-A inhibition prevented cell motility. To test whether ROS contributed to MAO-induced tumorigenesis, we used a mutated form of MAO-A which was unable to produce H2O2. Adenoviral transduction of the WT MAO-A stimulated the proliferation and migration of AY27 cells while the Lys305Met MAO-A mutant was inactive. This was consistent with the fact that the antioxidant Trolox strongly impaired proliferation and cell cycle progression. Most interestingly, AY27 cells were highly dependent on glucose metabolism to sustain their growth, and MAO inhibitors potently reduced glycolysis and oxidative phosphorylation, due to pyruvate depletion. Accordingly, MAO inhibitors decreased the expression of proteins involved in glucose transport (GLUT1) and transformation (HK2). In conclusion, urothelial cancer cells are characterized by a metabolic shift toward glucose-dependent metabolism, which is important for cell growth and is under the regulation of MAO-dependent oxidative stress.

Phytoestrogen Coumestrol Selectively Inhibits Monoamine Oxidase-A and Amyloid β Self-Aggregation.

Pueraria lobata leaves contain a variety of phytoestrogens, including flavonoids, isoflavonoids, and coumestan derivatives. In this study, we aimed to identify the active ingredients of P. lobata leaves and to elucidate their function in monoamine oxidase (MAO) activation and Aβ self-aggregation using in vitro and in silico approaches. To the best of our knowledge, this is the first study to elucidate coumestrol as a selective and competitive MAO-A inhibitor. We identified that coumestrol, a coumestan-derivative, exhibited a selective inhibitory effect against MAO-A (IC50 = 1.99 ± 0.68 µM), a key target protein for depression. In a kinetics analysis with 0.5 µg MAO-A, 40–160 µM substrate, and 25 °C reaction conditions, coumestrol acts as a competitive MAO-A inhibitor with an inhibition constant of 1.32 µM. During an in silico molecular docking analysis, coumestrol formed hydrogen bonds with FAD and pi–pi bonds with hydrophobic residues at the active site of the enzyme. Moreover, based on thioflavin-T-based fluorometric assays, we elucidated that coumestrol effectively prevented self-aggregation of amyloid beta (Aβ), which induces an inflammatory response in the central nervous system (CNS) and is a major cause of Alzheimer’s disease (AD). Therefore, coumestrol could be used as a CNS drug to prevent diseases such as depression and AD by the inhibition of MAO-A and Aβ self-aggregation.

Natural Products Inhibitors of Monoamine Oxidases—Potential New Drug Leads for Neuroprotection, Neurological Disorders, and Neuroblastoma

Monoamine oxidase inhibitors (MAOIs) are an important class of drugs prescribed for treatment of depression and other neurological disorders. Evidence has suggested that patients with atypical depression preferentially respond to natural product MAOIs. This review presents a comprehensive survey of the natural products, predominantly from plant sources, as potential new MAOI drug leads. The psychoactive properties of several traditionally used plants and herbal formulations were attributed to their MAOI constituents. MAO inhibitory constituents may also be responsible for neuroprotective effects of natural products. Different classes of MAOIs were identified from the natural product sources with non-selective as well as selective inhibition of MAO-A and -B. Selective reversible natural product MAOIs may be safer alternatives to the conventional MAOI drugs. Characterization of MAO inhibitory constituents of natural products traditionally used as psychoactive preparations or for treatment of neurological disorders may help in understanding the mechanism of action, optimization of these preparations for desired bioactive properties, and improvement of the therapeutic potential. Potential therapeutic application of natural product MAOIs for treatment of neuroblastoma is also discussed.

Quinazolinone-based benzenesulfonamides with low toxicity and high affinity as monoamine oxidase-A inhibitors: Synthesis, biological evaluation and induced-fit docking studies

The research in selective monoamine oxidases (MAO-A and MAO-B) inhibitors has been increased due to their therapeutic value for neurodegenerative diseases. In this study, 4-((2-(aryl)-4-oxoquinazolin-3(4H)-yl)amino)benzenesulfonamides were synthesized and their MAOs inhibition potentials were investigated applying in vitro fluorometric technique. The most potent compounds 7 and 8 against MAO-A had IC50 values of 0.058 ± 0.002 and 0.094 ± 0.003 µM, respectively, while the reference moclobemide had an IC50 value of 6.061 µM. Compounds 7 (>1724 times) and 8 (>1063 times) more selective and reversible inhibitors of MAO-A rather than MAO-B. Toxicity studies of 7 (IC50 = 210.23 µM) and 8 (IC50 = 259.27 µM) showed that compounds can be considered as non-toxic towards SH-SY5Y cell line at their effective concentrations against MAO-A. In silico docking simulations successfully explained the observed activities and also highlighted structural water molecules to play a key role in the ligand-enzyme interactions. Calculated molecular descriptors are also obeying Lipinski’s rule of five and brain/blood partition coefficients, a critical parameter in neurodegenerative diseases. These reversible inhibitors can have considerable advantages compared to irreversible inhibitors which may possess serious pharmacological side effects.

The evaluation of N-propargylamine-2-aminotetralin as an inhibitor of monoamine oxidase

Monoamine oxidase B (MAO-B) inhibitors are established therapy for Parkinson’s disease and act, in part, by blocking the MAO-catalysed metabolism of dopamine in the brain. Two propargylamine-containing MAO-B inhibitors, selegiline [(R)-deprenyl] and rasagiline, are currently used in the clinic for this purpose. These compounds are mechanism-based inactivators and, after oxidative activation, form covalent adducts with the FAD co-factor. An important consideration is that selegiline and rasagiline display specificity for MAO-B over the MAO-A isoform thus reducing the risk of tyramine-induced changes in blood-pressure. In the interest of discovering new propargylamine MAO inhibitors, the present study synthesises racemic N-propargylamine-2-aminotetralin (2-PAT), a compound that may be considered as both a six-membered ring analogue of rasagiline and a semi-rigid N-desmethyl ring-closed analogue of selegiline. The in vitro human MAO inhibition properties of this compound were measured and the results showed that 2-PAT is a 20-fold more potent inhibitor of MAO-A (IC50 = 0.721 µM) compared to MAO-B (IC50 = 14.6 µM). Interestingly, dialysis studies found that 2-PAT is a reversible MAO-A inhibitor, while acting as an inactivator of MAO-B. Since reversible MAO-A inhibitors are much less liable to potentiate tyramine-induced side effects than MAO-A inactivators, it is reasonable to suggest that 2-PAT could be a useful and safe therapeutic agent for disorders such as Parkinson’s disease and depression.

Molecular Modeling and Experimental Evaluation of Non-Chiral Components of Bergamot Essential Oil with Inhibitory Activity against Human Monoamine Oxidases.

Human monoamine oxidases (hMAOs) are well-established targets for the treatment of neurological disorders such as depression, Parkinson’s disease and Alzheimer’s disease. Despite the efforts carried out over the years, few selective and reversible MAO inhibitors are on the market. Thus, a continuous search for new compounds is needed. Herein, MAO inhibitors were searched among the non-chiral constituents of Bergamot Essential Oil (BEO) with the aid of computational tools. Accordingly, molecular modeling simulations were carried out on both hMAO-A and hMAO-B for the selected constituents. The theoretically predicted target recognition was then used to select the most promising compounds. Among the screened compounds, Bergamottin, a furocoumarin, showed selective hMAO-B inhibitory activity, fitting its active site well. Molecular dynamics simulations were used to deeply analyze the target recognition and to rationalize the selectivity preference. In agreement with the computational results, experimental studies confirmed both the hMAO inhibition properties of Bergamottin and its preference for the isoform B.

GABAA Receptor-Stabilizing Protein Ubqln1 Affects Hyperexcitability and Epileptogenesis after Traumatic Brain Injury and in a Model of In Vitro Epilepsy in Mice.

Posttraumatic epilepsy (PTE) is a major public health concern and strongly contributes to human epilepsy cases worldwide. However, an effective treatment and prevention remains a matter of intense research. The present study provides new insights into the gamma aminobutyric acid A (GABAA)-stabilizing protein ubiquilin-1 (ubqln1) and its regulation in mouse models of traumatic brain injury (TBI) and in vitro epilepsy. We performed label-free quantification on isolated cortical GABAergic interneurons from GAD67-GFP mice that received unilateral TBI and discovered reduced expression of ubqln1 24 h post-TBI. To investigate the link between this regulation and the development of epileptiform activity, we further studied ubqln1 expression in hippocampal and cortical slices. Epileptiform events were evoked pharmacologically in acute brain slices by administration of picrotoxin (PTX, 50 μM) and kainic acid (KA, 500 nM) and recorded in the hippocampal CA1 subfield using Multi-electrode Arrays (MEA). Interestingly, quantitative Western blots revealed significant decreases in ubqln1 expression 1–7 h after seizure induction that could be restored by application of the non-selective monoamine oxidase inhibitor nialamide (NM, 10 μM). In picrotoxin-dependent dose–response relationships, NM administration alleviated the frequency and peak amplitude of seizure-like events (SLEs). These findings indicate a role of the monoamine transmitter systems and ubqln1 for cortical network activity during posttraumatic epileptogenesis.

Site-activated multi target iron chelators with acetylcholinesterase (AChE) and monoamine oxidase (MAO) inhibitory activities for Alzheimer's disease therapy.

The first class of site-activated chelators with dual inhibition of acetyl-cholinesterase (AChE) and monoamine oxidase (MAO), rationally designed for simultaneously targeting the multiple pathogenic processes in Alzheimer's disease (AD) without significantly disrupting healthy metal metabolism in the body are discussed. It is demonstrated that the novel prochelator 2 was a selective and potent MAO-A inhibitor in vitro (IC50: 0.0077 ± 0.0007μM) with moderate inhibition of MAO-B (IC50: 7.90 ± 1.34μM). In vitro prochelator 2 also selectively inhibited AChE in a time-dependent manner and reach maximum inhibition of AChE after 2h preincubation (IC50: 0.52 ± 0.07μM for AChE, versus 44.90 ± 6.10μM for BuChE). Prochelator 2 showed little affinity for metal (Fe, Cu, and Zn) ions until it bound to and was activated by AChE that is located predominately in the brain, releasing an active iron chelator M30. M30 is an efficient chelator for metal (Fe, Cu, and Zn) ions with the capabilities to suppress oxidative stress, to selectively inhibit MAO-A and B in the brain, and to regulate cerebral biometals dyshomeostasis in vivo; M30 is also a neuroprotective-neurorestorative chelator with a broad spectrum of activities against β-amyloid (Aβ) generation, amyloid plaques and neurofibrillary tangles (NFT) formation, and Aβ aggregation induced by metal (Cu and Zn) ions. Both M30 and prochelator 2 were not toxic to Human SH-SY5Y neuroblastoma cells at low concentrations, but prochelator 2 shows limited cytotoxicity, at high concentrations. Together, these data suggest that prochelator 2 is a promise lead for simultaneously modulating multiple targets in AD.

The inhibition of monoamine oxidase by harmine derivatives

The monoamine oxidase (MAO) enzymes are established targets for the treatment of neuropsychiatric and neurodegenerative disorders. Inhibitors of MAO-A have been used for many decades in the treatment of depression while MAO-B inhibitors are used in Parkinson’s disease therapy. Harmine is one of many MAO inhibitors described in literature, and is a high potency reversible inhibitor of MAO-A (IC50 = 0.0041 µM). Even though the structures of MAO-A and MAO-B are highly similar, particularly the architectures of their active sites, harmine is not an inhibitor of MAO-B. Based on an academic interest in discovering novel MAO inhibitors, the present study synthesised series of harmine and related carbazole derivatives, and investigated their in vitro human MAO inhibition properties. Among 21 compounds synthesised, 7 compounds inhibited MAO-A with IC50 < 0.1 µM, while 3 compounds inhibited MAO-B with IC50 < 0.1 µM. The most potent MAO-A inhibitor (1f) exhibited an IC50 value of 0.0049 µM, while the most potent MAO-B inhibitor (1c) exhibited an IC50 value of 0.024 µM. An analysis of the structure–activity relationships for MAO inhibition shows that a large substituent (e.g., benzyloxy) is well tolerated on position 7 of harmine, while similar substitution on position 2 of carbazole resulted in no MAO-A inhibition. In contrast, substitution on position 4 of carbazole yielded, in certain instances, active MAO-A inhibitors. Interestingly, substitution on position 7 of harmine yielded good potency MAO-B inhibitors. In certain instances, substitution on positions 2 and 4 of carbazole also yielded active MAO-B inhibitors. Molecular docking suggests that electronic properties rather that steric factors are responsible for the potent MAO inhibition observed for β-carboline compounds compared to the carbazoles. This study concludes that active inhibitors identified in this study may serve as leads for the future development of drugs for the treatment of neuropsychiatric and neurodegenerative disorders.

Management of Psychiatric Disorders in Patients with Hepatic and Gastrointestinal Diseases.

Management of Psychiatric Disorders in Patients with Hepatic and Gastrointestinal Diseases.

Indoles and 1-(3-(benzyloxy)benzyl)piperazines: Reversible and selective monoamine oxidase B inhibitors identified by screening an in-house compound library

The therapeutic indications for monoamine oxidases A and B (MAO-A and MAO-B) inhibitors that have emerged from biological studies on animal and cellular models of neurological and oncological diseases have focused drug discovery projects upon identifying reversible MAO inhibitors. Screening of our in-house academic compound library identified two hit compounds that inhibit MAO-B with IC50 values in micromolar range. Two series of indole (23 analogues) and 3-(benzyloxy)benzyl)piperazine (16 analogues) MAO-B inhibitors were derived from hits, and screened for their structure-activity relationships. Both series yielded low micromolar selective inhibitors of human MAO-B, namely indole 2 (IC50 = 12.63 ± 1.21 µM) and piperazine 39 (IC50 = 19.25 ± 4.89 µM), which is comparable to selective MAO-B inhibitor isatin (IC50 = 6.10 ± 2.81 µM), yet less potent in comparison to safinamide (IC50 = 0.029 ± 0.002 µM). Selective MAO-B inhibitors 2, 14, 38 and 39 exhibited favourable permeation of the blood-brain barrier and low cytotoxicity in the human neuroblastoma cell line SH-SY5Y.

Novel thiazolyl-hydrazone derivatives including piperazine ring: synthesis, in vitro evaluation, and molecular docking as selective MAO-A inhibitor.

MAO-A inhibitors are used in the treatment of depression. There are many studies showing that the thiazolyl-hydrazone structure is a pharmacophore structure for the MAO enzyme. In previous studies by our team, activity studies were carried out with thiazolyl-hydrazone derivatives containing pyrrolidine, morpholine, and piperazine. All of them were displayed MAO-A selective inhibition profile. Additionally, derivatives containing piperazine ring were most active. For this purpose, thiazolyl-hydrazone derivatives containing piperazine were synthesized, but this time an active group, formyl group, was added to the piperazine ring as a substituent. Based on this view, new thiazolyl-hydrazone compounds were synthesized, characterized, and screened for their hMAO-A and hMAO-B inhibitory activity by an in vitro fluorometric method. The structure of the compound was tried to be fully elucidated using 2D NMR technique. The compound including 2,4-dimethyl substituent (3i) were found to be the most effective agents in the series against MAO-A enzyme with the IC50 value of 0.080±0.003µM. The docking study of compound 3i revealed that there is a strong interaction between the active sites of hMAO-A and analyzed compound.

Potent and Selective Inhibitors of Human Monoamine Oxidase A from an Endogenous Lichen Fungus Diaporthe mahothocarpus.

Using 126 endogenous lichen fungus (ELF) extracts, inhibitory activities against monoamine oxidases (MAOs) and cholinesterases (ChEs) were evaluated. Among them, extract ELF29 of the endogenous fungus Diaporthe mahothocarpus of the lichen Cladonia symphycarpia showed the highest inhibitory activity against hMAO-A. Compounds alternariol (AT), 5′-hydroxy-alternariol (HAT), and mycoepoxydiene (MED), isolated from the extract, had potent inhibitory activities against hMAO-A with IC50 values of 0.020, 0.31, and 8.68 µM, respectively. AT, HAT, and MED are reversible competitive inhibitors of hMAO-A with Ki values of 0.0075, 0.116, and 3.76 µM, respectively. The molecular docking studies suggested that AT, HAT, and MED had higher binding affinities for hMAO-A (−9.1, −6.9, and −5.6 kcal/mol, respectively) than for hMAO-B (−6.3, −5.2, and −3.7 kcal/mol, respectively). The relative tight binding might result from a hydrogen bond interaction of the three compounds with a Tyr444 residue in hMAO-A, whereas no hydrogen bond interaction was proposed in hMAO-B. In silico pharmacokinetics, the three compounds showed high gastrointestinal absorption without violating Lipinski’s five rules, but only MED showed high probability to cross the blood–brain barrier. These results suggest that AT, HAT, and MED are candidates for treating neuropsychiatric disorders, such as depression and cardiovascular disease.

Monoamine Oxidase (MAO) as a Potential Target for Anticancer Drug Design and Development.

Monoamine oxidases (MAOs) are oxidative enzymes that catalyze the conversion of biogenic amines into their corresponding aldehydes and ketones through oxidative deamination. Owing to the crucial role of MAOs in maintaining functional levels of neurotransmitters, the implications of its distorted activity have been associated with numerous neurological diseases. Recently, an unanticipated role of MAOs in tumor progression and metastasis has been reported. The chemical inhibition of MAOs might be a valuable therapeutic approach for cancer treatment. In this review, we reported computational approaches exploited in the design and development of selective MAO inhibitors accompanied by their biological activities. Additionally, we generated a pharmacophore model for MAO-A active inhibitors to identify the structural motifs to invoke an activity.

Treatment of antipsychotic-induced parkinsonism in schizophrenic patients

Antipsychotic-induced parkinsonism (AIP) is one of the prognostically unfavorable complications of psychopharmacotherapy in patients with schizophrenia. Many studies have investigated various drugs that are used to treat this neurological side effect. This review analyzes drugs that are used and may be perspective for the treatment of AIP. We searched for full-text publications in Russian and English in the following databases: E-Library, PubMed, Web of Science, Springer, using keywords and combined word searches over the past decade (2011—2020). The review covers drugs that are promising for the correction of AIP, including anticholinergic drugs; NMDA receptor antagonists; dopamine receptor agonists; selective inhibitors of monoamine oxidase B; catecholamine transferase inhibitors; melatonin preparations; melatonin receptor agonists; benzodiazepines; herbal preparations traditionally used for the prevention and correction of extrapyramidal syndrome of various etiologies. Currently, a small number of medications are used in clinical practice for the treatment of AIP. However, not all of them are registered in the Russian Federation. Along with the differences in the mechanisms of AIP pathogenesis in specific patients, the limited choice of AIP treatments makes it difficult to solve the problem of adverse neurological complications of psychopharmacotherapy in schizophrenia.

Chromenone Derivatives as Monoamine Oxidase Inhibitors from Marine-Derived MAR4 Clade Streptomyces sp. CNQ-031.

Three compounds were isolated from marine-derived Streptomyces sp. CNQ-031, and their inhibitory activities against monoamine oxidases (MAOs), acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and β-secretase (BACE-1) were evaluated. Compound 1 (5,7-dihydroxy-2-isopropyl-4H-chromen-4-one) was a potent and selective inhibitor of MAO-A, with a 50% inhibitory concentration (IC50) of 2.70 μM and a selectivity index (SI) of 10.0 versus MAO-B. Compound 2 [5,7-dihydroxy-2-(1-methylpropyl)-4H-chromen-4-one] was a potent and low-selective inhibitor of MAO-B, with an IC50 of 3.42 μM and an SI value of 2.02 versus MAO-A. Compound 3 (1-methoxyphenazine) did not inhibit MAO-A or MAO-B. All three compounds showed little inhibitory activity against AChE, BChE, and BACE-1. The Ki value of compound 1 for MAO-A was 0.94 ± 0.28 μM, and the Ki values of compound 2 for MAO-A and MAO-B were 3.57 ± 0.60 and 1.89 ± 0.014 μM, respectively, with competitive inhibition. The 1-methylpropyl group in compound 2 increased the MAO-B inhibitory activity compared with the isopropyl group in compound 1. Inhibition of MAO-A and MAO-B by compounds 1 and 2 was recovered by dialysis experiments. These results suggest that compounds 1 and 2 are reversible, competitive inhibitors of MAOs and can be considered potential therapies for neurological disorders such as depression and Alzheimer's disease.

Mapping Chromone-3-Phenylcarboxamide Pharmacophore: Quid Est Veritas?

Chromone-3-phenylcarboxamides (Crom-1 and Crom-2) were identified as potent, selective, and reversible inhibitors of human monoamine oxidase B (hMAO-B). Since they exhibit some absorption, distribution, metabolism, and excretion (ADME)-toxicity liabilities, new derivatives were synthesized to map the chemical structural features that compose the pharmacophore, a process vital for lead optimization. Structure-activity relationship data, supported by molecular docking studies, provided a rationale for the contribution of the heterocycle's rigidity, the carbonyl group, and the benzopyran heteroatom for hMAO-B inhibitory activity. From the study, N-(3-chlorophenyl)-4H-thiochromone-3-carboxamide (31) (hMAO-B IC50 = 1.52 ± 0.15 nM) emerged as a reversible tight binding inhibitor with an improved pharmacological profile. In in vitro ADME-toxicity studies, compound 31 showed a safe cytotoxicity profile in Caco-2, SH-SY5Y, HUVEC, HEK-293, and MCF-7 cells, did not present cardiotoxic effects, and did not affect P-gp transport activity. Compound 31 also protected SH-SY5Y cells from iron(III)-induced damage. Collectively, these studies highlighted compound 31 as the first-in-class and a suitable candidate for in vivo preclinical investigation.

Synthesis of N′-(4-/3-/2-/Non-substituted benzylidene)-4-[(4-methylphenyl)sulfonyloxy] Benzohydrazides and Evaluation of Their Inhibitory Activities against Monoamine Oxidases and β-Secretase

Nineteen tosylated acyl hydrazone derivatives were synthesized, and their inhibitory activities against monoamine oxidases (MAOs), acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and β-secretase (BACE-1) were evaluated. Compound 3o was the most potent inhibitor of MAO-A, with an IC50 value of 1.54 µM, followed by 3a (IC50 = 3.35 µM). A structural comparison with 3a indicated that the 3-F group in 3o increased its inhibitory activity against MAO-A. Compound 3s was the most potent inhibitor of MAO-B, with an IC50 value of 3.64 µM, followed by 3t (IC50 = 5.69 µM). The MAO-B inhibitory activity increased in the order of 3- &gt; 4- &gt; 2-NO2 groups in 3s, 3t, and 3r, respectively. All the compounds weakly inhibited AChE and BChE, which retained &gt;50% residual activity at 10 µM, except for 3a, which inhibited BChE with an IC50 value of 16.1 µM. Interestingly, 3e, 3f, and 3n inhibited BACE-1 with IC50 values of 8.63, 9.92, and 8.47 µM, respectively, which were lower than the IC50 of the quercetin reference. Compounds 3o and 3s were found to be reversible competitive inhibitors of MAO-A and MAO-B, respectively, with Ki values of 0.35 ± 0.074 and 1.97 ± 0.65 µM, respectively. Moreover, compounds 3e, 3f, and 3n were effective BACE-1 inhibitors. The lead molecules were further investigated by molecular docking studies to elucidate the binding interactions with the target enzymes.