Cu-promoted synthesis of triclosan-Mannich and Glaser adducts: anti-mycobacterial evaluation with in silico validations.

Aim: The WHO, Global tuberculosis report 2022 estimated number of tuberculosis (TB) cases reached 10.6 million in 2021, reflecting a 4.5% increase compared with the 10.1 million reported in 2020. The incidence rate of TB showed 3.6% rise from 2020 to 2021. Results/methodology: This manuscript discloses Cu-promoted single pot A3-coupling between triclosan (TCS)-based alkyne, formaldehyde and secondary amines to yield TCS-based Mannich adducts. Additionally, the coupling of TCS-alkynes in the presence of Cu(OAc)2 afforded the corresponding homodimers. Among tested compounds, the most potent one in the series 11 exhibited fourfold higher potency than rifabutin against drug-resistant Mycobacterium abscessus. The selectivity index was also substantially improved, being 26 (day 1) and 15 (day 3), which is four-times better than TCS.

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Discovery of novel 3-butyl-6-benzyloxyphthalide Mannich base derivatives as multifunctional agents against Alzheimer's disease.

Based on the multitarget-directed ligands strategy, a series of 3-butyl-6-benzyloxyphthalide Mannich base derivatives were designed, synthesized and identified for Alzheimer's disease (AD). Biological activity studies demonstrated that the designed hybrids showed multitarget activities toward AD. Among them, compound 7d was the most potent agent with excellent inhibitory activities on EeAChE (IC50 = 0.087 µM), HuAChE (IC50 = 0.041 µM) and MAO-B (IC50 = 0.30 µM). Furthermore, molecular docking studies were conducted to investigate the interaction mode with enzymes. Besides, 7d also possessed good effects of Cu2+ chelation, ameliorate oxidative stress, and anti-neuroinflammation, desirable BBB permeability and eligible drug-like properties. Altogether, the multifunctional profiles of 7d prove that it deserves further investigation as a novel drug candidate for AD treatment.

1,3,4-Oxadiazole N-Mannich Bases: Synthesis, Antimicrobial, and Anti-Proliferative Activities.

The reaction of 5-(3,4-dimethoxyphenyl)-1,3,4-oxadiazole-2(3H)-thione 3 with formaldehyde solution and primary aromatic amines or 1-substituted piperazines, in ethanol at room temperature yielded the corresponding N-Mannich bases 3-arylaminomethyl-5-(3,4-dimethoxyphenyl)-1,3,4-oxadiazole-2(3H)-thiones 4a-l or 3-[(4-substituted piperazin-1-yl)methyl]-5-(3,4-dimethoxyphenyl)-1,3,4-oxadiazole-2(3H)-thiones 5a-d, respectively. The in vitro inhibitory activity of compounds 4a-l and 5a-d was assessed against pathogenic Gram-positive, Gram-negative bacteria, and the yeast-like pathogenic fungus Candida albicans. The piperazinomethyl derivatives 5c and 5d displayed broad-spectrum antibacterial activities the minimal inhibitory concentration (MIC) 0.5-8 µg/mL) and compounds 4j, 4l, 5a, and 5b showed potent activity against the tested Gram-positive bacteria. In addition, the anti-proliferative activity of the compounds was evaluated against prostate cancer (PC3), human colorectal cancer (HCT-116), human hepatocellular carcinoma (HePG-2), human epithelioid carcinoma (HeLa), and human breast cancer (MCF7) cell lines. The optimum anti-proliferative activity was attained by compounds 4l, 5a, 5c, and 5d.

Novel 3-benzylidene/benzylphthalide Mannich base derivatives as potential multifunctional agents for the treatment of Alzheimer's disease.

To discover novel multifunctional agents for the treatment of Alzheimer's disease, a series of 3-benzylidene/benzylphthalide Mannich base derivatives were designed, synthesized and evaluated. The biological screening results indicated that most of these derivatives exhibited good multifunctional activities. Among them, compound (Z)-13c raised particular interest because of its excellent multifunctional bioactivities. It displayed excellent EeAChE and HuAChE inhibition (IC50 = 9.18 × 10-5 and 6.16 × 10-4 µM, respectively), good MAO-B inhibitory activity (IC50 = 5.88 µM) and high antioxidant activity (ORAC = 2.05 Trolox equivalents). Additionally, it also exhibited good antiplatelet aggregation activity, moderate self- and Cu2+-induced Aß1-42 aggregation inhibitory potency, disaggregation ability on Aß1-42 fibrils, biometal chelating ability, appropriate BBB permeability and significant neuroprotective effect. Furthermore, (Z)-13c can also ameliorate the learning and memory impairment induced by scopolamine in mice. These multifunctional properties highlight compound (Z)-13c as a promising candidate for further development of multifunctional drug against AD.

Synthesis, design, and assessment of novel morpholine-derived Mannich bases as multifunctional agents for the potential enzyme inhibitory properties including docking study.

The synthesized Schiff Bases were reacted with formaldehyde and secondary amine such as 2,6-dimethylmorpholine to afford N-Mannich bases through the Mannich reaction. 3-Substitued-4-(4-hydroxybenzylidenamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (4) were treated with 2,6-dimethylmorpholine in the presence of formaldehyde to synthesize eight new 1-(2,6-dimethylmorpholino-4-yl-methyl)-3-substitued-4-(4-hydroxybenzylidenamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (4a-h). The structures of the synthesized eight new compounds were characterized using IR, 1H NMR, 13C NMR, and HR-MS spectroscopic methods. Synthesized compounds inhibitory activity determined against the acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and glutathione S-transferase (GST) enzymes with Ki values in the range 25.23-42.19 µM for AChE, 19.37-34.22 µM for BChE, and 21.84-41.14 µM for GST, respectively. Binding scores of most active inhibitors against AChE, BChE, and GST enzymes were detected as -10.294 kcal/mol, -9.562 kcal/mol, and -7.112 kcal/mol, respectively. The hydroxybenzylidene moiety of the most active inhibitors caused to inhibition of the enzymes through hydrophobic interaction and hydrogen bond.

Evaluation of Water-Soluble Mannich Base Prodrugs of 2,3,4,5-Tetrahydroazepino[4,3-b]indol-1(6H)-one as Multitarget-Directed Agents for Alzheimer's Disease.

Different Mannich base derivatives have been studied with the aim of addressing the poor aqueous solubility of the recently disclosed 6-phenethyl-2,3,4,5-tetrahydroazepino[4,3-b]indol-1(6H)-one (1), a human butyrylcholinesterase inhibitor (hBChE, IC50 13 nM) and protective agent in NMDA-induced neurotoxicity, in in vivo assays. The N-(4-methylpiperazin-1-yl)methyl derivative 2 c showed a 50-fold increase in solubility in pH 7.4-buffered solution, high stability in serum and (half-life >24 h) and rapid (<3 min) conversion to 1 at acidic pH. Although less active than 1, 2 c retained moderate hBChE inhibition (IC50 =3.35 µM) and a significant protective effect against NMDA-induced neurotoxicity at 0.1 µM. Moreover, 2 c resulted a weaker serum albumin binder than 1, could pass the blood-brain barrier, and exerted negligible cytotoxicity on HepG2 cells. These findings suggest that 2 c could be a water-soluble prodrug candidate of 1 for oral administration or a slow-release injectable derivative in in vivoAlzheimer's disease models.

Synthesis, anti-inflammatory activity, and molecular docking studies of some novel Mannich bases of the 1,3,4-oxadiazole-2(3H)-thione scaffold.

A series of novel ibuprofen and salicylic acid-based 3,5-disubstituted-1,3,4-oxadiazole-2(3H)-thione derivatives was synthesized, and they were evaluated as potential anti-inflammatory agents. Following the structure identification studies employing IR, 1 H nuclear magnetic resonance (NMR), 13 C NMR, and elemental analysis, the title compounds were tested by cyclooxygenase (COX)-1 and COX-2 inhibition assays concomitant to lipopolysaccharide (LPS)-induced nitric oxide and prostaglandin production prevention experiments. The results indicated that the majority of the compounds displayed either a superior or comparable activity in preventing both LPS-induced NO production and COX-1 activity in comparison to the activities of the reference molecules. Furthermore, docking studies were also performed to reveal possible interactions with the COX enzymes.

Design, synthesis and antifungal activity of pterolactam-inspired amide Mannich bases.

Pterolactam (5-methoxypyrrolidin-2-one) is a heterocycle naturally occurring in plants. In an attempt to identify antifungal agents, a series of novel Mannich bases of amide derivated from Pterolactam have been designed, synthesized and their antifungal activities were evaluated on a panel of nine fungal strains and three non albicans candida yeasts species which have demonstrated reduced susceptibility to commonly used antifungal drugs. A third of the target compounds exhibited good to high antifungal activities on at least one strain with EC50 lower than the control antifungal agent. N,N'-aminals derivated from Pterolactam proved to be good candidates for the development of biosourced fungicides, with compound 3o being the most broader-spectrum agent, active against five strains and devoted of any cytotoxicity.

Mechanistic details of amino acid catalyzed two-component Mannich reaction: experimental study backed by density functional calculations.

The role of pH-dependent ionic structures of L-amino acids in catalysis has been investigated for the two-component Mannich reactions between dimethyl malonate (DMM)/ethyl acetoacetate (EAA) and imines. As catalysts, L-amino acids performed well, even better than corresponding base catalysts and provided the ß-amino carbonyl compounds in very high yields. Density functional calculations were used to gain the mechanistic insight of the reaction. High catalytic efficiency of amino acids was attributed to the facile formation of carbanion intermediate through barrierless transition state TS1 (- 19.43 kcal/mol) and then its stabilization owing to carbanion interaction with protonated amino acid.

Antiparasitic activities of new lawsone Mannich bases.

A series of new lawsone Mannich bases derived from salicylaldehydes or nitrofurfural were prepared and tested for their activities against Leishmania major, Toxoplasma gondii, and Trypanosoma brucei brucei parasites. The hydrochloride salts 5a and 6a of the Mannich bases 2a and 3a, derived from unsubstituted salicylaldehyde and long-chained alkyl amines, were selectively and strongly active against T. gondii cells and appear to be new promising drug candidates against this parasite. Compound 6a showed an even higher activity against T. gondii than the known lawsone Mannich base 1b. Compound 4a, derived from salicylaldehyde and 2-methylaminopyridine, was also distinctly active against T. gondii cells. The derivatives 3a (salicyl derivative), 3b (3,5-dichloro-2-hydroxyphenyl derivative), and 3d (5-nitrofuranyl derivative) as well as the hydrochlorides 6a and 6b were also efficacious against T. b. brucei cells with compounds 3a and 3b being more selective for T. b. brucei over Vero cells when compared with the known control compound 1b. The derivatives 5a, 5c, 6a, and 6c proved to be up to five times more active than 1b against L. major promastigotes and up to four times more efficacious against L. major amastigotes.

Rational modification of Mannich base-type derivatives as novel antichagasic compounds: Synthesis, in vitro and in vivo evaluation.

The current chemotherapy against Chagas disease is inadequate and insufficient. A series of ten Mannich base-type derivatives have been synthesized to evaluate their in vitro antichagasic activity. After a preliminary screening, compounds 7 and 9 were subjected to in vivo assays in a murine model. Both compounds caused a substantial decrease in parasitemia in the chronic phase, which was an even better result than that of the reference drug benznidazole. In addition, compound 9 also showed better antichagasic activity during the acute phase. Moreover, metabolite excretion, effect on mitochondrial membrane potential and the inhibition of superoxide dismutase (SOD) studies were also performed to identify their possible mechanism of action. Finally, docking studies proposed a binding mode of the Fe-SOD enzyme similar to our previous series, which validated our design strategy. Therefore, the results suggest that these compounds should be considered for further preclinical evaluation as antichagasic agents.

COX-1/COX-2 inhibition activities and molecular docking study of newly designed and synthesized pyrrolo[3,4-c]pyrrole Mannich bases.

In the present paper we describe the biological activity of newly designed and synthesized series of pyrrolo[3,4-c]pyrrole Mannich bases (7a-n). The Mannich bases were obtained in good yields by one-pot, three-component condensation of pyrrolo[3,4-c]pyrrole scaffold (6a-c) with secondary amines and an excess of formaldehyde solution in C2H5OH. The chemical structures of the compounds were characterized by 1H NMR, 13C NMR, FT-IR, and elemental analysis. Moreover, single crystal X-ray diffraction has been recorded for compound 7l. All synthesized derivatives were investigated for their potencies to inhibit COX-1 and COX-2 enzymes by colorimetric inhibitor screening assay. In order to analyse the intermolecular interactions between theligands and cyclooxygenase, experimental data were supported with the results of molecular docking simulations. According to the results, all of the tested compounds inhibited the activity of COX-1 and COX-2.

Synthesis and pharmacological evaluation of novel N-Mannich bases derived from 5,5-diphenyl and 5,5-di(propan-2-yl)imidazolidine-2,4-dione core.

The aim of this study was to design and synthesize two series of N-Mannich bases with imidazolidine-2,4-dione core as a potential anticonvulsant with reduced toxicity and broad antiseizure activity. Preliminary screening revealed that the majority of synthesized compounds were effective in the maximal electroshock seizure (MES) and/or subcutaneous pentylenetetrazole (scPTZ) test. The most active in vivo compound, 18 (3-((4-methylpiperazin-1-yl)methyl)-5,5-diphenylimidazolidine-2,4-dione), exhibited an ED50 value comparable to that of phenytoin in the MES test (38.5 mg/kg vs 28.1 mg/kg), and more importantly, it showed four times higher potency than phenytoin in the 6 Hz test (12.2 mg/kg vs > 60 mg/kg). Additionally, 18 exhibited antiallodynic properties in the von Frey test in neuropathic (oxaliplatin-treated) mice. Compound 18 also demonstrated a broader spectrum of anticonvulsant activity than phenytoin and showed statistically significant antinociceptive properties in selected models of chronic pain.

Discovery of coumarin Mannich base derivatives as multifunctional agents against monoamine oxidase B and neuroinflammation for the treatment of Parkinson's disease.

Due to the complexity of the pathogenesis of Parkinson's disease (PD), multimodal treatment may achieve better results. In this study, a series of coumarin Mannich base derivatives were designed and synthesized as multifunctional agents for PD treatment. Among the derivatives, 3-(3-(dimethylamino)propanoyl)-7-hydroxy-5-methyl- 2H-chromen-2-one hydrochloride (24) exhibited the most potent and selective hMAO-B inhibitory activity, and anti-inflammatory and neuroprotective effects in the in vitro studies. It significantly attenuated PD-associated behavioural deficits in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model of PD. Furthermore, preliminary mechanistic studies indicated that 24 could selectively inhibit MAO-B activity, decrease the neuroinflammatory process, and protect tyrosine hydroxylase-immunopositive dopaminergic neurons. These results suggest that 24 is a promising multifunctional agent for effective therapy for PD.

Mannich base Cu(II) complexes as biomimetic oxidative catalyst.

Galactose Oxidase (GOase) and catechol oxidase (COase) are the metalloenzymes of copper having monomeric and dimeric sites of coordination, respectively. This paper summarizes the results of our studies on the structural, spectral and catalytic properties of new mononuclear copper (II) complexes [CuL(OAc)] (1), and [CuL2] (2), (HL = 2,4­dichloro­6­{[(2'­dimethyl­aminoethyl)methylamino]methyl}­phenol) which can mimic the functionalities of the metalloenzymes GOase and COase. The structure of the compounds has been elucidated by X-ray crystallography and the mimicked Cu(II) catalysts were further characterized by EPR. These mimicked models were used for GOase and COase catalysis. The GOase catalytic results were identified by GC-MS and, analyzed by HPLC at room temperature. The conversion of benzyl alcohol to benzaldehyde were significant in presence of a strong base, Bu4NOMe in comparison to the neutral medium. Apart from that, despite of being monomeric in nature, both the homogeneous catalysts are very prone to participate in COase mimicking oxidation reaction. Nevertheless, during COase catalysis, complex 1 was found to convert 3,5­ditertarybutyl catechol (3,5-DTBC) to 3,5­ditertarybutyl quinone (3,5-DTBQ) having greater rate constant, kcat or turn over number (TON) value over complex 2. The generation of reactive intermediates during COase catalysis were accounted by electrospray ionization mass spectrometry (ESI-MS). Through mechanistic approach, we found that H2O2 is the byproduct for both the GOase and COase catalysis, thus, confirming the generation of reactive oxygen species during catalysis. Notably, complex 1 having mono-ligand coordinating atmosphere has superior catalytic activity for both cases in comparison to complex 2, that is having di-ligand environment.

Design, synthesis and evaluation of chalcone Mannich base derivatives as multifunctional agents for the potential treatment of Alzheimer's disease.

A series of chalcone Mannich base derivatives were designed, synthesized and evaluated as multifunctional agents for the treatment of Alzheimer's disease based on the multi-target directed ligands design strategy. In vitro assays demonstrated that most of the derivatives exerted potent selective inhibitory potency on AChE with good multifunctional properties. Among them, representative compound 7c exhibited moderate inhibitory potency for EeAChE (IC50 = 0.44 µM) and MAO-B inhibition (IC50 = 1.21 µM), good inhibitory effect on self-induced Aß1-42 aggregation (55.0%, at 25 µM), biometal chelating property, moderate antioxidant activity with a value 1.93-fold of Trolox. Moreover, both kinetic analysis of AChE inhibition and molecular modeling study revealed that 7c showed a mixed-type inhibition, binding simultaneously to CAS and PAS of AChE. In addition, 7c also displayed high BBB permeability. These properties indicated 7c may be a promising multifunctional agent for the treatment of AD.

A step towards development of promising trypanocidal agents: Synthesis, characterization and in vitro biological evaluation of ferrocenyl Mannich base-type derivatives.

Chagas disease is a neglected chronical parasitosis caused by the parasite Trypanosoma cruzi (T. cruzi). Nine ferrocenyl Mannich base derivatives were synthetized and characterized to explore their in vitro activity on three T. cruzi strains of the parasite and their cytotoxicity on Vero cells to calculate the selectivity index (SI). Compound 2, 1-ferrocenyl-3-(4-(4-(trifluoromethyl)phenyl)piperazin-1-yl)propan-1-one, stood out as the most promising derivative showing a half maximal inhibitory concentration (IC50) value around 5 µM in both amastigote and trypomastigote forms of T. cruzi and SI values higher than 13, being the best value on the trypomastigote forms of the Arequipa strain (SI = 41.7). Moreover, 2 decreased the number of infected cells and was not genotoxic. Furthermore, its possible mechanism of action was studied through the alteration of the metabolites excreted by the parasite during glucose metabolism, the detection of mitochondrial alterations and the inhibition of superoxide dismutase (SOD). Finally, docking studies were executed to analyze the binding mode of the studied compounds to Fe-SOD enzyme.

Synthesis, biological evaluation and molecular dynamics studies of 1,2,4-triazole clubbed Mannich bases.

The present work highlightsthe synthesis of a newer biologically active Mannich bases contributing 4-((4-fluorobenzylidene)amino)-5-(pyridin-4-yl)-4H-1,2,4-triazole-3-thiol and various heterocyclic amines via N-Mannich reaction by the conventional method as well as microwave heating approach as a part of an environmentally benign synthetic protocol. All the synthesized compounds were characterized by spectral analysis and were screened for in vitro antimicrobial, antitubercular and antiprotozoal activity. The compound 4k was found to be most active respectively against S. aureus (MIC 12.5 µM) and C. albicans (MIC 100 µM). The derivative 4 g displayed potency against L.mexicana and T. cruzi with IC50 value 1.01 and 3.33 µM better than reference drug Miltefosina and Nifurtimox. The compound 4b displayed excellent potency against M. tuberculosis (MIC 6.25 µM) in the primary screening. The computational studies revealed for that Mannich derivative (4b) showed a high affinity toward the active site of enzyme which provides a strong platform for new structure-based design efforts. The Lipinski's parameters showed good drug-likeness properties and can be developed as an oral drug candidate.

Indolyl Azaspiroketal Mannich Bases Are Potent Antimycobacterial Agents with Selective Membrane Permeabilizing Effects and in Vivo Activity.

The inclusion of an azaspiroketal Mannich base in the membrane targeting antitubercular 6-methoxy-1- n-octyl-1 H-indole scaffold resulted in analogs with improved selectivity and submicromolar activity against Mycobacterium tuberculosis H37Rv. The potency enhancing properties of the spiro-fused ring motif was affirmed by SAR and validated in a mouse model of tuberculosis. As expected for membrane inserting agents, the indolyl azaspiroketal Mannich bases perturbed phospholipid vesicles, permeabilized bacterial cells, and induced the mycobacterial cell envelope stress reporter promoter p iniBAC. Surprisingly, their membrane disruptive effects did not appear to be associated with bacterial membrane depolarization. This profile was not uniquely associated with azaspiroketal Mannich bases but was characteristic of indolyl Mannich bases as a class. Whereas resistant mycobacteria could not be isolated for a less potent indolyl Mannich base, the more potent azaspiroketal analog displayed low spontaneous resistance mutation frequency of 10-8/CFU. This may indicate involvement of an additional envelope-related target in its mechanism of action.

Synthesis, biological evaluation, and docking studies of some 5-chloro-2(3H)-benzoxazolone Mannich bases derivatives as cholinesterase inhibitors.

A series of N-substituted-5-chloro-2(3H)-benzoxazolone derivatives were synthesized and evaluated for their acetylcholinesterase (AChE), butyrylcholinesterase (BuChE) inhibitory, and antioxidant activities. The structures of the title compounds were confirmed by spectral and elemental analyses. The cholinesterase (ChE) inhibitory activity studies were carried out using Ellman's colorimetric method. The free radical scavenging activity was also determined by in vitro ABTS (2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)) assay. The biological activity results revealed that all of the title compounds displayed higher AChE inhibitory activity than the reference compound, rivastigmine, and were selective for AChE. Among the tested compounds, compound 7 exhibited the highest inhibition against AChE (IC50 = 7.53 ± 0.17 µM), while compound 11 was found to be the most active compound against BuChE (IC50 = 17.50 ± 0.29 µM). The molecular docking study of compound 7 showed that this compound can interact with the catalytic active site (CAS) of AChE and also has potential metal chelating ability and a proper log P value. On the other hand, compound 2 bearing a methyl substituent at the ortho position on the phenyl ring showed better radical scavenging activity (IC50 = 1.04 ± 0.04 mM) than Trolox (IC50 = 1.50 ± 0.05 mM).