Synthesis and evaluation of novel carbamate-substituted flavanone derivatives as potent acetylcholinesterase inhibitors and anti-amnestic agents

Antibacterial and Antioxidant Activity of Synthetic Polyoxygenated Flavonoids

Flavonoids are an abundant class of naturally occurring compounds with broad biological activities, but their limited abundance in nature restricts their use in medicines and food additives. Here we present the synthesis and determination of the antibacterial and antioxidant activities of twenty-two structurally related flavonoids (five of which are new) by scientifically validated methods. Flavanones (FV1-FV11) had low inhibitory activity against the bacterial growth of MRSA 97-7. However, FV2 (C5,7,3',4' = OH) and FV6 (C5,7 = OH; C4' = SCH3) had excellent bacterial growth inhibitory activity against Gram-negative E. coli (MIC = 25 µg/mL for both), while Chloramphenicol (MIC = 25 µg/mL) and FV1 (C5,7,3' = OCH3; 4' = OH) showed inhibitory activity against Gram-positive L. monocytogenes (MIC = 25 µg/mL). From the flavone series (FO1-FO11), FO2 (C5,7,3',4' = OH), FO3 (C5,7,4' = OH; 3' = OCH3), and FO5 (C5,7,4' = OH) showed good inhibitory activity against Gram-positive MRSA 97-7 (MIC = 50, 12, and 50 µg/mL, respectively), with FO3 being more active than the positive control Vancomycin (MIC = 25 µg/mL). FO10 (C5,7= OH; 4' = OCH3) showed high inhibitory activity against E. coli and L. monocytogenes (MIC = 25 and 15 µg/mL, respectively). These data add significantly to our knowledge of the structural requirements to combat these human pathogens. The positions and number of hydroxyl groups were key to the antibacterial and antioxidant activities.

Flavonoid and Chalcone Scaffolds as Inhibitors of BACE1: Recent Updates

Flavonoids and chalcones are two major classes of chemical moieties that have a vast background of pharmacological activities. Chalcone is a subclass of flavonoids whose therapeutic potential has been implicated due to an array of bioactivities. A lot of research works have shown interest in investigating the neuroprotective effect of these molecules, and have revealed them to be much more potent molecules that can be used to treat neurodegenerative disorders. Beta-site APP cleaving enzyme (BACE1), which is majorly found in the brain, is one of the reasons behind the development of Alzheimer's disease (AD). Flavonoids and chalcones have proven clinical data that they inhibit the production of Aβ plaques that are involved in the progression of AD. In this article, we have provided a detailed chronological review of the research work on the BACE1 inhibiting potency of both flavonoids and chalcones. Almost all the flavonoids and chalcones mentioned in this article have shown very good in vitro and in vivo BACE1 inhibiting activity. The docking studies and the structural importance of some BACE1-inhibiting flavonoids, as well as chalcones, are also mentioned here.

Synthesis and in vitro assessment of anticholinesterase and antioxidant properties of triazineamide derivatives

Aim: Cholinesterase inhibitors and radical scavengers have been recognized as powerful symptomatic anti-Alzheimer's disease agents. Hence, the present study aimed to develop new triazineamides as potent anticholinesterase and antioxidant agents. Methods: Triazineamide (7a-i) derivatives were synthesized using cyanuric chloride via nucleophilic substitution followed by condensation. Ellman assay, 2,2-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) radical scavenging assay and molecular docking studies with Autodock 4.2.3 program were conducted. Results: Triazineamide 7c was assessed as a potent, selective and mixed-type dual inhibitor of acetylcholinesterase, with and IC₅₀ of 5.306 ± 0.002 μM, by binding simultaneously with the catalytic active and peripheral anionic sites of acetylcholinesterase, and it had strong 2,2-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) radical scavenging abilities. Conclusion: These results suggest that triazineamides may be of interest to establish a structural basis for new anti-Alzheimer's disease agents.

Influence of a 4'-substituent on the efficiency of flavonol-based fluorescent indicators of β-glycosidase activity

This article presents novel fluorescent probes, based on the excited-state intramolecular proton transfer (ESIPT) phenomenon and flavonols, sensitive to the action of specific glycosidases. 4'-Substituted flavonols were synthesized, using various approaches, and glycosylated with d-glucose, N-acetyl-d-glucosamine and d-glucuronic acid. Evaluation of the β-glycosidase activities was performed in neutral and acidic pH. In all the cases examined, an acidic environment accelerated enzymatic hydrolysis. It was demonstrated that the 4'-chloroflavonyl glycosides of all sugars tested, both in neutral and acidic pH, are the ones most sensitive to the presence of hydrolase. In turn, 4'-dimethylaminoflavonyl glucoside is not sensitive to glucosidase action at all. Generally, the rate of enzymatic hydrolysis increases as the electron-withdrawing nature of the 4'-substituent increases. An exception is the trifluoromethyl group which, in spite of having the most favourable Hammett constant, does not contribute enough to increase the rate of hydrolysis of its glucoside. The presented experimental results are supported by the electrostatic potential (ESP) analysis and related to the mechanisms of glycoside bond enzymatic hydrolysis.

Design, synthesis and docking study of novel coumarin ligands as potential selective acetylcholinesterase inhibitors

New coumaryl-thiazole derivatives with the acetamide moiety as a linker between the alkyl chains and/or the heterocycle nucleus were synthesized and in vitro tested as acetylcholinesterase (AChE) inhibitors. 2-(diethylamino)-N-(4-(2-oxo-2H-chromen-3-yl)thiazol-2-yl)acetamide (6c, IC50 value of 43 nM) was the best AChE inhibitor with a selectivity index of 4151.16 over BuChE. Kinetic study of AChE inhibition revealed that 6c was a mixed-type inhibitor. Moreover, the result of H4IIE hepatoma cell toxicity assay for 6c showed negligible cell death. Molecular docking studies were also carried out to clarify the inhibition mode of the more active compounds. Best pose of compound 6c is positioned into the active site with the coumarin ring wedged between the residues of the CAS and catalytic triad of AChE. In addition, the coumarin ring is anchored into the gorge of the enzyme by H-bond with Tyr130.

Synthesis, characterization and in vitro evaluation of substituted N-(2-phenylcyclopropyl)carbamates as acetyl- and butyrylcholinesterase inhibitors

A serie of O-substituted N-2-phenylcyclopropylcarbamates was prepared and characterized. These carbamates were tested as inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). It was found, that these compounds exhibit moderate inhibition activity with values of IC₅₀ in the range of 54.8-94.4 μM (for AChE) and up to 5.8 μM (for BChE). The AChE/BChE selectivity for each carbamate was calculated. These values varied from 0.50 to 9.46, two carbamate derivatives inhibited only AChE selectively. The most promising derivative was prepared in all optically pure forms (four isomers). It was found that individual stereoisomers differed only slightly in the inhibition ability. The cytotoxicity of all carbamates was evaluated using the standard in vitro test with Jurkat cells. With regard to their inhibition activity and cytotoxicity as well as easy preparation, O-substituted N-2-phenylcyclopropylcarbamates can be considered as promising compounds for potential medicinal applications.

Design, synthesis, and evaluation of 7H-thiazolo-[3,2-b]-1,2,4-triazin-7-one derivatives as dual binding site acetylcholinesterase inhibitors

New dual binding site acetylcholinesterase (AChE) inhibitors have been designed and synthesized as a new drug candidate for the treatment of Alzheimer's disease (AD) through the binding to both catalytic and peripheral sites of the enzyme. Therefore, a series of 7H-thiazolo[3,2-b]-1,2,4-triazin-7-one derivatives 6a-j were synthesized and investigated for their ability to inhibit the activity of human AChE (hAChE) in comparison with huperzine-A. All the compounds were found to inhibit AChE activity, especially compounds 6c and 6i with the inhibition value of 76.10% and 77.82%, respectively. The molecular docking study indicated that they were nicely accommodated by AChE. The molecular docking study revealed that 6c and 6i possessed a more optimal binding conformation than 6a and can perfectly fit into the active and peripheral site of hAChE, and consequently exhibited highly improved inhibitor potency to hAChE.