Donepezil-based hybrids as multifunctional anti-Alzheimer's disease chelating agents: Effect of positional isomerization

Benzimidazole and Benzoxazole Derivatives Against Alzheimer's Disease

Benzimidazole and benzoxazole derivatives are included in the category of medical drugs in a wide range of areas such as anticancer, anticoagulant, antihypertensive, anti- inflammatory, antimicrobial, antiparasitic, antiviral, antioxidant, immunomodulators, proton pump inhibitors, hormone modulators, etc. Many researchers have focused on synthesizing more effective benzimidazole and benzoxazole derivatives for screening various biological activities. In addition, there are benzimidazole and benzoxazole rings as bioisosteres of aromatic rings found in drugs used in the treatment of Alzheimer's disease. Because of the diverse activity of the benzimidazole and benzoxazole rings and bioisosteres marketed as drugs for Alzheimer Diseases, designed compounds containing these rings are likely to be effective against Alzheimer's disease. In this study, the effectiveness of compounds containing benzimidazole and benzoxazole rings against Alzheimer's disease will be examined.

Effect of donepezil hydrochloride on the transgenic Drosophila expressing human Aβ-42

CONCLUSION

The results suggest that donepezil hydrochloride is potent enough to reduce the AD symptoms being mimicked in transgenic flies.

Rivastigmine-Benzimidazole Hybrids as Promising Multitarget Metal-Modulating Compounds for Potential Treatment of Neurodegenerative Diseases

With the goal of combating the multi-faceted Alzheimer's disease (AD), a series of Rivastigmine-Benzimidazole (RIV-BIM) hybrids was recently reported by us as multitarget-directed ligands, thanks to their capacity to tackle important hallmarks of AD. In particular, they exhibited antioxidant activity, acted as cholinesterase inhibitors, and inhibited amyloid-β (Aβ) aggregation. Herein, we moved forward in this project, studying their ability to chelate redox-active biometal ions, Cu(II) and Fe(III), with widely recognized roles in the generation of oxidative reactive species and in protein misfolding and aggregation in both AD and Parkinson's disease (PD). Although Cu(II) chelation showed higher efficiency for the positional isomers of series 5 than those of series 4 of the hybrids, the Aβ-aggregation inhibition appears more dependent on their capacity for fibril intercalation than on copper chelation. Since monoamine oxidases (MAOs) are also important targets for the treatment of AD and PD, the capacity of these hybrids to inhibit MAO-A and MAO-B was evaluated, and they showed higher activity and selectivity for MAO-A. The rationalization of the experimental evaluations (metal chelation and MAO inhibition) was supported by computational molecular modeling studies. Finally, some compounds showed also neuroprotective effects in human neuroblastoma (SH-SY5Y cells) upon treatment with 1-methyl-4-phenylpyridinium (MPP⁺), a neurotoxic metabolite of a Parkinsonian-inducing agent.

Development of new donepezil analogs: synthesis, biological screening and in silico study rational

Fifteen new benzothiophene-based compounds were designed, synthesized, and evaluated as potential anti-Alzheimer agents. Most of the synthesized compounds exhibited remarkable AChE inhibitory activity and effectively inhibited self-mediated β-amyloid protein in vitro. Compound 3g (IC50 = 72.488 ± 3.69 μM) showed a significant β-amyloid inhibitory effect exceeding that of donepezil (IC50 = 87.414 ± 4.46 μM). Furthermore, compound 3j (IC50 = 0.498 ± 0.02 μM) showed the best inhibitory activity comparable to that of donepezil (IC50 = 0.404 ± 0.03 μM). The in vivo evaluation of the promising compounds (3g and 3j) confirmed a significant memory improvement in scopolamine-induced memory impairment model in mice. The molecular docking simulation of compounds 3g and 3j in Torpedo californica-AChE (TcAChE) active site showed a good agreement with the obtained screening results. The in silico ADMET and other physicochemical parameters were also reported.

Promising heterocycle-based scaffolds in recent (2019-2021) anti-Alzheimer's drug design and discovery

Alzheimer's disease (AD) is one of the neurodegenerative diseases that led to morbidity and mortality world-wide. It is a complex disease whose etiology is not completely known that leads to difficulty in prevent or cure of the AD. Also, there are only few approved drugs for AD treatment. Apart from deaths due to AD, expenditure of treatment and care of AD patients is higher than that of treatment of HIV and cancer diseases combined. Hence, it leads to an economic burden also. Although research is being carried out on designing drugs for AD, most of them have ended up in poor inhibitors with high toxicity. Hence, researchers should shoulder a great responsibility of discovery of efficient drugs for AD treatment. In the field of drug discovery, heterocycles played an important role. Also, most of the heterocyclic scaffolds have been used in design of potent anti-AD agents. In view of this, heterocyclic molecules reported recently are compiled and evaluated comprehensively. Especially, the molecules which exhibited pronounced activity are emphasized and described with respect to structure-activity relationship (SAR) in brief.

Formulating The Structural Aspects Of Various Benzimidazole Cognates

BACKGROUND

Benzimidazole derivatives are widely used in clinical practice as potential beneficial specialists. Recently, the neuroprotective effect of derivatives of benzimidazole moiety has also shown positive outcomes.

OBJECTIVE

To develop favourable molecules for various neurodegenerative disorders using the versatile chemical behaviour of the benzimidazole scaffold.

METHODS

About 25 articles were collected that discussed various benzimidazole derivatives and categorized them under various subheadings based on the targets such as BACE 1, JNK, MAO, choline esterase enzyme, oxidative stress, mitochondrial dysfunction in which they act. The structural aspects of various benzimidazole derivatives were also studied.

CONCLUSION

To manage various neurodegenerative disorders, a multitargeted approach will be the most hopeful stratagem. Some benzimidazole derivatives can be considered for future studies, which are mentioned in the discussed articles.

The hybrid compounds as multi-target ligands for the treatment of Alzheimer's Disease: Considerations on Donepezil

The strategies to combat Alzheimer's Disease (AD) have been changing with respect to the failures of many drug candidates assessed in clinical studies, the complex pathophysiology of AD, and the limitations of the current drugs employed. So far, none of the targets, either validated or nonvalidated, have been shown to be purely causative in the generation and development of AD. Considering the progressive and the neurodegenerative characteristics of the disease, the main strategy has been based on the design of molecules capable of showing activity on more than one receptor, and it is defined as multi-target ligand design strategy. The hybrid molecule concept is an outcome of this approach. Donepezil, as one of the currently employed drugs for AD therapy, has also been utilized in hybrid drug design studies. This review has aimed to present the promising donepezil-like hybrid molecules introduced in the recent period. Particularly, multi-target ligands with additional activities concomitant to cholinesterase inhibition are preferred.

Novel Hydroxytyrosol-Donepezil Hybrids as Potential Antioxidant and Neuroprotective Agents

It is well-accepted that the endogenous antioxidant protection system progressively decays in elderly people, and that the oxidative stress contributes to different neurodegenerative disorders such as Alzheimer’s Diseases (AD). The lower incidence of AD in countries which feature the Mediterranean Diet was associated to the high consumption of extra virgin olive oil and its polyphenolic fraction, in particular hydroxytyrosol. The protective role of these bio-phenols against oxidative stress, suggested that we combine their antioxidant/free radical scavenging activity with donepezil, an active ingredient which has just been approved for the treatment of AD. Different synthetic strategies were tested to conjugate the two different synthons in good yields. Additionally, a nitro-hydroxytyrosol derivative was synthesized to extend the application to other neurodegeneration inflammatory models. Then, their bioactivity was measured in different chemical and biological tests on a human neuroblastoma cell line (SHSY-5Y). Remarkable results on cell viability and the regulation of the redox state of cells were obtained. All hybrids showed negligible cell death under 1 μM and are stable and non toxic. Reactive oxygen species (ROS) measurements showed that the nitro-hybrid was the more effective one at reducing the ROS amount to physiological values. Then, in light of the bio-metal hypothesis of diverse neurodegenerative disorders, we tested these new compounds on the chelation properties of redox-active metals. The nitro-hybrid was able to chelate all of the tested metal cations, suggesting that we propose it as potential lead compound for a new class of neuroprotective antioxidant agents.

Perspectives for New and More Efficient Multifunctional Ligands for Alzheimer's Disease Therapy

Despite tremendous research efforts at every level, globally, there is still a lack of effective drugs for the treatment of Alzheimer's disease (AD). The biochemical mechanisms of this devastating neurodegenerative disease are not yet clearly understood. This review analyses the relevance of multiple ligands in drug discovery for AD as a versatile toolbox for a polypharmacological approach to AD. Herein, we highlight major targets associated with AD, ranging from acetylcholine esterase (AChE), beta-site amyloid precursor protein cleaving enzyme 1 (BACE-1), glycogen synthase kinase 3 beta (GSK-3β), N-methyl-d-aspartate (NMDA) receptor, monoamine oxidases (MAOs), metal ions in the brain, 5-hydroxytryptamine (5-HT) receptors, the third subtype of histamine receptor (H3 receptor), to phosphodiesterases (PDEs), along with a summary of their respective relationship to the disease network. In addition, a multitarget strategy for AD is presented, based on reported milestones in this area and the recent progress that has been achieved with multitargeted-directed ligands (MTDLs). Finally, the latest publications referencing the enlarged panel of new biological targets for AD related to the microglia are highlighted. However, the question of how to find meaningful combinations of targets for an MTDLs approach remains unanswered.

Importance of Biometals as Targets in Medicinal Chemistry: An Overview about the Role of Zinc (II) Chelating Agents

Zinc (II) is an important biometal in human physiology. Moreover, in the last two decades, it was deeply studied for its involvement in several pathological states. In particular, the regulation of its concentration in synaptic clefts can be fundamental for the treatment of neurodegenerative diseases, such as Alzheimer’s disease (AD). Zinc (II) is also a constituent of metalloenzymes (i.e., matrix metalloproteinases, MMPs, and carbonic anhydrases, CAs) with catalytic function; therefore, it can be an important target for the inhibition of these proteins, frequently involved in cancer onset. This review is focused on the significance of zinc (II) chelating agents in past and future medicinal chemistry research, and on the importance of selectivity in order to revamp the possibility of their use in therapy, often hindered by possible side effects.

Design, Synthesis, and In Vitro Evaluation of Hydroxybenzimidazole-Donepezil Analogues as Multitarget-Directed Ligands for the Treatment of Alzheimer's Disease

A series of multi-target-directed ligands (MTDLs), obtained by attachment of a hydroxyphenylbenzimidazole (BIM) unit to donepezil (DNP) active mimetic moiety (benzyl-piperidine/-piperazine) was designed, synthesized, and evaluated as potential anti-Alzheimer's disease (AD) drugs in terms of biological activity (inhibition of acetylcholinesterase (AChE) and β-amyloid (Aβ) aggregation), metal chelation, and neuroprotection capacity. Among the DNP-BIM hybrids studied herein, the structural isomerization did not significantly improve the biological properties, while some substitutions, namely fluorine atom in each moiety or the methoxy group in the benzyl ring, evidenced higher cholinergic AChE activity. All the compounds are able to chelate Cu and Zn metal ions through their bidentate BIM moieties, but compound 5, containing a three-dentate chelating unit, is the strongest Cu(II) chelator. Concerning the viability on neuroblastoma cells, compounds 9 and 10 displayed the highest reduction of Aβ-induced cell toxicity. In silico calculations of some pharmacokinetic descriptors indicate that all the compounds but the nitro derivatives have good potential oral-bioavailability. Overall, it can be concluded that most of the studied DNP-BIM conjugates showed quite good anti-AD properties, therefore deserving to be considered in further studies with the aim of understanding and treating AD.