Synthesis and biological evaluation of a new series of ebselen derivatives as glutathione peroxidase (GPx) mimics and cholinesterase inhibitors against Alzheimer's disease

Novel neuroprotective 5,6-dihydropyrido[2',1':2,3]imidazo[4,5-c]quinoline derivatives acting through cholinesterase inhibition and CB2 signaling modulation

A novel group of 5,6-dihydropyrido [2',1':2,3]imidazo [4,5-c]quinolines was prepared via a microwave assisted one-pot telescopic approach. The synthetic sequence involves the formation of an amine precursor of imidazo [1,2-a]pyridine via condensation and reduction under microwave irradiation. Subsequently, the Pictet-Spengler cyclisation reaction occurs with ketones (cyclic or acyclic) to obtain substituted 5,6-dihydropyrido [2',1':2,3]imidazo [4,5-c]quinolines in excellent yields. The compounds were tested as neuroprotective agents. Observed protection of neuron-like cells, SH-SY5Y differentiated with ATRA, in Parkinson's and Huntington's disease models inspired further mechanistic studies of protective activity against damage induced by 1-methyl-4-phenylpyridinium (MPP+), a compound causing Parkinson's disease. The novel compounds exhibit similar or higher potency than ebselen, an established drug with antioxidant activity, in the cells against MPP + -induced total cellular superoxide production and cell death. However, they exhibit a significantly higher capacity to reduce mitochondrial superoxide and preserve mitochondrial membrane potential. We also observed marked differences between a selected derivative and ebselen in terms of normalizing MPP + -induced phosphorylation of Akt and ERK1/2. The cytoprotective activity was abrogated when signaling through cannabinoid receptor CB2 was blocked. The compounds also inhibit both acetylcholine and butyrylcholine esterases. Overall the data show that novel 5,6-dihydropyrido [2',1':2,3]imidazo [4,5-c]quinoline have a broad cytoprotective activity which is mediated by several mechanisms including mitoprotection.

Selenium-containing compounds: a new hope for innovative treatments in Alzheimer's disease and Parkinson's disease

Neurodegenerative diseases are challenging to cure. To date, no cure has been found for Alzheimer's disease or Parkinson's disease, and current treatments are able only to slow the progression of the diseases and manage their symptoms. After an introduction to the complex biology of these diseases, we discuss the beneficial effect of selenium-containing agents, which show neuroprotective effects in vitro or in vivo. Indeed, selenium is an essential trace element that is being incorporated into innovative organoselenium compounds, which can improve outcomes in rodent or even primate models with neurological deficits. Herein, we critically discuss recent findings in the field of selenium-based applications in neurological disorders.

Design, Synthesis, and Biological Evaluation of Novel Indanone Derivatives as Cholinesterase Inhibitors for Potential Use in Alzheimer's Disease

Indanone derivatives containing meta/para-substituted aminopropoxy benzyl/benzylidene moieties were designed based on the structures of donepezil and ebselen analogs as the cholinesterase inhibitors. The designed compounds were synthesized and their acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibitory activities were measured. Inhibitory potencies (IC50 values) for the synthesized compounds ranged from 0.12 to 11.92 μM and 0.04 to 24.36 μM against AChE and BChE, respectively. Compound 5 c showed the highest AChE inhibitory potency with IC50 value of 0.12 μM, whereas the highest BChE inhibition was achieved by structure 7 b (IC50 =0.04 μM). Structure-activity relationship (SAR) analysis revealed that there is no significant difference between meta and para-substituted derivatives in AChE and BChE inhibition. However, the most potent AChE inhibitor 5 c belongs to meta-substituted compounds, while the most active BChE inhibitor is para-substituted derivative 7 b. The order of enzyme inhibition potency based on the substituted amine group is dimethyl amine>piperidine>morpholine. Compounds containing C=C linkage are more potent AChE inhibitors than the corresponding saturated structures. Molecular docking studies indicated that 5 c interacts with AChE in a very similar way to that observed experimentally for donepezil. The introduced indanone-aminopropoxy benzylidenes could be used in drug-discovery against Alzheimer's disease.

A Competition between Hydrogen, Stacking, and Halogen Bonding in N-(4-((3-Methyl-1,4-dioxo-1,4-dihydronaphthalen-2-yl)selanyl)phenyl)acetamide: Structure, Hirshfeld Surface Analysis, 3D Energy Framework Approach, and DFT Calculation

N-(4-((3-Methyl-1,4-dioxo-1,4-dihydronaphthalen-2-yl)selanyl)phenyl)acetamide (5), C₁₉H₁₅NO₃Se, was prepared in two steps from 4,4'-diselanediyldianiline (3) via reduction and subsequent nucleophilic reaction with 2-methyl-3-bromo-1,4-naphthalenedione, followed by acetylation with acetic anhydride. The cytotoxicity was estimated against 158N and 158JP oligodendrocytes and the redox profile was also evaluated using different in vitro assays. The technique of single-crystal X-ray diffraction is used to confirm the structure of compound 5. The enantiopure 5 crystallizes in space group P21 with Flack parameter 0.017 (8), exhibiting a chiral layered absolute structure. Molecular structural studies showed that the crystal structure is foremost stabilized by N-H···O and relatively weak C-H···O contacts between molecules, and additionally stabilized by weak C-H···π and Se···N interactions. Hirshfeld surface analysis is used to quantitatively investigate the noncovalent interactions that stabilize crystal packing. Framework energy diagrams were used to graphically represent the stabilizing interaction energies for crystal packing. The analysis of the energy framework shows that the interactions energies of and C-H···π and C-O···π are primarily dispersive and are the crystal's main important forces. Density functional theory (DFT) calculations were used to determine the compound's stability, chemical reactivity, and other parameters by determining the HOMO-LUMO energy differences. The determination of its optimized surface of the molecular electrostatic potential (MEP) was also carried out. This study was conducted to demonstrate both the electron-rich and electron-poor sites.

Ebselen, a multi-target compound: its effects on biological processes and diseases

Ebselen is a well-known synthetic compound mimicking glutathione peroxidase (GPx), which catalyses some vital reactions that protect against oxidative damage. Based on a large number of in vivo and in vitro studies, various mechanisms have been proposed to explain its actions on multiple targets. It targets thiol-related compounds, including cysteine, glutathione, and thiol proteins (e.g., thioredoxin and thioredoxin reductase). Owing to this, ebselen is a unique multifunctional agent with important effects on inflammation, apoptosis, oxidative stress, cell differentiation, immune regulation and neurodegenerative disease, with anti-microbial, detoxifying and anti-tumour activity. This review summarises the current understanding of the multiple biological processes and molecules targeted by ebselen, and its pharmacological applications.

Ebselen and Analogues: Pharmacological Properties and Synthetic Strategies for Their Preparation

Ebselen is the leader of selenorganic compounds, and starting from its identification as mimetic of the key antioxidant enzyme glutathione peroxidase, several papers have appeared in literature claiming its biological activities. It was the subject of several clinical trials and it is currently in clinical evaluation for the treatment of COVID-19 patients. Given our interest in the synthesis and pharmacological evaluation of selenorganic derivatives with this review, we aimed to collect all the papers focused on the biological evaluation of ebselen and its close analogues, covering the timeline between 2016 and most of 2021. Our analysis evidences that, even if it lacks specificity when tested in vitro, being able to bind to every reactive cysteine, it proved to be always well tolerated in vivo, exerting no sign of toxicity whatever the administered doses. Besides, looking at the literature, we realized that no review article dealing with the synthetic approaches for the construction of the benzo[d][1,2]-selenazol-3(2H)-one scaffold is available; thus, a section of the present review article is completely devoted to this specific topic.

Toxicology and pharmacology of synthetic organoselenium compounds: an update

Here, we addressed the pharmacology and toxicology of synthetic organoselenium compounds and some naturally occurring organoselenium amino acids. The use of selenium as a tool in organic synthesis and as a pharmacological agent goes back to the middle of the nineteenth and the beginning of the twentieth centuries. The rediscovery of ebselen and its investigation in clinical trials have motivated the search for new organoselenium molecules with pharmacological properties. Although ebselen and diselenides have some overlapping pharmacological properties, their molecular targets are not identical. However, they have similar anti-inflammatory and antioxidant activities, possibly, via activation of transcription factors, regulating the expression of antioxidant genes. In short, our knowledge about the pharmacological properties of simple organoselenium compounds is still elusive. However, contrary to our early expectations that they could imitate selenoproteins, organoselenium compounds seem to have non-specific modulatory activation of antioxidant pathways and specific inhibitory effects in some thiol-containing proteins. The thiol-oxidizing properties of organoselenium compounds are considered the molecular basis of their chronic toxicity; however, the acute use of organoselenium compounds as inhibitors of specific thiol-containing enzymes can be of therapeutic significance. In summary, the outcomes of the clinical trials of ebselen as a mimetic of lithium or as an inhibitor of SARS-CoV-2 proteases will be important to the field of organoselenium synthesis. The development of computational techniques that could predict rational modifications in the structure of organoselenium compounds to increase their specificity is required to construct a library of thiol-modifying agents with selectivity toward specific target proteins.

Glutathione peroxidase-1 and neuromodulation: Novel potentials of an old enzyme

Glutathione peroxidase (GPx) acts in co-ordination with other signaling molecules to exert its own antioxidant role. We have demonstrated the protective effects of GPx,/GPx-1, a selenium-dependent enzyme, on various neurodegenerative disorders (i.e., Parkinson's disease, Alzheimer's disease, cerebral ischemia, and convulsive disorders). In addition, we summarized the recent findings indicating that GPx-1 might play a role as a neuromodulator in neuropsychiatric conditions, such as, stress, bipolar disorder, schizophrenia, and drug intoxication. In this review, we attempted to highlight the mechanistic scenarios mediated by the GPx/GPx-1 gene in impacting these neurodegenerative and neuropsychiatric disorders, and hope to provide new insights on the therapeutic interventions against these disorders.

The recent development of donepezil structure-based hybrids as potential multifunctional anti-Alzheimer's agents: highlights from 2010 to 2020

Dementia is a term used to define different brain disorders that affect memory, thinking, behavior, and emotion. Alzheimer's disease (AD) is the second cause of dementia that is generated by the death of cholinergic neurons (especially acetylcholine (ACh)), which have a vital role in cognition. Acetylcholinesterase inhibitors (AChEI) affect acetylcholine levels in the brain and are broadly used to treat Alzheimer's. Donepezil, rivastigmine, and galantamine, which are FDA-approved drugs for AD, are cholinesterase inhibitors. In addition, scientists are attempting to develop hybrid molecules and multi-target-directed ligands (MTDLs) that can simultaneously modulate multiple biological targets. This review highlights recent examples of MTDLs and fragment-based strategy in the rational design of new potential AD medications from 2010 onwards.

This review highlights recent examples of multi-target-directed ligands (MTDLs) based on donepezil structure modification from 2010 onwards.

Ebselen reversed peripheral oxidative stress induced by a mouse model of sporadic Alzheimer's disease

Intracerebroventricular streptozotocin injection (icv STZ) is a well established sporadic Alzheimer's disease (AD) model in rodents. AD is characterized by neuronal degeneration accompanied by central oxidative stress. Studies also indicate peripheral oxidative damage in AD, but if the icv STZ model of sporadic AD mimics this feature is an open question. This study aimed to investigate if icv STZ administration induces peripheral oxidative stress and the antioxidant action of Ebselen, compared to the reference drug (donepezil), in this sporadic AD model. Male adult Swiss mice received icv STZ (days 1 and 3). Mice received Ebselen (10 mg/kg, i.p) or Donepezil (5 mg/kg, i.p) for 14 days. Mice were killed and the kidney and liver were excised to determine parameters of oxidative stress and toxicity markers. The mice icv STZ-injected showed peripheral oxidative stress. Ebselen reversed renal lipid peroxidation in the icv STZ administered mice by modulating NPSH levels, SOD and CAT activities, whereas Donepezil, modulated only NPSH levels. Ebselen and Donepezil counteracted hepatic lipid peroxidation in STZ-injected mice by modulating NPSH levels and CAT activity. The δ-ALA-D activity was inhibited in the kidney, but not in the liver, whereas the icv STZ-injected mice had an increase in the GST activity in both tissues. Ebselen reversed the increase in the hepatic GST activity of the STZ-injected mice. Donepezil increased renal GST activity in the control mice. In conclusion, this study demonstrates that the icv STZ administration induced peripheral oxidative stress. Ebselen, similar to Donepezil, was effective against peripheral oxidative stress in a mouse model of sporadic AD.

Highly Significant Scaffolds to Design and Synthesis Cholinesterase Inhibitors as Anti-Alzheimer Agents

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Alzheimer, a progressive disease, is a common term for memory loss which interferes with daily life through severe influence on cognitive abilities. Based on the cholinergic hypothesis, and Xray crystallographic determination of the structure of acetylcholinesterase (AChE) enzyme, the level of acetylcholine (ACh, an important neurotransmitter associated with memory) in the hippocampus and cortex area of the brain has a direct effect on Alzheimer. This fact encourages scientists to design and synthesize a wide range of acetylcholinesterase inhibitors (AChEIs) to control the level of ACh in the brain, keeping in view the crystallographic structure of AChE enzyme and drugs approved by the Food and Drug Administration (FDA).

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AChEIs have slightly diverse pharmacological properties, but all of them work by inhibiting the segregation of ACh by blocking AChE. We reviewed significant scaffolds introduced as AChEIs. In some studies, the activity against butyrylcholinesterase (BuChE) has been evaluated as well because BuChE is a similar enzyme to neuronal acetylcholinesterase and is capable of hydrolyzing ACh. In order to study AChEIs effectively, we divided them structurally into 12 classes and briefly explained effective AChEIs and compared their activities against AChE enzyme.

Development and Therapeutic Potential of Selenazo Compounds

Incorporation of selenium (Se) atom into small molecules can substantially enhance their antioxidant, anti-inflammatory, antimutagenic, antitumoral or chemopreventive, antiviral, antibacterial, antifungal, antiparasitic, and neuroprotective effects. Specifically, selenazo compounds have received great attention owing to their chemical properties, pharmaceutical applications, and low toxicity. In this Perspective, we compile extensive literature evidence with the description and discussion of the most recent advances in different selenazo and selenadiazo motifs as potential pharmacological candidates. We also provide some perspectives on the challenges and future directions in the advancement of these selenazo compounds, each of which could generate drug candidates for various diseases.

Design, synthesis, biological evaluation, and molecular dynamics of novel cholinesterase inhibitors as anti-Alzheimer's agents

A series of novel chroman-4-one derivatives were designed and synthesized successfully with good to excellent yield (3a-l). In addition, the obtained products were evaluated for their cholinesterase (ChE) inhibitory activities. The results show that among the various synthesized compounds, analogs bearing the piperidinyl ethoxy side chain with 4-hydroxybenzylidene on the 3-positions of chroman-4-one (3l) showed the most potent activity with respect to acetylcholinesterase (anti-AChE activity; IC₅₀  = 1.18 μM). In addition, the structure-activity relationship was studied and the results revealed that the electron-donating groups on the aryl ring of the 3-benzylidene fragment (3k, 3l) resulted in the designed compounds to be more potent ChE inhibitors in comparison with those having electron-withdrawing groups (3h). In this category, the strongest ChE inhibition was found for the compound containing piperidine as cyclic amine, and a hydroxyl group (for AChE, compound 3l) and fluoro group (for butyrylcholinesterase (BuChE, compound 3i) on the para-position of the aryl ring of the benzylidene group. The molecular docking and dynamics studies of the most potent compounds (3i and 3l against BuChE and AChE, respectively) demonstrated remarkable interactions with the binding pockets of the ChE enzymes and confirmed the results obtained through in vitro experiments.

Profiling donepezil template into multipotent hybrids with antioxidant properties

Alzheimer’s disease is debilitating neurodegenerative disorder in the elderly. Current therapy relies on administration of acetylcholinesterase inhibitors (AChEIs) -donepezil, rivastigmine, galantamine, and N-methyl-d-aspartate receptor antagonist memantine. However, their therapeutic effect is only short-term and stabilizes cognitive functions for up to 2 years. Given this drawback together with other pathological hallmarks of the disease taken into consideration, novel approaches have recently emerged to better cope with AD onset or its progression. One such strategy implies broadening the biological profile of AChEIs into so-called multi-target directed ligands (MTDLs). In this review article, we made comprehensive literature survey emphasising on donepezil template which was structurally converted into plethora of MTLDs preserving anti-cholinesterase effect and, at the same time, escalating the anti-oxidant potential, which was reported as a crucial role in the pathogenesis of the Alzheimer’s disease.

Ebselen inhibits the activity of acetylcholinesterase globular isoform G4 in vitro and attenuates scopolamine-induced amnesia in mice

There is a well-known relationship between the cholinergic system and learning, memory, and other common cognitive processes. The process for researching and developing new drugs has lead researchers to repurpose older ones. This study investigated the effects of ebselen on the activity of acethylcholinesterase (AChE) isoforms in vitro and in an amnesia model induced by scopolamine in Swiss mice. In vitro, ebselen at concentrations equal or higher than 10 μM inhibited the activity of cortical and hippocampal G4/AChE, but not G1/AChE isoform. Treatment of mice with ebselen (50 mg/kg, i.p.) was effective against impairment of spatial recognition memory in both Y-maze and novel object recognition tests induced by scopolamine (1 mg/kg, i.p.). Ebselen (50 mg/kg) inhibited hippocampal AChE activity in mice. The present study demonstrates that ebselen inhibited the G4/AChE isoform in vitro and elicited an anti-amnesic effect in a mouse model induced by scopolamine. These findings reveal ebselen as a potential compound in terms of opening up valid therapeutic avenues for the treatment of memory impairment diseases.

Ebselen suppresses inflammation induced by Helicobacter pylori lipopolysaccharide via the p38 mitogen-activated protein kinase signaling pathway

Ebselen is a seleno-organic compound that has been demonstrated to have antioxidant and anti-inflammatory properties. A previous study determined that ebselen inhibits airway inflammation induced by inhalational lipopolysaccharide (LPS), however, the underlying molecular mechanism remains to be elucidated. The present study investigated the effect of ebselen on the glutathione peroxidase (GPX)‑reactive oxygen species (ROS) pathway and interleukin‑8 (IL‑8) expression induced by Helicobacter pylori LPS in gastric cancer (GC) cells. Cells were treated with 200 ng/ml H. pylori‑LPS in the presence or absence of ebselen for various durations and concentrations (µmol/l). The expression of toll‑like receptor 4 (TLR4), GPX2, GPX4, p38 mitogen‑activated protein kinase (p38 MAPK), phosphorylated‑p38 MAPK, ROS production and IL‑8 expression were detected with western blotting or ELISA. The present study revealed that TLR4 expression was upregulated; however, GPX2 and GPX4 expression was reduced following treatment with H. pylori LPS, which led to increased ROS production, subsequently altering the IL‑8 expression level in GC cells. Additionally, it was determined that ebselen prevented the reduction in GPX2/4 levels induced by H. pylori LPS, however, TLR4 expression was not affected. Ebselen may also block the expression of IL‑8 by inhibiting phosphorylation of p38 MAPK. These data suggest ebselen may inhibit ROS production triggered by H. pylori LPS treatment via GPX2/4 instead of TLR4 signaling and reduce phosphorylation of p38 MAPK, resulting in altered production of IL‑8. Ebselen may, therefore, be a potential therapeutic agent to mediate H. pylori LPS-induced cell damage.

Organoselenium compounds as mimics of selenoproteins and thiol modifier agents

Selenium is an essential trace element for animals and its role in the chemistry of life relies on a unique functional group: the selenol (-SeH) group. The selenol group participates in critical redox reactions. The antioxidant enzymes glutathione peroxidase (GPx) and thioredoxin reductase (TrxR) exemplify important selenoproteins. The selenol group shares several chemical properties with the thiol group (-SH), but it is much more reactive than the sulfur analogue. The substitution of S by Se has been exploited in organic synthesis for a long time, but in the last 4 decades the re-discovery of ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one) and the demonstration that it has antioxidant and therapeutic properties has renovated interest in the field. The ability of ebselen to mimic the reaction catalyzed by GPx has been viewed as the most important molecular mechanism of action of this class of compound. The term GPx-like or thiol peroxidase-like reaction was previously coined in the field and it is now accepted as the most important chemical attribute of organoselenium compounds. Here, we will critically review the literature on the capacity of organoselenium compounds to mimic selenoproteins (particularly GPx) and discuss some of the bottlenecks in the field. Although the GPx-like activity of organoselenium compounds contributes to their pharmacological effects, the superestimation of the GPx-like activity has to be questioned. The ability of these compounds to oxidize the thiol groups of proteins (the thiol modifier effects of organoselenium compounds) and to spare selenoproteins from inactivation by soft-electrophiles (MeHg⁺, Hg²⁺, Cd²⁺, etc.) might be more relevant for the explanation of their pharmacological effects than their GPx-like activity. In our view, the exploitation of the thiol modifier properties of organoselenium compounds can be harnessed more rationally than the use of low mass molecular structures to mimic the activity of high mass macromolecules that have been shaped by millions to billions of years of evolution.

Novel cinnamamide-dibenzylamine hybrids: Potent neurogenic agents with antioxidant, cholinergic, and neuroprotective properties as innovative drugs for Alzheimer's disease

By using fragments endowed with interesting and complementary properties for the treatment of Alzheimer's disease (AD), a novel series of cinnamamide-dibenzylamine hybrids have been designed, synthesized, and evaluated biologically. In vitro assay indicated that most of the target compounds exhibited a significant ability to inhibit ChEs, strong potency inhibitory of self-induced β-amyloid (Aβ) aggregation and to act as potential antioxidants and biometal chelators. A Lineweaver-Burk plot and molecular modeling study showed that compound 7f targeted both the CAS and PAS of AChE. In addition, compound 7f could chelate metal ions, reduce PC12 cells death induced by oxidative stress and penetrate the blood-brain barrier (BBB). Overall, all of these outstanding in vitro results in combination with promising in vivo outcomes highlighted derivative 7f as the lead structure worthy of further investigation.

Design, synthesis, molecular modeling and anticholinesterase activity of benzylidene-benzofuran-3-ones containing cyclic amine side chain

Aim: A series of 2-benzylidene-benzofuran-3-ones were designed from the structures of Ebselen analogs and aurone derivatives and synthesized in good yields. Materials & methods: The target compounds were prepared by the condensation reaction between appropriate benzofuranones with amino alkoxy aldehydes and evaluated as cholinesterase inhibitors by Ellman’s method. Results: The in vitro anti-acetylcholinesterase (AChE)/butyrylcholinesterase activities of the synthesized compounds revealed that 7e (IC50 = 0.045 μM) is the most active compound against AChE. Furthermore, the docking study confirmed the results obtained through in vitro experiments and predicted the possible binding conformation. Conclusion: The anticholinesterase activities of benzylidene-benzofurane-3-ones as aurone analogs revealed that the compounds bearing piperidinylethoxy residue showed better activities against AChE, introducing these compounds for further drug discovery developments.

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Selenium in the Therapy of Neurological Diseases. Where is it Going?

Selenium (₃₄Se), an antioxidant trace element, is an important regulator of brain function. These beneficial properties that Se possesses are attributed to its ability to be incorporated into selenoproteins as an amino acid. Several selenoproteins are expressed in the brain, in which some of them, e.g. glutathione peroxidases (GPxs), thioredoxin reductases (TrxRs) or selenoprotein P (SelP), are strongly involved in antioxidant defence and in maintaining intercellular reducing conditions. Since increased oxidative stress has been implicated in neurological disorders, including Parkinson’s disease, Alzheimer’s disease, stroke, epilepsy and others, a growing body of evidence suggests that Se depletion followed by decreased activity of Se-dependent enzymes may be important factors connected with those pathologies. Undoubtedly, the remarkable progress that has been made in understanding the biological function of Se in the brain has opened up new potential possibilities for the treatment of neurological diseases by using Se as a potential drug. However, further research in the search for optimal Se donors is necessary in order to achieve an effective and safe therapeutic income.

Design, synthesis and evaluation of clioquinol–ebselen hybrids as multi-target-directed ligands against Alzheimer's disease

A novel series of compounds obtained by fusing the metal-chelating agent clioquinol and the antioxidant ebselen were designed, synthesized and evaluated as multi-target-directed ligands against Alzheimer's disease (AD).

Construction of a smart microgel glutathione peroxidase mimic based on supramolecular self-assembly

In an effort to construct smart artificial glutathione peroxidase (GPx) featuring high catalytic activity in an efficient preparation process, an artificial microgel GPx (PPAM-ADA-Te) has been prepared using a supramolecular host-guest self-assembly technique. Herein, 6,6'-telluro-bis(6-deoxy-β-cyclodextrin) (CD-Te-CD) was selected as a tellurium-containing host molecule, which also served as the crosslinker for the scaffold of the supramolecular microgel. And an adamantane-containing block copolymer (PPAM-ADA) was designed and synthesized as a guest building block copolymer. Subsequently, PPAM-ADA-Te was constructed through the self-assembly of CD-Te-CD and PPAM-ADA. The formation of this self-assembled construct was confirmed by dynamic light scattering, NMR, SEM and TEM. Notably, PPAM-ADA-Te not only exhibits a significant temperature responsive catalytic activity, but also features the characteristic saturation kinetics behaviour similar to that of a natural enzyme catalyst. We demonstrate in this paper that both the hydrophobic microenvironment and the crosslinker in this supramolecular microgel network played significant roles in enhancing and altering the temperature responsive catalytic behaviour. The successful construction of PPAM-ADA-Te not only provides a novel method for the preparation of microgel artificial GPx with high catalytic activity but also provides properties suitable for the future development of intelligent antioxidant drugs.

Organoselenocyanates and symmetrical diselenides redox modulators: Design, synthesis and biological evaluation

Oxidative stress (OS) and disturbed intracellular redox balance have been predominantly observed in different types of cancer, including hepatocellular carcinoma (HCC). Agents which can stop OS multi-stressor events and modulate the intracellular redox state are becoming a major focus in HCC prevention. Among them, compounds with glutathione peroxidase (GPx)-like activity are of particularly concern. We herein report the synthesis of novel series of organoselenocyanates and symmetrical diselenide antioxidants, inspired by the natural redox enzyme, GPx and the synthetic organoselenium ebselen antioxidants. Their cytotoxic activity was evaluated against Hep G2 cells and their antimicrobial activities were evaluated against Candida albicans (C. albicans) fungus as well as against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), gram-negative and gram-positive bacteria, respectively. These compounds were also tested for their antioxidant activities using 2,2-diphenyl-1-picrylhydrazyl (DPPH), GPx-like activity and bleomycin dependent DNA damage assays and a basic structure-activity relationship was subsequently established. The physicochemical parameters and drug-likeness were computed employing the Molinspiration online property calculation toolkit and MolSoft software. Interestingly, some compounds proved to be more cytotoxic than ebselen and the known anticancer drug 5-Fu and in the same time they showed similar, sometime even more, antifungal activity than the reference antifungal drugs. Among these compounds, compound 16 was considered to be the most interesting with free radical-scavenging activity comparable to ascorbic acid and a GPx-like activity similar to ebselen. As most of these compounds comply with Lipinski's Rule of Five, they promise good bioavailability, which needs to be studied as part of future investigations.

Design, synthesis and anticholinesterase activity of novel benzylidenechroman-4-ones bearing cyclic amine side chain

A series of 3-(4-(aminoalkoxy)benzylidene)-chroman-4-ones 7a-r were designed and synthesized as analogs of homoisoflavonoids which are well known natural products with diverse pharmacological properties related to Alzheimer's disease. The in vitro anti-cholinesterase activity of designed compounds 7a-r against AChE and BuChE, revealed that compounds bearing piperidinylethoxy residue showed potent activity against AChE at sub-micromolar level (IC50 values = 0.122-0.207 μM), more potent than reference drug tacrine. The structure-activity relationships study of piperidinylethoxy series demonstrated that the selectivity and physicochemical properties of compounds could be optimized by selection of a proper substituent on the C-7 position of chroman ring, while the high potency of the molecule against AChE was reserved.

Synthesis and evaluation of selegiline derivatives as monoamine oxidase inhibitor, antioxidant and metal chelator against Alzheimer's disease

A series of compounds with monoamine oxidase inhibition and biometal chelation activities were designed, synthesised and evaluated as agents against Alzheimer's disease. The in vitro assay shows that most target compounds exhibit good MAO-B activities with submicromolar IC50 values and antioxidant activity (1.49-5.67 ORAC-FL values). The selected compounds were used to determine the biometal chelating ability using UV-vis spectrometry and high-resolution mass spectrometry, which confirm that they can effectively interact with copper(II), iron(II) and zinc(II). The ThT fluorescence binding assay indicates that the synthetic compounds can inhibit Cu(II)-induced Aβ1-42 aggregation. The parallel artificial membrane permeation assay shows that most target compounds can cross the BBB. Based on these results, compound 8a was selected as a potential multifunctional agent for the treatment of AD.

Recent development of multifunctional agents as potential drug candidates for the treatment of Alzheimer's disease

Alzheimer's disease (AD) is a complex and progressive neurodegenerative disorder. The available therapy is limited to the symptomatic treatment and its efficacy remains unsatisfactory. In view of the prevalence and expected increase in the incidence of AD, the development of an effective therapy is crucial for public health. Due to the multifactorial aetiology of this disease, the multi-target-directed ligand (MTDL) approach is a promising method in search for new drugs for AD. This review updates information on the development of multifunctional potential anti-AD agents published within the last three years. The majority of the recently reported structures are acetylcholinesterase inhibitors, often endowed with some additional properties. These properties enrich the pharmacological profile of the compounds giving hope for not only symptomatic but also causal treatment of the disease. Among these advantageous properties, the most often reported are an amyloid-β antiaggregation activity, inhibition of β-secretase and monoamine oxidase, an antioxidant and metal chelating activity, NOreleasing ability and interaction with cannabinoid, NMDA or histamine H3 receptors. The majority of novel molecules possess heterodimeric structures, able to interact with multiple targets by combining different pharmacophores, original or derived from natural products or existing therapeutics (tacrine, donepezil, galantamine, memantine). Among the described compounds, several seem to be promising drug candidates, while others may serve as a valuable inspiration in the search for new effective therapies for AD.

Design, synthesis, and evaluation of multitarget-directed selenium-containing clioquinol derivatives for the treatment of Alzheimer's disease

A series of selenium-containing clioquinol derivatives were designed, synthesized, and evaluated as multifunctional anti-Alzheimer's disease (AD) agents. In vitro examination showed that several target compounds exhibited activities such as inhibition of metal-induced Aβ aggregation, antioxidative properties, hydrogen peroxide scavenging, and the prevention of copper redox cycling. A parallel artificial membrane permeation assay indicated that selenium-containing clioquinol derivatives possessed significant blood-brain barrier (BBB) permeability. Compound 8a, with a propynylselanyl group linked to the oxine, demonstrated higher hydrogen peroxide scavenging and intracellular antioxidant activity than clioquinol. Furthermore, 8a exhibited significant inhibition of Cu(II)-induced Aβ1-42 aggregation and was capable of disassembling the preformed Cu(II)-induced Aβ aggregates. Therefore, 8a is an excellent multifunctional promising compound for development of novel drugs for AD.