Synthesis, characterization, structures and antioxidant activity of nicotinoyl based organoselenium compounds

Unravelling the molecular interaction of diselenodipropionic acid (DSePA) with human serum albumin (HSA)

DSePA, a pharmacologically efficient selenium compound shows strong binding with extracellular carrier protein, Human Serum Albumin.

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.

Redox reactions of organoselenium compounds: Implication in their biological activity

Antioxidant activity of organoselenium compounds belonging to different classes i.e. functionalized aliphatic, aromatic and cyclic selenoethers, are compared on the basis of their ability to scavenge reactive oxygen species like hydroxyl and peroxyl radicals and to exhibit glutathione peroxidase (GPx) like catalytic activity. The comparative analysis has revealed that the antioxidant activity of the organoselenium compounds show direct correlation with the energy of the highest occupied molecular orbital (HOMO) and neighboring group participation that stabilizes the reaction intermediate. Finally, structural features responsible for improving the rate of reaction of organoselenium compounds with free radical/molecular oxidants have been discussed on the basis of the compounds screened at our institute.

Zero-, one-, two- and three-dimensional supramolecular architectures sustained by Se…O chalcogen bonding: A crystallographic survey

The Cambridge Structural Database was evaluated for crystals containing Se…O chalcogen bonding interactions. These secondary bonding interactions are found to operate independently of complementary intermolecular interactions in about 13% of the structures they can potentially form. This number rises significantly when more specific interactions are considered, e.g. Se…O(carbonyl) interactions occur in 50% of cases where they can potentially form. In about 55% of cases, the supramolecular assemblies sustained by Se…O(oxygen) interactions are one-dimensional architectures, with the next most prominent being zero-dimensional assemblies, at 30%.

Selenium Donors at the Junction of Inflammatory Diseases

Selenium is an essential non-metal trace element, and the imbalance in the bioavailability of selenium is associated with many diseases ranking from acute respiratory distress syndrome, myocardial infarction and renal failure (Se overloading) to diseases associated with chronic inflammation like inflammatory bowel diseases, rheumatoid arthritis, and atherosclerosis (Se unload). The only source of selenium is the diet (animal and cereal sources) and its intestinal absorption is limiting for selenocysteine and selenomethionine synthesis and incorporation in selenoproteins. In this review, after establishing the link between selenium and inflammatory diseases, we envisaged the potential of selenium nanoparticles and organic selenocompounds to compensate the deficit of selenium intake from the diet. With high selenium loading, nanoparticles offer a low dosage to restore selenium bioavailability whereas organic selenocompounds can play a role in the modulation of their antioxidant or antiinflammatory activities.

2,2′-Dipyridyl diselenide (Py2Se2) induces G1 arrest and apoptosis in human lung carcinoma (A549) cells through ROS scavenging and reductive stress

This study demonstrates the cytotoxic activity and the underlying mechanisms of a synthetic organoselenium compound containing pyridine and diselenide moieties.

Internally functionalized multifaceted organochalcogen compounds

Internally functionalized multifaceted organochalcogen compounds have been designed and their ligand chemistry has been developed. The palladium complexes show remarkable homogeneous catalytic activity.

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.

Glutathione Peroxidase-Like Activity of Amino-Substituted Water-Soluble Cyclic Selenides: A Shift of the Major Catalytic Cycle in Methanol

We previously reported that water-soluble cyclic selenides can mimic the antioxidative function of glutathione peroxidase (GPx) in water through a simple catalytic cycle, in which the selenide (>Se) is oxidized by H₂O₂ to the selenoxide (>Se=O) and the selenoxide is reduced by a thiol back to the selenide. In methanol, however, the GPx-like activity could not be explained by this simple scenario. To look into the reasons for the unusual behaviors in methanol, monoamino-substituted cyclic selenides with a variable ring size were synthesized, and the intermediates of the catalytic cycle were characterized by means of ⁷⁷Se-NMR and LC–MS spectroscopies. In water, it was confirmed that the selenide and the selenoxide mainly contribute to the antioxidative function, though a slight contribution from the dihydroxy selenane (>Se(OH)₂) was also suggested. In methanol, on the other hand, other active species, such as hydroxyselenonium (>Se⁺–OH) and hydroxy perhydroxy selenane (>Se(OH)(OOH)), could be generated to build another catalytic cycle. This over-oxidation would be more feasible for amino-substituted cyclic selenides, probably because the ammonium (NH₃⁺) group would transfer a proton to the selenoxide moiety to produce a hydroxyselenonium species in the absence of an additional proton source. Thus, a shift of the major catalytic cycle in methanol would make the GPx-like antioxidative function of selenides perplexing.

Diphenyl diselenide derivatives inhibit microbial biofilm formation involved in wound infection

Background

Organoselenium compounds have antimicrobial activity against some bacteria and fungi; furthermore, the antioxidant activity of diselenides has been demonstrated. The aim of the present work was to examine the in vitro minimal inhibitory concentration of a panel of differently substituted diselenides and their effectiveness in inhibiting biofilm formation and dispersing preformed microbial biofilm of Staphylococcus epidermidis, Staphylococcus aureus, Streptococcus pyogenes and Pseudomonas aeruginosa and the yeast Candida albicans, all involved in wound infections. Moreover, the cytotoxicity of the compounds was determined in human dermal fibroblast and keratinocytes. In closing, we tested their direct antioxidant activity.

Results

Diselenides showed different antimicrobial activity, depending on the microorganism. All diselenides demonstrated a good antibiofilm activity against S. aureus and S. epidermidis, the compounds camphor diselenide, bis[ethyl-N-(2’-selenobenzoyl) glycinate] and bis[2’-seleno-N-(1-methyl-2-phenylethyl) benzamide] were active against S. pyogenes and C. albicans biofilm while only diselenides 2,2’-diselenidyldibenzoic acid and bis[ethyl-N-(2’-selenobenzoyl) glycinate] were effective against P. aeruginosa. Moreover, the compounds bis[ethyl-N-(2’-selenobenzoyl) glycinate] and bis[2’-seleno-N-(1-methyl-2-phenylethyl) benzamide] showed an antioxidant activity at concentrations lower than the 50 % of cytotoxic concentration.

Conclusions

Because microbial biofilms are implicated in chronic infection of wounds and treatment failure, the combination of antimicrobial activity and potential radical scavenging effects may contribute to the improvement of wound healing. Therefore, this study suggests that bis[ethylN-(2’-selenobenzoyl) glycinate] and bis[2’-seleno-N-(1-methyl-2-phenylethyl) benzamide] are promising compounds to be used in preventing and treating microbial wound infections.

Synthesis, structural analysis, antimicrobial evaluation and synergistic studies of imidazo[1,2-a]pyrimidine chalcogenides

Synthesis and structural analysis of novel imidazo[1,2-a]pyrimidine chalcogenides exhibiting effective antimicrobial activity and synergistic effects with known antibiotics have been reported.

Design and Synthesis of DiselenoBisBenzamides (DISeBAs) as Nucleocapsid Protein 7 (NCp7) Inhibitors with anti-HIV Activity

The interest in the synthesis of Se-containing compounds is growing with the discovery of derivatives exhibiting various biological activities. In this manuscript, we have identified a series of 2,2'-diselenobisbenzamides (DISeBAs) as novel HIV retroviral nucleocapsid protein 7 (NCp7) inhibitors. Because of its pleiotropic functions in the whole viral life cycle and its mutation intolerant nature, NCp7 represents a target of great interest which is not reached by any anti-HIV agent in clinical use. Using the diselenobisbenzoic scaffold, amino acid, and benzenesulfonamide derivatives were prepared and biologically profiled against different models of HIV infection. The incorporation of amino acids such as glycine and glutamate into DISeBAs 7 and 8 resulted in selective anti-HIV activity against both acutely and chronically infected cells as well as an interesting virucidal effect. DISeBAs demonstrated broad antiretroviral activity, encompassing HIV-1 drug-resistant strains including clinical isolates, as well as simian immunodeficiency virus (SIV). Time of addition experiments, along with the observed dose dependent inhibition of the Gag precursor proper processing, confirmed that their mechanism of action is based on NCp7 inhibition.

Redox control of GPx catalytic activity through mediating self-assembly of Fmoc-phenylalanine selenide into switchable supramolecular architectures

Artificial enzymes capable of achieving tunable catalytic activity through stimuli control of enzymatic structure transition are of significance in biosensor and biomedicine research. Herein we report a novel smart glutathione peroxidise (GPx) mimic with modulatory catalytic activity based on redox-induced supramolecular self-assembly. First, an amphiphilic Fmoc-phenylalanine-based selenide was designed and synthesized, which can self-assemble into nanospheres (NSs) in aqueous solution. The NSs demonstrate extremely low GPx activity. Upon the oxidation of hydroperoxides (ROOH), the selenide can be quickly transformed into the selenoxide form. The change of the molecular structure induces complete morphology transition of the self-assemblies from NSs to nanotubes (NTs), resulting in great enhancement in the GPx catalytic activity. Under the reduction of GSH, the selenoxide can be further reversibly reduced back into the selenide; therefore the reversible switch between the NSs and NTs can be successfully accomplished. The relationship between the catalytic activity and enzymatic structure was also investigated. The dual response nature makes this mimic play roles of both a sensor and a GPx enzyme at the same time, which can auto-detect the signal of ROOH and then auto-change its activity to achieve quick or slow/no scavenging of ROOH. The dynamic balance of ROOH is vital in organisms, in which an appropriate amount of ROOH does benefit to the metabolism, whereas surplus ROOH can cause oxidative damage of the cell instead and this smart mimic is of remarkable significance. We expect that such a mimic can be developed into an effective antioxidant drug and provide a new platform for the construction of intelligent artificial enzymes with multiple desirable properties.

Stable selones in glutathione-peroxidase-like catalytic cycle of selenonicotinamide derivative

Stable selone formation in 2,2′-diselenobis[3-amidopyridine], reduces unwanted sulfur exchange reaction in glutathione peroxidase like catalytic cycle and enhances its enzyme activity.