1-(Phenylselanyl)-2-(p-tolyl)indolizine: A selenoindolizine with potential antidepressant-like activity in mice mediated by the modulation of dopaminergic and noradrenergic systems

1-(Phenylselanyl)-2-(p-tolyl)indolizine (MeSeI) is a selenoindolizine with an antidepressant-like effect in mice by regulation of the serotonergic system. This study investigated the involvement of dopaminergic and noradrenergic systems in the antidepressant-like action of MeSeI. For this purpose, Swiss male mice were pretreated with different antagonists, after 15 min, the MeSeI was administrated by intragastric (i.g.) via; after 30 min, the mouse behavior was assessed in the forced swimming test (FST). The action of MeSeI on the activity of monoamine oxidase (MAO) was determined. The pretreatment of mice with haloperidol (0.05 mg/kg, intraperitoneally, i.p.; non-selective dopamine receptor antagonist), sulpiride (50 mg/kg, i.p.; D2 receptor antagonist), yohimbine (1 mg/kg, i.p.; α2 receptor antagonist), and propranolol (2 mg/kg, i.p.; non-selective β receptor antagonist), inhibited the anti-immobility action of MeSeI (50 mg/kg, i.g.) in the FST. This blocking effect was not observed when SCH23390 (0.01 mg/kg, i.p.; D1 receptor antagonist), and prazosin (1 mg/kg, i.p.; α1 receptor antagonist) were administered. The coadministration of subeffective doses of bupropion (3 mg/kg. i.g.; dopamine and noradrenaline reuptake inhibitor) and MeSeI (0.5 mg/kg. i.g.) reduced the immobility time in the FST. Furthermore, MeSeI inhibited MAO-A and B activities in vitro and ex vivo tests. These results suggest that MeSeI exerts its antidepressant-like effect via regulation of the D2, α2, and β1 receptors and the inhibition of MAO-A and B activities. Molecular docking investigations corroborated these results. This study provides comprehensive insights into the antidepressant-like mechanism of MeSeI in mice, suggesting its potential as a novel antidepressant candidate.

Exploring the antioxidant potential of chalcogen-indolizines throughout in vitro assays

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are highly reactive molecules produced naturally by the body and by external factors. When these species are generated in excessive amounts, they can lead to oxidative stress, which in turn can cause cellular and tissue damage. This damage is known to contribute to the aging process and is associated with age-related conditions, including cardiovascular and neurodegenerative diseases. In recent years, there has been an increased interest in the development of compounds with antioxidant potential to assist in the treatment of disorders related to oxidative stress. In this way, compounds containing sulfur (S) and/or selenium (Se) have been considered promising due to the relevant role of these elements in the biosynthesis of antioxidant enzymes and essential proteins with physiological functions. In this context, studies involving heterocyclic nuclei have significantly increased, notably highlighting the indolizine nucleus, given that compounds containing this nucleus have been demonstrating considerable pharmacological properties. Thus, the objective of this research was to evaluate the in vitro antioxidant activity of eight S- and Se-derivatives containing indolizine nucleus and different substituents. The in vitro assays 1,1-diphenyl-2-picryl-hydrazil (DPPH) scavenger activity, ferric ion (Fe3+) reducing antioxidant power (FRAP), thiobarbituric acid reactive species (TBARS), and protein carbonylation (PC) were used to access the antioxidant profile of the compounds. Our findings demonstrated that all the compounds showed FRAP activity and reduced the levels of TBARS and PC in mouse brains homogenates. Some compounds were also capable of acting as DPPH scavengers. In conclusion, the present study demonstrated that eight novel organochalcogen compounds exhibit antioxidant activity.

Bioactivity of selenium-containing pyridinium salts: Prospecting future pharmaceutical constituents to treat liver diseases involving oxidative stress

Redox imbalance leads to oxidative stress that causes irreversible cellular damage. The incorporation of the antioxidant element selenium (Se) in the structure of pyridinium salts has been used as a strategy in chemical synthesis and can be useful in drug development. We investigated the antioxidant activity of Se-containing pyridinium salts (named Compounds 3A, 3B, and 3C) through in vitro tests. We focused our study on liver protein carbonylation, liver lipoperoxidation, free radical scavenging activity (1,1-diphenyl-2-picryl-hydrazil [DPPH]; 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid [ABTS]), and enzyme-mimetic activity assays (glutathione S-transferase [GST]-like; superoxide dismutase [SOD]-like). In addition, 2-(4-chlorophenyl)-2-oxoethyl)-2-((phenylselanyl)methyl)pyridin-1-ium bromide (3C) was selected to evaluate the acute oral toxicity in mice due to the best antioxidant profile. The three compounds were effective in reducing the levels of protein carbonylation and lipoperoxidation in the liver in a µM concentration range. All compounds demonstrated scavenger activity of DPPH and ABTS radicals, and GST-like action. No significant effects were detected in the SOD-like assay. Experimental data also showed that the acute oral treatment of mice with Compound 3C (50 and 300 mg/kg) did not cause mortality or change markers of liver and kidney functions. In summary, our findings reveal the antioxidant potential of Se-containing pyridinium salts in liver tissue, which could be related to their radical scavenging ability and mimetic action on the GST enzyme. They also demonstrate a low toxicity potential for Compound 3C. Together, the promising results open space for future studies on the therapeutic application of these molecules.

Visible Light and Triselenium Dicyanide (TSD): New Horizons in the Synthesis of Organic Selenocyanates

Herein, we describe a new method for the synthesis of α-carbonyl selenocyanates by reacting triselenium dicyanide (TSD) and styrenes under blue light irradiation and O2 atmosphere. The reactions are triggered by the formation of Se-centered radical species, followed by the addition/oxidation of the styrene π-bond. α-Carbonyl selenocyanates and α-hydroxy selenocyanates were obtained in moderate to excellent yields from aryl- and alkyl-substituted alkenes, respectively. It was demonstrated that α-carbonyl selenocyanates could be used as a synthetic platform in a multicomponent reaction strategy to prepare 2-phenylimidazo[1,2-a]pyridine derivatives, which were evaluated for their photophysical properties. Overall, this new method provides a useful tool for synthesizing α-carbonyl selenocyanates, and demonstrates their potential for use in the synthesis of other compounds, thus giving new synthetic opportunities to construct organic selenocyanate compounds.

Involvement of the serotonergic system in the antidepressant-like effect of 1-(phenylselanyl)-2-(p-tolyl)indolizine in mice

RATIONALE

Depression is a mental disorder that affects approximately 280 million people worldwide. In the search for new treatments for mood disorders, compounds containing selenium and indolizine derivatives show promising results.

OBJECTIVES AND METHODS

To evaluate the antidepressant-like effect of 1-(phenylselanyl)-2-(p-tolyl)indolizine (MeSeI) (0.5-50 mg/kg, intragastric-i.g.) on the tail suspension test (TST) and the forced swim test (FST) in adult male Swiss mice and to elucidate the role of the serotonergic system in this effect through pharmacological and in silico approaches, as well to evaluate acute oral toxicity at a high dose (300 mg/kg).

RESULTS

MeSeI administered 30 min before the FST and the TST reduced immobility time at doses from 1 mg/kg and at 50 mg/kg and increased the latency time for the first episode of immobility, demonstrating an antidepressant-like effect. In the open field test (OFT), MeSeI did not change the locomotor activity. The antidepressant-like effect of MeSeI (50 mg/kg, i.g.) was prevented by the pre-treatment with p-chlorophenylalanine (p-CPA), a selective tryptophan hydroxylase inhibitor (100 mg/kg, intraperitoneally-i.p. for 4 days), with ketanserin, a 5-HT_2A/2C receptor antagonist (1 mg/kg, i.p.), and with GR113808, a 5-HT₄ receptor antagonist (0.1 mg/kg, i.p.), but not with WAY100635, a selective 5-HT_1A receptor antagonist (0.1 mg/kg, subcutaneous-s.c.) and ondansetron, a 5-HT₃ receptor antagonist (1 mg/kg, i.p.). MeSeI showed a binding affinity with 5-HT_2A, 5 -HT_2C, and 5-HT₄ receptors by molecular docking. MeSeI (300 mg/kg, i.g.) demonstrated low potential to cause acute toxicity in adult female Swiss mice.

CONCLUSION

In summary, MeSeI exhibits an antidepressant-like effect mediated by the serotonergic system and could be considered for the development of new treatment strategies for depression.

Arylseleninic acid derivatives decomposition towards Se(II)-based electrophiles: an elegant approach to construct 3-selanyl- imidazopyridines

Benzeneseleninic acid (BSA) derivatives were used as an alternative, but extremelly useful, source of Se(II)-based electrophiles, generated in situ by thermal decomposition, to construct C-Se bonds, accessing 3-selanylimidazopyridines after reaction...

Neuropharmacology of Organoselenium Compounds in Mental Disorders and Degenerative Diseases

Neurodegenerative and mental disorders are a public health burden with pharmacological treatments of limited efficacy. Organoselenium compounds are receiving great attention in medicinal chemistry mainly because of their antioxidant and immunomodulatory activities, with a multi-target profile that can favor the treatment of multifactorial diseases. Therefore, the purpose of this review is to discuss recent preclinical studies about organoselenium compounds as therapeutic agents for the management of mental (e.g., depression, anxiety, bipolar disorder, and schizophrenia) and neurodegenerative diseases (e.g., Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis). We have summarized around 70 peer-reviewed articles from 2016 to the present that used in silico, in vitro, and/or in vivo approaches to assess the neuropharmacology of selenium-containing compounds. Among the diversity of organoselenium molecules investigated in the last five years, diaryl diselenides, Ebselen-derivatives, and Se-containing heterocycles are the most representative. Ultimately, this review is expected to provide disease-oriented information regarding the neuropharmacology of organoselenium compounds that can be useful for the design, synthesis, and pharmacological characterization of novel bioactive molecules that can potentially be clinically viable candidates.

Antidepressant-Like Effect of a Selenoindolizine in Mice: In Vivo and In Silico Evidence for the Involvement of the Serotonergic 5-HT2A/C Receptors

The monoaminergic dysfunction plays a central role in major depressive disorder (MDD), a mental disturbance associated with constant feeling of sadness and lack of interest. The available treatments do not present a desirable efficacy and some of them provoke several adverse effects. In this context, organoselenium compounds and molecules containing the indolizine nucleus have demonstrated interesting pharmacological properties, including antidepressant-like effects. In this study, the antidepressant-like effect of 2-phenyl-1-(phenylselanyl)indolizine (SeI), a selenium-containing indolizine derivative, was investigated on the forced swimming test (FST) and on the tail suspension test (TST) in male Swiss mice. The involvement of the serotonergic system in this effect was also accessed. The selenium compound SeI (10-100 mg/kg, intragastrical (i.g.)) was administered 0.5 h before the behavioral tests, and it diminished the immobility on both FST and TST experiments, which is an indication of antidepressant-like effect. No changing in the locomotor motion was observed in the open-field test (OFT). The anti-immobility effect of SeI was not altered by the preadministration of the selective serotonergic receptor antagonists ondansetron (1 mg/kg, intraperitoneally (i.p.), antagonist of 5-HT₃ receptor) and WAY100635 (0.1 mg/kg, subcutaneous route (s.c.), antagonist of 5-HT_1A receptor). In contrast, the preadministration of ketanserin (1 mg/kg, i.p., antagonist of 5-HT_2A/C receptor) blocked this effect, demonstrating that the antidepressant-like effect of SeI involves 5-HT_2A/C. In addition, molecular docking studies showed a strong interaction between SeI and the receptors of 5-HT_2A and 5-HT_2C. The toxicological results demonstrated that SeI has low potential to cause adverse effects in mice. It was found that the antidepressant-like effect of SeI is related to modulation of the serotonergic system, and this selenium compound could be included in new treatment approaches for MDD.

UVA Light-promoted Catalyst-free Cyclization of Vinyl Selenides: Green and Efficient Synthesis of C3-Unsubstituted 2-Selanyl Benzochalcogenophenes

A metal- and catalyst-free photo-promoted cyclization of properly substituted vinyl selenides was developed using UVA irradiation. A total of eighteen new C3-unsubstituted 2-selanyl benzochalcogenophenes (benzofurans, benzothiophenes and benzoselenophenes) were prepared in 30-86% yield after irradiation with UVA at room temperature. The usefulness of the title compounds was demonstrated in the easy functionalization of the remaining free C-H bond of the benzochalcogenophenes to form new C-Se and C-Br bonds by simple procedures. Furthermore, the reaction can be performed under natural sunlight irradiation and the solvent is easily reused further in several subsequent runs.

Recent Advances in the Oxone-Mediated Synthesis of Heterocyclic Compounds

Oxone is a commercially available oxidant, composed of a mixture of three inorganic species, being the potassium peroxymonosulfate (KHSO5) the reactive one. Over the past few decades, this cheap and environmentally friendly oxidant has become a powerful tool in organic synthesis, being extensively employed to mediate the construction of a plethora of important compounds. This review summarizes the recent advances in the Oxone-mediated synthesis of N-, O- and chalcogen-containing heterocyclic compounds, through a wide diversity of reactions, starting from several kinds of substrate, highlighting the main synthetic differences, advantages, the scope and limitations.

Recent Advances in the Synthesis of Selenophenes and Their Derivatives

The selenophene derivatives are an important class of selenium-based heterocyclics. These compounds play an important role in prospecting new drugs, as well as in the development of new light-emitting materials. During the last years, several methods have been emerging to access the selenophene scaffold, employing a diversity of cyclization-based synthetic strategies, involving specific reaction partners and particularities. This review presents a comprehensive discussion on the recent advances in the synthesis of selenophene-based compounds, starting from different precursors, highlighting the main differences, the advantages, and limitations among them.

Arylseleninic acid as a green, bench-stable selenylating agent: synthesis of selanylanilines and 3-selanylindoles

C–Se bonds in electron-rich arenes are easily formed by the reaction of bench-stable arylseleninic acids as an electrophilic selenium source. The only waste in the reaction is water.

Synthesis of Isoxazolines by the Electrophilic Chalcogenation of β,γ-Unsaturated Oximes: Fishing Novel Anti-Inflammatory Agents

Herein, we describe a new strategy to prepare chalcogen-functionalized isoxazolines. The strategy involves the reaction of β,γ-unsaturated oximes with electrophilic selenium and tellurium species, affording 19 new selenium- and tellurium-containing isoxazolines in good yields after 1 h at room temperature. The method was efficiently extended to the synthesis of 5 new (bis)isoxazoline ditellurides. One of the prepared compounds, 3-phenyl-5-((phenylselanyl)methyl)-isoxazoline, demonstrated better anti-inflammatory and antiedematogenic effects than the reference drug Celecoxib.

Ultrasound-enhanced Ag-catalyzed decarboxylative coupling between α-keto acids and disulfides for the synthesis of thioesters

Herein, we described the ultrasound-assisted synthesis of thioesters via the Ag-catalyzed radical oxidative decarboxylation of α-keto acids, in the presence of disulfides. This protocol takes advantage of the sonication to prepare the title compounds in moderate to very good yields, in only 20 min of reaction. The positive effect of ultrasonic irradiation is attributed to both, the high mass transfer efficiency and to the induced radical formation in the reaction medium.

Synthesis of 2-(Arylselanyl)benzo[b]chalcogenophenes via Intramolecular Cyclization of Vinyl Selenides

An efficient protocol to access 2-arylselanylbenzo[b]chalcogenophene derivatives through the Cu(I)-catalyzed annulation of vinyl selenides is described. The key vinyl selenides were easily prepared from properly functionalized 1,1-dibromostyrenes and the method allowed the synthesis of 2-arylselanylfurans, -thiophenes, and -selenophenes in moderate to excellent yields.

Selenium dioxide-promoted selective synthesis of mono- and bis-sulfenylindoles

Easy access to mono- and bis-sulfenylindoles using the SeO₂/I₂ system.