Synthesis and antioxidant activity of new C-3 sulfenyl indoles

Synthesis and investigation of new indole-containing vinyl sulfide derivatives: In silico and in vitro studies for potential therapeutic applications

Indoles featuring organosulfur compounds serve as privileged structural scaffolds in various biologically active compounds. This study investigates the biological properties of five synthetic sulphenyl vinyl indoles (3 a-e) using both in silico and in vitro methods. Computational analyses employing Swiss ADME and Molinspiration software reveal the remarkable inhibitory activity of compound 3 d against proteases and kinases (scores of 0.18 and 0.06, respectively). Furthermore, it demonstrates the ability to modulate ionic and G protein-coupled receptors (scores: -0.06 and 0.31, respectively) and serves as a ligand for nuclear receptors (score 0.15). In vitro investigations highlight the compounds' efficacy in countering ABTS+ radical attacks and reducing lipid peroxidation levels. Particularly noteworthy is the superior efficacy of compounds 3 a, 3 b, and 3 e in DPPH (EC50 3 a: 268.5 μM) and TEAC assays (EC50 3 a: 49.9 μM; EC50 3 b: 133.4 μM, and EC50 3 e: 84.9 μM), as well as TBARS levels. Compound 3 c significantly reduces acetylcholinesterase activity, positioning itself as a noteworthy enzyme inhibitor. This study emphasizes the versatile biological potential of synthetic indole derivatives, suggesting their applicability for therapeutic purposes.

"Alkene-to-Alkene" Difunctionalization of Enaminones for the Synthesis of Polyfunctionalized Alkenes by Transition-Metal-Free C-H and C-N Bond Transformation

The three-component reactions of enaminones, disulfides, and alcohols for the synthesis of polyfunctionalized alkenes have been realized via the C-H and C-N bond transformation on enaminones. The reactions proceed in a novel "alkene-to-alkene" difunctionalization mode without using any transition metal. The application of the alkene products in the synthesis of divergent sulfenyl heteroaryls, including sulfenylated pyrazoles, pyrimidines, and isoxazoles, via simple annulation has also been verified.

Artificial Intelligence in Decrypting Cytoprotective Activity under Oxidative Stress from Molecular Structure

Artificial intelligence (AI) is widely explored nowadays, and it gives opportunities to enhance classical approaches in QSAR studies. The aim of this study was to investigate the cytoprotective activity parameter under oxidative stress conditions for indole-based structures, with the ultimate goal of developing AI models capable of predicting cytoprotective activity and generating novel indole-based compounds. We propose a new AI system capable of suggesting new chemical structures based on some known cytoprotective activity. Cytoprotective activity prediction models, employing algorithms such as random forest, decision tree, support vector machines, K-nearest neighbors, and multiple linear regression, were built, and the best (based on quality measurements) was used to make predictions. Finally, the experimental evaluation of the computational results was undertaken in vitro. The proposed methodology resulted in the creation of a library of new indole-based compounds with assigned cytoprotective activity. The other outcome of this study was the development of a validated predictive model capable of estimating cytoprotective activity to a certain extent using molecular structure as input, supported by experimental confirmation.

Indole Derivatives Bearing Imidazole, Benzothiazole-2-Thione or Benzoxazole-2-Thione Moieties-Synthesis, Structure and Evaluation of Their Cytoprotective, Antioxidant, Antibacterial and Fungicidal Activities

In the search for new bioactive compounds, a methodology based on combining two molecules with biological properties into a new hybrid molecule was used to design and synthesize of a series of ten indole derivatives bearing imidazole, benzothiazole-2-thione, or benzoxazole-2-thione moieties at the C-3 position. The compounds were spectroscopically characterized and tested for their antioxidant, antibacterial, and fungicidal activities. The crystal structures were determined for five of them. Comparison of the closely related structures containing either benzothiazole-2-thione or benzoxazole-2-thione clearly shows that the replacement of -S- and -O- ring atoms modify molecular conformation in the crystal, changes intermolecular interactions, and has a severe impact on biological activity. The results indicate that indole-imidazole derivatives with alkyl substituent exhibit an excellent cytoprotective effect against AAPH-induced oxidative hemolysis and act as effective ferrous ion chelating agents. The indole-imidazole compound with chlorine atoms inhibited the growth of fungal strains: Coriolus versicolor (Cv), Poria placenta (Pp), Coniophora puteana (Cp), and Gloeophyllum trabeum (Gt). The indole-imidazole derivatives showed the highest antibacterial activity, for which the largest growth-inhibition zones were noted in M. luteus and P. fluorescens cultures. The obtained results may be helpful in the development of selective indole derivatives as effective antioxidants and/or antimicrobial agents.

Synthesis, antioxidant and cytoprotective activity evaluation of C-3 substituted indole derivatives

A series of fifteen indole derivatives substituted at the C-3 position were synthesized and characterized. The antioxidant activity of all derivatives was investigated by three in vitro antioxidant assays, and the derivative with pyrrolidinedithiocarbamate moiety was the most active as a radical scavenger and Fe³⁺-Fe²⁺ reducer. It can be stated that possible hydrogen and electron transfer mechanism is suggested for the quenching of the free radical. Moreover, the indolyl radical stabilization and the presence of unsubstituted indole nitrogen atom are mandatory for the observed antioxidant activity, which strongly depends on the type of the substituent directly connected to the methylene group at the C-3 position. Human red blood cells (RBC) have been used as a cell model to study derivatives interaction with the cell membrane. Haemolytic activity and RBC shape transformation were observed for certain derivatives in a concentration-dependent manner. However, most of the derivatives at sublytic concentration showed high cytoprotective activity against oxidative haemolysis induced by 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AAPH). The cytoprotective properties of derivatives can be explained mostly due to their interactions with the RBC membrane components. Taking together, theoretical estimations and experimental data confirm the beneficial interactions between the selected C-3 substituted indole derivatives and the RBC membrane under oxidative stress conditions. These results encourage us to further structural optimization of C-3 substituted indole derivatives as potent antioxidant compounds.

Acid-Mediated Sulfonylthiolation of Arenes via Selective Activation of SS-Morpholino Dithiosulfonate

A trifluoroacetic-acid-mediated desulfurilative sulfonylthiolation of arenes using SS-morpholino dithiosulfonate is described. This system is based on selective activation of the morpholino group over the tosyl group of the doubly transformable sulfur surrogate. Mechanistic studies suggested that the reaction proceeds through electrophilic aromatic substitution followed by sulfur extrusion. The wide substrate scope of this reaction and the transformability of the resulting thiosulfonates enable expeditious access to divergent multifunctionalized sulfides.

NaI/TBHP-promoted reaction of indole-2-thiones with arylsulfonyl hydrazides: construction of achiral axial 3,3′-biindole-2,2′-dibenzenesulfonothioate derivatives

A new method for the synthesis of achiral axial 3,3′-biindole-2,2′-dibenzenesulfonothioate derivatives from indole-2-thiones with arylsulfonyl hydrazides promoted by NaI/TBHP is disclosed.

A brief review of the biological potential of indole derivatives

Background

Various bioactive aromatic compounds containing the indole nucleus showed clinical and biological applications. Indole scaffold has been found in many of the important synthetic drug molecules which gave a valuable idea for treatment and binds with high affinity to the multiple receptors helpful in developing new useful derivatives.

Main text

Indole derivatives possess various biological activities, i.e., antiviral, anti-inflammatory, anticancer, anti-HIV, antioxidant, antimicrobial, antitubercular, antidiabetic, antimalarial, anticholinesterase activities, etc. which created interest among researchers to synthesize a variety of indole derivatives.

Conclusion

From the literature, it is revealed that indole derivatives have diverse biological activities and also have an immeasurable potential to be explored for newer therapeutic possibilities.

Toxicological evaluation of 3-(4-Chlorophenylselanyl)-1-methyl-1H-indole through the bovine oocyte in vitro maturation model

The development of new bioactive molecules based on the molecular hybridization has been widely explored. In line with this, reliable tests should be employed to give information about the toxicology of these new molecules. In this sense, the use of in vitro tests is a valuable tool, especially the in vitro maturation of oocytes (IVM), which is an efficient resource to discover the potential toxicity of synthetic molecules. Thus, the aim of the present study was to evaluate the toxicological effects of the selenium-containing indolyl compound 3-(4-Chlorophenylselanyl)-1-methyl-1H-indole (CMI), on different quality parameters of bovine oocytes through the IVM. Different concentrations of the CMI compound (0, 25, 50, 100, 200 μM) were supplemented during the in vitro maturation process. After, the oocyte maturation rate, glutathione (GSH) levels, reactive oxygen species (ROS) levels, membrane, and mitochondrial integrity were evaluated. The results showed that the lowest concentration of CMI induced the highest GSH production (P < 0.05), an important marker of cytoplasmic quality and maturation. All treatments increased ROS production in relation to non-supplementation (P < 0.05). In addition, oocyte maturation was reduced only with the highest concentration of CMI (P < 0.05). Supplementation with CMI did not impact mitochondrial activity, integrity and cell membrane. To our knowledge, this is the first study that evaluates CMI on the oocyte in vitro maturation process. Importantly, our results did not find any toxic effect of CMI on bovine oocytes. CMI was efficient for cytoplasmic maturation by promoting an increase in the intracellular levels of glutathione.

Medicinal chemistry of indole derivatives: Current to future therapeutic prospectives

Indole is a versatile pharmacophore, a privileged scaffold and an outstanding heterocyclic compound with wide ranges of pharmacological activities due to different mechanisms of action. It is an superlative moiety in drug discovery with the sole property of resembling different structures of the protein. Plenty of research has been taking place in recent years to synthesize and explore the various therapeutic prospectives of this moiety. This review summarizes some of the recent effective chemical synthesis (2014-2018) for indole ring. This review also emphasized on the structure-activity relationship (SAR) to reveal the active pharmacophores of various indole analogues accountable for anticancer, anticonvulsant, antimicrobial, antitubercular, antimalarial, antiviral, antidiabetic and other miscellaneous activities which have been investigated in the last five years. The precise features with motives and framework of each research topic is introduced for helping the medicinal chemists to understand the perspective of the context in a better way. This review will definitely offer the platform for researchers to strategically design diverse novel indole derivatives having different promising pharmacological activities with reduced toxicity and side effects.

Dual vicinal functionalisation of heterocycles via an interrupted Pummerer coupling/[3,3]-sigmatropic rearrangement cascade

A dual vicinal functionalisation cascade involving the union of heterocycles and allyl sulfoxides is described. In particular, the approach provides efficient one-step access to biologically relevant and synthetically important C3 thio, C2 carbo substituted indoles. The reaction operates under mild, metal free conditions and without directing groups, via an interrupted Pummerer coupling of activated allyl sulfoxides, generating allyl heteroaryl sulfonium salts that are predisposed to a charge accelerated [3,3]-sigmatropic rearrangement.

Rhodium-catalyzed odorless synthesis of diaryl sulfides from borylarenes and S-aryl thiosulfonates

Various diaryl sulfides, including heteroaryl- and nitrogen-containing sulfides, have been efficiently prepared by rhodium-catalyzed odorless deborylative arylthiolation of organoborons with S-aryl thiosulfonates.

DMSO as oxidant and sulfenylating agent for metal-free oxidation and methylthiolation of alcohol-containing indoles

A new methylthiolation protocol was successfully established for the synthesis of substituted indoles bearing 3-methylthioether moiety, in which new C–S bond and C=O bond were formed using dimethyl sulfoxide as the sulfur source under mild conditions.

Metal-free synthesis of 3,5-disubstituted 1H- and 1-aryl-1H-pyrazoles from 1,3-diyne-indole derivatives employing two successive hydroaminations

The uncatalyzed synthesis of 3,5-disubstituted 1H- and 1-aryl-1H-pyrazoles derived from 1,3-diyne indoles was successfully carried out in PEG 400. The scope and limitations of the reaction were studied.

Spectroscopic studies on the in vitro antioxidant capacity of isopentyl ferulate

Essential oils have played a prominent role in research on natural products, due to the high level of bioactive constituents, which include those derived from phenylpropanoids or terpenoids. This study aimed to evaluate the antioxidant capacity of isopentyl ferulate (IF) employing in vitro experimental models for elimination of the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS+), hydroxyl (OH) and nitric oxide (NO), as well as its capacity to electron transfer by reducing potential and inhibition of lipid peroxidation by TBARS (thiobarbituric acid reactive substances) method. In all in vitro antioxidants protocols, isopentyl ferulate showed to be potent in a concentration of 54.4 nM, presenting a percentage inhibition of 91.29±0.57, 92.63±0.28, 83.62±0.18, 77.07±0.72 and 79.51±0.32% for DPPH, ABTS+, hydroxyl, nitric oxide and TBARS level, respectively. The increase of absorbance at 700 nm in the concentrations of 3.4, 6.8, 13.6, 27.2 and 54.4 nM shows the reducing potential of IF. Similar results were obtained with Trolox (559 nM), a hydrophilic synthetic analogue of α-tocopherol, which is widely used as a standard antioxidant. The present study demonstrated that isopentyl ferulate has an antioxidant activity in vitro experimental models, suggesting that this compound could enhance the development of a new product with antioxidant properties. However, further in vivo studies are needed to assign possible implications in the treatment of diseases related with free radicals.

A convenient eco-friendly system for the synthesis of 5-sulfenyl tetrazole derivatives of indoles and pyrroles employing CeCl3·7H2O in PEG-400

The use of CeCl₃·7H₂O in PEG-400 for the convenient synthesis of 5-sulfenyl tetrazoles derived from indoles and pyrroles, is reported. The scope and limitations of the transformation were also studied.