Synthesis, characterization and biological applications of selenoureas having ferrocene and substituted benzoyl functionalities

Recent Advances in the Synthesis and Antioxidant Activity of Low Molecular Mass Organoselenium Molecules

Selenium is an essential trace element in living organisms, and is present in selenoenzymes with antioxidant activity, like glutathione peroxidase (GPx) and thioredoxin reductase (TrxR). The search for small selenium-containing molecules that mimic selenoenzymes is a strong field of research in organic and medicinal chemistry. In this review, we review the synthesis and bioassays of new and known organoselenium compounds with antioxidant activity, covering the last five years. A detailed description of the synthetic procedures and the performed in vitro and in vivo bioassays is presented, highlighting the most active compounds in each series.

Selenourea and thiourea derivatives of chiral and achiral enetetramines: Synthesis, characterization and enzyme inhibitory properties

A series of chiral and achiral cyclic seleno- and thiourea compounds bearing benzyl groups on N-atoms were prepared from enetetramines and appropriate Group VI elements in good yields. All the synthesized compounds were characterized by elemental analysis, FT-IR, ¹H NMR and ¹³C NMR spectroscopy, and the molecular and crystal structures of (R,R)-4b and (R,R)-5b were confirmed by the single-crystal X-ray diffraction method. These assayed for their activities against metabolic enzymes acetylcholinesterase, butyrylcholinesterase, and α-glycosidase. These selenourea and thiourea derivatives of chiral and achiral enetetramines effectively inhibit AChE and BChE with IC₅₀ values in the range of 3.32-11.36 and 1.47-9.73 µM, respectively. Also, these compounds inhibited α-glycosidase enzyme with IC₅₀ values varying between 1.37 and 8.53 µM. The results indicated that all the synthesized compounds exhibited excellent inhibitory activities against mentioned enzymes as compared with standard inhibitors. Representatively, the most potent compound against α-glycosidase enzyme, (S,S)-5b, was 12-times more potent than standard inhibitor acarbose; 7b and 8a as most potent compounds against cholinesterase enzymes, were around 5 and 13-times more potent than standard inhibitor tacrine against achethylcholinesterase (AChE) and butyrylcholinesterase (BChE), respectively.

A review on diverse heterocyclic compounds as the privileged scaffolds in non-steroidal aromatase inhibitors

Breast cancer, emerging malignancy is common among women due to overexpression of estrogen. Estrogens are biosynthesized from androgens by aromatase, a cytochrome P450 enzyme complex, and play a pivotal role in stimulating cell proliferation. Therefore, deprivation of estrogen by blocking aromatase is considered as the effective way for the inhibition and treatment of breast cancer. In recent years, various non-steroidal heterocyclic functionalities have been extensively developed and studied for their aromatase inhibition activity. This review provides information about the structural-activity relationship of heterocycles (Type II) towards aromatase. This aids the medicinal chemist around the significance of different heterocyclic moieties and helps to design potent aromatase inhibitors.

Novel N,N'-Disubstituted Selenoureas as Potential Antioxidant and Cytotoxic Agents

A series of 30 novel N,N disubstituted selenoureas were synthesized, characterized, and their antioxidant ability was tested using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS) assays. Additionally, their cytotoxic activity was tested in vitro in a panel of three different cancer (breast, lung and colon) and two normal cell lines. Each selenourea entity contains a para-substituted phenyl ring with different electron-withdrawing and electron-donating groups, and different aliphatic and aromatic nuclei. All of the synthesized selenoureas present antioxidant capacity at high concentrations in the DPPH assay, and three of them (2b, 2c and 2d) showed greater radical scavenging capacity than ascorbic acid at lower concentrations. These results were confirmed by the ABTS assay, where these novel selenoureas present even higher antioxidant capacity than the reference compound Trolox. On the other hand, 10 selenoureas present IC₅₀ values below 10 µM in at least one cancer cell line, resulting in the adamantyl nucleus (6a–6e), the most interesting in terms of activity and selectivity. Outstanding results were found for selenourea 6c, tested in the NCI60 cell line panel and showing an average GI₅₀ of 1.49 µM for the 60 cell lines, and LC₅₀ values ranging from 9.33 µM to 4.27 µM against 10 of these cancer cell lines. To gain insight into its anticancer activity mechanism, we investigated the cell cycle progression of the promising compound 6c, as well as the type of programmed-cell death in a colon cancer cell line it provokes (HT-29). Compound 6c provoked S phase cell cycle arrest and the induction of cell death was independent of caspase activation, suggesting autophagy, though this assertion requires additional studies. Overall, we envision that this compound can be further developed for the potential treatment of colon cancer.

Effect of organo-selenium anticancer drugs on nitrite induced methemoglobinemia: A spectroscopic study

Selenium containing drugs like selenomethionine, selenocystine, selenourea and methylseleninic acid are reported to exhibit potential anticancer effect. However, these anticancer drugs may exert adverse effects when used over a prolonged period. Little is known about the interaction of these selenium containing drugs with the vital erythroid protein hemoglobin. In this work a comparative study of the interaction of organo-selenium drugs with hemoglobin and heme moiety has been performed using different spectroscopic techniques to find out their role on drug induced methemoglobinemia. We found that though these selenium containing drugs have similar binding affinity towards hemoglobin, they have differential interactions with the heme group. Isothermal calorimetric titration study showed that selenourea has the lowest binding affinity (K_d 19.28 μM) towards HbA as compared to other drugs, selenomethionine, selenocystine and methylseleninic acid (K_d 7.69 μM, 4.88 μM and 10.5 μM at 37 °C respectively). This result is also supported by the molecular docking study. Methylseleninic acid was found to have detrimental effects on nitrite induced methemoglobinemia, a hematological disorder caused due to excessive conversion of Fe²⁺ to Fe³⁺ in hemoglobin. Hence the results of the study would help to develop a better insight on the mechanism of action and anticipate the toxicity of these drugs which require further optimization before their actual use in the treatment of cancer.

One-Pot Four-Component Assembling for Selenoureas

An efficient and practical method for the straightforward construction of unsymmetrical selenoureas and cycloselenoureas via the combination of selenium powder, chloroform, and two different amines was comprehensively achieved in one-pot with only the assistance of a base under mild conditions. Thirty-three new structures of unsymmetrical selenoureas including three chiral examples and eight cycloselenoureas were achieved. 1,1-Dimethyl-3-phenylselenourea II, which shows good fungicidal activity, was practically synthesized through this protocol in gram-scale. Isoselenocyanate was further confirmed as a key intermediate by control experiment.

Ferrocene-containing hybrids as potential anticancer agents: Current developments, mechanisms of action and structure-activity relationships

Cancer is one of the most fatal threatens to human health throughout the world. The major challenges in the control and eradication of cancers are the continuous emergency of drug-resistant cancer and the low specificity of anticancer agents, creating an urgent need to develop novel anticancer agents. Organometallic compounds especially ferrocene derivatives possess remarkable structural and mechanistic diversity, inherent stability towards air, heat and light, low toxicity, low cost, reversible redox, ligand exchange, and catalytic properties, making them promising drug candidates for cancer therapy. Ferrocifen, a ferrocene-phenol hybrid, has demonstrated promising anticancer properties on drug-resistant cancers. Currently, Ferrocifen is in pre-clinical trial against cancers. Obviously, ferrocene moiety is a useful template for the development of novel anticancer agents. This review will provide an overview of ferrocene-containing hybrids with potential application in the treatment of cancers covering articles published between 2010 and 2020. The mechanisms of action, the critical aspects of design and structure-activity relationships are also discussed.

Novel N,N'-Disubstituted Acylselenoureas as Potential Antioxidant and Cytotoxic Agents

Selenium compounds are pivotal in medicinal chemistry for their antitumoral and antioxidant properties. Forty seven acylselenoureas have been designed and synthesized following a fragment-based approach. Different scaffolds, including carbo- and hetero-cycles, along with mono- and bi-cyclic moieties, have been linked to the selenium containing skeleton. The dose- and time-dependent radical scavenging activity for all of the compounds were assessed using the in vitro 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) assays. Some of them showed a greater radical scavenging capacity at low doses and shorter times than ascorbic acid. Therefore, four compounds were evaluated to test their protective effects against H₂O₂-induced oxidative stress. One derivative protected cells against H₂O₂-induced damage, increasing cell survival by up to 3.6-fold. Additionally, in vitro cytotoxic activity of all compounds was screened against several cancer cells. Eight compounds were selected to determine their half maximal inhibitory concentration (IC₅₀) values towards breast and lung cancer cells, along with their selectivity indexes. The breast cancer cells turned out to be much more sensitive than the lung. Two compounds (5d and 10a) stood out with IC₅₀ values between 4.2 μM and 8.0 μM towards MCF-7 and T47D cells, with selectivity indexes greater than 22.9. In addition, compound 10b exhibited dual antioxidant and cytotoxic activities. Although further evidence is needed, the acylselenourea scaffold could be a feasible frame to develop new dual agents.