Cytotoxic effect of a new 1,3,4-thiadiazolium mesoionic compound (MI-D) on cell lines of human melanoma

Evaluation of the antitumoral effects of the mesoionic compound MI-D: Implications for endothelial cells viability and angiogenesis inhibition

Angiogenesis is considered one of the hallmarks of cancer, assisting tumor progression and metastasis. The mesoionic compound, MI-D, can induce cell death and provoke cytoskeletal and metabolic changes in cancer cells. Using in vitro and in vivo models, this study aimed to evaluate the effects of MI-D on the viability of human endothelial cells (EC) and its ability to inhibit tumor-induced angiogenesis induced by tumoral cells. For in vitro analysis, colon carcinoma (HT29) and endothelial (EA.hy926) cells were used as the tumoral and angiogenesis models, respectively. To evaluate cytotoxicity, methylene blue viability stain and annexin-V/7AAD tests were performed with both cell types. For the angiogenesis experiments, scratch wound healing and capillary tube-like formation assays were performed with the EC. The in vivo tests were performed with the chorioallantoic membrane (HET-CAM) methodology, wherein gelatin sponge implants containing MI-D (5, 25, and 50 μM), HT29 cells, or both were grafted in the CAM. Our data showed that MI-D induced apoptosis in both endothelial and colon carcinoma cells, with a strong cytotoxic effect on the tumoral lineage. The drug inhibited the EC's migration and capillary-like structure formation in vitro. In the HET-CAM assays, MI-D reduced the number of blood vessels in the membrane when grafted alone and accompanied by tumor cells. In this study, MI-D interfered in important steps of angiogenesis, such as maintenance of endothelial cell viability, migration, formation of capillary-like structures, as well tumor-induced neovascularization, reinforcing the hypothesis that MI-D might act as an inhibitor of angiogenesis, and a potential antitumor agent.

Synthesis, molecular docking, and molecular dynamic simulation studies of new 1,3,4-thiadiazole derivatives as potential apoptosis inducers in A549 lung cancer cell line

1,3,4-Thiadiazoles are structures that are bioisosteres of 1,3,4-oxadiazole and pyrimidine ring, which are found in the structure of many drugs and anticancer active newly studied derivatives. In the past, high effect profiles have been observed in many molecules created, based on the anticancer effects of the 2-amino-1,3,4-thiadiazole (NSC 4728) molecule and acetazolamide molecules. Focusing on these molecules and evaluating them in terms of mechanistic effects, twelve new N-[5-((3,5-dichlorophenoxy) methyl]-1,3,4-thiadiazole derivatives (3a-3i) were synthesized and their biological activities were investigated in lung cancer cells. The anticancer effects of the compounds were evaluated on the A549 and L929 cell lines. Compound 3f, namely 2-[(5-chlorobenzotiyazol-2-yl)thio]-N-[5-[(3,5-dichlorophenoxy)methyl]-1,3,4-thiadiazol-2-yl]acetamide, showed better activity than cisplatin, exhibiting high inhibitory potency (IC50: <0.98 μg/mL) and selectivity against A549 cell line even at the lowest concentration tested. Compounds 3c, 3f, and 3h with the lowest IC50 values of the compounds exhibited an excellent percentage of apoptosis between 72.48 and 91.95% compared to cisplatin. The caspase-3 activation and mitochondrial membrane potential change of the aforementioned three compounds were also studied. Moreover, matrix metalloproteinase-9 (MMP-9) inhibition potential of all final compounds was also investigated and IC50 values for compounds 3b and 3g were identified as 154.23 and 107.28 µM. Molecular docking and molecular dynamic simulation studies for MMP-9 enzyme inhibition were realized on these compounds and the nitrogen atoms of amide and thiadiazole moieties' ascertained that they play a key role in chelating with Zn metal, at the same time, (thio)ether moieties allow conformational change resulting in the ligand can make more stable contacts.Communicated by Ramaswamy H. Sarma.

First Discovery of Imidazo[1,2-a]pyridine Mesoionic Compounds Incorporating a Sulfonamide Moiety as Antiviral Agents

The applications of mesoionic compounds and their analogues as agents against plant viruses remain unexplored. This was the first evaluation of the antiviral activities of mesoionic compounds on this issue. Our study involved the design and synthesis of a series of novel imidazo[1,2-a]pyridine mesoionic compounds containing a sulfonamide moiety and the assessment of their antiviral activities against potato virus Y (PVY). Compound A33 was assessed on the basis of three-dimensional quantitative structure-activity relationship (3D-QSAR) model analysis and displayed good curative, protective, and inactivating activity effects against PVY at 500 mg/L, up to 51.0, 62.0, and 82.1%, respectively, which were higher than those of commercial ningnanmycin (NNM, at 47.2, 50.1, and 81.4%). Significantly, defensive enzyme activities and proteomics results showed that compound A33 could enhance the defense response by activating the activity of defense enzymes, inducing the glycolysis/gluconeogenesis pathway of tobacco to resist PVY infection. Therefore, our study indicates that compound A33 could be applied as a potential viral inhibitor.

The mesoionic compound MI-D changes energy metabolism and induces apoptosis in T98G glioma cells

The mesoionic compound 4-phenyl-5-(4-nitro-cinnamoyl)-1,3,4-thiadiazolium-2-phenylamine chloride (MI-D) impairs mitochondrial oxidative phosphorylation and has a significant antitumour effect against hepatocarcinoma and melanoma. This study evaluated the cytotoxic effect of MI-D on T98G glioblastoma cells and investigated whether the impairment of oxidative phosphorylation promoted by MI-D is relevant to its cytotoxic effect. The effects of MI-D on T98G cells cultured in high glucose Dulbecco's modified Eagle's medium (DMEM) HG (glycolysis-dependent) and galactose plus glutamine-supplemented Dulbecco's modified Eagle's medium (DMEM) GAL (oxidative phosphorylation-dependent) were compared. T98G cells grown in DMEM GAL medium exhibited higher respiration rates and citrate synthase activity and lower lactate levels, confirming the metabolic shift to oxidative phosphorylation in these cells. MI-D significantly decreased the cell viability in a dose-dependent manner in both media; however, T98G cells cultured in DMEM GAL medium were more susceptible. The mesoionic significantly inhibited mitochondrial oxidative phosphorylation of glioma cells in both media. At the same time, lactate levels were not altered, indicating an absence of compensatory glycolysis activation. Additionally, MI-D increased the citrate synthase activity of cells in both media, which in DMEM HG-cultivated cells was followed by citrate accumulation. Apoptosis dependent on caspase-3 mediated the toxicity of MI-D on T98G cells. The higher susceptibility of glioma cells cultured in DMEM GAL medium to MI-D indicates that the impairment of mitochondrial functions is involved in mesoionic cytotoxicity. The results of this study indicate the potential use of MI-D for glioblastoma treatment.

The toxicity of 1,3,4-thiadiazolium mesoionic derivatives on hepatocarcinoma cells (HepG2) is associated with mitochondrial dysfunction

Mesoionic compounds, 4-phenyl-5-(4-X-cinnamoyl)-1,3,4-thiadiazolium-2-phenylamine chloride derivatives (MI-J: X = OH; MI-D: X = NO₂), possess significant antitumor and cytotoxic effects on several cancer cells. In this work, we evaluated the cytotoxicity of MI-J and MI-D on human hepatocellular carcinoma (HepG2 cells) grown in either high glucose (HG) or galactose medium (GAL) to clarify whether the effects of mesoionics on mitochondrial bioenergetics are associated with their cytotoxicity in these cells. MI-J and MI-D (5-50 μM) decreased the viability of HepG2 cells in a dose- and time-dependent manner, as assessed by MTT, LDH release and dye with crystal violet assays. Both compounds at lower (5 μM) and intermediate (25 μM) concentrations were more toxic to cells grown in GAL medium. MI-J inhibited the basal state of respiration in HepG2 cells cultured in HG and GAL media; however, in GAL medium, this effect occurred at the lowest concentration (5 μM). A leak-state stimulus was observed only after incubation with MI-J (5 μM) for GAL medium. MI-D stimulated and inhibited the leak state in cells grown in HG medium at concentrations of 5 μM and 25 μM, respectively. In cells cultured in GAL medium, respiration was strongly inhibited by MI-D at the highest concentration (25 μM). In contrast, at 5 μM, the mesoionic inhibited the basal and uncoupled states at 30% and 50%, respectively. The inhibition of the basal state by MI-J and MI-D was consistent with the increase in lactate levels in both media, which was higher for the GAL medium. Both mesoionics slightly decreased pyruvate levels only in cells cultured in GAL medium. Additionally, MI-J (25 μM) reduced the ATP amount in cells cultured in both media, while MI-D (25 μM) promoted a reduction only in cells grown in GAL medium. Our results show that MI-J and MI-D depress mitochondrial respiration and consequently change metabolism and reduce ATP levels, effects associated with their toxicity in hepatocarcinoma cells.

Antiproliferative, apoptosis-inducing activity and molecular docking studies of sydnones compounds

Objective

To evaluate the antiproliferative and apoptosis inducing activity of different sydnones on cancer cell lines and their interaction with cancer proteins by molecular docking studies.

Material and Methods

Antiproliferative activity was carried out by MTT assay and apoptosis inducing activity was performed by DAPI and Annexin V and propidium iodide staining. Molecular docking studies were performed using AutoDock Tools 1.5.6. Pharmacokinetics properties like ADME and toxicity were analysed by pkCSM web server.

Result

In this study, four new sydnone compounds 3-(4-nonylbiphenyl-4'-yl) sydnone (MC-182), 3-(4-propylbiphenyl-4'-yl) sydnone (MC-454), 3-(4-hexylbiphenyl-4'-yl) sydnone (MC-433), and 3-(4-methylbiphenyl-4'-yl) sydnone (MC-431) were screened for antiproliferative and apoptotic effect against BT-474 (human breast cancer), HeLa (human cervical cancer) and Jurkat (human myeloid leukemia) Mostly, all the sydnone compounds exhibited decent antiproliferative effectiveness, but compound MC-431, MC-433, and MC-454 showed more antiproliferative activity (IC50 1.71, 10.09 and 2.87 μM against BT-474, Hela and Jurkat cell line, respectively). The changes of morphological characteristics of cancer cells determined by staining techniques indicate the apoptotic cell death. The molecular docking and interaction studies were carried out between sydnones with cancer proteins (epidermal growth factor domain receptor tyrosine kinase [EGF-TK], tumor necrosis factor-alpha [TNF-α] and Caspase3. Among all four sydnone molecules, two compounds MC-454 and MC-431 showed good binding energy with targeted proteins. Drug-like property was predicted by ADME toxicity study.

Conclusion

The results indicate sydnone compounds were found to exhibit anticancer activity by inducing apoptosis. The molecular docking study of sydnones with cancer proteins showed a decent interaction affinity. The results of absorption, distribution, metabolism, excretion and toxicity studies by the Insilco approach also proved that MC-454 sydnone showed better In-Vivo administration. Thus, the current research work indicates that these sydnone compounds would be prospective in developing anticancer medicines.

Green biosynthesis, characterization, and cytotoxic effect of magnetic iron nanoparticles using Brassica Oleracea var capitata sub var rubra (red cabbage) aqueous peel extract

The green method of nanoparticle synthesis, which is an environment and living-friendly method, is an updated subject that has appeared as an alternative to conventional methods such as physical and chemical synthesis. In this presented study, the green synthesis of magnetic iron oxide nanoparticles (IONPs) from iron (III) chloride by using Brassica oleracea var. capitata sub.var. rubra aqueous peel extract has been reported. The prepared IONPs were characterized with fourier-transform infrared spectroscopy (FT-IR), ultraviolet-visible spectroscopy (UV-VIS), zeta potential, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The cytotoxic effects of IONPs on MCF-7 breast cancer cell line were studied by MTT assay, and migrative effect of its were carried out by the wound healing assay. It was found that the mean particle size of IONPs was 675 ± 25 nm, and the polydispersity index was 0.265 PDI. It was also determined that these nanoparticles had an anti-proliferative impact on the MCF-7 breast cancer cell line depending on the dosage. Characterization results support the successful synthesis of nanoparticles, and the dose-dependent cytotoxic effects of nanoparticles on MCF-7 cells also make it a potential chemotherapeutic agent for breast cancer treatment.

Silver Nanoparticles Stabilized with Phosphorus-Containing Heterocyclic Surfactants: Synthesis, Physico-Chemical Properties, and Biological Activity Determination

Phosphorus-containing heterocyclic cationic surfactants alkyldimethylphenylphospholium bromides with the alkyl chain length 14 to 18 carbon atoms were used for the stabilization of silver nanodispersions. Zeta potential of silver nanodispersions ranges from +35 to +70 mV, which indicates the formation of stable silver nanoparticles (AgNPs). Long-chain heptadecyl and octadecyl homologs of the surfactants series provided the most intensive stabilizing effect to AgNPs, resulting in high positive zeta potential values and smaller diameter of AgNPs in the range 50–60 nm. A comparison with non-heterocyclic alkyltrimethylphosphonium surfactants of the same alkyl chain length showed better stability and more positive zeta potential values for silver nanodispersions stabilized with heterocyclic phospholium surfactants. Investigations of biological activity of phospholium-capped AgNPs are represented by the studies of antimicrobial activity and cytotoxicity. While cytotoxicity results revealed an increased level of HepG2 cell growth inhibition as compared with the cytotoxicity level of silver-free surfactant solutions, no enhanced antimicrobial action of phospholium-capped AgNPs against microbial pathogens was observed. The comparison of cytotoxicity of AgNPs stabilized with various non-heterocyclic ammonium and phosphonium surfactants shows that AgNPs capped with heterocyclic alkyldimethylphenylphospholium and non-heterocyclic triphenyl-substituted phosphonium surfactants have the highest cytotoxicity among silver nanodispersions stabilized by the series of ammonium and phosphonium surfactants.

Recent Research Progress in and Perspectives of Mesoionic Insecticides: Nicotinic Acetylcholine Receptor Inhibitors

Triflumezopyrim exemplifies a new class of mesoionic insecticides and has attracted increasing attention as a result of its unique structure, high level of insecticidal activity, new mechanisms of action, low toxicity toward non-target organisms, and environmental friendliness. It inhibits the nicotinic acetylcholine receptor and has high potency against sucking pests, including the brown planthopper (Nilaparvata lugens), which has developed serious resistance to conventional neonicotinoids and low cross-resistance to some newly developed neonicotinoids. This review focuses on the discovery, synthesis, structure-activity relationships, and mechanism of action of mesoionic insecticides. Finally, potential directions for the development of mesoionic insecticides are discussed.

2-Amino-1,3,4-thiadiazoles as prospective agents in trypanosomiasis and other parasitoses

Parasitic diseases are a serious public health problem affecting hundreds of millions of people worldwide. African trypanosomiasis, American trypanosomiasis, leishmaniasis, malaria and toxoplasmosis are the main parasitic infections caused by protozoan parasites with over one million deaths each year. Due to old medications and drug resistance worldwide, there is an urgent need for new antiparasitic drugs. 1,3,4-Thiadiazoles have been widely studied for medical applications. The chemical, physical and pharmacokinetic properties recommend 1,3,4-thiadiazole ring as a target in drug development. Many scientific papers report the antiparasitic potential of 2-amino-1,3,4-thiadiazoles. This review presents synthetic 2-amino-1,3,4-thiadiazoles exhibiting antitrypanosomal, antimalarial and antitoxoplasmal activities. Although there are insufficient results to state the quality of 2-amino-1,3,4-thiadiazoles as a new class of antiparasitic agents, many reported derivatives can be considered as lead compounds for drug synthesis and a promise for the future treatment of parasitosis and provide a valid strategy for the development of potent antiparasitic drugs.

Cytotoxic Activity of the Mesoionic Compound MIH 2.4Bl in Breast Cancer Cell Lines

In this work, we report the synthesis of a new 1,3-thiazolium-5-thiolate derivative of a mesoionic compound (MIH 2.4Bl) and the characterization of its selective cytotoxicity on a panel of breast cancer cells lines. The cytotoxic effect of MIH 2.4Bl on breast cancer cell lines was determined by XTT and crystal violet assays, flow cytometry analysis, electron microscopy characterization, and terminal deoxynucleotidyl transferase (TdT) deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) apoptosis assays. As determined using XTT cell growth and survival assays, MIH 2.4Bl exhibited growth inhibition activity on most breast cancer cell lines tested, compared with normal human mammary epithelial cells. Three breast cancer cell lines (MCF-7, T-47D, and ZR-75-1) showed a more potent sensitivity index to growth inhibition by MIH 2.4Bl than the other breast cancer cell lines. Interestingly, these 3 cell lines were derived from tumors of Luminal A origin and have ER (estrogen receptor), PR (progesterone receptor), and HER2 (human epidermal growth factor receptor 2) positive expression. Additional analysis of cytotoxicity mediated by MIH 2.4Bl was performed using the MCF-7 cell line. MCF-7 cells displayed both time- and dose-dependent decreases in cell growth and survival, with a maximum cytotoxic effect observed at 72 and 96 hours. The MCF-7 cells were also characterized for cell cycle changes upon treatment with MIH 2.4Bl. Using flow cytometry analysis of cell cycle distribution, a treatment-dependent effect was observed; treatment of cells with MIH 2.4Bl increased the G2/M population to 34.2% compared with 0.1% in untreated (control) cells. Ultrastructural analysis of MFC-7 cells treated with MIH 2.4Bl at 2 different concentrations (37.5 and 75 μM) was performed by transmission electron microscopy. Cells treated with 37.5 μM MIH 2.4Bl showed morphologic changes beginning at 6 hours after treatment, while cells treated with 75 μM showed changes beginning at 3 hours after treatment. These changes were characterized by an alteration of nuclear morphology and mitochondrial degeneration consistent with apoptotic cell death. Results of a TUNEL assay performed on cells treated for 96 hours with MIH 2.4Bl supported the observation of apoptosis. Together, these results suggest that MIH 2.4Bl is a promising candidate for treating breast cancer and support further in vitro and in vivo investigation.

Mechanistic studies of cytotoxic activity of the mesoionic compound MIH 2.4Bl in MCF-7 breast cancer cells

In the present study, the cytotoxic effects of a 1,3-thiazolium-5-thiolate derivative of a mesoionic compound, MIH 2.4Bl, were assessed in the MCF-7 breast cancer cell line. The cytotoxic effects of MIH 2.4Bl were determined using a crystal violet assay. Using a dose-response curve, the IC₅₀ value of MIH 2.4Bl was determined to be 45.8±0.8 µM. Additionally, the effects of MIH 2.4Bl on mitochondrial respiration were characterized using oxygen consumption rate analysis. Treating MCF-7 cells with increasing concentrations of MIH 2.4Bl resulted in a significant reduction in all mitochondrial respiratory parameters compared with the control cells, indicative of an overall decrease in mitochondrial membrane potential. The induction of autophagy by MIH 2.4Bl was also examined by measuring changes in the expression of protein markers of autophagy. As shown by western blot analysis, treatment of MCF-7 cells with MIH 2.4Bl resulted in increased protein expression levels of Beclin-1 and ATG5, as well as an increase in the microtubule-associated protein 1A/1B light chain 3B (LC3B)-II to LC3B-I ratio compared with the control cells. Microarray analysis of changes in gene expression following MIH 2.4Bl treatment demonstrated 3,659 genes exhibited a fold-change ≥2. Among these genes, 779 were up-regulated, and 2,880 were down-regulated in cells treated with MIH 2.4Bl compared with the control cells. Based on the identity of the transcripts and fold-change of expression, six genes were selected for verification by reverse transcription-quantitative (RT-q)PCR; activating transcription factor 3, acidic repeat-containing protein, heparin-binding EGF-like growth factor, regulator of G-protein signaling 2, Dickkopf WNT signaling pathway inhibitor 1 and adhesion molecule with Ig like domain 2. The results of RT-qPCR analysis of RNA isolated from control and MIH 2.4Bl treated cells were consistent with the expression changes identified by microarray analysis. Together, these results suggest that MIH 2.4Bl may be a promising candidate for treating breast cancer and warrants further in vitro and in vivo investigation.

Design, synthesis and anticancer activity of novel pyrimidine and pyrimidine-thiadiazole hybrid glycosides

New 1,3,4-thiadiazole thioglycosides linked to substituted pyrimidines were synthesized via glycosylation of 1,3,4-thiadiazole thiol compounds. Also, novel 1,2,3-triazole derivatives linked to carbohydrate units were prepared using the standard click chemistry conditions employing the Cu(I)-catalyzed azide-alkyne cycloaddition of substituted-aryl-azides with a selection of alkyne-functionalized sugars. The chemical structures of the new derivatives were verified using various spectroscopic techniques, such as IR, ¹H NMR, ¹³C NMR and elemental analyses. The cytotoxic activities of the prepared compounds were investigated in vitro against human liver cancer (HepG-2) and human breast adenocarcinoma (MCF7) cell lines. In addition, the biological evaluation of the new compounds involved the investigation of their effects on a human normal retinal pigmented epithelial cell line (RPE1) using the MTT assay.

Synthetic Compounds with 2-Amino-1,3,4-Thiadiazole Moiety Against Viral Infections

Viral infections have resulted in millions of victims in human history. Although great efforts have been made to find effective medication, there are still no drugs that truly cure viral infections. There are currently approximately 90 drugs approved for the treatment of human viral infections. As resistance toward available antiviral drugs has become a global threat to health, there is an intrinsic need to identify new scaffolds that are useful in discovering innovative, less toxic and highly active antiviral agents. 1,3,4-Thiadiazole derivatives have been extensively studied due to their pharmacological profile, physicochemical and pharmacokinetic properties. This review provides an overview of the various synthetic compounds containing the 2-amino-1,3,4-thiadiazole moiety that has been evaluated for antiviral activity against several viral strains and could be considered possible prototypes for the development of new antiviral drugs.

Design, synthesis and biological evaluation of benzoxazolinone-containing 1,3,4-thiadiazoles as TNF-α inhibitors

A library of nineteen benzoxazolinone-based 1,3,4-thiadiazoles has been synthesized and screened for their anti-inflammatory activity. The compound 1f exhibited a potent anti-inflammatory activity with an inhibition of 65.83% and 32.50% after 3 h and 5 h respectively. It also exhibited a significant in vitro (p < 0.01), TNF- α inhibitory activity with 51.44 % inhibition. The compound 1f showed hydrogen bonding with GLN 61 and interactions with TYR 119, TYR 151 and GLY 121. The histopathology report showed that none of the compounds caused gastric ulceration. The results from the in vivo & in vitro antiinflammatory activity along with In Silico studies exhibit that benzoxazolinone-based 1,3,4-thiadiazoles may be used in the future development of anti-inflammatory drugs.

Future Prospects in the Treatment of Parasitic Diseases: 2-Amino-1,3,4-Thiadiazoles in Leishmaniasis

Neglected tropical diseases affect the lives of a billion people worldwide. Among them, the parasitic infections caused by protozoan parasites of the Trypanosomatidae family have a huge impact on human health. Leishmaniasis, caused by Leishmania spp., is an endemic parasitic disease in over 88 countries and is closely associated with poverty. Although significant advances have been made in the treatment of leishmaniasis over the last decade, currently available chemotherapy is far from satisfactory. The lack of an approved vaccine, effective medication and significant drug resistance worldwide had led to considerable interest in discovering new, inexpensive, efficient and safe antileishmanial agents. 1,3,4-Thiadiazole rings are found in biologically active natural products and medicinally important synthetic compounds. The thiadiazole ring exhibits several specific properties: it is a bioisostere of pyrimidine or benzene rings with prevalence in biologically active compounds; the sulfur atom increases lipophilicity and combined with the mesoionic character of thiadiazoles imparts good oral absorption and good cell permeability, resulting in good bioavailability. This review presents synthetic 2-amino-1,3,4-thiadiazole derivatives with antileishmanial activity. Many reported derivatives can be considered as lead compounds for the synthesis of future agents as an alternative to the treatment of leishmaniasis.

2-Amino-1,3,4-thiadiazole as a potential scaffold for promising antimicrobial agents

Pathogenic microorganisms are causative agents for different types of serious and even lethal infectious diseases. Despite advancements in medication, bacterial and fungal infections continue to be a growing problem in health care. As more and more bacteria become resistant to antibiotics used in therapy and an increasing number of invasive fungal species become resistant to current antifungal medications, there is considerable interest in the development of new compounds with antimicrobial activity. The compounds containing a heterocyclic ring play an important role among organic compounds with biological activity used as drugs in human and veterinary medicine or as insecticides and pesticides in agriculture. Thiadiazoles belong to the classes of nitrogen-sulfur heterocycles with extensive application as structural units of biologically active molecules and as useful intermediates in medicinal chemistry. The potency of the thiadiazole nucleus is demonstrated by the drugs currently used. 1,3,4-Thiadiazoles and some of their derivatives are extensively studied because of their broad spectrum of pharmacological activities. The aim of this review was to highlight the main antimicrobial properties exhibited by derivatives possessing 2-amino-1,3,4-thiadiazole moiety. Many of the reported 2-amino-1,3,4-thiadiazole derivatives can be considered as lead compounds for drug synthesis, and several of them have demonstrated higher antimicrobial activity in comparison to standard drugs. Furthermore, taking into account the reactivity of the amine group in the derivatization process, 2-amino-1,3,4-thiadiazole moiety may be a good scaffold for future pharmacologically active 1,3,4-thiadiazole derivatives.

Derivatives of the triaminoguanidinium ion, 5. Acylation of triaminoguanidines leading to symmetrical tris(acylamino)guanidines and mesoionic 1,2,4-triazolium-3-aminides

Depending on the reaction conditions, N,N',N''-tris(benzylamino)guanidinium salts can react with carboxylic acid chlorides to form either symmetrical N,N',N''-tris(N-acyl-N-benzylamido)guanidines 6 or mesoionic 4-amino-1,2,4-triazolium-3-hydrazinides 7. The latter were converted into 1,2,4-triazolium salts by protonation or methylation at the hydrazinide nitrogen atom. Neutral 1,2,4-triazoles 10 were obtained by catalytic hydrogenation of an N-benzyl derivative. Crystal structure analyses of a 4-benzylamino-1,2,4-triazolium-3-hydrazinide and of two derived 1,2,4-triazolium salts are presented.

Synthesis and insecticidal assessment of some innovative heterocycles incorporating a thiadiazole moiety against the cotton leafworm, Spodoptera littoralis

A new 2-cyano-N-(5-ethyl-1,3,4-thiadiazol-2-yl)acetamide was utilized as a versatile precursor for the synthesis of various heterocycles.

Molecular docking studies and biological evaluation of 1,3,4-thiadiazole derivatives bearing Schiff base moieties as tyrosinase inhibitors

1,3,4-Thiadiazole derivatives bearing Schiff base moieties were designed, synthesized, and their tyrosinase inhibitory activities were evaluated. Some compounds displayed potent tyrosinase inhibitory activities, especially, 4-(((5-mercapto-1,3,4-thiadiazol-2-yl)-imino)methyl)-2-methoxy-phenol (14) exhibited superior inhibitory effect to the other compounds with an IC₅₀ value of 0.036μM. The structure-activity relationships (SARs) were preliminarily discussed and docking studies showed compound 14 had strong binding affinity to mushroom tyrosinase. Hydroxy might be the active groups. The inhibition kinetics study revealed that compounds (13 and 14) inhibited tyrosinase by acting as uncompetitive inhibitors. The LD₅₀ value of the compound 14 was 5000mg/kg.

Antioxidant effect of 1,3,4-thiadiazolium mesoionic derivatives on isolated mitochondria

Mesoionic compounds have shown antitumor and citotoxic activity against different tumor cells lines, which has been attributed to their physical and chemical characteristics. Among these compounds, the 1,3,4-thiadiazolium-2-phenylamine derivatives have been highlighted due to their important anti-melanoma activity. In this work, the effects of three derivatives that belong this class, MI-J, MI-4F and MI-2,4diF, on the oxidative stress parameters were evaluated using rat liver mitochondria. All the derivatives prevented natural and calcium induced oxidation of pyridine nucleotides at lower concentrations (6.5 and 32.5nmol/mg protein). The calcium uptake was inhibited by all the derivatives at higher concentrations (65 and 130nmol/mg protein), whereas the cation efflux was inhibited only by the MI-J (52%) and MI-4F (50%), possibly by inhibiting the formation of the permeability transition pore (PTP) by 100% and 50%, respectively, as observed in the same experimental conditions. MI-2,4diF did not inhibit the mitochondrial permeability transition or calcium efflux. The enzymatic activity of glutathione reductase, glutathione peroxidase and catalase was not affected by any derivative, but superoxide dismutase was inhibited by all the derivatives. MI-J inhibited enzyme activity significantly (85%) at the highest concentration (130nmol/mg protein); on the other hand, their activity was less affected by fluorine derivatives (MI-4F-20% and MI-2,4diF-32%). These results suggest that these derivatives exert antioxidant effects on isolated mitochondria.

A topological assessment of the electronic structure of mesoionic compounds

Mesoionic compounds belonging to the 1,3-oxazol-5-one, 1,3-diazole-4-thione and 1,3-thiazole-5-thione rings have been evaluated by a combination of Density Functional Theory, Quantum Theory of Atoms in Molecules, Electron Localization Function, Natural Bond Orbitals and Geodesic Electrostatic Potential Charge calculations. Atomic, bond, and ring properties have been considered to describe the electronic structure of mesoionic compounds. The results show that not only the ring type, but also the substituent groups have great influence on these properties. In addition, there is a significant and heterogeneous π-bonding contribution throughout the mesoionic rings. Finally, we conclude that some classical conceptions of charge localization and π-bonding contribution in these compounds are misleading or incomplete. © 2015 Wiley Periodicals, Inc.

Selective Cytotoxicity of 1,3,4-Thiadiazolium Mesoionic Derivatives on Hepatocarcinoma Cells (HepG2)

In this work, we evaluated the cytotoxicity of mesoionic 4-phenyl-5-(2-Y, 4-X or 4-X-cinnamoyl)-1,3,4-thiadiazolium-2-phenylamine chloride derivatives (MI-J: X=OH, Y=H; MI-D: X=NO2, Y=H; MI-4F: X=F, Y=H; MI-2,4diF: X=Y=F) on human hepatocellular carcinoma (HepG2), and non-tumor cells (rat hepatocytes) for comparison. MI-J, M-4F and MI-2,4diF reduced HepG2 viability by ~ 50% at 25 μM after 24-h treatment, whereas MI-D required a 50 μM concentration, as shown by 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyltetrazolium bromide assays. The cytotoxicity was confirmed with lactate dehydrogenase assay, of which activity was increased by 55, 24 and 16% for MI-J, MI-4F and MI-2,4diF respectively (at 25 μM after 24 h). To identify the death pathway related to cytotoxicity, the HepG2 cells treated by mesoionic compounds were labeled with both annexin V and PI, and analyzed by flow cytometry. All compounds increased the number of doubly-stained cells at 25 μM after 24 h: by 76% for MI-J, 25% for MI-4F and MI-2,4diF, and 11% for MI-D. It was also verified that increased DNA fragmentation occurred upon MI-J, MI-4F and MI-2,4diF treatments (by 12%, 9% and 8%, respectively, at 25 μM after 24 h). These compounds were only weakly, or not at all, transported by the main multidrug transporters, P-glycoprotein, ABCG2 and MRP1, and were able to slightly inhibit their drug-transport activity. It may be concluded that 1,3,4-thiadiazolium compounds, especially the hydroxy derivative MI-J, constitute promising candidates for future investigations on in-vivo treatment of hepatocellular carcinoma.

Synthesis and biological activities of novel pleuromutilin derivatives with a substituted thiadiazole moiety as potent drug-resistant bacteria inhibitors

A series of novel pleuromutilin derivatives possessing thiadiazole moieties were synthesized via acylation reactions under mild conditions. The in vitro antibacterial activities of the derivatives against methicillin-resistant Staphylococcus aureus, methicillin-resistant Staphylococcus epidermidis, Escherichia coli, and Streptococcus agalactiae were tested by the agar dilution method and Oxford cup assay. The majority of the tested compounds displayed moderate antibacterial activities. Importantly, the three compounds with amino or tertiary amine groups in their side chains, 11, 13b, and 15c, were the most active antibacterial agents. Docking experiments carried out on the peptidyl transferase center (PTC) of 23S rRNA proved that there is a reasonable direct correlation between the binding free energy (ΔGb, kcal/mol) and the antibacterial activity. Moreover, the pharmacokinetic profiles of 11 and 15c in rat were characterized by moderate clearance and oral bioavailability.

On the Importance of the Aromatic Ring Parameter in Studies of the Solvolyses of Cinnamyl and Cinnamoyl Halides

In solvolysis studies using Grunwald-Winstein plots, dispersions were observed for substrates with aromatic rings at the α-carbon. Several examples for the unimolecular solvolysis of monoaryl benzylic derivatives and related diaryl- or naphthyl- substituted derivatives have now been reported, where the application of the aromatic ring parameter (I) removes this dispersion. A recent claim suggesting the presence of an appreciable nucleophilic component to the I scale, has now been shown, in a review of the solvolysis of highly-hindered alkyl halides, to be unlikely to be correct. Attention is now focused on the application of the hI term for the solvolysis of compounds containing a double bond in the vicinity of any developing carbocation. Available specific rates of solvolysis (plus some new values) at 25°C of cinnamyl chloride, cinnamyl bromide, cinnamoyl chloride, p-chlorocinnamoyl chloride, and p-nitrocinnamoyl chloride are analyzed using the simple and extended (including the hI term) Grunwald-Winstein equations.

Effect of sydnone SYD-1, a mesoionic compound, on energy-linked functions of rat liver mitochondria

An important antitumour effect of SYD-1 (3-[4-chloro-3-nitrophenyl]-1,2,3-oxadiazolium-5-olate) has been shown. We now report the effects of this mesoionic compound on mitochondrial metabolism. SYD-1 (1.5 micromol mg(-1) protein) dose-dependently inhibited the respiratory rate by 65% and 40% in state 3 using sodium glutamate and succinate, respectively, as substrates. Phosphorylation efficiency was depressed by SYD-1, as evidenced by stimulation of the state 4 respiratory rate, which was more accentuated with glutamate ( approximately 180%) than with succinate ( approximately 40%), with 1.5 micromol mg(-1) protein of SYD-1. As a consequence of the effects on states 3 and 4, the RCC and ADP/O ratios were lowered by SYD-1 using both substrates, although this effect was stronger with glutamate. The formation of membrane electrical potential was inhibited by approximately 50% (1.5 micromol SYD-1mg(-1) protein). SYD-1 interfered with the permeability of the inner mitochondrial membrane, as demonstrated by assays of mitochondrial swelling in the presence of sodium acetate and valinomycin +K(+). SYD-1 (1.5 micromol mg(-1) protein) inhibited glutamate completely and succinate energized-mitochondrial swelling by 80% in preparations containing sodium acetate. The swelling of de-energized mitochondria induced by K(+) and valinomycin was inhibited by 20% at all concentrations of SYD-1. An analysis of the segments of the respiratory chain suggested that the SYD-1 inhibition site goes beyond the complex I and includes complexes III and IV. Glutamate dehydrogenase was inhibited by 20% with SYD-1 (1.5 micromol mg(-1) protein). The hydrolytic activity of complex F(1)F(o) ATPase in intact mitochondria was greatly increased ( approximately 450%) in the presence of SYD-1. Our results show that SYD-1 depresses the efficiency of electron transport and oxidative phosphorylation, suggesting that these effects may be involved in its antitumoural effect.

Synthesis and antiproliferative activity of some 5-substituted 2-(2,4-dihydroxyphenyl)-1,3,4-thiadiazoles

A series of new 5-substituted 2-(2,4-dihydroxyphenyl)-1,3,4-thiadiazoles has been synthesised and evaluated for their antiproliferative activity. The compounds were prepared by the reaction of the sulphinylbis(2,4-dihydroxythiobenzoyl) (STB) wit hydrazides or carbazates. The panel substitution included alkyl, alkoxy, aryl and heteroaryl derivatives. The structures of compounds were identified from the elemental, IR, (1)H NMR and MS spectra analysis. The highest antiproliferative activity against the cells of human cancer lines for 2-(2,4-dihydroxyphenyl)-5-(4-methoxybenzyloxy)-1,3,4-thiadiazole was found with ID(50) values comparable (HCV29T and SW707) or significantly lower (T47D) than for cisplatin applied as the reference compound. The influence of 5-substiution type of 2-(2,4-dihydroxyphenyl)-1,3,4-thiadiazoles on antiproliferative activity is discussed.

Evaluation of Antiproliferative Effect in Vitro of Some 2-Amino-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole Derivatives

New compounds of N-substituted 2-amino-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole set were synthesized and tested for their antiproliferative activity as part of our research in the antitumour field. Title compounds were obtained by reaction of sulfinylbis(2,4-dihydroxythiobenzoyl) (STB) with 4-substituted 3-thiosemicarbazides. The structures of compounds were identified from elemental, IR, 1H-, 13C-NMR and MS spectra analyses. The cytotoxicity in vitro against human bladder cancer HCV29T cells was determined. The most active compounds were also tested against human cancer cell lines: SW707 (rectal), A549 (lung) and T47D (breast). The antiproliferative effect of some compounds was higher than cisplatin studied comparatively.