Synthesis and anticancer activity of novel 3,6-disubstituted 1,2,4-triazolo-[3,4-b]-1,3,4-thiadiazole derivatives

Copper-mediated cyclization of thiosemicarbazones leading to 1,3,4-thiadiazoles: Structural elucidation, DFT calculations, in vitro biological evaluation and in silico evaluation studies

Cancer's global impact necessitates innovative and less toxic treatments. Thiosemicarbazones (TSCs), adaptable metal chelators, offer such potential. In this study, we have synthesized N (4)-substituted heterocyclic TSCs from syringaldehyde (TSL1, TSL2), and also report the unexpected copper-mediated cyclization of the TSCs to form thiadiazoles (TSL3, TSL4), expanding research avenues. This work includes extensive characterization and studies such as DNA/protein binding, molecular docking, and theoretical analyses to demonstrate the potential of the as-prepared TSCs and thiadiazoles against different cancer cells. The DFT results depict that the thiadiazoles exhibit greater structural stability and reduced reactivity compared to the corresponding TSCs. The docking results suggest superior EGFR inhibition for TSL3 with a binding constant value of - 6.99 Kcal/mol. According to molecular dynamics studies, the TSL3-EGFR complex exhibits a lower average RMSD (1.39 nm) as compared to the TSL1-EGFR complex (3.29 nm) suggesting that both the thiadiazole and thiosemicarbazone examined here can be good inhibitors of EGFR protein, also that TSL3 can inhibit EGFR better than TSL1. ADME analysis indicates drug-likeness and oral availability of the thiadiazole-based drugs. The DNA binding experiment through absorption and emission spectroscopy discovered that TSL3 is more active towards DNA which is quantitatively calculated with a Kb value of 4.74 × 106 M-1, Kq value of 4.04 × 104 M-1and Kapp value of 5 × 106 M-1. Furthermore, the BSA binding studies carried out with fluorescence spectroscopy showed that TSL3 shows better binding capacity (1.64 × 105 M-1) with BSA protein. All the compounds show significant cytotoxicity against A459-lung, MCF-7-breast, and HepG2-liver cancer cell lines; TSL3 exhibits the best cytotoxicity, albeit less effective than cisplatin. Thiadiazoles demonstrate greater cytotoxicity than the TSCs. Overall, the promise of TSCs and thiadiazoles in cancer research is highlighted by this study. Furthermore, it unveils unexpected copper-mediated cyclization of the TSCs to thiadiazoles.

Design, Synthesis, and Mode of Action of Thioacetamide Derivatives as the Algicide Candidate Based on Active Substructure Splicing Strategy

Lakes and reservoirs worldwide are experiencing a growing problem with harmful cyanobacterial blooms (HCBs), which have significant implications for ecosystem health and water quality. Algaecide is an effective way to control HCBs effectively. In this study, we applied an active substructure splicing strategy for rapid discovery of algicides. Through this strategy, we first optimized the structure of the lead compound S5, designed and synthesized three series of thioacetamide derivatives (series A, B, C), and then evaluated their algicidal activities. Finally, compound A3 with excellent performance was found, which accelerated the process of discovering and developing new algicides. The biological activity assay data showed that A3 had a significant inhibitory effect on M. aeruginosa. FACHB905 (EC50 = 0.46 μM) and Synechocystis sp. PCC6803 (EC50 = 0.95 μM), which was better than the commercial algicide prometryn (M. aeruginosa. FACHB905, EC50 = 6.52 μM; Synechocystis sp. PCC6803, EC50 = 4.64 μM) as well as better than lead compound S5 (M. aeruginosa. FACHB905, EC50 = 8.80 μM; Synechocystis sp. PCC6803, EC50 = 7.70 μM). The relationship between the surface electrostatic potential, chemical reactivity, and global electrophilicity of the compounds and their activities was discussed by density functional theory (DFT). Physiological and biochemical studies have shown that A3 might affect the photosynthesis pathway and antioxidant system in cyanobacteria, resulting in the morphological changes of cyanobacterial cells. Our work demonstrated that A3 might be a promising candidate for the development of novel algicides and provided a new active skeleton for the development of subsequent chemical algicides.

An effort to find new α-amylase inhibitors as potent antidiabetics compounds based on indole-based-thiadiazole analogs

Inhibition of α-amylase enzyme is of key significance for the therapy of diabetes mellitus (DM). Numerous indole-based compounds have earlier been described for broad range of bioactivities. From our previous study, we knew that indole and thiadiazole are potent inhibitors of diabetics II. We design the hybrid molecules of them and synthesized 18 derivatives of indole-based-thiadiazole (1-18). All synthesized compounds were characterized using different spectroscopic methods and evaluated for their α-amylase inhibitory activities. All synthetic compounds, except 4, 13, 15 and 16, were found to be strongly active (IC₅₀ values in the range of 0.80 ± 0.05 - 9.30 ± 0.20 µM) than the standard drug, acarbose (IC₅₀ = 11.70 ± 0.10 µM). Nevertheless, compound 18 was found to be inactive. The modes of binding interactions of five most active compounds 2, 3, 5, 10 and 17 were also studies through molecular docking study. In brief, current study identifies a novel class of α-amylase inhibitors which can be further studied for the treatment of hyperglycemia and obesity.Communicated by Ramaswamy H. Sarma.

Synthesis and antimicrobial activity of functional derivatives of thiazolo[2,3-c][1,2,4]triazoles

Background:

Condensed triazoles are a well-known class of heterocyclic compounds due to a wide range of biological activity. The study is dedicated to the evaluation of the antimicrobial potential of new functional derivatives of thiazolo[2,3-c][1,2,4]triazoles.

Methods:

Effective, easy-to-implement and low-cost routes to the production of title compounds via electrophilic intramolecular heterocyclization are reported. Bactericidal and fungicidal activities against Gram-positive and Gram-negative bacteria, and fungus were studied. The influence of functional groups on the biological activity of tested thiazolo[2,3-c][1,2,4]triazoles is discussed.

Results:

Microbiological evaluation shows that 6-[(trichlorotellanyl)methyl]-[1,3]thiazolo[2,3-c][1,2,4]triazol-3-amine hydrogen chloride 2a and 3-(2-hydroxyphenyl)-6-[(trichloro-λ4-tellanyl)methyl]-5,6-dihydro-[1,3]thiazolo[2,3-c][1,2,4]triazole 2g have a high bactericidal activity and Cu (I) salts of 3-(2-hydroxyphenyl)-6-iodomethyl/6-methylidene-5,6-dihydro-[1,3]thiazolo-[2,3-c][1,2,4]triazoles 5a,c have a high fungicidal activity.

Conclusion:

it must be concluded that these products or their derivatives may be of practical benefit as bactericidal and fungicidal agents.

Monoamine oxidase A and B inhibitory activities of 3,5-diphenyl-1,2,4-triazole substituted [1,2,4]triazolo[3,4-b][1,3,4]thiadiazole derivatives

Monoamine oxidase (EC 1.4.3.4, MAO) is a flavin adenine dinucleotide-containing flavoenzyme located on the outer mitochondrial membrane and catalyzes the oxidative deamination of monoaminergic neurotransmitters and dietary amines. MAO exists in humans as two isoenzymes, hMAO-A and hMAO-B, which are distinguished by their tertiary structures, preferred substrates and inhibitors, and selective inhibition of these isoenzymes are used in the treatment of different diseases such as Alzheimer's, Parkinson's and depression. In the present study, we report the design, synthesis and characterization of 3,5-diphenyl-1,2,4-triazole substituted [1,2,4]triazolo[3,4-b][1,3,4]thiadiazole derivatives as novel and selective inhibitors of hMAO-B. Twenty one compounds (38, 39a-h, 41a-d, 42a-h) were screened for their inhibitory activity against hMAO-A and hMAO-B by using in vitro Amplex Red® reagent based fluorometric method and all compounds were found to be as selective h-MAO-B inhibitors to a different degree. The compound 42e and 42h displayed the highest inhibitory activity against hMAO-B with IC₅₀ values of 2.51 and 2.81 µM, respectively, and more than 25-fold selectivity towards inhibition of hMAO-B. A further kinetic evaluation of the most potent derivative (42e) was also performed and a mixed mode of inhibition of hMAO-B by the compound 42e was determined (K_i = 0,26 µM). According to our findings the [1,2,4]triazolo[3,4-b][1,3,4]thiadiazole emerged as a promising scaffold for the development of novel and selective hMAO-B inhibitors.

Expedition of sulfur-containing heterocyclic derivatives as cytotoxic agents in medicinal chemistry: A decade update

This review article proposes a comprehensive report of the design strategies engaged in the development of various sulfur-bearing cytotoxic agents. The outcomes of various studies depict that the sulfur heterocyclic framework is a fundamental structure in diverse synthetic analogs representing a myriad scope of therapeutic activities. A number of five-, six- and seven-membered sulfur-containing heterocyclic scaffolds, such as thiazoles, thiadiazoles, thiazolidinediones, thiophenes, thiopyrans, benzothiazoles, benzothiophenes, thienopyrimidines, simple and modified phenothiazines, and thiazepines have been discussed. The subsequent studies of the derivatives unveiled their cytotoxic effects through multiple mechanisms (viz. inhibition of tyrosine kinases, topoisomerase I and II, tubulin, COX, DNA synthesis, and PI3K/Akt and Raf/MEK/ERK signaling pathways), and several others. Thus, our concise illustration explains the design strategy and anticancer potential of these five- and six-membered sulfur-containing heterocyclic molecules along with a brief outline on seven-membered sulfur heterocycles. The thorough assessment of antiproliferative activities with the reference drug allows a proficient assessment of the structure-activity relationships (SARs) of the diversely synthesized molecules of the series.

Triazolo Based-Thiadiazole Derivatives. Synthesis, Biological Evaluation and Molecular Docking Studies

The goal of this research is to investigate the antimicrobial activity of nineteen previously synthesized 3,6-disubstituted-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole derivatives. The compounds were tested against a panel of three Gram-positive and three Gram-negative bacteria, three resistant strains, and six fungi. Minimal inhibitory, bactericidal, and fungicidal concentrations were determined by a microdilution method. All of the compounds showed antibacterial activity that was more potent than both reference drugs, ampicillin and streptomycin, against all bacteria tested. Similarly, they were also more active against resistant bacterial strains. The antifungal activity of the compounds was up to 80-fold higher than ketoconazole and from 3 to 40 times higher than bifonazole, both of which were used as reference drugs. The most active compounds (2, 3, 6, 7, and 19) were tested for their inhibition of P. aeruginosa biofilm formation. Among them, compound 3 showed significantly higher antibiofilm activity and appeared to be equipotent with ampicillin. The prediction of the probable mechanism by docking on antibacterial targets revealed that E. coli MurB is the most suitable enzyme, while docking studies on antifungal targets indicated a probable involvement of CYP51 in the mechanism of antifungal activity. Finally, the toxicity testing in human cells confirmed their low toxicity both in cancerous cell line MCF7 and non-cancerous cell line HK-2.

Effects of a Novel Thiadiazole Derivative with High Anticancer Activity on Cancer Cell Immunogenic Markers: Mismatch Repair System, PD-L1 Expression, and Tumor Mutation Burden

Microsatellite instability (MSI), tumor mutation burden (TMB), and programmed cell death ligand-1 (PD-L1) are particularly known as immunotherapy predictive biomarkers. MSI and TMB are closely related to DNA mismatch repair (MMR) pathway functionality, while the PD-L1 checkpoint mediates cancer cell evasion from immune surveillance via the PD-L1/PD-1 axis. Among all the novel triazolo[3,4-b]thiadiazole derivatives, the compound KA39 emerged as the most potent anticancer agent. In the present study, potential alterations in MSI, TMB, and/or PD-L1 expression upon cell treatment with KA39 are explored. We tested three MMR-deficient (DLD-1, LS174T, and DU-145) and two MMR-proficient (HT-29 and PC-3) human cancer cell lines. Our findings support KA39-induced PD-L1 overexpression in all cancer cell lines, although the most outstanding increase was observed in MMR-proficient HT-29 cells. MSI analysis showed that KA39 affects the MMR system, impairing its recognition or repair activity, particularly in MMR-deficient DLD-1 and DU-145 cells, enhancing oligonucleotide production. There were no remarkable alterations in the TMB between untreated and treated cells, indicating that KA39 does not belong to mutagenic agents. Taking together the significant in vitro anticancer activity with PD-L1 upregulation and MSI increase, KA39 should be investigated further for its implication in chemo-immunotherapy of cancer.

Immobilization and Release Studies of Triazole Derivatives from Grafted Copolymer Based on Gellan-Carrying Betaine Units

New polymer-bioactive compound systems were obtained by immobilization of triazole derivatives onto grafted copolymers and grafted copolymers carrying betaine units based on gellan and N-vinylimidazole. For preparation of bioactive compound, two new types of heterocyclic thio-derivatives with different substituents were combined in a single molecule to increase the selectivity of the biological action. The 5-aryl-amino-1,3,4 thiadiazole and 5-mercapto-1,2,4-triazole derivatives, each containing 2-mercapto-benzoxazole nucleus, were prepared by an intramolecular cyclization of thiosemicarbazides-1,4 disubstituted in acidic and basic medium. The structures of the new bioactive compounds were confirmed by elemental and spectral analysis (FT-IR and 1H-NMR). The antimicrobial activity of 1,3,4 thiadiazoles and 1,2,4 triazoles was tested on gram-positive and gram-negative bacteria. The triazole compound was chosen to be immobilized onto polymeric particles by adsorption. The Langmuir, Freundlich, and Dubinin-Radushkevich adsorption isotherm were used to describe the adsorption equilibrium. Also, the pseudo-first and pseudo-second models were used to elucidate the adsorption mechanism of triazole onto grafted copolymer based on N-vinylimidazole and gellan (PG copolymer) and grafted copolymers carrying betaine units (PGB1 copolymer). In vitro release studies have shown that the release mechanism of triazole from PG and PGB1 copolymers is characteristic of an anomalous transport mechanism.

3,6-Disubstituted 1,2,4-Triazolo[3,4-b]Thiadiazoles with Anticancer Activity Targeting Topoisomerase II Alpha

BACKGROUND

Topoisomerase IIα (topIIα) maintains the topology of DNA in order to ensure the proper functioning of numerous DNA processes. Inhibition of topIIα leads to the killing of cancer cells thus constituting such inhibitors as useful tools in cancer therapeutics. Triazolo[3,4-b]thiadiazole derivatives are known for their wide range of pharmacological activities while previous studies have documented their in vitro anticancer activity. The purpose of the current study was to investigate if these chemical compounds can act as topIIα inhibitors in cell-free and cell-based systems.

MATERIALS AND METHODS

The MTT assay was performed in DLD-1, HT-29, and LoVo cancer cells so as to evaluate the antiproliferative activity of KA25, KA26, and KA39 triazolo[3,4-b]thiadiazole derivatives. The KA39 compound was tested as a potential topIIα inhibitor using the plasmid-based topoisomerase II drug screening kit. The inhibitory effect of the three derivatives on topIIα phosphorylation was studied in HT-29 and LoVo cancer cells according to Human Phospho-TOP2A/Topoisomerase II Alpha Cell-Based Phosphorylation ELISA Kit. Moreover, flow cytometry was utilized in order to explore apoptotic induction and cell cycle growth arrest, upon treatment with KA39, in DLD-1 and HT-29 cells, respectively. In silico studies were also carried out for further investigation.

RESULTS

All three triazolo[3,4-b]thiadiazole derivatives showed an in vitro antiproliferative effect with the KA39 compound being the most potent one. Our results indicated that KA39 induced both early and late apoptosis as well as cell cycle growth arrest in S phase. In addition, the compound blocked the relaxation of supercoiled DNA while it also inhibited topIIα phosphorylation (upon treatment; P<0.001).

CONCLUSION

Among the three triazolo[3,4-b]thiadiazole derivatives, KA39 was shown to be the most potent anticancer agent and catalytic inhibitor of topIIα phosphorylation as well.