Synthesis, SAR and antibacterial activity of hybrid chloro, dichloro-phenylthiazolyl-s-triazines

A Review on Synthetic Thiazole Derivatives as an Antimalarial Agent

BACKGROUND

Thiazole is a widely studied core structure in heterocyclic chemistry and has proven to be a valuable scaffold in medicinal chemistry. The presence of thiazole in both naturally occurring and synthetic pharmacologically active compounds demonstrates the adaptability of these derivatives.

METHODS

The current study attempted to review and compile the contributions of numerous researchers over the last 20 years to the medicinal importance of these scaffolds, with a primary focus on antimalarial activity. The review is based on an extensive search of PubMed, Google Scholar, Elsevier, and other renowned journal sites for a thorough literature survey involving various research and review articles.

RESULTS

A comprehensive review of the antimalarial activity of the thiazole scaffold revealed potential therapeutic targets in Plasmodium species. Furthermore, the correlation of structure-activity-relationship (SAR) studies from various articles suggests that the thiazole ring has therapeutic potential.

CONCLUSION

This article intends to point researchers in the right direction for developing potential thiazole-based compounds as antimalarial agents in the future.

Molecular docking and antimalarial evaluation of hybrid para-aminobenzoic acid 1,3,5 triazine derivatives via inhibition of Pf-DHFR

In this study, a structurally guided pharmacophore hybridization strategy is used to combine the two key structural scaffolds, para-aminobenzoic acid (PABA), and 1,3,5 triazine in search of new series of antimalarial agents. A combinatorial library of 100 compounds was prepared in five different series as [4A (1-22), 4B (1-21), 4 C (1-20), 4D (1-19) and 4E (1-18)] using different primary and secondary amines, from where 10 compounds were finally screened out through molecular property filter analysis and molecular docking study as promising PABA substituted 1,3,5-triazine scaffold as an antimalarial agent. The docking results showed that compounds 4A12 and 4A20 exhibited good binding interaction with Phe58, IIe164, Ser111, Arg122, Asp54 (-424.19 to -360.34 kcal/mol) and Arg122, Phe116, Ser111, Phe58 (-506.29 to -431.75 kcal/mol) against wild (1J3I) and quadruple mutant (1J3K) type of Pf-DHFR. These compounds were synthesized by conventional as well as microwave-assisted synthesis and characterized by different spectroscopic methods. In-vitro antimalarial activity results indicated that two compounds 4A12 and 4A20 showed promising antimalarial activity against chloroquine-sensitive (3D7) and chloroquine-resistant (Dd2) strains of Plasmodium falciparum with IC50 (1.24-4.77 μg mL-1) and (2.11-3.60 μg mL-1). These hybrid PABA substituted 1,3,5-triazine derivatives might be used in the lead discovery towards a new class of Pf-DHFR inhibitors.Communicated by Ramaswamy H. Sarma.

A Review of the Development of Multitarget Molecules against HIV-TB Coinfection Pathogens

The human immunodeficiency virus (HIV) produces the pathologic basis of acquired immunodeficiency syndrome (AIDS). An increase in the viral load in the body leads to a decline in the number of T lymphocytes, compromising the patient's immune system. Some opportunistic diseases may result, such as tuberculosis (TB), which is the most common in seropositive patients. Long-term treatment is required for HIV-TB coinfection, and cocktails of drugs for both diseases are used concomitantly. The most challenging aspects of treatment are the occurrence of drug interactions, overlapping toxicity, no adherence to treatment and cases of resistance. Recent approaches have involved using molecules that can act synergistically on two or more distinct targets. The development of multitarget molecules could overcome the disadvantages of the therapies used to treat HIV-TB coinfection. This report is the first review on using molecules with activities against HIV and Mycobacterium tuberculosis (MTB) for molecular hybridization and multitarget strategies. Here, we discuss the importance and development of multiple targets as a means of improving adherence to therapy in cases of the coexistence of these pathologies. In this context, several studies on the development of structural entities to treat HIV-TB simultaneously are discussed.

Discovery of novel 1,3,5-triazines as potent antibacterial agent against urinary tract infection-causing clinical isolates of Escherichia coli via inhibition of DNA Gyrase

A novel series of 1,3,5-triazine-phenylthiazole-pyrazole derivatives were synthesized and subsequently tested for Escherichia coli DNA Gyrase inhibitory activity where they showed excellent inhibitory activity. The top-three ranked DNA gyrase inhibitor (4e, 4g and 4h) were further subjected to antibacterial and anti-biofilm activity against clinical isolates of resistant E. coli strains obtained from Urinary Tract Infection (UTI) patients (CREC81, CREC106, CREC163). Compound 4h was identified as most potent antibacterial agent in the above study. The compound 4h was further evaluated in murine model of E. coli UTI in BALB/c mice infected by transurethral injection of CREC106 strain. Results of the study suggest that compound 4h reduces bacterial load of CREC106 in the treated mice and found approximately equipotent to Novobiocin as standard.

Chemical synthesis, molecular docking and MepA efflux pump inhibitory effect by 1,8-naphthyridines sulfonamides

This study aimed to evaluate the antibacterial activity and to verify, in silico and in vitro, the inhibition of efflux mechanisms using a series of synthesized 1,8-naphthyridines sulfonamides against Staphylococcus aureus strains carrying MepA efflux pumps. The chemical synthesis occurred through the thermolysis of the Meldrum's acid adduct. The sulfonamide derivatives were obtained by the sulfonylation of 2-amino-5‑chloro-1,8-naphthyridine with commercial benzenesulfonyl chloride. Antibacterial activity was assessed by the broth microdilution test. Efflux pump inhibitory capacity was evaluated in silico by molecular docking and in vitro by analyzing synergistic effects on ciprofloxacin and ethidium bromide (EtBr) and by EtBr fluorescence emission assays. The following 1,8-naphthyridines were synthesized: 4-methyl-N-(5‑chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Compound 10a); 2,5-dichloro-N-(5‑chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Compound 10b); 4-fluoro-N-(5‑chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Compound 10c); 2,3,4-trifluoro-N-(5‑chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Compound 10d); 3-trifluoromethyl-N-(5‑chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Compound 10e); 4‑bromo-2,5-difluoro-N-(5‑chloro-1,8-naphthyridin-2-yl)-benzenesulfonamide (Compound 10f). The 1,8-naphthyridines derivatives associated with sulfonamides did not show antibacterial activity. However, they showed a favorable pharmacokinetic profile with possible MepA efflux pump inhibitory action, demonstrated in molecular docking. In addition to the promising results in reducing the concentration of intracellular EtBr. 1,8-naphthyridines act as putative agents in the inhibitory action of the MepA efflux pump.

Three Multi-Components Reaction: Synthesis and X-Ray Single-Crystal of Hydroacridinone-Based Hydrazino-S-Triazine Derivative as a New Class of Urease Inhibitor

The one-pot fashion of three multi-component reaction provides the desired hydroacridinone-based hydrazino-s-triazine scaffold 4. Compound 4 was crystallized in an orthorhombic crystal system and Pbca space group with a = 11.6271(2) Å, b = 18.2018(4) Å, c = 32.4721(6) Å, and α = β = γ = 90° with one formula unit per asymmetric unit and eight molecules per unit cell. Additionally, structural features, Hirshfeld surfaces, and DFT studies were also investigated. Its packing in the crystal is controlled by H…H (63.4%), O…H (12.7%), Cl…H (7.2%), N…H (4.7%), and C…H (10.2%) contacts, where the O…H and Cl…H contacts were found the strongest. In vitro urease inhibition evaluation showed that the hydroacridinone-based hydrazino-s-triazine is more active (IC50 = 17.9 ± 0.47 µM) than the standard acetohydroxamic acid (IC50 = 20.3 ± 0.43 µM).

Discovery of potential 1,3,5-Triazine compounds against strains of Plasmodium falciparum using supervised machine learning models

The Malaria burden was an escalating global encumbrance and need to be addressed with critical care. Anti-malarial drug discovery was integrated with supervised machine learning (ML) models to identify potent thiazolyl-traizine derivatives. This assimilated approach of Direct Kernel-based Partial Least Squares regression (DKPLS) with molprint 2D fingerprints in Quantitative Structure Activity Relationship models was utilized to map the knowledge of known actives and to design novel molecules. This QSAR study had revealed the structural features required for better antimalarial activity. Two of the molecules which were designed based on the results of this QSAR study, had shown good percentage of parasitemia against both chloroquine sensitive (3D7) and chloroquine resistant (Dd2) strains of Plasmodium falciparum respectively. The IC₅₀ of 201D and 204D was 3.02 and 2.17 µM against chloroquine resistant Dd2 strain of Plasmodium falciparum. This result had proved the efficiency of a multidisciplinary approach of medicinal chemistry and machine learning for the design of novel potent anti-malarial compounds.

Structure-activity relationships (SAR) of triazine derivatives: Promising antimicrobial agents

The emergence of drug resistance has created unmet medical need for the development of new classes of antibiotics. Innovation of new antibacterial agents with new mode of action remains a high priority universally. Triazines are six-membered, nitrogen-containing heterocyclic scaffold with a wide range of pharmaceutical properties such as antibacterial, antifungal, anticancer, antioxidants, antitubercular, antimalarial, anti-HIV, anticonvulsant, anti-inflammatory, antiulcer, and analgesic activities. The present review focuses on the recent developments in the area of medicinal chemistry to discover various chemical structures as potential antimicrobial agents and their structure-activity relationships (SAR) studies are also discussed for further rational design of this kind of derivatives.

Recent development of leucyl-tRNA synthetase inhibitors as antimicrobial agents

Aminoacyl-tRNA synthetases (aaRSs) widely exist in organisms and mediate protein synthesis. Inhibiting these synthetases can lead to the termination of protein synthesis and subsequently achieve antibacterial and antiparasitic purposes. Moreover, the structures of aaRSs found in eukaryotes have considerable structural differences compared to those in prokaryotes, based on which it is possible to develop highly selective inhibitors. Leucyl-tRNA synthetase (LeuRS) with unique synthesis and editing sites is one of 20 kinds of aaRSs. Many inhibitors targeting LeuRS have been designed and synthesized, some of which have entered clinical use. For example, the benzoxaborole compound AN2690 has been approved by the FDA for the treatment of onychomycosis. AN3365 is suspended in the phase II clinical trial due to the rapid development of AN3365 resistance, but it may be used in combination with other antibiotics. The aaRSs, especially LeuRS, are being considered as targets of new potential anti-infective drugs for the treatment of not only bacterial or fungal infections but also infections by trypanosomes and malaria parasites. This review mainly describes the development of LeuRS inhibitors, focusing on their mechanisms of action, structure-activity relationships (SARs), and in vitro and in vivo activities.

Targeting HIV-TB coinfection by developing novel piperidin-4-substituted imines: Design, synthesis, in vitro and in silico studies

Tuberculosis is the "Achilles heel" of the human immunodeficiency (HIV) ministration. HIV-positive people are 16-27 times more prone to contract tuberculosis. But the adverse interaction between antiretroviral drugs and antitubercular drugs has made it necessary to look for a single drug regimen for HIV-TB coinfection. Piperidine derivatives have been reported as anti-HIV and anti-TB agents. This inspired us to design, synthesize, and characterize a series of 3,5-bis(furan-2-ylmethylidene)-piperidin-4-substituted imines (R1-R25) and these were further screened for in vitro antitubercular activity against Mycobacterium tuberculosis H37Rv and anti-HIV activity. Molecular docking studies showed energetically favorable binding interactions with both EACP reductase (1ZID.pdb) and reverse-transcriptase (1REV.pdb) targets. The compounds R7, R12, R17, R18, R19, R20 were found to be more potent as anti-TB agents than ethambutol (MIC 3.125 μg/ml). Compound R7 was found to be moderately active with an IC₅₀ of 2.1 ± 0.04 μM in multicycle infection assays, in comparison with the standard drug, zidovudine (IC₅₀  = 5.7 ± 0.04 nM), used as anti-HIV drug. The cytotoxicity assay was done on Vero, MT-2, and TZM-bl cells to assess the safety of these compounds and they were found to be safe. From the above results, R7 seems to be a promising lead for anti-HIV and anti-TB activity.

Rational design, synthesis and biological screening of triazine-triazolopyrimidine hybrids as multitarget anti-Alzheimer agents

In our endeavor towards the development of potent multitarget ligands for the treatment of Alzheimer's disease, a series of triazine-triazolopyrimidine hybrids were designed, synthesized and characterized by various spectral techniques. Docking and scoring techniques were used to design the inhibitors and to display their interaction with key residues of active site. Organic synthesis relied upon convergent synthetic routes were mono and di-substituted triazines were connected with triazolopyrimidine using piperazine as a linker. In total, seventeen compounds were synthesized in which the di-substituted triazine-triazolopyrimidine derivatives 9a-d showed better acetylcholinesterase (AChE) inhibitory activity than the corresponding tri-substituted triazine-triazolopyrimidine derivatives 10a-f. Out of the disubstituted triazine-triazolopyrimidine based compounds, 9a and 9b showed encouraging inhibitory activity on AChE with IC₅₀ values 0.065 and 0.092 μM, respectively. Interestingly, 9a and 9b also demonstrated good inhibition selectivity towards AChE over BuChE by ∼28 folds. Furthermore, kinetic analysis and molecular modeling studies showed that 9a and 9b target both catalytic active site as well as peripheral anionic site of AChE. In addition, these derivatives effectively modulated Aβ self-aggregation as investigated through CD spectroscopy, ThT fluorescence assay and electron microscopy. Besides, these compounds exhibited potential antioxidants (2.15 and 2.91 trolox equivalent by ORAC assay) and metal chelating properties. In silico ADMET profiling highlighted that, these novel triazine derivatives have appropriate drug like properties and possess very low toxic effects in the primarily pharmacokinetic study. Overall, the multitarget profile exerted by these novel triazine molecules qualified them as potential anti-Alzheimer drug candidates in AD therapy.

Hybrid phenylthiazole and 1,3,5-triazine target cytosolic leucyl-tRNA synthetase for antifungal action as revealed by molecular docking studies

BACKGROUND

Leucyl-tRNA synthetase (LeuRS) is one of the essential enzymes belonging to the family of aminoacyl-tRNA synthetases (aaRSs), which executes the translation of genetic code by catalyzing the specific attachment of amino acids to their cognate tRNAs. This process is very crucial for survival of micro-organism and thus the inhibition of LeuRS offered a novel and lucrative target for developing new antimicrobials.

FINDINGS

Docking studies using hybrid phenylthiazole-1,3,5-triazine derivatives revealed that these molecules acted as probable inhibitors of candida albicans cytosolic leucyl-tRNA synthetase.

CONCLUSION

The conjugates of phenylthiazole and 1,3,5-triazine can act as lead molecules towards the development of potential leucyl-tRNA synthetase inhibitors on the basis of molecular docking runs, which contribute to the possible mechanism of antifungal activity of these analogues.