Antimicrobial and antiquorum-sensing studies. Part 3: Synthesis and biological evaluation of new series of [1,3,4]thiadiazoles and fused [1,3,4]thiadiazoles

Design and synthesis of new quinazolinone derivatives: investigation of antimicrobial and biofilm inhibition effects

New quinazolin-4-ones 9-32 were synthesized in an attempt to overcome the life-threatening antibiotic resistance phenomenon. The antimicrobial screening revealed that compounds 9, 15, 16, 18, 19, 20 and 29 are the most broad spectrum antimicrobial agents in this study with safe profile on human cell lines. Additionally, compounds 19 and 20 inhibited biofilm formation in Pseudomonas aeruginosa, which is regulated by quorum sensing system, at sub-minimum inhibitory concentrations (sub-MICs) with IC50 values 3.55 and 6.86 µM, respectively. By assessing other pseudomonal virulence factors suppression, it was found that compound 20 decreased cell surface hydrophobicity compromising bacterial cells adhesion, while both compounds 19 and 20 curtailed the exopolysaccharide production which constitutes the major component of the matrix binding biofilm components together. Also, at sub-MICs Pseudomonas cells twitching motility was impeded by compounds 19 and 20, a trait which augments the cells pathogenicity and invasion potential. Molecular docking study was performed to further evaluate the binding mode of candidates 19 and 20 as inhibitors of P. aeruginosa quorum sensing transcriptional regulator PqsR. The achieved results demonstrate that both compounds bear promising potential for discovering new anti-biofilm and quorum quenching agents against Pseudomonas aeruginosa without triggering resistance mechanisms as the normal bacterial life cycle is not disturbed.

Synthetic non-toxic anti-biofilm agents as a strategy in combating bacterial resistance

The tremendous increase in the bacterial resistance to the available antibiotics is a serious problem for the treatment of various infections. Biofilm formation in bacteria significantly contributes to the bacterial survival in host cells, and is considered as an crucial factor, responsible for bacterial resistance. The response of the bacterial cells in the biofilm to antibiotics is completely different from that of the free floating planktonic cells of the same strain. The anti-biofilm agents that could inhibit the biofilm production without affecting the bacterial growth, apply less selective pressure over the bacterial strains than the traditional antibiotics; thus the development of bacterial resistance would be of low incidence. Many attempts have been performed to discover novel agents capable of interfering with the bacterial biofilm life cycle, and several compounds have shown promising activities in suppressing the biofilm production or in dispersing mature existing biofilms. This review describes the different chemical classes that have anti-biofilm effects against different Gram-positive and Gram-negative bacteria without affecting the bacterial growth.

In vitro and in silico evaluation of N-(alkyl/aryl)-2-chloro-4-nitro-5- [(4-nitrophenyl)sulfamoyl]benzamide derivatives for antidiabetic potential using docking and molecular dynamic simulations

A series of N-(alkyl/aryl)-2-chloro-4-nitro-5-[(4-nitrophenyl)sulfamoyl]benzamide derivatives were synthesized and evaluated for its in vitro antidiabetic potential against α-glucosidase and α-amylase enzymes and also for its antimicrobial potential. Compounds N-(2-methyl-4-nitrophenyl)-2-chloro-4-nitro-5-[(4-nitrophenyl)sulfamoyl]benzamide and N-(2-methyl-5-nitrophenyl)-2-chloro-4-nitro-5-[(4-nitrophenyl)sulfamoyl]benzamide were found to be the most potent α-glucosidase and α-amylase inhibitors with IC₅₀ values of 10.13 and 1.52 µM, respectively. The docking results depicted reasonable dock score -10.2 to -8.0 kcal/mol (α-glucosidase), -11.1 to -8.3 kcal/mol (α-amylase) and binding interactions of synthesized molecules with respective targets with enzymes. During molecular dynamic simulations, analysis of RMSD of ligand protein complex suggested stability of the most active compound at binding site of target proteins. Compound N-(2-chloro-4-nitrophenyl)-2-chloro-4-nitro-5-[(4-nitrophenyl)sulfamoyl] benzamide showed antibacterial potential against Gram positive and Gram negative bacteria and compound N-(2-methyl-5-nitrophenyl)-2-chloro-4-nitro-5-[(4-nitrophenyl)sulfamoyl] benzamide showed excellent antifungal potential against Candida albicans and Aspergillus niger. The computational studies were also executed to predict the drug-likeness and ADMET properties of the title compounds. The N-(alkyl/aryl)-2-chloro-4-nitro-5-[(4-nitrophenyl)sulfamoyl]benzamide derivatives showed significant antidiabetic and antimicrobial potential which is equally supported by the molecular dynamic and docking studies. This study will prove useful in revealing the molecular structure and receptor target site details which can be further utilized for the development of newer active antidiabetic and antimicrobial agents.

Synthesis and biological screening of new thiadiazolopyrimidine-based polycyclic compounds

Novel tri-and tetra-cyclic compounds based on the thiadiazolopyrimidine ring system were synthesized, and their antimicrobial activity was estimated. The obtained results evidenced the substantial efficiencies of pyrano-thiadiazolopyrimidine compounds 8a-b and 9a-b toward the two strains of gram-positive bacteria (S. aureus and B. cereus). Besides, tetracyclic pyrazolopyrimido-thiadiazolopyrimidine derivatives 16a-b and 17a-b displayed prominent efficiencies toward the two strains of gram-negative bacteria (E. coli and P. aeruginosa). In addition, compounds 8a-b and 9a-b displayed good efficacy toward C. albicans. The activity of antiquorum sensing (anti-QS) inhibition of the newly synthesized thiadiazolopyrimidine-based compounds toward C. violaceum was tested, suggesting satisfactory activity for derivatives 16a-b, 17a-b, 8b, and 9a. The cytotoxic activity of these derivatives was screened toward various cancer cell lines (MCF-7, PC3, Hep-2, and HepG2) and standard normal fibroblast cells (WI38) by utilizing the MTT assay. The pyrazolopyrimido-thiadiazolopyrimidine derivatives 16a, 16b17a, and 17b showed potent cytotoxic efficacy against the MCF-7 cells with the IC50 values ranging from 5.69 to 9.36 µM. Also, the endorsed structural activity relationship (SAR) of the inspected thiadiazolopyrimidine derivatives provided a correlation between the chemical structure and anticancer efficiency. The in silico docking studies were implemented for silencing the hormonal signaling in the breast (PDB Code-5NQR). The results were found to be consistent with the cytotoxic activity.

Anti-biofilm Fe3O4@C18-[1,3,4]thiadiazolo[3,2-a]pyrimidin-4-ium-2-thiolate Derivative Core-shell Nanocoatings

The derivatives 5,7-dimethyl[1,3,4]thiadiazolo[3,2-a]pyrimidin-4-ium-2-thiolate (1) and 7-methyl-5-phenyl[1,3,4]thiadiazolo[3,2-a]pyrimidin-4-ium-2-thiolate (2) were fully characterized by single-crystal X-ray diffraction. Their supramolecular structure is built through both π–π stacking and C=S–π interactions for both compounds. The embedment of the tested compounds into Fe₃O₄@C₁₈ core-shell nanocoatings increased the protection degree against Candida albicans biofilms on the catheter surface, suggesting that these bioactive nanocoatings could be further developed as non-cytotoxic strategies for fighting biofilm-associated fungal infections.

Alkylated benzimidazoles: Design, synthesis, docking, DFT analysis, ADMET property, molecular dynamics and activity against HIV and YFV

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New benzimidazole analogs synthesized as antivirals against HIV-1 and yellow fever virus.

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Molecular dynamics simulation studies indicated a stable ligand-protein complex of compound 3a within NNIBP of HIV-RT.

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DFT analysis confirmed the stability of hydrogen bonding interaction between the TRP 229 residue of HIV-RT and compound 3a.

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Molecules were tested for their anti-HIV and broad spectrum antiviral properties against different DNA and RNA viruses.

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Antiviral properties and cytotoxicity determined using MTT assay.

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Compound 3a showed anti-HIV activity and compound 2b showed excellent inhibition property against yellow fever virus.

A series of alkylated benzimidazole derivatives was synthesized and screened for their anti-HIV, anti-YFV, and broad-spectrum antiviral properties. The physicochemical parameters and drug-like properties of the compounds were assessed first, and then docking studies and MD simulations on HIV-RT allosteric sites were conducted to find the possible mode of their action. DFT analysis was also performed to confirm the nature of the hydrogen bonding interaction of active compounds. The in silico studies indicated that the molecules behaved like possible NNRTIs. The nature – polar or non-polar and position of the substituent present at fifth, sixth, and N-1 positions of the benzimidazole moiety played an important role in determining the antiviral properties of the compounds. Among the various compounds, 2-(5,6-dibromo-2-chloro-1H-benzimidazol-1-yl)ethan-1-ol (3a) showed anti-HIV activity with an appreciably low IC₅₀ value as 0.386 × 10⁻⁵μM. Similarly, compound 2b, 3-(2-chloro-5-nitro-1H-benzimidazol-1-yl) propan-1-ol, showed excellent inhibitory property against the yellow fever virus (YFV) with EC₅₀ value as 0.7824 × 10⁻²μM.

Synthesis, molecular docking and molecular dynamic simulation studies of 2-chloro-5-[(4-chlorophenyl)sulfamoyl]-N-(alkyl/aryl)-4-nitrobenzamide derivatives as antidiabetic agents

A series of 2-chloro-5-[(4-chlorophenyl)sulfamoyl]-N-(alkyl/aryl)-4-nitrobenzamide derivatives (5a-5v) has been synthesized and confirmed by physicochemical(R_f, melting point) and spectral means (IR, ¹HNMR, ¹³CNMR). The results of in vitro antidiabetic study against α-glucosidase indicated that compound 5o bearing 2-CH₃-5-NO₂ substituent on phenyl ring was found to be the most active compound against both enzymes. The electron donating (CH₃) group and electron withdrawing (NO₂) group on a phenyl ring highly favoured the inhibitory activity against these enzymes. The docking simulations study revealed that these synthesized compounds displayed hydrogen bonding, electrostatic and hydrophobic interactions with active site residues. The structure activity relationship studies of these compounds were also corroborated with the help of molecular modeling studies. Molecular dynamic simulations have been done for top most active compound for validating its α-glucosidase and α-amylase inhibitory potential, RMSD analysis of ligand protein complex suggested the stability of top most active compound 5o in binding site of target proteins. In silico ADMET results showed that synthesized compounds were found to have negligible toxicity, good solubility and absorption profile as the synthesized compounds fulfilled Lipinski's rule of 5 and Veber's rule.

Green synthesis and characterisation of novel [1,3,4]thiadiazolo/benzo[4,5]thiazolo[3,2-a]pyrimidines via multicomponent reaction using vanadium oxide loaded on fluorapatite as a robust and sustainable catalyst

We synthesised materials with different loadings of vanadia on fluorapatite (V₂O₅/FAp), fully characterised their structural properties using various spectral techniques including TEM, BET, XRD, FT-IR, SEM and EDX and assessed their prowess as catalysts. The 2.5% V₂O₅/FAp exhibited excellent activity for the synthesis of novel [1,3,4]thiadiazolo[3,2-a]pyrimidines and benzo[4,5]thiazolo[3,2-a]pyrimidines. The one-pot three-component fusion reaction between chosen substrates of 1,3,4-thiadiazole-amines or 2-amino-benzothiazole, aldehydes and active methylene compounds in ethanol solvent at room temperature gave an excellent yield of products (90–97%) in a swift reaction (25–30 min). The advantages of this protocol are rapid synthesis, mild reaction conditions, green solvent, easy work-up, eco-friendliness, reusability of catalyst and no need for column chromatography.

We synthesized material with different loading of vanadia on fluorapatite (V₂O₅/FAp), and excellent activity was showed for the synthesis of pyrimidine derivatives (90–97%) in ethanol medium for short reaction time.

2,4-Dichloro-5-[(N-aryl/alkyl)sulfamoyl]benzoic Acid Derivatives: In Vitro Antidiabetic Activity, Molecular Modeling and In silico ADMET Screening

BACKGROUND

Postprandial hyperglycemia can be reduced by inhibiting major carbohydrate hydrolyzing enzymes, such as α-glucosidase and α-amylase which is an effective approach in both preventing and treating diabetes.

OBJECTIVE

The aim of this study was to synthesize a series of 2,4-dichloro-5-[(N-aryl/alkyl)sulfamoyl] benzoic acid derivatives and evaluate α-glucosidase and α-amylase inhibitory activity along with molecular docking and in silico ADMET property analysis.

METHOD

Chlorosulfonation of 2,4-dichloro benzoic acid followed by reaction with corresponding anilines/amines yielded 2,4-dichloro-5-[(N-aryl/alkyl)sulfamoyl]benzoic acid derivatives. For evaluating their antidiabetic potential α-glucosidase and α-amylase inhibitory assays were carried out. In silico molecular docking studies of these compounds were performed with respect to these enzymes and a computational study was also carried out to predict the drug-likeness and ADMET properties of the title compounds.

RESULTS

Compound 3c (2,4-dichloro-5-[(2-nitrophenyl)sulfamoyl]benzoic acid) was found to be highly active having 3 fold inhibitory potential against α-amylase and 5 times inhibitory activity against α-glucosidase in comparison to standard drug acarbose.

CONCLUSION

Most of the synthesized compounds were highly potent or equipotent to standard drug acarbose for inhibitory potential against α-glucosidase and α-amylase enzyme and hence this may indicate their antidiabetic activity. The docking study revealed that these compounds interact with active site of enzyme through hydrogen bonding and different pi interactions.

Synthesis and biological screening of new thiazolo[4,5-d]pyrimidine and dithiazolo[3,2-a:5',4'-e]pyrimidinone derivatives as antimicrobial, antiquorum-sensing and antitumor agents

New thiazolopyrimidine and dithiazolopyrimidinone derivatives 2-11 were synthesized and estimated for antimicrobial activity against S. aureus, B. cereus, E. coli, C. albicans, A. fumigatus and A. terreus. The attained results proved that 4, 8a and 11g have significant effectiveness against S. aureus and B. cereus. On the other hand, 7, 10b, 10c and 11h exhibited prominent activity against B. cereus, whereas 8a, 10b and 11g were proved to be active against E. coli. From another point of view, 4 and 8a exhibited promising efficacy against A. fumigatus and A. terreus; moreover, 8a showed outstanding efficacy against C. albicans. Quorum-sensing inhibitory activity of the new compounds was esteemed against C. violaceum, where 7, 8a, 9b, 10a-c, 11d and 11g have acceptable efficacy. In vitro antitumor efficacy of the same compounds against HepG2, HCT-116 and MCF-7 cancer cell lines was also tested. Compounds 4 and 11h showed enhanced effectiveness against the three cell lines, whereas 10b displayed eminent activity against HCT-116 and MCF-7 cells. Moreover, 11a was found to have outstanding activity against MCF-7 cells, while 11i showed promising efficacy against HepG2 cells. The in vitro active antitumor compounds were evaluated for in vivo antitumor effectiveness against EAC in mice, as well as in vitro cytotoxicity against WI38 and WISH normal cells. Results manifested that 4 has the strongest in vivo activity, and that all investigated analogs are less cytotoxic than 5-FU against both normal cell lines. DNA-binding affinity of the active compounds was examined, where 4, 8a, 10c, 11d and 11g,h displayed strong affinity. In silico studies proved that majority of the analyzed compounds are in conformity with the optimum needs for good oral absorption.

Realizing Over 13% Efficiency in Green-Solvent-Processed Nonfullerene Organic Solar Cells Enabled by 1,3,4-Thiadiazole-Based Wide-Bandgap Copolymers

Two novel wide-bandgap copolymers, PBDT-TDZ and PBDTS-TDZ, are developed based on 1,3,4-thiadiazole (TDZ) and benzo[1,2-b:4,5-b']dithiophene (BDT) building blocks. These copolymers exhibit wide bandgaps over 2.07 eV and low-lying highest occupied molecular orbital (HOMO) levels below -5.35 eV, which match well with the typical low-bandgap acceptor of ITIC, resulting in a good complementary absorption from 300 to 900 nm and a low HOMO level offset (≤0.13 eV). Compared to PBDT-TDZ, PBDTS-TDZ with alkylthio side chains exhibits the stronger optical absorption, lower-lying HOMO level, and higher crystallinity. By using a single green solvent of o-xylene, PBDTS-TDZ:ITIC devices exhibit a large open-circuit voltage (V_oc ) up to 1.10 eV and an extremely low energy loss (E_loss ) of 0.48 eV. At the same time, the desirable high short-circuit current density (J_sc ) of 17.78 mA cm^-2 and fill factor of 65.4% are also obtained, giving rise to a high power conversion efficiency (PCE) of 12.80% without any additive and post-treatment. When adopting a homotandem device architecture, the PCE is further improved to 13.35% (certified as 13.19%) with a much larger V_oc of 2.13 V, which is the best value for any type of homotandem organic solar cells reported so far.

A thiadiazole reduces the virulence of Xanthomonas oryzae pv. oryzae by inhibiting the histidine utilization pathway and quorum sensing

Thiazole, isothiazole, thiadiazole and their derivatives are widely thought to induce host defences against plant pathogens. In this article, we report that bismerthiazol, a thiadiazole molecule, reduces disease by inhibiting the histidine utilization (Hut) pathway and quorum sensing (QS). Bismerthiazol provides excellent control of bacterial rice leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo), but does not greatly inhibit Xoo growth in vitro. According to RNA-sequencing analysis, the transcription of the Hut pathway genes of Xoo ZJ173 was inhibited after 4.5 and 9.0 h of bismerthiazol treatment. Functional studies of hutG and hutU indicated that the Hut pathway had little effect on the growth and bismerthiazol sensitivity of Xoo in vitro, but significantly reduced the aggregation of Xoo cells. Deletion mutants of hutG or hutU were more motile, produced less biofilm and were less virulent than the wild-type, indicating that the Hut pathway is involved in QS and contributes to virulence. The overexpression of the hutG-U operons in ZJ173 reduced Xoo control by bismerthiazol. Bismerthiazol did not inhibit the transcription of Hut pathway genes, QS or virulence of the bismerthiazol-resistant strain 2-1-1. The results indicate that bismerthiazol reduces Xoo virulence by inhibiting the Hut pathway and QS.

Synthesis and biological evaluation of a new series of benzimidazole derivatives as antimicrobial, antiquorum-sensing and antitumor agents

New benzimidazole derivatives were synthesized and assessed for antimicrobial efficacy toward Escherichia coli, Bacillus cereus, Staphylococcus aureus, Candida albicans and Aspergillus fumigatus 293. Results indicated that compounds 3c and 3n have promising activity toward S. aureus, whereas 3i exhibited remarkable efficacy toward B. cereus. Moreover, compound 3c was proved to be the most active antifungal analog toward C. albicans. On the other hand, 3n displayed the highest activity against A. fumigatus 293. Antiquorum-sensing activity of the same compounds was also tested against Chromobacterium violacium ATCC 12472, whereas compounds 3c-f, 3i-k and 3m-o showed acceptable activity. In vitro antitumor testing of these compounds toward liver cancer (HepG2), colon cancer (HCT-116) and breast cancer (MCF-7) cell lines revealed that compound 3p has the highest potency against the three tested cell lines. Moreover, 3f, 3m and 3n displayed promising activity toward all tested cell lines. Compounds 3f, 3m, 3n and 3p were esteemed for in vivo antitumor activity against EAC cells. The active antimicrobial and antitumor analogs, 3a, 3c, 3f, 3i-k, 3m, 3n and 3p were assessed for DNA-binding affinity, and results indicated that 3c, 3f, 3i, 3k and 3n have strong DNA-binding affinity. The computational studies affirmed that almost all of the inspected compounds meet the optimal requirements for good absorption and oral bioavailability.