Synthesis, anti-bacterial and anti-fungal activities of some novel Schiff bases containing 2,4-disubstituted thiazole ring

Synthesis, Molecular Docking, and Anticancer Screening of Ester-based Thiazole Derivatives

This study investigates the potential of five compounds as novel anticancer agents. We examined their efficacy, mechanisms of action, and impact on various cancer cell lines, through a comprehensive set of experiments. Notably, compound 3e demonstrated superior activity compared to the positive control cisplatin, with a GI50 value of 6.3±0.7 μM against the breast cancer cell line (MCF-7). Compound 3b also displayed remarkable growth inhibition, yielding GI50 values of 8.7±0.2 μM (MCF-7) and 8.9±0.5 μM against the colon cancer cell line (HCT-116). Cell count experiments further confirmed the potent inhibitory effects of compounds 3e, 3b, and 3c on MCF-7 and HCT-116 cell growth. Compound 3e demonstrated a reduction of 55-60 % at GI50 and complete inhibition (100 %) at 2x GI50. Compound 3b exhibited 50-55 % reduction (GI50) and 90-95 % inhibition (2x GI50) in HCT-116 cells. Compound 3c displayed 75-80 % inhibition (2x GI50) and 35-40 % inhibition (GI50) in HCT-116 cells. In-depth mechanistic investigations unveiled valuable insights into the mode of action of compound 3e. The cell-cycle assay demonstrated G2/M phase arrest, DNA damage, and caspase-mediated apoptosis in both MCF-7 and HCT-116 cells. Caspase activation indicated a significant increase in apoptosis following exposure to compound 3e. Furthermore, compound 3e induced reactive oxygen species (ROS) production, influencing HCT-116 and MCF-7 cells differently. Elevated ROS production in HCT-116 cells and distinct effects in MCF-7 cells contribute to a deeper understanding of the cytotoxic mechanisms of compound 3e. Overall, these findings highlight the potential of the investigated compounds, particularly compound 3e, as effective inducers of apoptosis in cancer cells. Mechanistic insights into cell cycle arrest, caspase-mediated apoptosis, and ROS modulation provide a comprehensive understanding of their cytotoxic effects. This study offers significant contribution to the development of promising anticancer agents and their therapeutic applications.

An Insight into Rational Drug Design: The Development of In-House Azole Compounds with Antimicrobial Activity

Antimicrobial resistance poses a major threat to global health as the number of efficient antimicrobials decreases and the number of resistant pathogens rises. Our research group has been actively involved in the design of novel antimicrobial drugs. The blueprints of these compounds were azolic heterocycles, particularly thiazole. Starting with oxadiazolines, our research group explored, one by one, the other five-membered heterocycles, developing more or less potent compounds. An overview of this research activity conducted by our research group allowed us to observe an evolution in the methodology used (from inhibition zone diameters to minimal inhibitory concentrations and antibiofilm potential determination) correlated with the design of azole compounds based on results obtained from molecular modeling. The purpose of this review is to present the development of in-house azole compounds with antimicrobial activity, designed over the years by this research group from the departments of Pharmaceutical and Therapeutical Chemistry in Cluj-Napoca.

Kinetic Insights into the Antioxidant Effect of Isatin-Thiosemicarbazone in Biodiesel Blends

Biodiesel has several drawbacks, such as being prone to oxidation, having reduced stability, and having limited storage time. Antioxidants compatible with biodiesel are being used to address its drawbacks. Utilizing antioxidants effectively improves the quality of biodiesel. Enhancing the quality of biodiesel for use as a clean energy source benefits both the global economy and ecology. Therefore, we believe that our work will contribute to the advancement of the biodiesel industry worldwide. This study used blends consisting of 20% biodiesel and 80% diesel fuel. Isatin-thiosemicarbazones were tested as additives in blends at a concentration of 3000 parts per million (ppm) using an oxifast device and were compared with the chemical antioxidant Trolox. FT-IR, DSC, and TGA were used to characterize these samples. DSC measured sample crystallization temperatures (Tc). Samples with antioxidants showed decreased values compared to the non-antioxidant diesel sample D100. Several DSC tests were conducted to determine the antioxidant strengths of various samples. The results show that the FT-IR spectrum's antioxidant effect regions grow clearer with antioxidants. The extra antioxidant is effective. Biodiesel's oxidative stability improves with isatin-thiosemicarbazones at varying concentrations. The kinetics of thermal decomposition of isatin-thiosemicarbazones under non-isothermal conditions were determined using the Kissinger, Ozawa, and Boswell techniques. The activation energies of compounds 1 and 2 were calculated as 137-147 kJ mol-1 and 173-183 kJ mol-1, respectively.

Antimicrobial Activity of Novel Ni(II) and Zn(II) Complexes with (E)-2-((5-Bromothiazol-2-yl)imino)methyl)phenol Ligand: Synthesis, Characterization and Molecular Docking Studies

In order to address the challenges associated with antibiotic resistance by bacteria, two new complexes, Ni(II) and Zn(II), have been synthesized using the conventional method based on Schiff base ligand (E)-2-((5-bromothiazol-2-yl) imino) methyl) phenol. The Schiff base ligand (HL) was synthesized using salicylaldehyde and 5-(4-bromophenyl)thiazol-2-amine in both traditional and efficient, ecologically friendly, microwave-assisted procedures. The ligand and its complexes were evaluated by elemental analyses, FTIR spectroscopy, UV-Vis spectroscopy, nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA) and magnetic susceptibility. The ligand and its complexes were tested for antibacterial activity against three Gram-positive bacteria (Staphylococcus aureus ATCC 25923, Methicillin-resistant Staphylococcus aureus ATCC 43300 and Enterococcus faecalis ATCC 29212) and three Gram-negative bacteria (Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922 and Klebsiella pneumoniae ATCC 700603). The findings demonstrate the potent activity of the ligand and its complexes against selective bacteria but the Ni(II) complex with MIC values ranging from 1.95 to 7.81 µg/mL outperformed all other compounds, including the widely used antibiotic Streptomycin. Furthermore, the docking study provided evidence supporting the validity of the antimicrobial results, since the Ni complex showed superior binding affinity against to E. coli NAD synthetase, which had a docking score (-7.61 kcal/mol).

Synthesis, Structural Characterization, Cytotoxicity, and Protein/DNA Binding Properties of Pyridoxylidene-Aminoguanidine-Metal (Fe, Co, Zn, Cu) Complexes

Pyridoxylidene-aminoguanidine (PLAG) and its transition metal complexes are biologically active compounds with interesting properties. In this contribution, three new metal-PLAG complexes, Zn(PLAG)(SO4)(H2O)].∙H2O (Zn-PLAG), [Co(PLAG)2]SO4∙2H2O (Co-PLAG), and [Fe(PLAG)2]SO4∙2H2O) (Fe-PLAG), were synthetized and characterized by the X-ray crystallography. The intermolecular interactions governing the stability of crystal structure were compared to those of Cu(PLAG)(NCS)2 (Cu-PLAG) within Hirshfeld surface analysis. The structures were optimized at B3LYP/6-31+G(d,p)(H,C,N,O,S)/LanL2DZ (Fe,Co,Zn,Cu), and stability was assessed through Natural Bond Orbital Theory and Quantum Theory of Atoms in Molecules. Special emphasis was put on investigating the ligand's stability and reactivity. The binding of these compounds to Bovine and Human serum albumin was investigated by spectrofluorometric titration. The importance of complex geometry and various ligands for protein binding was shown. These results were complemented by the molecular docking study to elucidate the most important interactions. The thermodynamic parameters of the binding process were determined. The binding to DNA, as one of the main pathways in the cell death cycle, was analyzed by molecular docking. The cytotoxicity was determined towards HCT116, A375, MCF-7, and A2780 cell lines. The most active compound was Cu-PLAG due to the presence of PLAG and two thiocyanate ligands.

Synthesis of amantadine clubbed N-aryl amino thiazoles as potent urease, α-amylase & α-glucosidase inhibitors, kinetic and molecular docking studies

A series of ten novel compounds were synthesized by incorporating a 1,3 thiazole core into amantadine and their structures were validated using different analytical and spectral methods such as FTIR, EI-MS, 1H NMR, and 13C NMR. The antibacterial and enzyme inhibitory properties of these newly synthesized compounds were evaluated. Remarkably, the compounds exhibited significant antibacterial activity against Escherichia coli and Bacillus subtilis. Additionally, the in vitro inhibitory activities of the synthesized compounds, against α-amylase, α-glucosidase, and urease were investigated. Among the tested compounds, compound 6d demonstrated potent and selective inhibition of α-amylase IC50 = 97.37 ± 1.52 μM, while acarbose was used as positive control and exhibited IC50 = 5.17 ± 0.25 μM. Compound 6d and 6e exhibited prominent inhibition against α-glucosidase IC50 = 38.73 ± 0.80 μM and 41.63 ± 0.26 μM respectively. Furthermore, compound 6d inhibited urease with exceptional efficacy IC50 = 32.76 μM, while positive control thiourea showed more prominent activity having IC50 = 1.334 μM. Molecular docking studies disclosed the binding mechanism and affinity of these new inhibitors within the binding sites of various amino acids. To investigate the association between molecular structural characteristics and inhibitory actions of synthesized derivatives, preliminary structure-activity relationship (SAR) studies were performed. These findings indicated that compounds 6a, 6c, 6d and 6e are potential candidates for hit-to-lead follow-up in the drug-discovery process for treating diabetes and hyperglycemia.

Novel Thiazolidine-2,4-dione-trimethoxybenzene-thiazole Hybrids as Human Topoisomerases Inhibitors

Cancer is a complex and heterogeneous disease and is still one of the leading causes of morbidity and mortality worldwide, mostly as the population ages. Despite the encouraging advances made over the years in chemotherapy, the development of new compounds for cancer treatments is an urgent priority. In recent years, the design and chemical synthesis of several innovative hybrid molecules, which bring different pharmacophores on the same scaffold, have attracted the interest of many researchers. Following this strategy, we designed and synthetized a series of new hybrid compounds that contain three pharmacophores, namely trimethoxybenzene, thiazolidinedione and thiazole, and tested their anticancer properties on two breast cancer (MCF-7 and MDA-MB-231) cell lines and one melanoma (A2058) cell line. The most active compounds were particularly effective against the MCF-7 cells and did not affect the viability of the normal MCF-10A cells. Docking simulations indicated the human Topoisomerases I and II (hTopos I and II) as possible targets of these compounds, the inhibitory activity of which was demonstrated by the mean of direct enzymatic assays. Particularly, compound 7e was proved to inhibit both the hTopo I and II, whereas compounds 7c,d blocked only the hTopo II. Finally, compound 7e was responsible for MCF-7 cell death by apoptosis. The reported results are promising for the further design and synthesis of other analogues potentially active as anticancer tools.

Catalysis-free synthesis of thiazolidine-thiourea ligands for metal coordination (Au and Ag) and preliminary cytotoxic studies

The reaction of propargylamines with isothiocyanates results in the selective formation of iminothiazolidines, aminothiazolines or mixed thiazolidine-thiourea compounds under mild conditions. It has been observed that secondary propargylamines lead to the selective formation of cyclic 2-amino-2-thiazoline derivatives, while primary propargylamines form iminothiazoline species. In addition, these cyclic thiazoline derivatives can further react with an excess of isothiocyanate to give rise to thiazolidine-thiourea compounds. These species can also be achieved by reaction of propargylamines with isothiocynates in a molar ratio of 1 : 2. Coordination studies of these heterocyclic species towards silver and gold with different stoichiometries have been carried out and complexes of the type [ML(PPh₃)]OTf, [ML₂]OTf (M = Ag, Au) or [Au(C₆F₅)L] have been synthesised. Preliminary studies of the cytotoxic activity in lung cancer cells have also been performed in both ligands and complexes, showing that although the ligands do not exhibit anticancer activity, their coordination to metals, especially silver, greatly enhances the cytotoxic activity.

Synthesis and in vitro antiprotozoal evaluation of novel metronidazole-Schiff base hybrids

Herein we report the synthesis of 21 novel small molecules inspired by metronidazole and Schiff base compounds. The compounds were evaluated against Trichomonas vaginalis and cross-screened against other pathogenic protozoans of clinical relevance. Most of these compounds were potent against T. vaginalis, exhibiting IC₅₀ values < 5 µM. Compound 20, the most active compound against T. vaginalis, exhibited an IC₅₀ value of 3.4 µM. A few compounds also exhibited activity against Plasmodium falciparum and Trypanosomal brucei brucei, with compound 6 exhibiting an IC₅₀ value of 0.7 µM against P. falciparum and compound 22 exhibiting an IC₅₀ value of 1.4 µM against T.b. brucei. Compound 22 is a broad-spectrum antiprotozoal agent, showing activities against all three pathogenic protozoans under investigation.

Visiblelight-induced ternary electron donor-acceptor complex enabled synthesis of 2-(2-hydrazinyl) thiazole derivatives and the assessment of their antioxidant and antidiabetic therapeutic potential

A mild and eco-friendly visible-light-induced synthesis of 2-(2-hydrazinyl) thiazole from readily accessible thiosemicarbazide, carbonyl, and phenacyl bromide in the absence of a metal catalyst and/or any extrinsic photosensitizer is reported. This approach only requires a source of visible light and a green solvent at room temperature to produce the medicinally privileged scaffolds of hydrazinyl-thiazole derivatives in good to outstanding yields. Experimental studies support the in situ formation of a visible-light-absorbing, photosensitized colored ternary EDA complex. The next step is to prepare a pair of radicals in an excited state, which makes it easier to prepare thiazole derivatives through a SET and PCET process. DFT calculations additionally supported the mechanistic analysis of the course of the reaction. The antioxidant and antidiabetic properties of some of the compounds in the synthesized library were tested in vitro. All the investigated compounds demonstrated appreciable antioxidant activity, as evidenced by the reducing power experiment and the IC₅₀ values of the DPPH radical scavenging experiment. Furthermore, the IC₅₀ values for 4c, 4d, and 4g also demonstrated a strong α-amylase inhibitory effect.

Synthesis, Structure and Molecular Docking of New 4,5-Dihydrothiazole Derivatives Based on 3,5-Dimethylpyrazole and Cytisine and Salsoline Alkaloids

The interaction results of 1,2-dibromo-3-isothiocyanatopropane with some pyrazoles as well as cytisine and salsoline alkaloids were presented in this paper. It was shown that the reaction resulted in one one-step and rather mild method for the preparation of the corresponding 1,3-thiazoline bromomethyl derivatives. The yield of this reaction was affected by the presence of a base and an order in which reagents were added. Molecular docking of the synthesized 1,3-thiazoline derivatives for putative antibacterial activity was carried out using the penicillin-binding target protein (PBP4) of the bacteria E. coli "Homo sapiens" and S. aureus "Homo sapiens" as an example. Molecular docking demonstrated that the compounds had insignificant binding energies at the level of selected reference drugs (Cephalotin and Chloramphenicol). The presence of natural alkaloids in the structure of thiazoline derivatives somewhat increased the affinity of these substrates for target proteins selected.

Syntheses, Molecular Docking and Biological Evaluation of 2-(2- hydrazinyl)thiazoles as Potential Antioxidant, Anti-Inflammatory and Significant Anticancer Agents

BACKGROUND

Recently, researchers have worked on the development of new methods for the synthesis of bioactive heterocycles using polyethylene glycol as a green solvent. In this context, we report the synthesized 2-(2-hydrazinyl) thiazoles for their in vitro antioxidant, in vitro anti-inflammatory and in vitro anti-cancer activities.

OBJECTIVE

The objective of the study was to develop novel antioxidant, anti-inflammatory and anti-cancer drugs.

METHODS

At the outset, the condensation of substituted acetophenones 1, thiosemicarbazide 2, and α-haloketones 3 was carried out using PEG-400 (20 mL) in the presence of 5 mol% glacial acetic acid to afford thiosemicarbazones intermediate. Furthermore, these thiosemicarbazones were reacted with α-haloketones 3 to obtain appropriate 2-(2-hydrazinyl) thiazoles. The synthesized compounds were in vitro tested for their antioxidant, anti-inflammatory, and anti-cancer activity.

RESULTS

In vitro evaluation report showed that nearly all molecules possessed potential antioxidant activity against 2,2-Diphenyl-1-picrylhydrazyl (DPPH), nitric oxide (NO), superoxide radical (SOR) and hydrogen peroxide (H₂O₂) radical scavenging activity. Most 2-(2-hydrazinyl) thiazoles derivatives have shown potential anti-inflammatory activity as compared to diclofenac sodium as a reference standard. 2-(2-Hydrazinyl) thiazoles derivatives showed significant anticancer activity for human leukemia cell line K-562 compared to adriamycin as a reference standard.

CONCLUSION

All tested compounds showed potential 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide (NO) radical scavenging activity. Among the tested series, 4b, 4d and 4e exhibited good hydrogen peroxide and 4b, 4e, 4f and 4g showed excellent superoxide radical scavenging activity. In addition, the 4b, 4e and 4g compounds revealed potent in vitro anti-inflammatory activity against standard diclofenac sodium drug. 2-(2-Hydrazinyl) thiazole derivatives, such as 4c and 4d, showed significant anticancer activity against human leukemia cell line K-562. Thus, these molecules provide an interesting template for the design and development of new antioxidant, anti-inflammatory, and anti-cancer agents.

Synthesis, crystal structure, Hirshfeld surface analysis, energy frameworks and computational studies of Schiff base derivative

The compound (E)-ethyl 3-(2-(2,4-dinitrophenyl)hydrazono)butanoate (3) was synthesised and crystallized using ethanol as a solvent. The compound was characterized by ¹H NMR, and single crystal X-ray diffraction. The compound crystallizes in the monoclinic crystal system with the space group P2₁/c. The intermolecular interactions and the interaction energies responsible for the stabilization of the molecules were determined by Hirshfeld surface analysis and energy framework calculations. The structure of the compound was optimized by Density Functional Theory calculations and HOMO–LUMO energy gap was calculated. The non–covalent interactions were revealed by reduced density gradient analysis. The Mulliken atomic charges and natural atomic charges were calculated by density functional theory calculations. The reactive sites present in the molecule are shown by molecular electrostatic potential map. The inter and intra molecular charge transfer were investigated by NBO analysis.

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Crystal structure was confirmed by X-ray diffraction analysis and the atomic coordinates were optimized by DFT calculations.

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Hirshfeld surface analysis and energy frameworks calculations were carried out.

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HOMO - LUMO frontier molecular orbitals and molecular electrostatic potential were studied.

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Reduced density gradient (RDG), and topology analyses were performed.

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Natural bond orbital analysis was performed to study intramolecular charge transfer.

Synthesis, crystal structure, Hirshfeld surface investigation and comparative DFT studies of ethyl 2-[2-(2-nitrobenzylidene)hydrazinyl]thiazole-4-carboxylate

The ethyl 2-[2-(2-nitrobenzylidene)hydrazinyl]thiazole-4-carboxylate (1), a thiazole ester, was synthesized by refluxing 1-(2-nitrobenzylidene)thiosemicarbazide and ethyl bromopyruvate. The compound is characterized by spectrometric, spectroscopic and single crystal (SC-XRD) techniques. Non-covalent interactions that are responsible for crystal packing are explored by Hirshfeld surface analysis. All theoretical calculations were performed by DFT quantum chemical methods using 6-311G(d,p) and cc-pVTZ basis sets and compared. Theoretical harmonic frequencies of ethyl 2-[2-(2-nitrobenzylidene)hydrazinyl]thiazole-4-carboxylate (1) were optimized. Confirmation of hydrogen bonding sites was analyzed by molecular electrostatic potential (MEP) and Mulliken population analysis. The vibrational frequencies of characteristic functional groups and chemical shifts were found in good agreement with experimental assignments. Frontier molecular orbital (FMO) revealed relatively small HOMO–LUMO (highest occupied molecular orbital-lowest unoccupied molecular orbital) gape, which speaks off the nearly planar geometry and extended conjugation, as compared to the substituents with no conjugation possible. It has also been observed that –NO₂ substituent plays a vital role for this relatively small HOMO–LUMO gape and overall electronic properties when compared with similar thiazole carboxylates (2–6, Table 6). Ethyl 2-[2-(2-nitrobenzylidene)hydrazinyl]thiazole-4-carboxylate (1) was also evaluated for its anti-oxidant and anti-microbial activities.

Acetylene containing 2-(2-hydrazinyl)thiazole derivatives: design, synthesis, and in vitro and in silico evaluation of antimycobacterial activity against Mycobacterium tuberculosis

Mycobacterium tuberculosis resistance to commercially available drugs is increasing day by day. To address this issue, various strategies were planned and are being implemented. However, there is a need for new drugs and rapid diagnostic methods. For this endeavour, in this paper, we present the synthesis of acetylene containing 2-(2-hydrazinyl) thiazole derivatives and in vitro evaluation against the H37Rv strain of Mycobacterium tuberculosis. Among the developed 26 acetylene containing 2-(2-hydrazinyl) thiazole derivatives, eight compounds inhibited the growth of Mycobacterium tuberculosis with MIC values ranging from 100 μg ml-1 to 50 μg ml-1. The parent acetylene containing thiosemicarbazones showed promising antimycobacterial activity by inhibiting up to 75% of the Mycobacterium at 50 μg ml-1. In addition, in silico studies were employed to understand the binding mode of all the novel acetylene-containing derivatives against the KasA protein of the Mycobacterium. Interestingly, the KasA protein interactions with the compounds were similar to the interactions of KasA protein with thiolactomycin and rifampicin. Cytotoxicity study results indicate that the compounds tested are non-toxic to human embryonic kidney cells.

Quinazolinone-based hybrids with diverse biological activities: A mini-review

Quinazolinone and quinazoline have been shown different pharmacological activities, namely anticancer, anti-inflammatory, anti-hyperlipidemia, analgesic, antihypertensive, and antibacterial. On the other hand, molecular hybridization is a structural modification technique in the design of new ligands which consist of two or more pharmacologically active molecules in one structure. Therefore, due to the importance of the biological activities of quinazolinones for the development of new therapeutic agents, this review emphasizes current findings on various quinazolinone-based hybrids in medicinal chemistry. Moreover, it highlights the biological activities and structure-activity relationship of these hybrids.

Synthesis, antibacterial and antioxidant activities of Thiazole-based Schiff base derivatives: a combined experimental and computational study

BACKGROUND

Thiazole-based Schiff base compounds display significant pharmacological potential with an ability to modulate the activity of many enzymes involved in metabolism. They also demonstrated to have antibacterial, antifungal, anti-inflammatory, antioxidant, and antiproliferative activities. In this work, conventional and green approaches using ZnO nanoparticles as catalyst were used to synthesize thiazole-based Schiff base compounds.

RESULTS

Among the synthesized compounds, 11 showed good activities towards Gram-negative E. coli (14.40 ± 0.04), and Gram-positive S. aureus (15.00 ± 0.01 mm), respectively, at 200 μg/mL compared to amoxicillin (18.00 ± 0.01 mm and 17.00 ± 0.04). Compounds 7 and 9 displayed better DPPH radical scavenging potency with IC50 values of 3.6 and 3.65 μg/mL, respectively, compared to ascorbic acid (3.91 μg/mL). The binding affinity of the synthesized compounds against DNA gyrase B is within - 7.5 to - 6.0 kcal/mol, compared to amoxicillin (- 6.1 kcal/mol). The highest binding affinity was achieved for compounds 9 and 11 (- 6.9, and - 7.5 kcal/mol, respectively). Compounds 7 and 9 displayed the binding affinity values of - 5.3 to - 5.2 kcal/mol, respectively, against human peroxiredoxin 5. These values are higher than that of ascorbic acid (- 4.9 kcal/mol), in good agreement with the experimental findings. In silico cytotoxicity predictions showed that the synthesized compounds Lethal Dose (LD50) value are class three (50 ≤ LD50 ≤ 300), indicating that the compounds could be categorized under toxic class. Density functional theory calculations showed that the synthesized compounds have small band gap energies ranging from 1.795 to 2.242 eV, demonstrating that the compounds have good reactivities.

CONCLUSIONS

The synthesized compounds showed moderate to high antibacterial and antioxidant activities. The in vitro antibacterial activity and molecular docking analysis showed that compound 11 is a promising antibacterial therapeutics agent against E. coli, whereas compounds 7 and 9 were found to be promising antioxidant agents. Moreover, the green synthesis approach using ZnO nanoparticles as catalyst was found to be a very efficient method to synthesize biologically active compounds compared to the conventional method.

Development of novel indolin-2-one derivative incorporating thiazole moiety as DHFR and quorum sensing inhibitors: Synthesis, antimicrobial, and antibiofilm activities with molecular modelling study

Nowadays, it's imperative to develop novel antimicrobial agents active against both drug-sensitive and drug-resistant bacterial infections with favorable profiles as high efficacy, low toxicity, and short therapy duration. Accordingly, a series of new thiazolo-indolin-2-one derivatives were synthesized based on acid and base catalyzed condensation or reaction of thiosemicarbazone 8 with different electrophilic reagents. The structure of the new compounds was confirmed based on elemental analysis and spectral data. Based on the MIC results, the most active thiazolo-indoline derivatives 2, 4, 7a, and 12 exhibited promising antibacterial activity against gram-positive and gram-negative bacteria with weak to moderate antifungal activities. Surprisingly, the N-(thiazol-2-yl)benzenesulfonamide derivative 4 was found to be most active on antibiofilm activity against both S. aureus (ATCC 29213) with BIC₅₀ (1.95 ± 0.01 µg/mL), while 5-(2-oxoindolin-3-ylidene)-thiazol-4(5H)-one derivative 7a exhibited the strongest antibiofilm activity against P. aeruginosa pathogens with BIC₅₀ (3.9 ± 0.16 µg/mL). Further, the thiazole derivatives 2, 4 and 12 exhibited a significant inhibition activity against the fsr system in a dose-dependent manner without affecting bacterial growth. The target derivatives behaved synergistic and additively effect against MDR p. aeruginosa, and thiazole derivative 12 exhibited a high synergistic effect with most tested antibiotics except Cefepime with FIC value ranging between 0.249 and 1.0, reducing their MICs. Interestingly, the 3-(2-(4-thiazol-2-yl)hydrazono)indolin-2-one derivative 12 displayed the highest selectivity to DHFR inhibitory with IC₅₀ value 40.71 ± 1.86 nM superior to those of the reference Methotrexate. Finally, in silico molecular modeling simulation, some physicochemical properties and toxicity predictions were performed for the most active derivatives.

Pyrazolopyrimidines as anticancer agents: A review on structural and target-based approaches

Pyrazolopyrimidine scaffold is one of the privileged heterocycles in drug discovery. This scaffold produced numerous biological activities in which anticancer is important one. Previous studies showed its importance in interactions with various receptors such as growth factor receptor, TGFBR2 gene, CDK2/cyclin E and Abl kinase, adenosine receptor, calcium-dependent Protein Kinase, Pim-1 kinase, Potent Janus kinase 2, BTK kinase, P21-activated kinase 1, extracellular signal-regulated kinase 2, histone lysine demethylase and Human Kinesin-5. However, there is a need of numerous studies for the discovery of target based potential compounds. The structure activity relationship studies may help to explore the generation of potential compounds in short time period. Therefore, in the present review we tried to explore the structural aspects of Pyrazolopyrimidine with their structure activity relationship against various targets for the development of potential compounds. The current review is the compilation of significant advances made on Pyrazolopyrimidines reported between 2015 and 2020.

Synthesis and cytotoxic evaluation of some novel 3-[2-(2-phenyl-thiazol-4-yl)-ethyl]-3H-pyrido[2,3-d]pyrimidin-4-one derivatives

Background and purpose

Pyridopyrimidine and its derivatives have a variety of chemical and biological significances. Thiazole-containing compounds have also been reported to have a wide range of biological activities. Due to the valuable cytotoxic effects of both thiazole and pyridopyrimidinone derivatives, a series of pyridopyrimidinone-thiazole hybrids were synthesized in the present study.

Experimental approach

Briefly, different acyl chlorides were reacted with 2-amino nicotinic acid followed by anhydride acetic to give the corresponding pyridobenzoxazinones. The aminothiazole derivative G was also prepared via a multistep procedure and incorporated into the benzoxazinones to furnish the target pyridopyrimidinone, K1-K5. Furthermore, the cytotoxic activity of the final compounds was determined against MCF-7 and HeLa cell lines using MTT assay.

Findings/Results

The results indicated that aromatic substitution on C2 of pyridopyrimidine nucleus was in favor of cytotoxic activity on both cell lines, of which, compound K5 bearing a chlorophenyl group showed the highest cytotoxicity.

Conclusion and implications

The results of the present study are valuable in terms of synthesis of hybrid molecules and also cytotoxic evaluations which can be useful for future investigations about the design of novel pyridopyrimidinone-thiazole hybrids possessing better cytotoxic activities.

Synergistic effects of dual antimicrobial combinations of synthesized N-heterocycles or MgO nanoparticles with nisin against the growth of Aspergillus fumigatus: In vitro study

Introduction of new inhibitory agents such as peptides, heterocyclic derivatives and nanoparticles (NPs) along with preventive proceedings are effective ways to deal with standard and drug-resistant strains of microorganisms. In this regard, inhibitory activities of some recently synthesized 4-thiazolylpyrazoles, imidazolidine- and tetrahydropyrimidine-2-thiones and magnesium oxide (MgO) NPs alone and in combination with nisin have been assessed against Aspergillus fumigatus. Antimicrobial susceptibility tests were done via broth microdilution, disk diffusion and streak plate methods according to the modified Clinical and Laboratory Standards Institute (CLSI) guidelines. Synergistic effects were also determined as fractional inhibitory concentration (FIC) and fractional fungicidal concentration (FFC) values. Inhibitory potentials of all heterocycles and NPs against A. fumigatus were proved based on inhibition zone diameter (IZD) values in the range of 7.72 - 16.85 mm, minimum inhibitory concentration (MIC) values in the range of 64.00 - 512 µg mL^-1 and minimum fungicidal concentration (MFC) values in the range of 256 - 2048 µg mL^-1. Tetrahydropyrimidine derivative 3f showed the best inhibitory properties. Inhibitory activity was not significant with nisin. While antifungal effects of major derivatives were improved by combination with it. The results indicated that the combined treatment of heterocycles used in the present study with nisin might be efficient for mold prevention and removal in foodstuffs or other products.

Mechanisms of Candida Resistance to Antimycotics and Promising Ways to Overcome It: The Role of Probiotics

Pathogenic Candida and infections caused by those species are now considered as a serious threat to public health. The treatment of candidiasis is significantly complicated by the increasing resistance of pathogenic strains to current treatments and the stagnant development of new antimycotic drugs. Many species, such as Candida auris, have a wide range of resistance mechanisms. Among the currently used synthetic and semi-synthetic antifungal drugs, the most effective are azoles, echinocandins, polyenes, nucleotide analogs, and their combinations. However, the use of probiotic microorganisms and/or the compounds they produce is quite promising, although underestimated by modern pharmacology, to control the spread of pathogenic Candida species.

Enhanced Efficacy of Thiosemicarbazone Derivative-Encapsulated Fibrin Liposomes against Candidiasis in Murine Model

Candida albicans is the most studied species for the candidiasis infection and is becoming resistant towards existing antifungal drugs. Considering this, in the current study, we developed and characterized a fibrin liposome-based formulation encapsulating a novel thiosemicarbazone derivative, 2C, and evaluated its antifungal efficacy against murine candidiasis. The 2C-containing formulation was prepared by encapsulating 2C within the liposomes (2C-L) that were further encapsulated in the fibrin beads (2C-FL). The in-house synthesized 2C-FLs were spherical with a zeta potential of −34.12 ± 0.3 mV, an entrapment efficiency of 72.6 ± 4.7%, and a loading efficiency of 9.21 ± 2.3%, and they showed a slow and sustained release of 2C. Compared to free 2C, the formulation was non-toxic and exhibited serum stability, increased tissue specificity, and penetration. The 2C-FL formulation had a minimum inhibitory concentration (MIC) value of 4.92 ± 0.76 µg/mL and was able to induce apoptosis and necrosis in C. albicans in vitro. The administration of 2C-FL in C. albicans-infected mice prolonged their survival and antifungal effects when compared with the free 2C. The 2C-FL antifungal therapy significantly reduced the fungal burden and displayed an improved survival rate. In conclusion, the 2C thiosemicarbazone derivative possesses a potent antifungal activity that became more advantageous upon its encapsulation in the fibrin liposome delivery system.

Synthesis, molecular docking and ADME studies of thiazole-thiazolidinedione hybrids as antimicrobial agents

New thiazole-thiazolidinedione hybrids (5a-k) were efficiently synthesized and evaluated for their in-vitro antimicrobial activity against four fungal and bacterial strains. The chemical structures of the compounds were elucidated by FTIR, ¹H NMR, and ¹³C NMR spectral data. Most of the synthesized compounds were sensitive against gram positive, gram negative bacterial and fungal strains. Among the synthesized molecules, compounds 5h, and 5i exhibited promising inhibitory activity against all selected fungal strains and gram positive bacteria namely, Staphylococcus aureus, and Enterococcus faecalis. The molecular docking results predicted that the thiazole-thiazolidinedione derivatives bind to the active site protein ATP-binding pocket from E. coli, S. aureus and C. albicans with good interaction energy scores. Ct-DNA was used to evaluate the binding interactions of the selected compounds by means of absorption spectroscopy. To further characterize the drug-likeness and ADME properties were calculated using the Qikprop, the result of present study suggests that thiazole-thiazolidinedione hybrid could be an interesting approach for the design of new antimicrobial agents.Communicated by Ramaswamy H. Sarma.

Synthesis, biological evaluation of antioxidant-antibacterial activities and computational studies of novel anthracene- and pyrene-based Schiff base derivatives

Schiff base derivatives with anthracene- and pyrene-based units, A1-A6 and P1-P6 were synthesized (89%–99% yields). Schiff base derivatives were designed to possess an heterocyclic moiety on one side to enhance the coordination ability towards metals. To investigate the biological assay of the newly synthesized compounds, their DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging, metal chelating, reducing power, antibacterial and DNA binding activities were tested. A6 (63.1%) showed the maximum free radical scavenging activity among all. However, compound P3 at concentration of 200 μg/mL possessed the highest metal chelating (45.8%) activity and power of reduction. In addition, P3 and A6 showed antibacterial activity against all bacteria tested and both compounds were very well bound to CT-DNA. Density functional theory method with B3LYP/6-311++G(d,p) basis set was performed to get information about the structural and electronic properties of the present compounds. In addition, the metal coordination properties of the dimers of the parent Schiff bases were investigated through interactions with Zn²⁺.