Piperazine-azole-fluoroquinolone hybrids: Conventional and microwave irradiated synthesis, biological activity screening and molecular docking studies

N-Heterocycles as Promising Antiviral Agents: A Comprehensive Overview

Viruses are a real threat to every organism at any stage of life leading to extensive infections and casualties. N-heterocycles can affect the viral life cycle at many points, including viral entrance into host cells, viral genome replication, and the production of novel viral species. Certain N-heterocycles can also stimulate the host's immune system, producing antiviral cytokines and chemokines that can stop the reproduction of viruses. This review focused on recent five- or six-membered synthetic N-heterocyclic molecules showing antiviral activity through SAR analyses. The review will assist in identifying robust scaffolds that might be utilized to create effective antiviral drugs with either no or few side effects.

Development of novel 1,2,4-triazole containing compounds with anticancer and potent anti-CB1 activity

There is still an unmet need for novel and improved anti-cancer compounds. Nitrogen atoms have heterocyclic ring moieties, which have been shown to have powerful anticancer properties in both natural and synthetic derivatives. Due to their dipole character, hydrogen bonding capacity, rigidity and solubility, 1,2,4-triazoles are particularly effective pharmacophores, interacting with biological receptors with high affinity. Thus, novel 1,2,4-triazole-containing molecular derivatives were synthesized using green chemistry methods, microwave irradiation and ultrasonication, and these methods' operational simplicity and maximum greener synthetic efficiency with green chemistry metrics calculations will be attractive for academic and industrial research and tested against three distinct human cancer cell lines including PANC1 (pancreatic cancer), DU145 (prostate cancer), MCF7 (breast cancer) and one fibroblast cell line (HDF). Here, we showed that compounds 5e and 5f were similar to CB1 antagonists in structure, binding affinity and poses. In addition, compounds 5e-g decreased the viability of pancreatic and prostate cancer cells, albeit with cytotoxicity to HDF cells. The IC50 values for PANC1 cells were between 5.9 and 7.3 µM for compounds 5e-g. Cell cycle analysis showed that the effect of compounds 5e-g in cancer cell growth was largely due to cell cycle arrest at S-phase. In sum, novel 1,2,4-triazole-containing compounds with anticancer and potent anti-CB1 activity have been developed.Communicated by Ramaswamy H. Sarma.

Direct Growth Control of Antibiotic-Resistant Bacteria Using Visible-Light-Responsive Novel Photoswitchable Antibiotics

In addition to the discovery of new (modified) potent antibiotics to combat antibiotic resistance, there is a critical need to develop novel strategies that would restrict their off-target effects and unnecessary exposure to bacteria in our body and environment. We report a set of new photoswitchable arylazopyrazole-modified norfloxacin antibiotics that present a high degree of bidirectional photoisomerization, impressive fatigue resistance and reasonably high cis half-lives. The irradiated isomers of most compounds were found to exhibit nearly equal or higher antibacterial activity than norfloxacin against Gram-positive bacteria. Notably, against norfloxacin-resistant S. aureus bacteria, the visible-light-responsive p-SMe-substituted derivative showed remarkably high antimicrobial potency (MIC of 0.25 μg/mL) in the irradiated state, while the potency was reduced by 24-fold in case of its non-irradiated state. The activity was estimated to be retained for more than 7 hours. This is the first report to demonstrate direct photochemical control of the growth of antibiotic-resistant bacteria and to show the highest activity difference between irradiated and non-irradiated states of a photoswitchable antibiotic. Additionally, both isomers were found to be non-harmful to human cells. Molecular modellings were performed to identify the underlying reason behind the high-affinity binding of the irradiated isomer to topoisomerase IV enzyme.

Recent advances in triazoles as tyrosinase inhibitors

The tyrosinase enzyme, which is widely found in microorganisms, animals and plants, has a significant position in melanogenesis, plays an important role in undesirable browning of fruits and vegetables, antibiotic resistance, skin pigment formation, sclerotization of cuticle, neurodegeneration, etc. Therefore, with the wide potential application fields of tyrosinase in food, agriculture, cosmetics and pharmaceutical industries, which has become the target enzyme for the development of therapeutic agents such as antibrowning, anticancer, antibacterial, skin whitening, insecticides, etc., a large number of synthetic tyrosinase inhibitors have been widely reported in recent years. The triazole ring, which has a broad spectrum of biological action, is of increasing interest in the synthesis of new tyrosinase inhibitors. In this review, tyrosinase inhibition effects, structure-activity relationships, enzyme inhibition kinetics and mechanisms of action of 1,2,3- or 1,2,4-triazole derivatives were investigated. The data gathered is anticipated to supply rational guidance and an influential strategy for the development of novel, potent and safe tyrosinase inhibitors for better practical application in the future.

Current scenario of quinolone hybrids with potential antibacterial activity against ESKAPE pathogens

The ESKAPE (Escherichia coli/E. coli, Staphylococcus aureus/S. aureus, Klebsiella pneumonia/K. pneumoniae, Acinetobacter Baumannii/A. baumannii, Pseudomonas aeroginosa/P. aeroginosa and Enterobacter spp.) pathogens, which could escape or evade common therapies through diverse antimicrobial resistance mechanisms and biofilm formation, are deemed as highly virulent bacteria responsible for life-threatening diseases, calling for novel chemotherapeutics. Quinolones including 2-quinolones and 4-quinolones have occupied a propitious place in drug design and development due to their excellent pharmacological profiles. Quinolones especially fluoroquinolones could inhibit the synthesis of nucleic acid of ESKAPE pathogens, leading to the rupture of bacterial chromosome. However, the resistance of ESKAPE pathogens to quinolones develops rapidly and spreads widely. Accordingly, it has become increasingly urgent to enhance the potency of quinolones against both drug-susceptible and drug-resistant ESKAPE pathogens. Quinolone hybrids can bind with different drug targets simultaneously and have been considered as useful prototypes to circumvent drug resistance. The purpose of this review is to summarize the current scenario (2018-present) of quinolone hybrids with potential antibacterial activity against ESKAPE pathogens, together with the structure-activity relationships and mechanisms of action to facilitate further rational design of more effective candidates.

Hybrid Azine Derivatives: A Useful Approach for Antimicrobial Therapy

Nowadays, infectious diseases caused by microorganisms are a major threat to human health, mostly because of drug resistance, multi-drug resistance and extensive-drug-resistance phenomena to microbial pathogens. During the last few years, obtaining hybrid azaheterocyclic drugs represents a powerful and attractive approach in modern antimicrobial therapy with very promising results including overcoming microbial drug resistance. The emphasis of this review is to notify the scientific community about the latest recent advances from the last five years in the field of hybrid azine derivatives with antimicrobial activity. The review is divided according to the main series of six-member ring azaheterocycles with one nitrogen atom and their fused analogs. In each case, the main essential data concerning synthesis and antimicrobial activity are presented.

Fluoroquinolones' Biological Activities against Laboratory Microbes and Cancer Cell Lines

Development of novel derivatives to rein in and fight bacteria have never been more demanding, as microbial resistance strains are alarmingly increasing. A multitude of new fluoroquinolones derivatives with an improved spectrum of activity and/or enhanced pharmacokinetics parameters have been widely explored. Reporting novel antimicrobial agents entails comparing their potential activity to their parent drugs; hence, parent fluoroquinolones have been used in research as positive controls. Given that these fluoroquinolones possess variable activities according to their generation, it is necessary to include parent compounds and market available antibiotics of the same class when investigating antimicrobial activity. Herein, we provide a detailed guide on the in vitro biological activity of fluoroquinolones based on experimental results published in the last years. This work permits researchers to compare and analyze potential fluoroquinolones as positive control agents and to evaluate changes occurring in their activities. More importantly, the selection of fluoroquinolones as positive controls by medicinal chemists when investigating novel FQs analogs must be correlated to the laboratory pathogen inquest for reliable results.

Design and synthesis of ciprofloxacin-sulfonamide hybrids to manipulate ciprofloxacin pharmacological qualities: Potency and side effects

Fluoroquinolones are a class of antibacterial agents used clinically to treat a wide array of bacterial infections. Although being potent, susceptibility to CNS side effects limits their use. It was observed that improvements in absorption, activity and side effects were achieved via modifications at the N atom of the C7 of the side chain. To meet the increasing demand for development of new antibacterial agents, nineteen novel ciprofloxacin-sulfonamide hybrid molecules were designed, synthesized and characterized by IR, ¹H NMR and ¹³C NMR as potential antibacterial agents with dual DNA gyrase/topoisomerase IV inhibitory activity. Most of the synthesized compounds showed significant antibacterial activity that was revealed by testing their inhibitory activity against DNA gyrase, DNA topoisomerase IV as well as their minimum inhibitory concentration against Staphylococcus aureus. Six ciprofloxacin-sulfonamide hybrids (3f, 5d, 7a, 7d, 7e and 9b) showed potent inhibitory activity against DNA topoisomerase IV, compared to ciprofloxacin (IC50: 0.55 μM), with IC50 range: 0.23-0.44 μM. DNA gyrase was also efficiently inhibited by five ciprofloxacin-sulfonamide hybrids (3f, 5d, 5e, 7a and 7d) with IC50 range: 0.43-1.1 μM (IC50 of ciprofloxacin: 0.83 μM). Compounds 3a and 3b showed a marked improvement in the antibacterial activity over ciprofloxacin against both Gram-positive and Gram-negative pathogens, namely, Staphylococcus aureus Newman and Escherichia coli ATCC8739, with MIC = 0.324 and 0.422 μM, respectively, that is 4.2-fold and 3.2-fold lower than ciprofloxacin (MIC = 1.359 μM) against the Gram-positive Staphylococcus aureus, and MIC = 0.025 and 0.013 μM, respectively, that is 10.2-fold and 19.6-fold lower than ciprofloxacin (MIC = 0.255 μM) against the Gram-negative Escherichia coli ATCC8739. Also, the most active compounds showed lower CNS and convulsive side effects compared to ciprofloxacin with a concomitant decrease in GABA expression.

Synthesis, characterization, DFT calculation, antioxidant activity, ADMET and molecular docking of thiosemicarbazide derivatives and their Cu (II) complexes

In this work, new thiosemicarbazides (ECA-1, ECA-2) and their Cu (II) complexes (ECA-1-Cu, ECA-2-Cu) were synthesized and their structures were characterized by ¹H NMR, ¹³C NMR, FT-IR, LC-MS, UV-Vis, and thermogravimetric analysis methods. Also, the surface morphology of the all compounds were examined by SEM (Scanning Electron Microscope). In the second stage, in vitro antioxidant capacity of the obtained compounds was investigated. The evaluation of the antioxidant properties of both synthesized ligands and complexes in this study was carried out by DPPH and FRAP methods. According to the results, both complexes exhibited more antioxidant capacity than the corresponding ligands. When antioxidant effects are compared for DPPH (SC₅₀ = 5.27 ± 0.05 μM) and for FRAP (7845.69 ± 16.75 mmolTE/g), compound ECA-2-Cu appears to have the best inhibition effect. The complexes were found non-electrolytic in nature with melting point of above 250 °C, and electronic spectra and magnetic behavior demonstrated that the complexes were found to be tetrahedral geometry. Further, in silico the ADMET properties which studies are a significant role in improving and predicting drug compounds were calculated using web-based platforms. The theoretical calculations were made using the method of Density Functional Theory (Frontier molecular orbital analyze and Nonlinear optical properties). Also, molecular docking studies were performed to evaluate the binding interactions between the ligand and complex compounds and Human Peroxiredoxin 2. Both in vitro and in silico results indicated that synthesized compounds could act as potent antioxidant agents.

Synthesis, molecular docking, and evaluation of antibacterial activity of 1,2,4-triazole-norfloxacin hybrids

A series of 1,2,4-triazole-norfloxacin hybrids was designed, synthesized, and evaluated for in vitro antibacterial activity against common pathogens. All the newly synthesized compounds were characterized by Fourier-transform infrared spectrophotometry, proton and carbon nuclear magnetic resonance, and electrospray ionization-mass spectrometry. Representative compounds from each step of the synthesis were further characterized by X-ray crystallography. Many of the compounds synthesized exhibited antibacterial activity superior to that of norfloxacin toward both, gram-positive and gram-negative bacteria. The toxicity of the 1,2,4-triazole-norfloxacin hybrids toward bacterial cells was 32-512 times higher than that toward mouse fibroblast cells. Moreover, hemolysis was not observed at concentrations of 64 μg/mL, suggesting good biocompatibility. Molecular docking showed a least binding energy of -9.4 to -9.7 kcal/mol, and all compounds were predicted to show remarkable affinity for the bacterial topoisomerase IV.

Antimicrobial Activity of 1,3,4-Oxadiazole Derivatives

The worldwide development of antimicrobial resistance forces scientists to search for new compounds to which microbes would be sensitive. Many new structures contain the 1,3,4-oxadiazole ring, which have shown various antimicrobial activity, e.g., antibacterial, antitubercular, antifungal, antiprotozoal and antiviral. In many publications, the activity of new compounds exceeds the activity of already known antibiotics and other antimicrobial agents, so their potential as new drugs is very promising. The review of active antimicrobial 1,3,4-oxadiazole derivatives is based on the literature from 2015 to 2021.

Recent studies of nitrogen containing heterocyclic compounds as novel antiviral agents: A review

N-heterocycles are important, not only because of their abundance, but above all because of their chemical, biological and technical significance. They play an important role in biological investigation such as anticancer, antiinflammatory, antibacterial, antiviral, anti-tumor, antidiabetic, etc. In this study, we focused on examining synthesized some 5- or 6-ring N-heterocyclic compounds that showed the antiviral activity in last 5 years, and investigation of these compounds structure-activity relationship studies. This review will be useful to scientists in research fields of organic synthesis, medicinal chemistry, and pharmacology.

1,2,4-Triazoles as Important Antibacterial Agents

The global spread of drug resistance in bacteria requires new potent and safe antimicrobial agents. Compounds containing the 1,2,4-triazole ring in their structure are characterised by multidirectional biological activity. A large volume of research on triazole and their derivatives has been carried out, proving significant antibacterial activity of this heterocyclic core. This review is useful for further investigations on this scaffold to harness its optimum antibacterial potential. Moreover, rational design and development of the novel antibacterial agents incorporating 1,2,4-triazole can help in dealing with the escalating problems of microbial resistance.

An insight on medicinal attributes of 1,2,4-triazoles

The present review aims to summarize the pharmacological profile of 1,2,4-triazole, one of the emerging privileged scaffold, as antifungal, antibacterial, anticancer, anticonvulsant, antituberculosis, antiviral, antiparasitic, analgesic and anti-inflammatory agents, etc. along with structure-activity relationship. The comprehensive compilation of work carried out in the last decade on 1,2,4-triazole nucleus will provide inevitable scope for researchers for the advancement of novel potential drug candidates having better efficacy and selectivity.