Synthesis of novel tetrazole containing hybrid ciprofloxacin and pipemidic acid analogues and preliminary biological evaluation of their antibacterial and antiproliferative activity

Benzopyrone-mediated quinolones as potential multitargeting antibacterial agents

A new type of benzopyrone-mediated quinolones (BMQs) was rationally designed and efficiently synthesized as novel potential antibacterial molecules to overcome the global increasingly serious drug resistance. Some synthesized BMQs effectively suppressed the growth of the tested strains, outperforming clinical drugs. Notably, ethylidene-derived BMQ 17a exhibited superior antibacterial potential with low MICs of 0.5-2 μg/mL to clinical drugs norfloxacin, it not only displayed rapid bactericidal performance and inhibited bacterial biofilm formation, but also showed low toxicity toward human red blood cells and normal MDA-kb2 cells. Mechanistic investigation demonstrated that BMQ 17a could effectually induce bacterial metabolic disorders and promote the enhancement of reactive oxygen species to disrupt the bacterial antioxidant defense system. It was found that the active molecule BMQ 17a could not only form supramolecular complex with lactate dehydrogenase, which disturbed the biological functions, but also effectively embed into calf thymus DNA, thus affecting the normal function of DNA and achieving cell death. This work would provide an insight into developing new molecules to reduce drug resistance and expand antibacterial spectrum.

Synthesis and in Silico Studies of Some New 1,2,3-Triazolyltetrazole Bearing Indazole Derivatives as Potent Antimicrobial Agents

1,2,3-Triazole and tetrazole derivatives bearing pyrrolidines are found to exhibit notable biological activity and have become useful scaffolds in medicinal chemistry for application in lead discovery and optimization. Novel indazole bearing 1,2,3-triazolyltetrazoles were designed as potential antimicrobial candidates. The structure of duel heterocyclics was validated by a spectroscopic technique of infrared (IR), nuclear magnetic resonance (1 H and 13 C NMR), and mass spectral data. Compounds 4b, 4c, 4d, and 4h were found to have a stronger antibacterial effect against Gram-positive (S. aureus, B. subtilis, M. Luteus) and Gram-negative (E. coli, P. aeruginosa) microorganisms with MICs ranging from 5±0.03-18±0.02 μM, respectively. Moreover, scaffolds 4a, 4h showed potent antifungal activity against A. flavus, M. gypsuem strains with MIC values of 10±0.02, 11±0.01 μM, which are similar activity that of the standard Itraconazole (MIC=8±0.02, 10±0.01 μM). The binding mode for compound 4 inside the catalytic pocket of S. aureus complexed with nicotinamide adenine dinucleotide phosphate and trimethoprim and produced a network of hydrophobic and hydrophilic interactions (3FRE). From in silico results, 4b demonstrated highly stable hydrogen binding amino acids Leu62(X) [N18…O, 2.47 Å], Arg44(X) [N17…N, 3.11 Å], Thr96(X) [N10…OG1, 3.05 Å], Gly94(X) [F7…N, 2.82 Å], and Gly43(X) [F7…N, 2.90 Å], which are plays a crucial role in ensuring efficient binding of the ligand in a crystal structure of antibacterial receptor. Furthermore, the physicochemical and ADME filtration molecular properties, estimation of toxicity, and bioactivity scores of these novel scaffolds were evaluated by using SwissADME and ADMETlab2.0 online protocols. Thus, the significant antimicrobial activity of indazole linked to duel heterocyclic compounds can be used for development of new antimicrobial agents with further modifications.

Synthesis and biological evaluation of ciprofloxacin - 1,2,3-triazole hybrids as antitumor, antibacterial, and antioxidant agents

Six novel ciprofloxacin-1,2,3-triazole hybrids (6a-f) were synthesized via click reaction, by reacting of methyl 1-cyclopropyl-6-fluoro-4-oxo-7-(4-(3-oxobutanoyl)piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylate (5) with various aryl azides (9a-f). The new compounds were characterized using High-Resolution Mass Spectrometry (HRMS), 1H NMR, 13C NMR, and elemental analysis. Compounds (6a-f) screened for their in vitro anticancer activity against three cell lines, namely, non-small cell lung cancer (A549), glioblastoma (U-87 MG), and breast cancer (MCF7). Hybrids 6a and 6b exhibited remarkable anti-proliferative activity against all three cell-lines. IC50 values of 6b for all cancer cell lines were significantly lower comparing to the standard reference compound IC50. The IC50 of 6b for the normal cell (HDF) line was significantly higher than the reported for cisplatin [IC50 = 170.7 ± 8.1 μM/ml (HDF), (p ≤ 0.001)], indicating less toxicity towards normal cells and thereby has a better therapeutic index, with a selectivity index of 142.3 for U87 cell line. Compounds 6e, 6d, and 6f displayed significant cytotoxic activity against only U-87 and MCF-7 cancer cell lines, compared to normal cells (HDF). Compound 6f [IC50 = 7.9 ± 2.3 μM/ml (U-87) and 10.6 ± 3 μM/ml (MCF-7)] was more potent than cisplatin [IC50 = 28.3 ± 5.3 μM/ml (U-87) and 26.9 ± 4.7 μM/ml (MCF-7)] in displaying anti-proliferative effect against U-87 and MCF-7 cells, with less cytotoxic to normal cells [IC50 = 141.7 ± 4.1] than cisplatin [IC50 = 40.9 ± 5.4]. Moreover, they were tested for their antioxidant activity in DPPH and ABTS assays and antibacterial activity.

Topoisomerase II inhibitors design: Early studies and new perspectives

The DNA topoisomerase enzymes are widely distributed throughout all spheres of life and are necessary for cell function. Numerous antibacterial and cancer chemotherapeutic drugs target the various topoisomerase enzymes because of their roles in maintaining DNA topology during DNA replication and transcription. Agents derived from natural products, like anthracyclines, epipodophyllotoxins and quinolones, have been widely used to treat a variety of cancers. A very active field of fundamental and clinical research is the selective targeting of topoisomerase II enzymes for cancer treatment. This thematic review summarizes the recent advances in the anticancer activity of the most potent topoisomerase II inhibitors (anthracyclines, epipodophyllotoxins and fluoroquinolones) their modes of action, and structure-activity relationships (SARs) organized chronologically in the last ten years from 2013 to 2023. The review also highlights the mechanism of action and SARs of promising new topoisomerase II inhibitors.

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.

Nano-CuFe2O3-catalyzed green synthesis of novel quinazolinone-tetrazole hybrids as anti-cancer agents

A novel green protocol has been developed for the synthesis of quinazolinone-tetrazole conjugates (7a-g, 8a-g and 9a-g) using recyclable nano-CuFe₂O₃ catalyst in water. Initially, 2-mercapto-3-substituted phenethylquinazolin-4(3H)-one (5a-c) was prepared by using nano-CuFe₂O₃ catalyst in water. Then, compounds (5a-c) were reacted with 1-bromo-3-chloropropane under nano-CuFe₂O₃ catalyst in water solvent to give S-alkylated quinazolinone core intermediate (6a-c), which was subsequently reacted with 1-substituted-1H-tetrazole-5-thiol (2a-g) by employing the similar reaction conditions to afford the final target compounds. The regioselective formation of C-S bond was unambiguously confirmed by single-crystal X-ray diffraction. The anti-cancer activity of the derivatives on various cancer cell lines such as SIHA, MD-AMB-231 and HepG2 was evaluated. Remarkably, compounds, 7f, 8f, 9a, 9d and 9f, showed potent activity in MD-AMB-231 cancer cell line (IC₅₀: 9.13-10.3 µM), while the same derivatives showed significant potent activity in SiHa and HepG2 cancer cell lines (IC₅₀: 17.46-27.0 µM). Most significantly, compound 7o (IC₅₀: 8.15 µM) showed potent activity, compared to the drug etoposide (IC₅₀: 18.11 µM) against MD-AMB-231 cell line. Flow cytometry analysis revealed that compounds 7f, 8f, 9a, 9d and 9f arrested the cell growth in the G1 phase in MD-AMB-231 cell line.

Synthesis and characterization of Ni0.5Al0.5Fe2O4 nanoparticles for potent antifungal activity against dry rot of ginger (Fusarium oxysporum)

Current study signifies the use of nanoparticles as alternative in plant disease management to avoid harmful effect of pesticide and fungicide residue. Synthesis of nanoparticles (Ni0.5Al0.5Fe2O4) by hydrothermal method and studied their X-ray diffraction analysis (XRD), Raman spectra, and UV spectra and further successfully evaluated for antifungal activity against a soil and seed borne pathogenic fungus (Fusarium oxysporum).Among various pests, fungal pathogens are the main cause of crop destruction and we developed nanoparticles (Ni0.5Al0.5Fe2O4) which is successfully evaluated for antimycotic activity against dry rot (F. oxysporum) of ginger which causes 50-70% losses in the ginger plant. In vitro and in vivo analysis designated that the nanoparticles (Ni0.5Al0.5Fe2O4) has shown an excellent antifungal activity against F. oxysporum at 0.5 mg/ml concentration. Similarly, no disease incidence was recorded when Ni0.5Al0.5Fe2O4 nanoparticles used at 0.5 mg/ml concentration under in vivo conditions. In plants various environmental stresses (biotic and abiotic) leads to excessive production of reactive oxygen species (ROS) causing progressive oxidative damage and ultimately leads to cell death. The role of ROS in nanoparticles (Ni0.5Al0.5Fe2O4) represents by reduction in the growth inhibition of F. oxysporum. We speculated in light of these results that the cytotoxic effect of Ni0.5Al0.5Fe2O4 nanoparticles on F. oxysporum may be mediated through ROS. We can suggest the role of nanoparticles (Ni0.5Al0.5Fe2O4) gives a promising result as a fungicidal activity and could be a novel family of future new generation fungicide.

Novel ciprofloxacin and norfloxacin-tetrazole hybrids as potential antibacterial and antiviral agents: targeting S. aureus topoisomerase and SARS-CoV-2-MPro

This study was designed to synthesize hybridizing molecules from ciprofloxacin and norfloxacin by enhancing their biological activity with tetrazoles. The synthesized compounds were investigated in the interaction with the target enzyme of fluoroquinolones (DNA gyrase) and COVID-19 main protease using molecular similarity, molecular docking, and QSAR studies. A QSAR study was carried out to explore the antibacterial activity of our compounds over Staphylococcus aureus a QSAR study, using descriptors obtained from the docking with DNA gyrase, in combination with steric type descriptors, was done obtaining suitable statistical parameters (R2=87.00, QLMO2=71.67, and QEXT2=73.49) to support our results. The binding interaction of our compounds with CoV-2-Mpro was done by molecular docking and were compared with different covalent and non-covalent inhibitors of this enzyme. For the docking studies we used several crystallographic structures of the CoV-2-Mpro. The interaction energy values and binding mode with several key residues, by our compounds, support the capability of them to be CoV-2-Mpro inhibitors. The characterization of the compounds was completed using FT-IR, ¹H-NMR, ¹³C-NMR, ¹⁹F-NMR and HRMS spectroscopic methods. The results showed that compounds 1, 4, 5, 10 and 12 had the potential to be further studied as new antibacterial and antiviral compounds

Quinolones as a Potential Drug in Genitourinary Cancer Treatment-A Literature Review

Quinolones, broad-spectrum antibiotics, are frequently prescribed by urologists for many urological disorders. The mechanism of their bactericidal activity is based on the inhibition of topoisomerase II or IV complex with DNA, which consequently leads to cell death. It has been observed that these antibiotics also act against the analogous enzymes present in eukaryotic cells. Due to their higher accumulation in urine and prostate tissue than in serum, these drugs seem to be ideal candidates for application in genitourinary cancer treatment. In this study, an extensive literature review has been performed to collect information about concentrations achievable in urine and prostate tissue together with information about anticancer properties of 15 quinolones. Special attention was paid to the application of cytotoxic properties of quinolones for bladder and prostate cancer cell lines. Data available in the literature showed promising properties of quinolones, especially in the case of urinary bladder cancer treatment. In the case of prostate cancer, due to low concentrations of quinolones achievable in prostate tissue, combination therapy with other chemotherapeutics or another method of drug administration is necessary.

Recent Advancements in the Development of Anti-Breast Cancer Synthetic Small Molecules

Among all cancer types, breast cancer (BC) still stands as one of the most serious diseases responsible for a large number of cancer-associated deaths among women worldwide, and diagnosed cases are increasing year by year worldwide. For a very long time, hormonal therapy, surgery, chemotherapy, and radiotherapy were used for breast cancer treatment. However, these treatment approaches are becoming progressively futile because of multidrug resistance and serious side effects. Consequently, there is a pressing demand to develop more efficient and safer agents that can fight breast cancer belligerence and inhibit cancer cell proliferation, invasion and metastasis. Currently, there is an avalanche of newly designed and synthesized molecular entities targeting multiple types of breast cancer. This review highlights several important synthesized compounds with promising anti-BC activity that are categorized according to their chemical structures.

Nanomaterial catalyzed green synthesis of tetrazoles and its derivatives: a review on recent advancements

Tetrazoles are indispensable nitrogen containing heterocyclic scaffolds that offer a broad spectrum of applications in various domains such as medicinal chemistry, high energy material science, biochemistry, pharmacology etc. Owing to their useful applications, a wide range of catalysts have been explored for green synthesis of tetrazole derivatives. In recent times, nanomaterials have been emerged as extremely efficient catalysts for different organic transformations because of their high surface area-to-volume ratio, easy surface modification, simple fabrications, easy recovery and reusability. In this article, we have presented an overview of utilization of various nano-catalysts, nanocomposites and other solid-supported nanomaterials as an efficient environmental benign catalytic system for green synthesis of tetrazoles and derivatives. This review will provide an exclusive emphasis on boehmite, magnetic, copper, carbon, MCM-41, and composite based nanomaterials that have been developed since the year 2010 for the synthesis of tetrazole derivatives. In addition, we have briefly discussed the fabrication, functionalization and characterization of some novel nanomaterials and their advantages in the synthesis of tetrazole and its derivatives along with the reaction mechanism that involves synthesis of tetrazole derivatives via nanomaterials catalysed reactions.

The antibacterial activity of fluoroquinolone derivatives: An update (2018-2021)

Bacterial infection is amongst the most common diseases in community and hospital settings. Fluoroquinolones, exerting the antibacterial activity through binding to type II bacterial topoisomerase enzymes, DNA gyrase and topoisomerase IV, are mainstays of chemotherapy. At present, fluoroquinolones are the most valuable antibacterial agents used popularly. However, the emergence of more virulent and resistant pathogens by the development of either mutated DNA-binding proteins or efflux pump mechanism for fluoroquinolones results in an urgent demand to develop new fluoroquinolones to withstand the drug resistance and to obtain a broader spectrum of activity. This review aims to outline the recent advances of fluoroquinolone derivatives with antibacterial potential and to summarize the structure-activity relationship (SAR) so as to provide an insight for rational design of more active candidates, covering articles published between January 2018 and June 2021.

Synthesis and biological evaluation of hybrid quinolone-based quaternary ammonium antibacterial agents

A series of novel fluoroquinolone-Safirinium dye hybrids was synthesized by means of tandem Mannich-electrophilic amination reactions from profluorophoric isoxazolones and antibiotics bearing a secondary amino group at position 7 of the quinoline ring. The obtained fluorescent spiro fused conjugates incorporating quaternary nitrogen atoms were characterized by ¹H NMR, IR, MS, and elemental analysis. All the synthetic analogues (3a-h and 4a-h) were evaluated for their in vitro antimicrobial, bactericidal, and antibiofilm activities against a panel of Gram positive and Gram-negative pathogenic bacteria. The most active Safirinium Q derivatives of lomefloxacin (4d) and ciprofloxacin (4e) exhibited molar-based antibacterial activities comparable to the unmodified drugs and displayed considerable inhibitory potencies in E. coli DNA gyrase supercoiling assays with IC₅₀ values in the low micromolar range. Zwiterionic hybrids were noticeably less lipophilic than the parent quinolones in micellar electrokinetic chromatography (MECK) experiments. The tests performed in the presence of phenylalanine-arginine β-naphthylamide (PAβN) or carbonyl cyanide m-chlorophenylhydrazone (CCCP) revealed that the conjugates are to some extent subject to bacterial efflux and cellular accumulation, respectively. Moreover, the hybrids did not exhibit notable cytotoxicity towards the HEK 293 control cell line and demonstrated low propensity for resistance development, as exemplified for compounds 3g and 4b. Finally, molecular docking experiments revealed that the synthesized compounds were able to bind in the fluoroquinolone-binding mode at S. aureus DNA gyrase and S. pneumoniae topoisomerase IV active sites.

Tetrazole hybrids with potential anticancer activity

Cancer is one of the main causes of death throughout the world. The anticancer agents are indispensable for the treatment of various cancers, but most of them currently on the market are not specific, resulting in series of side effects of chemotherapy. Moreover, the emergency of drug-resistance towards cancers has already increased up to alarming level in the recent decades. Therefore, it's imperative to develop novel anticancer candidates with excellent activity against both drug-susceptible and drug-resistant cancers, and low toxicity as well. Tetrazole is the bioisoster of carboxylic acid, and its derivatives demonstrated promising anticancer activity. Hybridization of tetrazole with other anticancer pharmacophores may provide novel candidates with anticancer potency. The present review described the anticancer activity of tetrazole hybrids, and the structure-activity relationship (SAR) is also discussed to provide an insight for rational designs of tetrazole anticancer candidates with higher efficiency.

Quinolone derivatives and their activities against methicillin-resistant Staphylococcus aureus (MRSA)

Methicillin-resistant Staphylococcus aureus (MRSA) is the most common pathogen both in hospital and community settings, and is capable of causing serious and even fatal infections. Several antibiotics have been approved for the treatment of infections caused by MRSA, but MRSA has already developed resistance to them. More than ever, it's imperative to develop novel, high effective and fast acting anti-MRSA agents. Quinolones are one of the most common antibiotics in clinical practice used to treat various bacterial infections, and some of them displayed excellent in vitro and in vivo anti-MRSA activities, so quinolone derivatives are one of the most promising candidates. This review summarizes the recent developments of quinolone derivatives with potential activity against MRSA, and the structure-activity relationship is also discussed.