Current Trends and Future Directions of Fluoroquinolones

Advancements in Synthetic Strategies and Biological Effects of Ciprofloxacin Derivatives: A Review

Ciprofloxacin is a widely used antibiotic in the fluoroquinolone class. It is widely acknowledged by various researchers worldwide, and it has been documented to have a broad range of other pharmacological activities, such as anticancer, antiviral, antimalarial activities, etc. Researchers have been exploring the synthesis of ciprofloxacin derivatives with enhanced biological activities or tailored capability to target specific pathogens. The various biological activities of some of the most potent and promising ciprofloxacin derivatives, as well as the synthetic strategies used to develop them, are thoroughly reviewed in this paper. Modification of ciprofloxacin via 4-oxo-3-carboxylic acid resulted in derivatives with reduced efficacy against bacterial strains. Hybrid molecules containing ciprofloxacin scaffolds displayed promising biological effects. The current review paper provides reported findings on the development of novel ciprofloxacin-based molecules with enhanced potency and intended therapeutic activities which will be of great interest to medicinal chemists.

Investigation of bacterial DNA gyrase Inhibitor classification models and structural requirements utilizing multiple machine learning methods

Infections from multidrug-resistant (MDR) bacteria have emerged as a paramount global health concern, and the therapeutic effectiveness of current treatments is swiftly diminishing. An urgent need exists to explore innovative strategies for countering drug-resistant bacteria. Bacterial DNA gyrase, functioning as an ATP-dependent enzyme, plays a pivotal role in the intricate processes of transcription, replication, and chromosome segregation within bacterial DNA. This renders it a prime target for the development of innovative antibacterial agents. However, the experimental identification of bacterial DNA gyrase inhibitors faces multifaceted challenges due to current methodological constraints. Recognizing its significance, this study developed 56 computational models designed for predicting bacterial DNA gyrase inhibitors. These models employed seven distinct molecular fingerprints and eight machine learning algorithms. Among these models, Model_2D, created using KlekotaRoth fingerprints and the SVM algorithm, stands out as the most robust performer (ACC = 0.86, MCC = 0.63, G-mean = 0.82). Moreover, given the limited exploration of structural fragments required for DNA Gyrase B inhibitors, crucial structural fingerprints influencing DNA Gyrase B inhibitors were identified through Bayesian classification. Subsequently, we conducted molecular docking to reveal the binding modes between these crucial structural fingerprints and the active site of DNA gyrase B. In conclusion, the present study aimed to develop the optimal classification model for bacterial DNA gyrase inhibitors, offering invaluable support to medicinal chemists creating innovative DNA gyrase inhibitors.

Novel Fluoroquinolones with Possible Antibacterial Activity in Gram-Negative Resistant Pathogens: In Silico Drug Discovery

Antibiotic resistance is a global threat to public health, and the search for new antibacterial therapies is a current research priority. The aim of this in silico study was to test nine new fluoroquinolones previously designed with potential leishmanicidal activity against Campylobacter jejuni, Escherichia coli, Neisseria gonorrhoeae, Pseudomonas aeruginosa, and Salmonella typhi, all of which are considered by the World Health Organization to resistant pathogens of global concern, through molecular docking and molecular dynamics (MD) simulations using wild-type (WT) and mutant-type (MT) DNA gyrases as biological targets. Our results showed that compound 9FQ had the best binding energy with the active site of E. coli in both molecular docking and molecular dynamics simulations. Compound 9FQ interacted with residues of quinolone resistance-determining region (QRDR) in GyrA and GyrB chains, which are important to enzyme activity and through which it could block DNA replication. In addition to compound 9FQ, compound 1FQ also showed a good affinity for DNA gyrase. Thus, these newly designed molecules could have antibacterial activity against Gram-negative microorganisms. These findings represent a promising starting point for further investigation through in vitro assays, which can validate the hypothesis and potentially facilitate the development of novel antibiotic drugs.

Synthesis and molecular docking of new N4-piperazinyl ciprofloxacin hybrids as antimicrobial DNA gyrase inhibitors

A series of N-4 piperazinyl ciprofloxacin derivatives as urea-tethered ciprofloxacin-chalcone hybrids 2a-j and thioacetyl-linked ciprofloxacin-pyrimidine hybrids 5a-i were synthesized. The target compounds were investigated for their antibacterial activity against S. aureus, P. aeruginosa, E. coli, and C. albicans strains, respectively. Ciprofloxacin derivatives 2a-j and 5a-i revealed broad antibacterial activity against either Gram positive or Gram negative strains, with MIC range of 0.06-42.23 µg/mL compared to ciprofloxacin with an MIC range of 0.15-3.25 µg/mL. Among the tested compounds, hybrids 2b, 2c, 5a, 5b, 5h, and 5i exhibited remarkable antibacterial activity with MIC range of 0.06-1.53 µg/mL against the tested bacterial strains. On the other hand, compounds 2c, 2e, 5c, and 5e showed comparable antifungal activity to ketoconazole against candida albicans with MIC range of 2.03-3.89 µg/mL and 2.6 µg/mL, respectively. Further investigations showed that some ciprofloxacin hybrids have inhibitory activity against DNA gyrase as potential molecular target compared to ciprofloxacin with IC50 range of 0.231 ± 0.01-7.592 ± 0.40 µM and 0.323 ± 0.02 µM, respectively. Docking studies of compounds 2b, 2c, 5b, 5c, 5e, 5h, and 5i on the active site of DNA gyrase (PDB: 2XCT) confirmed their ability to form stable complex with the target enzyme like that of ciprofloxacin.

Triphenylphosphonium (TPP)-Conjugated Quinolone Analogs Displayed Significantly Enhanced Fungicidal Activity Superior to Its Parent Molecule

Although 1-hydroxy-4-quinolone derivatives, such as 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO), aurachin C, and floxacrine, have been reported as effective cytochrome bc₁ complex inhibitors, the bioactivity of these products is not ideal, presumably due to their low bioavailability in tissues, particularly their poor solubility and low mitochondrial accumulation. In order to overcome the drawbacks of these compounds and develop their use as agricultural fungicides acting by cytochrome bc₁ inhibition, in this study, three novel mitochondria-targeting quinolone analogs (mitoQNOs) were designed and synthesized by conjugating triphenylphosphonium (TPP) with quinolone. They exhibited greatly enhanced fungicidal activity compared to the parent molecule, especially mitoQNO₁₁, which showed high antifungal activity against Phytophthora capsici and Sclerotinia sclerotiorum with EC₅₀ values of 7.42 and 4.43 μmol/L, respectively. In addition, mitoQNO₁₁ could inhibit the activity of the cytochrome bc₁ complex of P. capsici in a dose-dependent manner and effectively depress its respiration and ATP production. The greatly decreased mitochondrial membrane potential and massively generated reactive oxygen species (ROS) strongly suggested that the inhibition of complex III led to the leakage of free electrons, which resulted in the damage of the pathogen cell structure. The results of this study indicated that TPP-conjugated QNOs might be used as agricultural fungicides by conjugating them with TPP.

Design, Synthesis and Biological Evaluation of Novel Indole-piperazine Derivatives as Antibacterial Agents

Herein, a series of novel indole-piperazine derivatives were synthesized. Bioassay results showed the title compounds exhibited moderate to good bacteriostatic efficacy against the test Gram-positive bacteria and Gram-negative bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Among theses compounds, three remarkable compounds 8f, 9a, and 9h exhibited superior in vitro antibacterial profiles for anti- S. aureus and anti-MRSA to that of gentamicin. Hit compound 9a manifested a rapid bactericidal kinetic effect on MRSA,with no resistance observed after 19 days of sequential passaging. And 8 µg/mL of compound 9a displayed considerable post antibacterial effects to that of ciprofloxacin at the concentration of 2 µg/mL. Cytotoxic and ADMET studies indicated, to some extent, compounds 8f, 9a, and 9h were up to the standard for antibacterial drugs. These results suggest that indole/piperazine derivatives based on the title compounds can serve as a new scaffold for antimicrobial development.

Situational analysis on fluoroquinolones use and characterization of high-level ciprofloxacin-resistant Enterococcus faecalis by integrated broiler operations in South Korea

Fluoroquinolones are classified as "critically important antimicrobials for human medicine"; however, their extensive use in livestock poses a significant health risk to humans as it leads to the rapid spread of antimicrobial resistance. This study confirmed that 40.0%-71.4% of the farms in three of the five integrated broiler operations were administered ciprofloxacin (CIP). Moreover, preventive purposes (60.9%), veterinarian prescriptions (82.6%), drinking water route (100%), and 1 to 3 days (82.6%) of age were significantly highest (P < 0.05). 194 high-level ciprofloxacin-resistant (HLCR) Enterococcus faecalis (E. faecalis) were found in 65 of 74 farms, and of which, the prevalence of qnrA (63.9%), tetM (60.3%), ermB (64.9%), blaz (38.7%), and catA (34.0%) was significantly highest (P < 0.05). 154 (79.4%) isolates showed MDR, and the distribution of MDR was significantly differences among the operations (P < 0.05). All HLCR E. faecalis possessed double mutations in gyrA and parC, and S83I/S80I (90.7%) mutations were most commonly identified. Interestingly, the distribution of isolates with MICs ≥ 512 for both CIP and moxifloxacin was significantly higher in CIP-administered farms (56.5%) than in non-CIP-administered farms (41.4%) (P < 0.05). Also, the prevalence of strong or moderate biofilm formers in HLCR E. faecalis was significantly higher than that of weak and no biofilm formers (P < 0.05). HLCR E. faecalis were heavily distributed in the broiler farms in Korea; therefore, it is necessary to minimize the prevalence of resistant bacteria via structural management regulations such as cleaning and disinfection of farm environments.

A Comprehensive Review on Chemical Synthesis and Chemotherapeutic Potential of 3-Heteroaryl Fluoroquinolone Hybrids

Fluoroquinolones have been studied for more than half a century. Since the 1960s, four generations of these synthetic antibiotics have been created and successfully introduced into clinical practice. However, they are still of interest for medicinal chemistry due to the wide possibilities for chemical modification, with subsequent useful changes in the pharmacokinetics and pharmacodynamics of the initial molecules. This review summarizes the chemical and pharmacological results of fluoroquinolones hybridization by introducing different heterocyclic moieties into position 3 of the core system. It analyses the synthetic procedures and approaches to the formation of heterocycles from the fluoroquinolone carboxyl group and reveals the most convenient ways for such procedures. Further, the results of biological activity investigations for the obtained hybrid pharmacophore systems are presented. The latter revealed numerous promising molecules that can be further studied to overcome the problem of resistance to antibiotics, to find novel anticancer agents and more.

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

New 1,2,3-triazole linked ciprofloxacin-chalcones induce DNA damage by inhibiting human topoisomerase I& II and tubulin polymerization

A series of novel 1,2,3-triazole-linked ciprofloxacin-chalcones 4a-j were synthesised as potential anticancer agents. Hybrids 4a-j exhibited remarkable anti-proliferative activity against colon cancer cells. Compounds 4a-j displayed IC₅₀s ranged from 2.53-8.67 µM, 8.67-62.47 µM, and 4.19-24.37 µM for HCT116, HT29, and Caco-2 cells; respectively, whereas the doxorubicin, showed IC₅₀ values of 1.22, 0.88, and 4.15 µM. Compounds 4a, 4b, 4e, 4i, and 4j were the most potent against HCT116 with IC₅₀ values of 3.57, 4.81, 4.32, 4.87, and 2.53 µM, respectively, compared to doxorubicin (IC₅₀ = 1.22 µM). Also, hybrids 4a, 4b, 4e, 4i, and 4j exhibited remarkable inhibitory activities against topoisomerase I, II, and tubulin polymerisation. They increased the protein expression level of γH2AX, indicating DNA damage, and arrested HCT116 in G2/M phase, possibly through the ATR/CHK1/Cdc25C pathway. Thus, the novel ciprofloxacin hybrids could be exploited as potential leads for further investigation as novel anticancer medicines to fight colorectal carcinoma.

Evaluation of biological activities of quinone-4-oxoquinoline derivatives against pathogens of clinical importance

BACKGROUND

Microbial resistance has become a worldwide public health problem, and may lead to morbidity and mortality in affected patients.

OBJECTIVE

Therefore, this work aimed to evaluate the antibacterial activity of quinone-4-oxoquinoline derivatives.

METHOD

These derivatives were evaluated against Gram-positive and Gram-negative bacteria by their antibacterial activity, anti-biofilm, and hemolytic activities and by in silico assays.

RESULTS

The quinone-4-oxoquinoline derivatives presented broad-spectrum antibacterial activities, and in some cases were more active than commercially available reference drugs. These compounds also inhibited bacterial adhesion and the assays revealed seven non-hemolytic derivatives. The derivatives seem to cause damage to the bacterial cell membrane and those containing the carboxyl group at the C-3 position of the 4-quinolonic nucleus were more active than those containing a carboxyethyl group.

CONCLUSION

The isoquinoline-5,8-dione nucleus also favored antimicrobial activity. The study showed that the target of the derivatives must be a non-conventional hydrophobic allosteric binding pocket on the DNA gyrase enzyme.

Effects of fluoroquinolones and tetracyclines on mitochondria of human retinal MIO-M1 cells

Our goal was to explore the detrimental impacts of ciprofloxacin (CPFX) and tetracycline (TETRA) on human retinal Müller (MIO-M1) cells in vitro. Cells were exposed to 30, 60 and 120 μg/ml of CPFX and TETRA. The cellular metabolism was measured with the MTT assay. The JC-1 and CM-H2DCFDA assays were used to evaluate the levels of mitochondrial membrane potential (MMP) and ROS (reactive oxygen species), respectively. Mitochondrial DNA (mtDNA) copy number, along with gene expression levels associated with apoptotic (BAX, BCL2-L13, BCL2, CASP-3 and CASP-9), inflammatory (IL-6, IL-1β, TGF-α, TGF-β1 and TGF-β2) and antioxidant pathways (SOD2, SOD3, GPX3 and NOX4) were analyzed via Quantitative Real-Time PCR (qRT-PCR). Bioenergetic profiles were measured using the Seahorse® XF Flux Analyzer. Cells exposed 24 h to 120 μg/ml TETRA demonstrated higher cellular metabolism compared to vehicle-treated cells. At each time points, (i) all TETRA concentrations reduced MMP levels and (ii) ROS levels were reduced by TETRA 120 μg/ml treatment. TETRA caused (i) higher expression of CASP-3, CASP-9, TGF-α, IL-1B, GPX3 and SOD3 but (ii) decreased levels of TGF-B2 and SOD2. ATP production and spare respiratory capacity declined with TETRA treatment. Cellular metabolism was reduced with CPFX 120 μg/ml in all cultures and 60 μg/ml after 72 h. The CPFX 120 μg/ml reduced MMP in all cultures and ROS levels (72 h). CPFX treatment (i) increased expression of CASP-3, CASP-9, and BCL2-L13, (ii) elevated the basal oxygen consumption rate, and (iii) lowered the mtDNA copy numbers and expression levels of TGF-B2, IL-6 and IL-1B compared to vehicle-control cells. We conclude that clinically relevant dosages of bactericidal and bacteriostatic antibiotics can have negative effects on the cellular metabolism and mitochondrial membrane potential of the retinal MIO-M1 cells in vitro. It is noteworthy to mention that apoptotic and inflammatory pathways in exposed cells were affected significantly This is the first study showing the negative impact of fluoroquinolones and tetracyclines on mitochondrial behavior of human retinal MIO-M1 cells.

Tertiary Nanosystem Composed of Graphene Quantum Dots, Levofloxacin and Silver Nitrate for Microbiological Control

BACKGROUND

Infectious diseases have the highest mortality rate in the world and these numbers are associated with scarce and/or ineffective diagnosis and bacterial resistance. Currently, with the development of new pharmaceutical formulations, nanotechnology is gaining prominence.

METHODS

Nanomicelles were produced by ultrasonication. The particle size and shape were evaluated by scanning electron microscopy and confirmed by dynamic light scattering, also thermogravimetric analysis was performed to evaluate the thermal stability. Finally, antibacterial activity has been performed.

RESULTS

The results showed that a rod-shaped nanosystem, with 316.1 nm and PDI of 0.243 was formed. The nanosystem was efficient against Staphylococcus aureus, Pseudomonas aeruginosa, and Bacillus subtilis subsp. spizizenii with MIC inferior to 0.98 and a synergistic effect between silver graphene quantum dots and levofloxacin was observed.

CONCLUSION

The nanosystem produced may rise as a promising agent against the bacterial threat, especially regarding bacterial resistance.

The Search for New Antibacterial Agents among 1,2,3-Triazole Functionalized Ciprofloxacin and Norfloxacin Hybrids: Synthesis, Docking Studies, and Biological Activity Evaluation

Among all modern antibiotics, fluoroquinolones are well known for their broad spectrums of activity and efficiency toward microorganisms and viruses. However, antibiotic resistance is still a problem, which has encouraged medicinal chemists to modify the initial structures in order to combat resistant strains. Our current work is aimed at synthesizing novel hybrid derivatives of ciprofloxacin and norfloxacin and applying docking studies and biological activity evaluations in order to find active promising molecules. We succeeded in the development of a synthetic method towards 1,2,3-triazole-substituted ciprofloxacin and norfloxacin derivatives. The structure and purity of the obtained compounds were confirmed by 1H NMR, 13C NMR, 19F NMR, LC/MS, UV-, IR- spectroscopy. Docking studies, together with in vitro research against Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, Bacillus subtilis ATCC 6633, Pseudomonas aeruginosa ATCC 27853, Candida albicans NCTC 885-653 revealed compounds in which activity exceeded the initial molecules.

Nitric Oxide Photo-Donor Hybrids of Ciprofloxacin and Norfloxacin: A Shift in Activity from Antimicrobial to Anticancer Agents

The potential anticancer effect of fluoroquinolone antibiotics has been recently unveiled and related to their ability to interfere with DNA topoisomerase II. We herein envisioned the design and synthesis of novel Ciprofloxacin and Norfloxacin nitric oxide (NO) photo-donor hybrids to explore the potential synergistic antitumor effect exerted by the fluoroquinolone scaffold and NO eventually produced upon light irradiation. Anticancer activity, evaluated on a panel of tumor cell lines, showed encouraging results with IC50 values in the low micromolar range. Some compounds displayed intense antiproliferative activity on triple-negative and doxorubicin-resistant breast cancer cell lines, paving the way for their potential use to treat aggressive, refractory and multidrug-resistant breast cancer. No significant additive effect was observed on PC3 and DU145 cells following NO release. Conversely, antimicrobial photodynamic experiments on both Gram-negative and Gram-positive microorganisms displayed a significant killing rate in Staphylococcus aureus, accounting for their potential effectiveness as selective antimicrobial photosensitizers.

Antimicrobial and antioxidant activity of Evernia prunastri extracts and their isolates

Lichens are symbiotic organisms formed by a fungus and one or more photosynthetic partners which are usually alga or cyanobacterium. Their diverse and scarcely studied metabolites facilitate adaptability to extreme living conditions. We investigated Evernia prunastri (L.) Ach., a widely distributed lichen, for its antimicrobial and antioxidant potential. E. prunastri was sequentially extracted by hexane (Hex), dichloromethane (DCM) and acetonitrile (ACN) that were screened for their antioxidant and antimicrobial (against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Candida albicans) activities. The Hex extract possessed the highest antioxidant capacity (87 mg ascorbic acid/g extract) corresponding to the highest content of phenols (73 mg gallic acid/g extract). The DCM and Hex extracts were both active against S. aureus (MICs of 4 and 21 µg/ml, respectively) but were less active against Gram-negative bacteria and yeast. The ACN extract exhibited activity on both S. aureus (MIC 14 µg/ml) and C. albicans (MIC 38 µg/ml) and was therefore further fractionated by silica gel column chromatography. The active compound of the most potent fraction was subsequently characterized by 1H and 13C-NMR spectroscopy and identified as evernic acid. Structural similarity analyses were performed between compounds from E. prunastri and known antibiotics from different classes. The structural similarity was not present. Antioxidant and antimicrobial activities of E. prunastri extracts originate from multiple chemical compounds; besides usnic acid, most notably evernic acid and derivatives thereof. Evernic acid and its derivatives represent possible candidates for a new class of antibiotics.

Cytotoxicity assessment of antibiotics on Ctenopharyngodon idellus kidney cells by a sensitive electrochemical method

As emerging pollutants, antibiotics are ubiquitous in the environment and pose a threat to human health, giving rise to an urgent need to assess their biological toxicity. In the present study, a cell electrochemical method based on the bromocresol violet/carbon nanotubes/glassy carbon electrode (BCP/MWCNTs/GCE) was established to evaluate the cytotoxicities of sulfamethoxazole (SMZ), ciprofloxacin (CIP), and tetracycline (TC). BCP/MWCNTs/GCE has advantages due to its excellent electrocatalytic activity for the oxidation of electroactive species of the Ctenopharyngodon idellus kidney (CIK) cells. The half-maximal inhibitory concentration (IC₅₀) values of SMZ, CIP, and TC obtained by the electrochemical method were 831.51 μM, 354.98 μM, and 184.51 μM, which were lower than those of the traditional methyl-thiazolyl-tetrazolium (MTT) assay (907.47 μM, 414.87 μM, and 208.11 μM). These results indicate the higher sensitivity of the electrochemical method. This study provided a sensitive tool for the cytotoxicity evaluation of antibiotics in the environmental toxicology field.

Design, Synthesis, and Antibacterial Screening of Some Novel Heteroaryl-Based Ciprofloxacin Derivatives as DNA Gyrase and Topoisomerase IV Inhibitors

A novel series of ciprofloxacin hybrids comprising various heterocycle derivatives has been synthesized and structurally elucidated using ¹H NMR, ¹³C NMR, and elementary analyses. Using ciprofloxacin as a reference, compounds 1-21 were screened in vitro against Gram-positive bacterial strains such as Staphylococcus aureus and Bacillus subtilis and Gram-negative strains such as Escherichia coli and Pseudomonas aeruginosa. As a result, many of the compounds examined had antibacterial activity equivalent to ciprofloxacin against test bacteria. Compounds 2-6, oxadiazole derivatives, were found to have antibacterial activity that was 88 to 120% that of ciprofloxacin against Gram-positive and Gram-negative bacteria. The findings showed that none of the compounds tested had antifungal activity against Aspergillus flavus, but did have poor activity against Candida albicans, ranging from 23% to 33% of fluconazole, with compound 3 being the most active (33% of fluconazole). The most potent compounds, 3, 4, 5, and 6, displayed an IC₅₀ of 86, 42, 92, and 180 nM against E. coli DNA gyrase, respectively (novobiocin, IC₅₀ = 170 nM). Compounds 4, 5, and 6 showed IC₅₀ values (1.47, 6.80, and 8.92 µM, respectively) against E. coli topo IV in comparison to novobiocin (IC₅₀ = 11 µM).

Novel Mannich bases of ciprofloxacin with improved physicochemical properties, antibacterial, anticancer activities and caspase-3 mediated apoptosis

The design, synthesis and identification of a novel series of Mannich bases of ciprofloxacin was reported. Naphthol derivatives 2a and 2b showed highly potent cytotoxic activity among the tested compounds. Compound 2a showed broad spectrum antiproliferative activity with GI₅₀ of 2.5-6.79 µM with remarkable selectivity towards renal and prostate cancers with selectivity ratios ranging from 0.17 to 6.79. Independently, 2a showed outstanding activity against colon cancer HOP-92 cell lines with IC₅₀ of 6.66 µM while 2b showed highly potent activity against ovarian cancer cell lines with IC₅₀ of 0.97 µM. Results showed that 2b induced cell cycle arrest at G2/M phase and apoptosis; compound 2b showed over-expression of caspase-3 protein level (449.2 ± 7.95) compared to doxorubicin (578.7 ± 14.4 pg/mL). Meanwhile, compounds 2a and 2b experienced outstanding activity against both Gram-positive and Gram-negative microorganisms. Interestingly, compound 2j experienced high activity against Escherichia coli and Pseudomonas aeruginosa with MIC of 0.036 and 0.043, respectively. Compound 2d revealed 27 folds and 22 folds, respectively increasing of activity over ciprofloxacin against Staphylococcus aureus and MRSA(reference strain). Compound 2d showed high activity against Staphylococcus aureus, MRSA (reference strain) and MRSA (clinical strain) with MIC of 0.57, 0.52, 0.082 µg/mL, respectively. Interestingly, the most active tested compounds were found to have promising physicochemical and drug likeness properties. The Mannich bases 2j, 2d and 2g showed promising antibacterial activities, while naphthols 2a and 2b showed promising antiproliferative and antibacterial activities that require further optimization.

Novel urea linked ciprofloxacin-chalcone hybrids having antiproliferative topoisomerases I/II inhibitory activities and caspases-mediated apoptosis

A novel series of urea-linked ciprofloxacin (CP)-chalcone hybrids 3a-j were synthesized and screened by NCI-60 cancer cell lines as potential cytotoxic agents. Interestingly, compounds 3c and 3j showed remarkable antiproliferative activities against both colon HCT-116 and leukemia SR cancer cells compared to camptothecin, topotecan and staurosporine with IC₅₀ = 2.53, 2.01, 17.36, 12.23 and 3.1 μM for HCT-116 cells, respectively and IC₅₀ = 0.73, 0.64, 3.32, 13.72 and 1.17 μM for leukemia SR cells, respectively. Also, compounds 3c and 3j exhibited inhibitory activities against Topoisomerase (Topo) I with % inhibition = 51.19% and 56.72%, respectively, compared to camptothecin (% inhibition = 60.05%) and Topo IIβ with % inhibition = 60.81% and 60.06%, respectively, compared to topotecan (% inhibition = 71.09%). Furthermore, compound 3j arrested the cell cycle of leukemia SR cells at G2/M phase. It induced apoptosis both intrinsically and extrinsically via activation of proteolytic caspases cascade (caspases-3, -8, and -9), release of cytochrome C from mitochondria, upregulation of proapoptotic Bax and down-regulation of Bcl-2 protein level. Thus, the new ciprofloxacin derivative 3j could be considered as a potential lead for further optimization of antitumor agent against leukemia and colorectal carcinoma.

Combating Antibiotic Tolerance Through Activating Bacterial Metabolism

The emergence of antibiotic tolerance enables genetically susceptible bacteria to withstand the killing by clinically relevant antibiotics. As is reported, an increasing body of evidence sheds light on the critical and underappreciated role of antibiotic tolerance in the disease burden of bacterial infections. Considering this tense situation, new therapeutic strategies are urgently required for combating antibiotic tolerance. Herein, we provide an insightful illustration to distinguish between antibiotic resistance and tolerance, and highlight its clinical significance and complexities of drug-tolerant bacteria. Then, we discuss the close relationship between antibiotic tolerance and bacterial metabolism. As such, a bacterial metabolism-based approach was proposed to counter antibiotic tolerance. These exogenous metabolites including amino acids, tricarboxylic acid cycle (TCA cycle) metabolites, and nucleotides effectively activate bacterial metabolism and convert the tolerant cells to sensitive cells, and eventually restore antibiotic efficacy. A better understanding of molecular mechanisms of antibiotic tolerance particularly in vivo would substantially drive the development of novel strategies targeting bacterial metabolism.

Molecular targets and anticancer activity of quinoline-chalcone hybrids: literature review

α,β-Unsaturated chalcone moieties and quinoline scaffolds play an important role in medicinal chemistry, especially in the identification and development of potential anticancer agents. The multi-target approach or hybridization is considered as a promising strategy in drug design and discovery. Hybridization may improve the affinity and potency while simultaneously decreasing the resistance and/or side effects. The conjugation of quinolines with chalcones has been a promising approach to the identification of potential anticancer agents. Most of these hybrids showed anticancer activities through the inhibition of tubulin polymerization, different kinases, topoisomerases, or by affecting DNA cleavage activity. Accordingly, this class of compounds can be classified based on their molecular modes of action. In this article, the quinolone-chalcone hybrids with potential anticancer activity have been reviewed. This class of compounds might be helpful for the design, discovery and development of new and potential multi-target anticancer agents or drugs.

Potential adverse effects of ciprofloxacin and tetracycline on ARPE-19 cell lines

Background

We aim to determine the possible adverse effects of ciprofloxacin (CPFX) and tetracycline (TETRA), as examples of bactericidal and bacteriostatic agents, respectively, on cultured human retinal pigment epithelial cells (ARPE-19).

Methods

Cells were treated with 30, 60 and 120 µg/mL of CPFX and TETRA. Cell metabolism was measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. JC-1 dye (5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolylcarbocyanine iodide) assay was conducted to measure the mitochondrial membrane potential (MMP). The level of reactive oxygen species (ROS) was measured using the -2’,7’-dichlorodihydrofluorescein diacetate assay (H2DCFDA). Quantitative real-time PCR was performed to analyse the gene expression levels associated with apoptosis (BAX, BCL2-L13, BCL2, Caspase 3, Caspase 7 and Caspase 9), inflammatory (interleukin-1β (IL-1β), IL-6, IL-33, transforming growth factor-α (TGF-α), TGF-β1 and TGF-β2) and antioxidant pathways (SOD2, SOD3, GPX3 and NOX4), along with the mitochondrial DNA (mtDNA) copy numbers.

Results

Results illustrated that while all three concentrations of CPFX decreased cellular viability of ARPE-19 during all incubation periods, the 120 µg/mL TETRA resulted in increased cellular viability. At 48 and 72 hours, levels of MMP and ROS decreased significantly with each antibiotic. BAX, BCL2-L13, CASP-7, CASP-9, SOD2 and GPX3 genes overexpressed by either antibiotics. There was higher expression of IL-6 and IL-1B with TETRA treatment. The level of mtDNA decreased using both treatments.

Conclusions

Clinically relevant concentrations of CPFX and TETRA have detrimental impacts on ARPE-19 cell lines in vitro, including upregulation of genes related to apoptosis, inflammation and antioxidant pathways. Additional studies are warranted to investigate if these harmful effects might be seen in retinal degeneration models in vivo.

A three-component reaction of phosphorus ylides with isocyanates: facile synthesis of 2-amino-3-carboxylate-4-quinolones

A three-component reaction between one molecule of phosphorus ylides (P-ylides) and two molecules of isocyanates for the rapid assembly of 2-amino-3-carboxylate-4-quinolones is described. The mechanism may involve the addition of a P-ylide to an isocyanate followed by 1,3-H shift to form a carbamoyl stabilized P-ylide. The intermediate then reacts with another aryl isocyanate via Wittig/ketenimine-ketene rearrangement/6π-electrocyclization/1,3-H shift to finally afford the 4-quinolones.

Synthesis, evaluation of thymidine phosphorylase and angiogenic inhibitory potential of ciprofloxacin analogues: Repositioning of ciprofloxacin from antibiotic to future anticancer drugs

Over expression of thymidine phosphorylase (TP) in various human tumors compared to normal healthy tissue is associated with progression of cancer and proliferation. The 2-deoxy-d-ribose is the final product of thymidine phosphorylase (TP) catalyzed reaction. Both TP and 2-deoxy-d-ribose are known to promote unwanted angiogenesis in cancerous cells. Discovery of potent inhibitors of thymidine phosphorylase (TP) can offer appropriate approach in cancer treatment. A series of ciprofloxacin 2, 3a-3c, 4a-4d, 5a-5b, 6 and 7 has been synthesized and characterized using spectroscopic techniques. Afterwards, inhibitory potential of synthesized ciprofloxacin 2, 3a-3c, 4a-4d, 5a-5b, 6 and 7 against thymidine phosphorylase enzyme was assessed. Out of these twelve analogs of ciprofloxacin nine analogues 3a-3c, 4a-4c, 5a-5b and 6 showed good inhibitory activity against thymidine phosphorylase. Inhibitory activity as presented by their IC₅₀ values was found in the range of 39.71 ± 1.13 to 161.89 ± 0.95 μM. The 7-deazaxanthine was used as a standard inhibitor with IC₅₀ = 37.82 ± 0.93 μM. Furthermore, the chick chorionic allantoic membrane (CAM) assay was used to investigate anti-angiogenic activity of the most active ciprofloxacin-based inhibitor 3b. To enlighten the important binding interactions of ciprofloxacin derivatives with target enzyme, the structure activity relationship and molecular docking studies of chosen ciprofloxacin analogues was discussed. Docking studies revealed key π-π stacking, π-cation and hydrogen bonding interactions of ciprofloxacin analogues with active site residues of thymidine phosphorylase enzyme.