Synthesis, characterization, and biological activity of Co(II) and Zn(II) complexes of imidazoles-based azo-functionalized Schiff bases

Discovery of new Schiff bases of the disalicylic acid scaffold as DNA gyrase and topoisomerase IV inhibitors endowed with antibacterial properties

DNA gyrase and topoisomerase IV show great potential as targets for antibacterial medicines. In recent decades, various categories of small molecule inhibitors have been identified; however, none have been effective in the market. For the first time, we developed a series of disalicylic acid methylene/Schiff bases hybrids (5a-k) to act as antibacterial agents targeting DNA gyrase and topoisomerase IV. The findings indicated that the new targets 5f-k exhibited significant antibacterial activity against Gram-positive and Gram-negative bacteria, with efficacy ranging from 75% to 115% of the standard ciprofloxacin levels. Compound 5h demonstrated the greatest efficacy compared to the other compounds tested, with minimum inhibitory concentration (MIC) values of 0.030, 0.065, and 0.060 μg/mL against S. aureus, E. coli, and P. aeruginosa. 5h had a MIC value of 0.050 μg/mL against B. subtilis, which is five times less potent than ciprofloxacin. The inhibitory efficacy of the most potent antibacterial derivatives 5f, 5h, 5i, and 5k against E. coli DNA gyrase was assessed. The tested compounds demonstrated inhibitory effects on E. coli DNA gyrase, with IC50 values ranging from 92 to 112 nM. These results indicate that 5f, 5h, 5i, and 5k are more effective than the reference novobiocin, which had an IC50 value of 170 nM. Compounds 5f, 5h, 5i, and 5k were subjected to additional assessment against E. coli topoisomerase IV. Compounds 5h and 5i, which have the highest efficacy in inhibiting E. coli gyrase, also demonstrated promising effects on topoisomerase IV. Compounds 5h and 5i exhibit IC50 values of 3.50 µM and 5.80 µM, respectively. These results are much lower and more potent than novobiocin's IC50 value of 11 µM. Docking studies demonstrate the potential of compound 5h as an effective dual inhibitor against E. coli DNA gyrase and topoisomerase IV, with ADMET analysis indicating promising pharmacokinetic profiles for antibacterial drug development.

Synthesis, theoretical studies, antibacterial, and antibiofilm activities of novel azo-azomethine chelates against the pathogenic bacterium Proteus mirabilis

2-((1-(4-((2,4,6-trioxohexahydropyrimidin-5-yl)diazenyl) phenyl) ethylidene) amino) benzoic acid (H3L), and its V(IV), Co(II), Ni(II), Cu(II), Pd(II) and Ag(I) chelates were synthesized. They were defined using multiple spectral and analytical techniques. With the exception of Ag(I) chelate, all chelates possessed non-electrolytic character. Square pyramidal shape was proposed for V(IV) chelate and Square planar for the other chelates. The analysis of functional group bands of H3L and its coordination compounds alludes that H3L chelated as neutral tetradentate via nitrogen atoms of azo and azomethine groups, oxygen atom of carbonyl of barbituric acid and OH of the carboxylic group. TG/DTG predicted the thermal behaviors of all compounds. The antibacterial activity of H3L and its coordination compounds was conducted against Proteus mirabilis at concentrations of 250, 500, and 1000 µg/mL. Ag(I) at 1000 µg/mL, showed the most inhibiting potency against P. mirabilis and registered zone of inhibition of 28.33 ± 0.84 mm and highest biofilm inhibition of 70.31%. At 50 Gy of gamma irradiation, the reducing effect of Ag(I) chelate was improved. The protein interruption of P. mirabilis was greatly interrupted by increasing the concentration of the chaletes. Also, Ag(I) showed the highest cytotoxicity with IC50 value of 11.5 µg/ mL. The novelty of this study is the synthesis of a new azo-Schiff base and this is almost the first publication of the effect of azo-Schiff ligands against that bacterial strain P. mirabilis.

First iron(II) organometallic compound acting as ABCB1 inhibitor

Five new iron (II) complexes bearing imidazole-based (Imi-R) ligands with the general formula [Fe(η⁵-C₅H₅)(CO)(PPh₃)(Imi-R)][CF₃SO₃] were synthesized and fully characterized by several spectroscopic and analytical techniques. All compounds crystallize in centrosymmetric space groups in a typical "piano stool" distribution. Given the growing importance of finding alternatives to overcome different forms of multidrug resistance, all compounds were tested against cancer cell lines with different ABCB1 efflux pump expression, namely, the doxorubicin-sensitive (Colo205) and doxorubicin-resistant (Colo320) human colon adenocarcinoma cell lines. Compound 3 bearing 1-benzylimidazole was the most active in both cell lines with IC₅₀ values of 1.26 ± 0.11 and 2.21 ± 0.26 μM, respectively, being also slightly selective against the cancer cells (vs. MRC5 normal human embryonic fibroblast cell lines). This compound, together with compound 2 bearing 1H-1,3-benzodiazole, were found to display very potent ABCB1 inhibitory effect. Compound 3 also showed the ability to induce cell apoptosis. Iron cellular accumulation studies by ICP-MS and ICP-OES methods revealed that the compounds' cytotoxicity is not related to the extent of iron accumulation. Yet, it is worth mentioning that, from the compounds tested, 3 was the only one where iron accumulation was greater in the resistant cell line than in the sensitive one, validating the possible role of ABCB1 inhibition in its mechanism of action.

Comprehensive Insights into Medicinal Research on Imidazole-Based Supramolecular Complexes

The electron-rich five-membered aromatic aza-heterocyclic imidazole, which contains two nitrogen atoms, is an important functional fragment widely present in a large number of biomolecules and medicinal drugs; its unique structure is beneficial to easily bind with various inorganic or organic ions and molecules through noncovalent interactions to form a variety of supramolecular complexes with broad medicinal potential, which is being paid an increasing amount of attention regarding more and more contributions to imidazole-based supramolecular complexes for possible medicinal application. This work gives systematical and comprehensive insights into medicinal research on imidazole-based supramolecular complexes, including anticancer, antibacterial, antifungal, antiparasitic, antidiabetic, antihypertensive, and anti-inflammatory aspects as well as ion receptors, imaging agents, and pathologic probes. The new trend of the foreseeable research in the near future toward imidazole-based supramolecular medicinal chemistry is also prospected. It is hoped that this work provides beneficial help for the rational design of imidazole-based drug molecules and supramolecular medicinal agents and more effective diagnostic agents and pathological probes.

Novel imidazolium-thiohydantoin hybrids and their Mn(iii) complexes for antimicrobial and anti-liver cancer applications

We present the effective synthesis and structural characterization of three novel imidazolium-thiohydantoin ligands (IMTHs, 5a–c) and their Mn(iii) complexes (Mn(iii)IMTHs, 6a–c) in this study. The findings of elemental analyses, spectral analyses and magnetic measurements will be used to infer the stoichiometry, coordination styles, and geometrical aspects of Mn(iii)IMTHs. The new compounds were evaluated for their chemotherapeutic potential against ESKAPE pathogens and liver cancer (HepG2). According to the MIC and MBC values, the bactericidal and bacteriostatic activities of IMTHs have been significantly improved following coordination with the Mn(iii) ion. The MTT assay results showed that all Mn(iii)IMTHs had the potential to reduce the viability of liver carcinoma (HepG2) cells in a dose-dependent manner, with the BF₄-supported complex (6b) outperforming its counterparts (6a and 6c) as well as a clinical anticancer drug (VBL). Additionally, Mn-IMTH₂ (6b) showed the highest level of selectivity (SI = 32.05) for targeting malignant cells (HepG2) over healthy cells (HL7702).

We present the effective synthesis and structural characterization of three novel imidazolium-thiohydantoin ligands (IMTHs, 5a–c) and their Mn(iii) complexes (Mn(iii)IMTHs, 6a–c) in this study.