Synthesis, molecular docking and DNA binding studies of phthalimide-based copper(II) complex: In vitro antibacterial, hemolytic and antioxidant assessment

Phthalimides: developments in synthesis and functionalization

Phthalimides, an important class of biologically active N-heterocycles, are not only found in pharmaceuticals, natural products, agrochemicals, polymers, and dyes, but also serve as building blocks in organic transformations. Many synthetic methods, including metal catalysis and metal-free systems, have been developed to prepare functionalized phthalimides. In this review, we describe the developments in the synthesis and functionalization of phthalimides over the past two decades.

Anti-Inflammatory and Antioxidant Pyrrolo[3,4-d]pyridazinone Derivatives Interact with DNA and Bind to Plasma Proteins-Spectroscopic and In Silico Studies

From the point of view of the search for new pharmaceuticals, pyridazinone derivatives are a very promising group of compounds. In our previous works, we have proved that newly synthesized ligands from this group have desirable biological and pharmacokinetic properties. Therefore, we decided to continue the research evaluating the activity of pyrrolo[3,4-dpyridazinone derivatives. In this work, we focused on the interactions of five pyridazinone derivatives with the following biomolecules: DNA and two plasma proteins: orosomucoid and gamma globulin. Using several of spectroscopic methods, such as UV-Vis, CD, and fluorescence spectroscopy, we proved that the tested compounds form stable complexes with all biomacromolecules selected for analysis. These findings were also confirmed by the results obtained by molecular modeling. All tested pyridazinone derivatives bind to the ctDNA molecule via groove binding mechanisms. All these molecules can also be bound and transported by the tested plasma proteins; however, the stability of the complexes formed is lower than those formed with serum albumin.

Exploring the antioxidant, antimicrobial, cytotoxic and biothermodynamic properties of novel morpholine derivative bioactive Mn(ii), Co(ii) and Ni(ii) complexes - combined experimental and theoretical measurements towards DNA/BSA/SARS-CoV-2 3CLPro

A novel class of bioactive complexes (1-3) [MII(L)2(bpy)], where, L = 2-(4-morpholinobenzylideneamino)phenol, bpy = 2,2'-bipyridine, MII = Mn (1), Co (2) or Ni (3), were assigned to octahedral geometry based on analytical and spectral measurements. Gel electrophoresis showed that complex (2) demonstrated significant DNA cleavage activity compared to the other complexes under the action of oxidation agent (H2O2). The DNA binding constant properties measured by various techniques were in the following sequence: (2) > (3) > (1) > (HL), which suggests that the complexes might intercalate DNA, a possibility that is also supported by their biothermodynamic characteristics. The binding constant results for BSA from electronic absorption and fluorometric titrations demonstrate that complex (2) exhibits the highest binding effectiveness among them all, which means that all the compounds could interact with BSA through a static approach, additionally supported by FRET measurements. DFT and docking calculations were employed to realize the electronic structure, reactivity, and interaction capability of all substances with DNA, BSA, and the SARS-CoV-2 main protease. These binding energies fell within the ranges -7.7 to -8.5, -8.2 to -10.1 and -6.7 to -9.3 kcal mol-1, respectively. The higher reactivity of the complexes than the ligand is supported by FMO theory. The in vitro antibacterial, cytotoxicity, and radical scavenging characteristics revealed that complexes (2-3) have better biological efficacy than the others. The cytotoxicity and binding properties also show good correlation with the partition coefficient (log P), which is encouraging because all of the experimental findings are closely correlated with the theoretical measurements.

Novel N-α-amino acid spacer-conjugated phthalimide-triazine derivatives: synthesis, antimicrobial and molecular docking studies

To design and develop novel antimicrobial agents, a series of phthalimide-triazine-based derivatives (6a-6e) were synthesized, characterized and evaluated for their potential antibacterial activities. The compounds were prepared through reaction of 6-phenyl-1,3,5-triazine-2,4-diamine with phthalimide moiety containing aliphatic amino acid. Structural analysis of the synthesized compounds was carried out by various characterization techniques such as FT-IR, ¹H and ¹³C-NMR and mass spectroscopy. After the confirmation of the structure, the antibacterial screening of the synthesized compounds was performed against two strains of Gram-positive (Staphylococcus aureus, and Bacillus subtilis) and two strains of Gram-negative (Escherichia coli and Salmonella enteritidis) bacteria. The results of antimicrobial activity showed that compound 6d was the most active against all the tested strains of microorganisms with the MIC value 1.25 µg/µl. The synthesized compounds were docked into the binding sites of E. coli-DNA gyrase B and S. aureus-DNA gyrase complex to explore their theoretically binding mode and possible interactions of these ligands with these two targets. Docking study showed the importance of both hydrogen bonding and hydrophobic interactions as a key interaction with the targets. Based on the obtained results, the hybrid derivatives of triazine and phthalimide could be regarded as efficient candidates for further molecular developments of antimicrobial agents.

An Integrated Analysis of Mechanistic Insights into Biomolecular Interactions and Molecular Dynamics of Bio-Inspired Cu(II) and Zn(II) Complexes towards DNA/BSA/SARS-CoV-2 3CLpro by Molecular Docking-Based Virtual Screening and FRET Detection

Novel constructed bioactive mixed-ligand complexes (1b) [Cu^II(L)₂(phen)] and (2b) [Zn^II(L)₂(phen)] {where, L = 2-(4-morpholinobenzylideneamino)phenol), phen = 1,10-phenanthroline} have been structurally analysed by various analytical and spectroscopic techniques, including, magnetic moments, thermogravimetric analysis, and X-ray crystallography. Various analytical and spectral measurements assigned showed that all complexes appear to have an octahedral geometry. Agar gel electrophoresis's output demonstrated that the Cu(II) complex (1b) had efficient deoxyribonucleic cleavage and complex (2b) demonstrated the partial cleavage accomplished with an oxidation agent, which generates spreadable OH^● through the Fenton type mechanism. The DNA binding constants observed from viscosity, UV-Vis spectral, fluorometric, and electrochemical titrations were in the following sequence: (1b) > (2b) > (HL), which suggests that the complexes (1b-2b) might intercalate DNA, a possibility that is supported by the biothermodynamic measurements. In addition, the observed binding constant results of BSA by electronic absorption and fluorometric titrations indicate that complex (1b) revealed the best binding efficacy as compared to complex (2b) and free ligand. Interestingly, all compounds are found to interact with BSA through a static approach, as further attested by FRET detection. The DFT and molecular docking calculations were also performed to realize the electronic structure, reactivity, and binding capability of all test samples with CT-DNA, BSA, and the SARS-CoV-2 3CL^Pro, which revealed the binding energies were in a range of -8.1 to -8.9, -7.5 to -10.5 and -6.7--8.8 kcal/mol, respectively. The higher reactivity of the complexes than the free ligand is supported by the FMO theory. Among all the observed data for antioxidant properties against DPPH^᛫, ^᛫OH, O₂^-• and NO^᛫ free radicals, complex (1a) had the best biological efficacy. The antimicrobial and cytotoxic characteristics of all test compounds have been studied by screening against certain selected microorganisms as well as against A549, HepG2, MCF-7, and NHDF cell lines, respectively. The observed findings revealed that the activity enhances coordination as compared to free ligand via Overtone's and Tweedy's chelation mechanisms. This is especially encouraging given that in every case, the experimental findings and theoretical detections were in perfect accord.

Comprehensive Assessment of Biomolecular Interactions of Morpholine-Based Mixed Ligand Cu(II) and Zn(II) Complexes of 2,2'-Bipyridine as Potential Anticancer and SARS-CoV-2 Agents: A Synergistic Experimental and Structure-Based Virtual Screening

A new class of pharmacologically active mixed-ligand complexes (1a-2a) [M^II(L)₂ (bpy)], where L = 2-(4-morpholinobenzylideneamino)phenol), bpy = 2,2'-bipyridine, M^II = Cu (1a), and Zn (2a), were assigned an octahedral geometry by analytical and spectral measurements. Gel electrophoresis showed that complex (1a) demonstrated the complete DNA cleavage mediated by H₂O₂. The overall DNA-binding constants observed from UV-vis, fluorometric, hydrodynamic, and electrochemical titrations were in the following sequence: (1a) > (2a) > (HL), which suggests that the complexes might intercalate DNA, a possibility that is further supported by the biothermodynamic characteristics. The binding constant results of BSA by electronic absorption and fluorometric titration demonstrate that complex (1a) exhibits the highest binding effectiveness among others, which means that all compounds could interact with BSA through a static approach, additionally supported by FRET measurements. Density FunctionalTheory (DFT) and molecular docking calculations were relied on to unveil the electronic structure, reactivity, and interacting capability of all substances with DNA, BSA, and SARS-CoV-2 main protease (Mpro). These observed binding energies fell within the following ranges: -7.7 to -8.6, -7.2 to -10.2, and -6.7 to -8.2 kcal/mol, respectively. The higher reactivity of the complexes compared to free ligand is supported by the Frontier MolecularOrbital (FMO) theory. The in vitro antibacterial, cytotoxic, and radical scavenging characteristics revealed that complex (1a) has the best biological efficacy compared to others. This is encouraged because all experimental findings are closely correlated with the theoretical measurements.

Antimicrobial Agents Based on Metal Complexes: Present Situation and Future Prospects

The rise in antimicrobial resistance is a cause of serious concern since the ages. Therefore, a dire need to explore new antimicrobial entities that can combat against the increasing threat of antibiotic resistance is realized. Studies have shown that the activity of the strongest antibiotics has reduced drastically against many microbes such as microfungi and bacteria (Gram-positive and Gram-negative). A ray of hope, however, was witnessed in early 1940s with the development of new drug discovery and use of metal complexes as antibiotics. Many new metal-based drugs were developed from the metal complexes which are potentially active against a number of ailments such as cancer, malaria, and neurodegenerative diseases. Therefore, this review is an attempt to describe the present scenario and future development of metal complexes as antibiotics against wide array of microbes.

Spectro-electrochemical, fluorometric and biothermodynamic evaluation of pharmacologically active morpholine scaffold single crystal ligand and its metal(II) complexes: A comparative study on in-vitro and in-silico screening towards DNA/BSA/SARS-CoV-19

A novel series of metal(II) complexes (1-5) [M^II(L)₂]{Where M = Cu (1), Co (2), Mn (3), Ni (4) and Zn (5)} constructed from 2-(4-morpholinobenzylideneamino)phenol Schiff base ligand (HL) in a 1:2 M ratio and the spectral and analytical results put forward square planar geometry. Spectro-electrochemical, hydrodynamic, gel electrophoresis, and DNA binding/cleavage results for all the compounds demonstrate that complex (1) had excellent DNA binding/cleavage properties compared to other compounds. The observation also suggests that test compounds could intercalate with DNA, and the biothermodynamic property more strongly supports the stabilizing of the double helix DNA with the complexes. BSA binding constant results show that complex (1) exposes the best binding property via a static mode, which is further confirmed by FRET calculations. The DFT calculations and docking results for all compounds towards DNA, BSA and SARS-CoV-19 main protease (3CLPro), reveal the binding energies were in the range of -7.8 to -9.4, -6.6 to -10.2 and - 6.1 - -8.2 kcal/mol for all test compounds respectively. In this case, complexes showed favorable binding energies compared to free ligand, which stimulates further studies aimed at validating the predicted activity as well as contributing to tackling the current and future viral pandemics. The in-vitro antioxidant, antimicrobial, and anticancer results for all compounds revealed that copper complex (1) has better activity compared to others. This might result in an effective anticancer drug for future research, which is especially promising since the observed experimental results for all cases were in close agreement with the theoretical calculations.

Mixed-ligand complexes of copper(ii) with thienoyltrifluoroacetonate and nitrogen containing ligands: synthesis, structures, antimicrobial activity, cytotoxicity, Hirshfeld surface analysis and DFT studies

Mixed-ligand complexes of copper(ii) with thienoyltrifluoroacetonate (TTA-H), 2,2'-bipyridine (bipy), 1,10-phenanthroline (phen), and tetramethylethylenediamine (tmen), associated with counter ions such as Cl-, and NO3 - have been synthesized and characterized by molar conductance measurements, elemental analysis, mass spectrometry, IR and UV-Vis spectroscopy, antimicrobial activity, cytotoxicity assay studies, and single-crystal X-ray diffraction. The UV-Vis spectra and crystal structures are consistent with the adoption of square pyramidal geometry for all of the complexes except [Cu(TTA)tmen]NO3 and [Cu(TTA)2tmen] which have square planar and octahedral geometries, respectively. Conductance measurements of the mixed-ligand complexes indicated that they were all non-electrolytes, with the ligands and anions being coordinated to Cu except [Cu(TTA)tmen]NO3 which is a 1 : 1 electrolyte. All of the complexes were moderately active on all the fungi tested (Candida albicans, Aspergillus niger, Penicillium notatum, Rhizopus stolonifer) except [Cu(TTA)bipyCl] which showed increased activity in Candida albicans and Aspergillus niger. All of the compounds tested showed LC50 values greater than 100 with [Cu(TTA)(phen)NO3] being the least toxic of the compounds. Molecular geometries of the complexes were optimized at the PBE1PBE/def2SVP and PBE1PBE/6-311g(d,p) level of theory and the results were compared with the single-crystal X-ray diffraction data. Electronic properties such as HOMO, LUMO, HOMO-LUMO gaps and global reactivity descriptors are reported at the PBE1PBE/6-311g(d,p) level of theory. Hirshfeld surface analysis was carried out to investigate the cooperative non-covalent supramolecular interactions within the various complexes.

Synthesis, Molecular Modeling Study, and Quantum-Chemical-Based Investigations of Isoindoline-1,3-diones as Antimycobacterial Agents

The condensation of phthalic anhydride afforded structurally modified isoindoline-1,3-dione derivatives with selected amino-containing compounds. The title compounds (2-30) have been characterized by thin-layer chromatography (TLC), infrared spectroscopy, ¹H and ¹³C NMR spectroscopy, and mass spectroscopy. All of the compounds were assessed for their antimycobacterial activity toward the H37Rv strain by a dual read-out assay method. Among the synthesized compounds, compound 27 possessed a significant IC₅₀ of 18 μM, making it the most potent compound of the series. The InhA inhibitory (IC₅₀) activity of compound 27 was 8.65 μM in comparison to Triclosan (1.32 μM). Computational studies like density functional theory (DFT) study, molecular docking, and dynamic simulation studies illustrated the reactivity and stability of the synthesized compounds as InhA inhibitors. A quantum-mechanics-based DFT study was carried out to investigate the molecular and electronic properties, reactivities, and nature of bonding present in the synthesized compounds and theoretical vibrational (IR) and isotropic value (¹H and ¹³C NMR) calculations.

Copper(ii) salen-based complexes as potential anticancer agents

The systematic design and synthesis of four Cu(ii) salen compounds and their potential as excellent anticancer agents is discussed using biological studies.

Antibacterial and molecular docking studies of newly synthesized nucleosides and Schiff bases derived from sulfadimidines

A new series of nucleosides, moieties, and Schiff bases were synthesized from sulfadimidine. Infrared (IR), ¹HNMR, ¹³C NMR, and mass spectrometry techniques and elemental analysis were employed to elucidate the synthesized compounds. The prepared analogues were purified by different chromatographic techniques (preparative TLC and column chromatography). Molecular docking studies of synthesized compounds 3a, 4b, 6a, and 6e demonstrated the binding mode involved in the active site of DNA gyrase. Finally, all synthesized compounds were tested against selected bacterial strains. The most effective synthesized compounds against S. aureus were 3a, 4d, 4b, 3b, 3c, 4c, and 6f, which exhibited inhibition zones of inhibition of 24.33 ± 1.528, 24.67 ± 0.577, 23.67 ± 0.577, 22.33 ± 1.528, 18.67 ± 1.528 and 19.33 ± 0.577, respectively. Notably, the smallest zones were observed for 4a, 6d, 6e and 6g (6.33 ± 1.528, 11.33 ± 1.528, 11.67 ± 1.528 and 14.66 ± 1.155, respectively). Finally, 6b and 6c gave negative zone values. K. pneumoniae was treated with the same compounds and the following results were obtained. The most effective compounds were 4d, 4c, 4b and 3c, which showed inhibition zones of 29.67 ± 1.528, 24.67 ± 0.577, 23.67 ± 1.155 and 19.33 ± 1.528, respectively, followed by 4a and 3d (15.33 ± 1.528 for both), while moderate results (13.67 ± 1.155 and 11.33 ± 1.528) were obtained for 6f and 6g, respectively. Finally, 6a, 6b, 6c, 3a, and 3b did not show any inhibition. The most effective compounds observed for the treatment of E. coli were 4d, 4b, 4c, 3d, 6e and 6f (inhibition zones of 26.33 ± 0.577, 21.67 ± 1.528, 21.67 ± 1.528, 19.67 ± 1.528, 17.67 ± 1.155 and 16.67 ± 1.155, respectively). Compounds 3b, 3c, 6a, 6c, and 6g gave moderate results (13.67 ± 1.528, 12.67 ± 1.528, 11.33 ± 0.577, 15.33 ± 1.528 and 12.67 ± 1.528, respectively), while 6b showed no effect. The MIC values against S. aureus ranged from 50 to 3.125 mg, while those against E. coli and K. pneumoniae ranged from 50 to 1562 mg. In vitro, the antibacterial effects were promising. Further research is required to study the in vivo antibacterial effects of these compounds and determine therapeutic doses.

New Antimicrobial Strategies Based on Metal Complexes

Traditional organic antimicrobials mainly act on specific biochemical processes such as replication, transcription and translation. However, the emergence and wide spread of microbial resistance is a growing threat for human beings. Therefore, it is highly necessary to design strategies for the development of new drugs in order to target multiple cellular processes that should improve their efficiency against several microorganisms, including bacteria, viruses or fungi. The present review is focused on recent advances and findings of new antimicrobial strategies based on metal complexes. Recent studies indicate that some metal ions cause different types of damages to microbial cells as a result of membrane degradation, protein dysfunction and oxidative stress. These unique modes of action, combined with the wide range of three-dimensional geometries that metal complexes can adopt, make them suitable for the development of new antimicrobial drugs.

Macrocyclic Schiff base complexes as potent antimicrobial agents: Synthesis, characterization and biological studies

A series of Cu^II, Co^II, Zn^II and Ni^II, complexes of 3⁴,7⁴-dimethyl-1²,1⁵,5²,5⁵-tetrahydro-2,4,6,8-tetraaza-1,5(2,5)-difurana-3,7(1,2)-dibenzenacyclooctaphane based ligand have been synthesized by template methodology. Characterization of the synthesized complexes has been carried out with the help of various physicochemical and spectroscopic techniques like Infra-Red, ESI-MS, ESR, UV-visible, CHN (elemental analyses), molar conductance, magnetic moment and NMR. Antimicrobial efficacy of the newly designed macrocyclic complexes has performed by the assistance of agar well diffusion method. In-vitro hemolytic and DNA binding studies were also performed in order to analyze or interpret the mode and binding efficiencies as well as the % hemolysis exhibited by the complexes. DFT/TD-DFT studies were carried out in order to elucidate the better insight into the structural parameters. Energy minimization and quantum chemical parameters were calculated using Gaussian09W program.

Spectro-electrochemical assessments of DNA/BSA interactions, cytotoxicity, radical scavenging and pharmacological implications of biosensitive and biologically active morpholine-based metal(ii) complexes: a combined experimental and computational investigation

Biosensitive and biologically active morpholine-based transition metal(ii) complexes (1-5) were constructed as [MII(L) AcO]·nH2O {where M = Cu (1) n = 1; Co (2), Mn (3), Ni (4), n = 4 and Zn (5) n = 2}, which were synthesized from 2-(-(2-morpholinoethylimino) methyl)-4-bromophenol ligand (HL) and structurally characterized by various analytical and spectroscopic techniques, which proposed a square planar and tetrahedral geometry around the central metal ion with lattice water molecules. The gel electrophoresis results revealed that complexes 1 and 5 had more potent DNA cleavage efficacy in the presence of an oxidizing agent (H2O2) as compared to the others. The observed DNA binding results for all the compounds as determined by spectro-electrochemical and hydrodynamic techniques were in the order 3.36 (1) > 3.06 (2) > 2.73 (4) > 2.61 (5) > 1.84 (3) > 1.00 (HL) × 104 M-1. The obtained bovine serum albumin (BSA) protein binding constant (K b) results put forward the following order 2.38 (1) > 2.21 (2) > 2.18 (5) > 1.76 (4) > 1.40 (3) > 1.26 (HL) × 104 M-1. Also, the biothermodynamic parameters (, , ΔH° and ΔS°) and binding results divulged that all the complexes (1-5) could bind to DNA via intercalation in a spontaneous manner. Density functional theory calculations were employed to optimize the structure of ligand (HL) and its complexes (1-5) to gain insights into their electronic structures. Molecular docking analysis was carried out to identify the preferential binding modes of these complexes toward DNA and BSA protein. The theoretical observations of all cases were found to be very close to the experimental observations. Among the radical scavenging activity results for all the cases toward DPPH, hydroxyl radical, superoxide, nitric oxide and ferric reducing agents, complex (1) revealed a superior scavenging potency over the other compounds. In the screened antimicrobial reports against 10 different selected pathogenic species, although all the complexes (1-5) exhibited a greater significant inhibitory effect than the free ligand, complexes 4 and 5 achieved the best potency over standard drugs. The observed percentage of growth inhibition for all the compounds against the A549, HepG2, MCF-7 and NHDF cell lines suggested that complex 1 had enhanced growth-inhibitory potency over the other compounds and slightly affected normal cells as compared to the standard drug cisplatin, which may lead to its investigation as a promising anticancer agent in future research.

Synthesis, theoretical, spectroscopic and electrochemical DNA binding investigations of 1, 3, 4-thiadiazole derivatives of ibuprofen and ciprofloxacin: Cancer cell line studies

Two new 1,3,4-thiadiazole derivatives of ibuprofen and ciprofloxacin namely {(5-(1-(4-isobutylphenyl)ethyl)-1,3,4-thiadiazol-2-amine)} 1 and {(3-(5-amino-1,3,4-thiadiazol-2-yl)-1-cyclopropyl-6-fluoro-7-(piperazin-1-yl)quinolin-4(1H)-one)} 2 were synthesized and characterized by spectroscopic and elemental analysis. DFT and molecular docking were done initially for theoretical binding possibilities of the investigated compounds. In vitro DNA binding investigations were carried out with UV-visible spectroscopic, fluorescence spectroscopic, cyclic voltammetric (CV) experiments under physiological conditions of the stomach (4.7) and blood (7.4) pH and at normal body temperature (37 °C). Both theoretical and experimental results suggested spontaneous and significant intercalative binding of the compounds with DNA. Kinetic and thermodynamic parameters (K_b, ΔG) were evaluated greater for compound 2 which showed comparatively more binding and more spontaneity of 2 than 1 to bind with DNA at both pH values. Binding site sizes were found greater (n > 1) and revealed the possibility of other sites for interactions along with intercalation. Overall results for DNA binding were found more significant for 2 at Stomach (4.7) pH. Viscometric studies further verified intercalation as a prominent binding mode for both compounds. IC₅₀ values obtained from human hepatocellular carcinoma (Huh-7) cell line studies revealed 2 as potent anticancer agent than 1 as value found 25.75 μM (lesser than 50 μM). Theoretical and experimental DNA binding studies showed good correlation with cancer cell (Huh-7) line activity of 1 and 2 and further suggested that these compounds could act as potential anti-cancer drug candidates.