Synthesis and characterization of sulfonamide metal complexes as antimicrobial agents

Current development of 1,2,3-triazole derived potential antimalarial scaffolds: Structure- activity relationship (SAR) and bioactive compounds

Malaria is among one of the most devastating and deadliest parasitic disease in the world claiming millions of lives every year around the globe. It is a mosquito-borne infectious disease caused by various species of the parasitic protozoan of the genus Plasmodium. The indiscriminate exploitation of the clinically used antimalarial drugs led to the development of various drug-resistant and multidrug-resistant strains of plasmodium which severely reduces the therapeutic effectiveness of most frontline medicines. Therefore, there is urgent need to develop novel structural classes of antimalarial agents acting with unique mechanism of action(s). In this context, design and development of hybrid molecules containing pharmacophoric features of different lead molecules in a single entity represents a unique strategy for the development of next-generation antimalarial drugs. Research efforts by the scientific community over the past few years has led to the identification and development of several heterocyclic small molecules as antimalarial agents with high potency, less toxicity and desired efficacy. Triazole derivatives have become indispensable units in the medicinal chemistry due to their diverse spectrum of biological profiles and many triazole based hybrids and conjugates have demonstrated potential in vitro and in vivo antimalarial activities. The manuscript compiled recent developments in the medicinal chemistry of triazole based small heterocyclic molecules as antimalarial agents and discusses various reported biologically active compounds to lay the groundwork for the rationale design and discovery of triazole based antimalarial compounds. The article emphasised on biological activities, structure activity relationships, and molecular docking studies of various triazole based hybrids with heterocycles such as quinoline, artemisinins, naphthyl, naphthoquinone, etc. as potential antimalarial agents which could act on the dual stage and multi stage of the parasitic life cycle.

New Copper Complexes with Antibacterial and Cytotoxic Activity

The discovery of a new non-toxic metal complex with biological activity represents a very active area of research. Two Cu+2 complexes, [Cu4(L1)4(OH)4(DMF)2(H2O)] (C1) (HL1 = N-(5-ethyl-[1,3,4]-thiadiazole-2-yl)-benzenesulfonamide) and [Cu(L2)2(phen)(H2O)] (C2) (HL2 = N-(5-(4-methylphenyl)-[1,3,4]-thiadiazole-2-yl)-naphtalenesulfonamide), with two new ligands were synthesized. The X-ray crystal structures of the complexes were determined. In both complexes, Cu+2 is five-coordinated, forming a CuN2O3 and CuN4O chromophore, respectively. The ligands act as monodentate, coordinating the metal ion through a single Nthiadiazole atom; for the two complexes, the molecules from the reaction medium (phenantroline, dimethylformamide and water) are also involved in the coordination of Cu+2. The complexes have a distorted square pyramidal square-planar geometry. The compounds were characterized by FT-IR and UV-Vis spectroscopy. Using the microdilution method, the antibacterial activity of the complexes was determined against four Gram-positive and two Gram-negative bacteria, with Gentamicin as the positive control. Cytotoxicity studies were carried out on two tumor cell lines (HeLa, DLD-1) and on a normal cell line (HFL1) using the MTT method and Cisplatin as a positive control. Flow cytometric assessment of apoptosis induced by the complexes on the three cell lines was also performed. Both complexes present in vitro biological activities but complex C2 is more active.

Structural and theoretical study of π-stacking interactions in new complexes based on CuCl2 and 3-sulfonamide-substituted imidazo[2,1-b]thiazoles

CONTEXT

At present, sulfonamides and their metal complexes have received a new impetus for development. Of particular interest is the study of molecular and crystal structures, which takes into account weak non-valent interactions. Despite the low energy of such interactions, in many cases, they act collectively, and the sum of their actions can play a significant role. As a result, the spectrum of medical and biological activity of new metal complexes is expanded. In this regard, the synthesis and study of the molecular and crystal structure of sulfonamides and their metal complexes is of undoubted relevance. In this work, we studied non-valent intra- and intermolecular interactions in ligands of sulfonamide-substituted imidazo[2,1-b]thiazoles and their previously unknown complexes with CuCl₂. The performed analysis of the data obtained by X-ray diffraction analysis made it possible to establish the intramolecular π-stacking interaction in imidazothiazole ligands, which is retained in their complexes with CuCl₂. Within the framework of QTAIM topological analysis of electron density and DORI analysis, stereoelectronic and topological structures were studied. In the complexes, tetral, chalcogen, and pnycogen new interligand non-valent interactions were established. The energies of all established types of non-valent interactions have been calculated, and their comparative evaluation has been made.

METHODS

X-ray data of new arylsulfonylamino-substituted derivatives of imidazo[2,1-b]thiazoles and their metal complexes with CuCl₂ have been studied. To determine the theoretical prerequisites for the occurrence of π-stacking in the molecules under study, the QTAIM method was used in the framework of the DFT/B3LYP/6-311 + G(d) calculation using the GAUSSIAN 09 program. In addition, the DORI electron density region overlap indicator and the Multiwfn program were used to analyze non-valent interactions.

A new complex of silver(I) with probenecid: Synthesis, characterization, and studies of antibacterial and extended spectrum β-lactamases (ESBL) inhibition activities

This article describes the in vitro antibacterial and β-lactamase inhibition of a novel silver(I) complex with the sulfonamide probenecid (Ag-PROB). The formula Ag₂C₂₆H₃₆N2O₈S₂·2H₂O for the Ag-PROB complex was proposed based on elemental analysis. High-resolution mass spectrometric studies revealed the existence of the complex in its dimeric form. Infrared, nuclear magnetic resonance spectroscopies and Density Functional Theory calculations indicated a bidentate coordination of probenecid to the silver ions by the oxygen atoms of the carboxylate. In vitro antibacterial activities of Ag-PROB showed significant growth inhibitory activity over Mycobacterium tuberculosis, S. aureus, and P. aeruginosa PA01biofilm-producers, B. cereus, and E. coli. The Ag-PROB complex was active over multi-drug resistant of uropathogenic E. coli extended spectrum β-lactamases (ESBL) producing (EC958 and BR43), enterohemorrhagic E. coli (O157:H7) and enteroaggregative E. coli (O104:H4). Ag-PROB was able to inhibit CTX-M-15 and TEM-1B ESBL classes, at concentrations below the minimum inhibitory concentration for Ag-PROB, in the presence of ampicillin (AMP) concentration in which EC958 and BR43 bacteria were resistant in the absence of Ag-PROB. These results indicate that, in addition to ESBL inhibition, there is a synergistic antibacterial effect between AMP and the Ag-PROB. Molecular docking results revealed potential key residues involved in interactions between Ag-PROB, CTX-M-15 and TEM1B, suggesting the molecular mechanism of the ESBL inhibition. The obtained results added to the absence of mutagenic activity and low cytotoxic activity over non-tumor cell of the Ag-PROB complex open a new perspective for future in vivo tests demonstrating its potential of use as an antibacterial agent.

Hydroxytriazenes incorporating sulphonamide derivatives: evaluation of antidiabetic, antioxidant, anti-inflammatory activities, and computational study

The existent investigation deals with synthesis, characterization, computational analysis, and biological activities of some hydroxytriazene derivatives containing sulphonamide moiety. The compounds were screened for antidiabetic, antioxidant, and anti-inflammatory activities. The antidiabetic activity was assessed using α-glucosidase and α-amylase inhibition assays with IC₅₀ values ranging from 32.0 to 759.13 μg/mL and 157.77 to 340.47 μg/mL while standard drug acarbose showed IC₅₀ values 12.21 and 69.74 μg/mL, respectively. The antioxidant activity was evaluated using DPPH and ABTS radical scavenging assays with IC₅₀ value ranging from 54.01 to 912.66 μg/mL and 33.22 to 128.11 μg/mL, and standard drug ascorbic acid showed IC₅₀ values 29.12 μg/mL and 69.13 μg/mL, respectively. Anti-inflammatory activity was investigated using the carrageenan-induced paw edema method, where percentage inhibition was up to 93.0 and 98.57 for 2 h and 4 h, respectively, and all the compounds were found to exhibit excellent anti-inflammatory activity. Moreover, prediction of activity spectra for substance and molecular docking were also performed. The PASS prediction hypothesized the potential of the compounds for anti-inflammatory activity, and docking results suggested the best binding pose for compounds 1b and 2b with the least energy value from which compounds can be considered as potent COX-2 inhibitors. Furthermore, possible interactions between hydroxytriazene analogues and the targets of antioxidant NADPH oxidase and antidiabetic human maltase-glucoamylase enzyme have been identified. The HOMO and LUMO analysis revealed charge transfer within the compounds. These findings suggested that the synthesized compounds can be potential agents for the treatment of diabetes and inflammation.

Degradation of the Selected Antibiotic in an Aqueous Solution by the Fenton Process: Kinetics, Products and Ecotoxicity

Sulfonamides used in veterinary medicine can be degraded via the Fenton processes. In the premise, the process should also remove the antimicrobial activity of wastewater containing antibiotics. The kinetics of sulfathiazole degradation and identification of the degradation products were investigated in the experiments. In addition, their toxicity against Vibrio fischeri, the MARA^® assay, and unselected microorganisms from a wastewater treatment plant and the river was evaluated. It was found that in the Fenton process, the sulfathiazole degradation was described by the following kinetic equation: r₀ = k C_STZ^{-1 or 0} C_Fe(II)³ C_H2O2^{0 or 1} C_TOC^-2, where r₀ is the initial reaction rate, k is the reaction rate constant, C is the concentration of sulfathiazole, Fe(II) ions, hydrogen peroxide and total organic carbon, respectively. The reaction efficiency and the useful pH range (up to pH 5) could be increased by UVa irradiation of the reaction mixture. Eighteen organic degradation products of sulfathiazole were detected and identified, and a possible degradation mechanism was proposed. An increase in the H₂O₂ dose, to obtain a high degree of mineralization of sulfonamide, resulted in an increase in the ecotoxicity of the post-reaction mixture.

Synthesis, DFT, Biological and Molecular Docking Analysis of Novel Manganese(II), Iron(III), Cobalt(II), Nickel(II), and Copper(II) Chelate Complexes Ligated by 1-(4-Nitrophenylazo)-2-naphthol

Novelmanganese(II), iron(III), cobalt(II), nickel(II), and copper(II) chelates were synthesized and studied using elemental analysis (EA), infrared spectroscopy, mass spectrometry, ultraviolet-visible spectroscopy, and conductivity, as well as magnetic measurements and thermogravimetric analysis (TG). The azo-ligand 1-[(4-nitrophenyl)diazenyl]-2-naphthol (HL) chelates to the metal ions via the nitrogen and oxygen centers of the azo group and the hydroxyl, respectively. The amounts of H₂O present and its precise position were identified by thermal analysis. Density functional theory (DFT) was employed to theoretically elucidate the molecular structures of the ligand and the metal complexes. Furthermore, the quantum chemical parameters were also evaluated. The antimicrobial properties were evaluated against a group of fungal and bacterial microbes. Interestingly, the bioactivity of the complexes is enhanced compared to free ligands. Within this context, the CuL complex manifested the lowest activity, whereas the FeL complex had the greatest. Molecular docking was used to foretell the drugs' binding affinity for the structure of Escherichia coli (PDB ID: 1hnj). Protein-substrate interactions were resolved, and binding energies were accordingly calculated.

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.

Probing the Effect and Mechanism of Flue Gas on the Performance of Resorcinol/Hexamethylenetetramine-Based Polymer Gel in Flue Gas Flooding Reservoir

Polymer gel plugging is an effective method for gas mobility control in flue gas flooding reservoirs. However, the effect and mechanism of flue gas on the performance of polymer gels have rarely been reported. In this study, a polymer gel was prepared by cross-linking hydrolyzed polyacrylamide (HPAM) and resorcinol/ hexamethylenetetramine (HMTA) to illuminate the influencing mechanism of flue gas composition on gel. The gel rheological testing results showed that flue gas promoted gelation performance, whereas it seriously threatened gel long-term stability, especially at high pressure conditions. The influence of CO₂ on the polymer gel had the characteristic of multiplicity. The hydrodynamic radius (R_h) and the initial viscosity of HPAM solution decreased in the presence of CO₂. Nonetheless, the dissolved CO₂ expedited the decomposition rate of HMTA into formaldehyde, which promoted the cross-linking process of the HPAM, leading to a shorter gelation time. Oxidation-reduction potential (ORP) tests and Fourier transform infrared spectroscopy (FTIR) analysis indicated that O₂ played a leading role in the oxidative degradation of HPAM compared to CO₂ and threatened the gel long-term stability at elevated gas pressures. To address the adverse effects caused by flue gas, it is highly desirable to develop polymer gels by adding oxygen scavengers or strengthening additives.

Pincer Complexes Derived from Tridentate Schiff Bases for Their Use as Antimicrobial Metallopharmaceuticals

Within the current challenges in medicinal chemistry, the development of new and better therapeutic agents effective against infectious diseases produced by bacteria, fungi, viruses, and parasites stands out. With chemotherapy as one of the main strategies against these diseases focusing on the administration of organic and inorganic drugs, the latter is generally based on the synergistic effect produced by the formation of metal complexes with biologically active organic compounds. In this sense, Schiff bases (SBs) represent and ideal ligand scaffold since they have demonstrated a broad spectrum of antitumor, antiviral, antimicrobial, and anti-inflammatory activities, among others. In addition, SBs are synthesized in an easy manner from one-step condensation reactions, being thus suitable for facile structural modifications, having the imine group as a coordination point found in most of their metal complexes, and promoting chelation when other donor atoms are three, four, or five bonds apart. However, despite the wide variety of metal complexes found in the literature using this type of ligands, only a handful of them include on their structures tridentate SBs ligands and their biological evaluation has been explored. Hence, this review summarizes the most important antimicrobial activity results reported this far for pincer-type complexes (main group and d-block) derived from SBs tridentate ligands.

QuEChERS-based analysis and ecotoxicological risk of select antibiotics in dumpsite leachates, hospital wastewater and effluent receiving water in Ibadan, Nigeria

There is currently a dearth of information on the determination, occurrence and ecotoxicological risk of antibiotics in dumpsite leachates and hospital wastewater in Africa. A quick, easy, cheap, effective, rugged and safe (QuEChERS) protocol which combines extraction and clean-up in one step was optimized for the determination of antibiotics sulfadoxine, sulfamethazine and trimethoprim in dumpsite leachates and hospital wastewater. The occurrence and ecotoxicological risk of target antibiotics were investigated in wastewater from two hospitals, effluent receiving water and leachates from three dumpsites in Ibadan, Nigeria. Recoveries in hospital wastewater ranged from 53 to 116% while recoveries ranged from 50 to 89% in leachates. Method limits of quantification ranged from 0.7 to 12.1 µg L^-1 in hospital wastewater and from 6.2 to 38.8 µg L^-1 in leachates. Intra-day precisions (% RSD) were ≤ 21%. High concentrations of target antibiotics were measured: up to 475 µg L^-1 for sulfamethazine in leachates, 118 µg L^-1 for trimethoprim in hospital wastewater and 117 µg L^-1 for sulfadoxine in effluent receiving water. Sulfadoxine presented high risk to algae, daphnid and fish in hospital wastewater, effluent receiving water and leachates. This work highlights the need for adequate and sound management of wastes containing pharmaceuticals in Nigeria.

Intracellular Bacterial Targeting by a Thiazolyl Benzenesulfonamide and Octaarginine Peptide Complex

A brominated thiazolyl benzenesulfonamide (BTB) derivative is conjugated with the cell-penetrating peptide octaarginine (R8) in an effort to construct innovative antibacterial products. The noncovalent complex of BTB and R8 is characterized by Fourier transform infrared (FTIR) spectroscopy, which indicates hydrogen bonding between the two constituents. Attachment of the peptide moiety renders aqueous solubility to the hydrophobic benzenesulfonamide drug and bestows bactericidal activity. Confocal imaging in conjunction with dye probes shows successful clearance of intracellular Staphylococcus aureus bacteria by the BTB-R8 complex. Scanning electron micrographs and studies with a set of fluorescent dyes suggest active disruption of the bacterial cell membrane by the BTB-R8 complex. In contrast, the complex of BTB with octalysine (K8) fails to cause membrane damage and displays a modest antibacterial effect. A complex of BTB with the water-soluble hydrophilic polymer poly(vinylpyrrolidone) (PVP) does not display any antibacterial effect, indicating the distinctive role of the cell-penetrating peptide (CPP) R8 in the cognate complex. The leakage of the encapsulated dye from giant unilamellar vesicles upon interaction with the BTB-R8 complex further highlights the membrane activity of the complex, which cannot be accomplished by bare sulfonamide alone. This work broadens the scope of use of CPPs with respect to eliciting antibacterial activity and potentially expands the limited arsenal of membrane-targeting antibiotics.

Ligation Motifs in Zinc-Bound Sulfonamide Drugs Assayed by IR Ion Spectroscopy

The sulfonamide–zinc ion interaction, performing a key role in various biological contexts, is the focus of the present study, with the aim of elucidating ligation motifs in zinc complexes of sulfa drugs, namely sulfadiazine (SDZ) and sulfathiazole (STZ), in a perturbation-free environment. To this end, an approach is exploited based on mass spectrometry coupled with infrared multiple photon dissociation (IRMPD) spectroscopy backed by quantum chemical calculations. IR spectra of Zn(H2O+SDZ−H)+ and Zn(H2O+STZ−H)+ ions are consistent with a three-coordinate zinc complex, where ZnOH+ binds to the uncharged sulfonamide via N(heterocycle) and O(sulfonyl) donor atoms. Alternative prototropic isomers Zn(OH2)(SDZ−H)+ and Zn(OH2)(STZ−H)+ lie 63 and 26 kJ mol−1 higher in free energy, respectively, relative to the ground state Zn(OH)(SDZ)+ and Zn(OH)(STZ)+ species and do not contribute to any significant extent in the sampled population.

Amalgamation and Scrutinizing of Leucine Derivatives Schiff bases Complexes as Antimicrobial Agent

The enhanced applications of Schiff bases metal complexes of amino acid derivatives have captured the attention of researchers for the synthesis of leucine derivatives of Schiff bases metal complexes. Amino acids are considered to be essential part of food supplements as well as derivatives of Schiff bases in coordination chemistry due to their donor ability. The leucine derivatives Schiff bases ligand have been synthesized by condensation reaction between amine of leucine with aldehyde or ketone bearing molecules attached with them. These complexes were characterized by different spectroscopic tools in order to confirm their structural geometries. The structural geometries are considered to be very important in order to improve the antimicrobial potential of leucine derivative metal complexes. By taking into account the antimicrobial potential of titled compounds, a comprehensive review of leucine derivatives of Schiff bases metal complexes has been compiled.

A New Mechanism of the Selective Photodegradation of Antibiotics in the Catalytic System Containing TiO2 and the Inorganic Cations

The mechanism of sulfisoxazole (SFF) selective removal by photocatalysis in the presence of titanium (IV) oxide (TiO2) and iron (III) chloride (FeCl3) was explained and the kinetics and degradation pathways of SFF and other antibiotics were compared. The effects of selected inorganic ions, oxygen conditions, pH, sorption processes and formation of coordination compounds on the photocatalytic process in the presence of TiO2 were also determined. The Fe3+ compounds added to the irradiated sulfonamide (SN) solution underwent surface sorption on TiO2 particles and act as acceptors of excited electrons. Most likely, the SFF degradation is also intensified by organic radicals or cation organic radicals. These radicals can be initially generated by reaction with electron holes, hydroxyl radicals and as a result of electron transfer mediated by iron ions and then participate in propagation processes. The high sensitivity of SFF to decomposition caused by organic radicals is associated with the steric effect and the high bond polarity of the amide substituent.

Bioactive Co(II), Ni(II), and Cu(II) Complexes Containing a Tridentate Sulfathiazole-Based (ONN) Schiff Base

New Co(II), Ni(II), and Cu(II) complexes were synthesized with the Schiff base ligand obtained by the condensation of sulfathiazole with salicylaldehyde. Their characterization was performed by elemental analysis, molar conductance, spectroscopic techniques (IR, diffuse reflectance and UV–Vis–NIR), magnetic moments, thermal analysis, and calorimetry (thermogravimetry/derivative thermogravimetry/differential scanning calorimetry), while their morphological and crystal systems were explained on the basis of powder X-ray diffraction results. The IR data indicated that the Schiff base ligand is tridentate coordinated to the metallic ion with two N atoms from azomethine group and thiazole ring and one O atom from phenolic group. The composition of the complexes was found to be of the [ML₂]∙nH₂O (M = Co, n = 1.5 (1); M = Ni, n = 1 (2); M = Cu, n = 4.5 (3)) type, having an octahedral geometry for the Co(II) and Ni(II) complexes and a tetragonally distorted octahedral geometry for the Cu(II) complex. The presence of lattice water molecules was confirmed by thermal analysis. XRD analysis evidenced the polycrystalline nature of the powders, with a monoclinic structure. The unit cell volume of the complexes was found to increase in the order of (2) < (1) < (3). SEM evidenced hard agglomerates with micrometric-range sizes for all the investigated samples (ligand and complexes). EDS analysis showed that the N:S and N:M atomic ratios were close to the theoretical ones (1.5 and 6.0, respectively). The geometric and electronic structures of the Schiff base ligand 4-((2-hydroxybenzylidene) amino)-N-(thiazol-2-yl) benzenesulfonamide (HL) was computationally investigated by the density functional theory (DFT) method. The predictive molecular properties of the chemical reactivity of the HL and Cu(II) complex were determined by a DFT calculation. The Schiff base and its metal complexes were tested against some bacterial strains (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis). The results indicated that the antibacterial activity of all metal complexes is better than that of the Schiff base.

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.

A water-soluble bithiophene with increased photoluminescence efficiency and metal recognition ability

A new water-soluble tri-tert-butyl-bithiophenesulfonamide (α2-tbS) was synthesized and a comprehensive spectroscopic and photophysical study was undertaken in organic solvents and water at different pH values. In contrast to the behaviour found for the parent (and un-substituted) α,α'-bithiophene (α2), in which radiationless decay processes are the main excited-state deactivation channels, the tert-butylsulfonamide derivative presents a significant fluorescence quantum yield (φF) (ca. one order of magnitude higher than that of α2). The high φF allowed further exploring α2-tbS as a selective fluorimetric sensor for metal ions. A strong selectivity towards Cu(ii) is observed at neutral pH values, whereas at pH = 9.5 a strong quenching upon the addition of Hg(ii) is observed. An additional high sensitivity of 0.64 ± 0.02 ppm towards Cu(ii) was observed, well below 1.25 ppm (∼20 μM), the maximum value allowed in drinking water by the EPA.