Antimicrobial Activity Studies Research Articles

Spectroscopic characterization, DFT calculations, antimicrobial activity, and molecular docking studies of 5-methoxy-1H-benzo[d]imidazole and its Ag(I) complex

The 5-methoxy-1H-benzo[d]imidazole (5MeOBM) and the synthesized new silver(I) complex were characterized using elemental analysis and spectroscopic methods such as 1H NMR, FT-IR, UV–Vis and mass spectrometry. To compare the spectroscopic results and establish the molecular structures of the free ligand and its metal complex, density functional theory (DFT) computations were performed. UV–Vis spectrum analysis was performed to better understand the optical properties, and quantum chemical properties were computed theoretically utilizing HOMO and LUMO energy levels. Topological analyses were carried out using Multiwfn to identify the complex's primary binding areas and weak interactions. NBO analyses were performed in order to predict potential reactivity features and critical intramolecular interactions. Biological study of the ligand and its Ag(I) complex were tested for their in vitro antimicrobial activities. The molecular docking investigations were performed to explore the possible interaction of each compound with an antimicrobial agent. Also, molecular docking studies were carried out to learn how these compounds interact with biomolecules.

New 2-Chloroimidazo[1,2-a]pyridine induced Schiff bases: Synthesis, characterization, antimicrobial and A-498 and A-549 anticancer activity, molecular modeling, in-silico pharmacokinetics, and DFT studies

The novel 1-(2-chloroimidazo[1,2-a]pyridin-3-yl)-N-(substitutedphenyl) methanimines have been synthesized and characterized by spectral (IR, MS, 1H, and 13C NMR) and elemental analysis. Molecular docking studies were conducted with three cancer target proteins (PDB IDs: 1M17, 2OF4, and 3LCK) and assorted microbial target proteins (1KZN, 2XCT, 1D7U, 1BAG, and 1EA1) to explore their binding interactions. Further in-silico target prediction study suggested a 26.7 % probability that VIf acts on kinases. The synthesized analogs were subjected to in-vitro anticancer activity assessments against A-498 (kidney carcinoma) and A-549 (lung carcinoma) cell lines and compound VIf exhibited good inhibition (GI50<10) of the A-498 cell line. Additionally, all analogs showed moderate to good in-vitro antimicrobial activity against S. aureus, B. subtilis, E. coli, K. pneumoniae (bacterial strains), and C. albicans (fungal strain). The optimized geometries, FMO energies, MEP plots, and global reactivity descriptors (µ, ɳ, S, and ω) were achieved employing DFT at B3LYP/6-31G (d) level to explore structural features and probable reactivity and toxicity of the synthesized compounds. Compound VIg exhibited high reactivity (ɳ: 1.8218 eV, S: 0.2744 eV) and low toxicity (ω: 3.2061 eV) among all analogs. These findings collectively underscore the potential of the synthesized compounds, with VIf and VIg standing out as particularly promising candidates for further exploration.

Study of the Antimicrobial Activity of Staphylococcal Bacteriophage on a Model of an Infected Skin Wound

The purpose of this study was to investigate the antimicrobial activity of staphylococcal bacteriophage on a model of a skin wound infected with Staphylococcus aureus. The study of antimicrobial activity was carried out in vivo by experimental modeling of a skin wound infected with S.aureus in the interscapular region in nonlinear male rats. All manipulations with animals were performed in accordance with the requirements of regulatory documentation overseeing the management of laboratory animals and work with them. The results obtained indicate the pronounced antimicrobial activity of staphylococcal bacteriophage in conditions of wound infection when applied externally, which is confirmed by a decrease in the degree of bacterial contamination of wound discharge, as well as a decrease in inflammatory phenomena, both at the local level in the form of a decrease in hyperemia, and generalized in the form of a decrease in C-reactive protein levels, total leukocyte count, as well as a decrease in the leukocyte inflammatory index. The identified antimicrobial effect is comparable to the external use of an antiseptic drug — a solution of chlorhexidine digluconate 0.05%, however, when assessing microbial contamination, it was found that the bacteriophage exhibits more pronounced antibacterial activity. Thus, the staphylococcal bacteriophage showed pronounced antimicrobial activity in a model of a skin wound infected with S.aureus, confirmed by a decrease in the number of colonies of the microorganism in the wound discharge, as well as a decrease in the severity of inflammation.

Solvent role in molecular structure level, structural and topology investigations, molecular docking and antimicrobial activity studies on sulpha drug derivative

The Schiff base (5FSATH) was synthesized and characterized by different experimental techniques. In the context of local energy decomposition analysis (LED), the binding energy of 5FSATH-water interaction is determined to be -15.63 kcal/mol, while the bond distance between the two objects is measured to be 1.9781 A°. The absorption spectrum was recorded using different solvents like DMSO, water, and chloroform. The experimental absorption spectrum wavelengths 206, 220, and 300 nm, were recorded from DMSO solvent. In the emission (fluorescence) spectrum we observed three different wavelengths such as 352, 510, and 609 nm. For the calculated NMR spectrum, used the standard GIAO method and DMSO as the solvent. The HOMO-LUMO analysis indicates the charge transfer within the molecule, it is calculated by different solvents. NBO confirms the synthesized compound stability, hyper conjugative interaction, and charge delocalization. To test for antibacterial and antifungal activity, an agar disc well diffusion method is utilized. Synthesized compound tested against Escherichia coli, Candida albicans, Staphylococcus aureus, and Streptococcus pneumoniae microorganisms. Amoxicillin was used as the reference drug for testing antibacterial and antifungal activity. According to the findings of the antimicrobial activity, the result of the molecular docking experiment showed that the compound 5FSATH had an extremely high binding affinity score.

Study of Antimicrobial Activity &amp; Structural Elucidation of Purified Compound from Potential Solvent Extract of Bruguiera cylindrica [L

Study of Antimicrobial Activity &amp; Structural Elucidation of Purified Compound from Potential Solvent Extract of Bruguiera cylindrica [L

Ginger essential oil-loaded hydrogels: preparation, characterization, cytotoxicity, antimicrobial and anti-inflammatory activity

ABSTRACT The present study aimed to develop ginger essential oil hydrogel formulations, using sodium carboxymethyl cellulose (Na CMC), Carbopol, and xanthan gum for dental and oromucosal infections. The physicochemical properties of the hydrogels were evaluated, and their bioadhesive characteristics were determined. Antimicrobial activity, cytotoxicity, and lipoxygenase (LOX) inhibitory activities of the essential oil and its formulations were investigated, respectively. The major components of ginger essential oil were confirmed as α-zingiberene (39.0%) and ar-curcumene (23.7%) by GC-FID and GC/MS analyses. The initial results showed that none of the tested gel formulations selected for the application were non-cytotoxic. According to antimicrobial and LOX enzyme activity studies, the essential oil-loaded xanthan gum gel (X3) was more effective compared to the essential oil itself. The initial formulation and biological evaluation studies concluded that ginger essential oil hydrogels (X3, C3) can be further developed for oral and dental health by providing a long residence time due to their bioadhesive properties.

Study of antimicrobial activity and fermentability of the yeast Wickerhamomyces anomalus in wheat dough

The work is aimed at assessing the potential of using the yeast culture Wickerhamomyces anomalus CBS605T in bread baking. The in vitro antimicrobial activity of the yeast culture Wickerhamomyces anomalus (CBS605T) against the causative agent of potato disease, Bacillus subtilis, was studied. A rheoenzymemetric assessment of the gas-forming and gas-retaining abilities of the studied strain during fermentation in wheat dough was carried out. The study showed that the yeast culture Wickerhamomyces anomalus (CBS605T) effectively inhibits the growth of Bacillus subtilis and has higher fermentation activity than the control organism Saccharomyces cerevisiae var. boulardii (Y3925), also known for antimicrobial activity against the pathogen of potato disease.

Search for new biologically active compounds: in vitro studies of antitumor and antimicrobial activity of dirhodium(II,II) paddlewheel complexes.

Four neutral Rh1-Rh4 complexes of the general formula [Rh2(CH3COO)4L2], where L is an N-alkylimidazole ligand, were synthesized and characterized using various spectroscopic techniques, and in the case of Rh4 the crystal structure was confirmed. Investigation of the interactions of these complexes with HSA by fluorescence spectroscopy revealed that the binding constants Kb are moderately strong (∼104 M-1), and site-marker competition experiments showed that the complexes bind to Heme site III (subdomain IB). Competitive binding studies for CT DNA using EB and HOE showed that the complexes bind to the minor groove, which was also confirmed by viscosity experiments. Molecular docking confirmed the experimental data for HSA and CT DNA. Antimicrobial tests showed that the Rh2-Rh4 complexes exerted a strong inhibitory effect on G+ bacteria B. cereus and G- bacteria V. parahaemolyticus as well as on the yeast C. tropicalis, which showed a higher sensitivity compared to fluconazole. The cytotoxic activity of Rh1-Rh4 complexes tested on three cancer cell lines (HeLa, HCT116 and MDA-MB-231) and on healthy MRC-5 cells showed that all investigated complexes elicited more efficient cytotoxicity on all tested tumor cells than on control cells. Investigation of the mechanism of action revealed that the Rh1-Rh4 complexes inhibit cell proliferation via different mechanisms of action, namely apoptosis (increase in expression of the pro-apoptotic Bax protein and caspase-3 protein in HeLa and HCT116 cells; changes in mitochondrial potential and mitochondrial damage; release of cytochrome c from the mitochondria; cell cycle arrest in G2/M phase in both HeLa and HCT116 cells together with a decrease in the expression of cyclin A and cyclin B) and autophagy (reduction in the expression of the protein p62 in HeLa and HCT116 cells).

Antimicrobial activity and molecular docking studies of some imidazo[2,1-b]thiazole derivatives

The synthesis of bioactive molecules is of major importance in the pharmaceutical industry. In this context, the study was conducted to determine the antimicrobial and antifungal potential of four chalcone-based imidazo[2,1-b]thiazole derivatives already synthesized by our research group. The synthetized compounds obtained in good yield were evaluated for their antibacterial and antifungal activities against E. coli, Staphylococcus aureus, Pseudomonas aeruginosa and Fusarium, the results obtained are compared with the standard. Molecular docking studies were utilized to forecast the potential of these molecules as antimicrobial agents, the results obtained in vitro antibacterial were well confirmed by this method.

Novel 1, 2, 3-triazolic compounds derived from cytosine: Synthesis, spectroscopic characterization, in vitro antimicrobial activity and molecular docking studies

The development of novel antimicrobial drugs is crucial due to the increasing problem of antibiotic resistance. A new series of 1,4-disubstituted-1,2,3-triazole derivatives containing a cytosine moiety (3a, 3b, 3c and 3d) were synthesized using 1,3-dipolar cycloaddition in a mixture of ethanol and water under Cu(I)-catalyzed with N-alkyl: 1-(prop-2-ynyl)-4-amino-2-oxopyrimidine 2 as dipolarophiles and azide derivatives (sucre-azoture) as dipoles. The desired products were obtained in good yields by reacting with a catalytic amount of copper (II) sulfate and sodium ascorbate. The structure of these compounds was analyzed and characterized using spectroscopic measurements such as 1H NMR, 13C NMR, and mass spectroscopy. Encouragingly, all cycloaddition molecules exhibited promising activity against various bacterial strains including Staphylococcus aureus and Escherichia coli. The crystal structure modeling of protein 7AZ5 demonstrated strong binding affinities through hydrogen bonds with these molecules. The cycloaddition compounds displayed the highest binding energies in terms of antimicrobial efficacy. This suggests that these substances could serve as an effective model for the development and production of new and potent antimicrobial agents.

Vitex Negundo-Fe3O4-CuO green nanocatalyst (VN-Fe3O4-CuO): synthesis of pyrazolo[3,4-c]pyrazole derivatives via the cyclization of isoniazid with pyrazole and their antimicrobial activity, cytotoxicity, and molecular docking studies.

In this study, we developed a novel pyrazolo[3,4-c]pyrazole derivative with antibacterial and antifungal activities that shows great potential for treating infectious diseases. To evaluate the binding affinity of 1AJ0 and 1AI9 proteins for developing potent antibacterial and antifungal compounds, we used the Vitex negundo (VN) leaf extract as the capping and reducing agent and reacted it with Fe2O3 and Cu(OAc)2 solutions to synthesize the VN-Fe3O4-CuO nanocatalyst. The newly synthesized compounds were confirmed using Fourier transform infrared spectroscopy, transmission electron microscopy, UV-visible spectroscopy, and X-ray diffraction analyses. Antibacterial screening revealed that compound 1g was highly active against Escherichia coli (MIC: 1 μg mL-1) and was much more effective than the standard ciprofloxacin. Compound 1b showed a higher antifungal activity than clotrimazole against Candida albicans (MIC: 0.25 μg mL-1) and cytotoxic activity against MCF-7 cancer cell lines. Compounds 1a-1l were exhibited low cytotoxicity activity compared to the standard doxorubicin (LC50: 21.05 ± 0.82 μg mL-1). To further support the discovery of new active antibacterial agents, compounds 1g and 1b and proteins 1AJ0 and 1AI9 were examined using the AutoDock Vina program and were compared with the standards ciprofloxacin and clotrimazole. With the 1AJ0 protein, compound 1g had a higher docking score (-3.7 kcal mol-1) than ciprofloxacin (-5.6 kcal mol-1), and with the 1AI9 protein, compound 1b had a higher docking score (-4.8 kcal mol-1) than clotrimazole (-4.4 kcal mol-1). Additionally, molecular dynamics simulation was used to investigate the most probable binding mode of compounds 1b and 1g with 1AI9 and 1AJ0, respectively. The VN-Fe3O4-CuO catalyst was used to prepare pyrazolo[3,4-c]pyrazole derivatives, which were successfully characterized and screened for antimicrobial and cytotoxic activities, molecular docking, and molecular dynamics simulation studies.

Isolation and Screening of Pigment Producing Bacteria from Soil and Study of Antimicrobial Activity of Pigments

Pigments are colored compounds that play important roles in various biological systems, such as photosynthesis, vision, and signalling. Pigment-producing bacteria are a diverse group of microorganisms that can produce a wide range of pigments with different colors and properties. The present study is aimed to isolate the pigment-producing bacteria from the soil with the antibacterial activity of pigments. Soil samples were collected from nearby Karad city. All eight different pigmented colonies were isolated that produced the pigments like Yellow, Red, Golden Yellow, and Orange and they were designated as YP-I, YP-II, YP-II, GYP-I, GYP-II, RP-I, RP-II, and OP. The isolated organisms were characterized with the help of Bergey’s Manual of Determinative Bacteriology. The pigments were extracted with a solvent like chloroform and the antibacterial activity of the extract was tested against E. coli, Pseudomonas aeruginosa, and Staphylococcus aureus. The extracted pigments had an inhibitory effect on both Gram-positive and Gramnegative bacteria. The pigments of isolates designated as YP-III, GYP-I, GY-II, and RP-II showed the highest antibacterial activity against E. coli.

BENZAMINE DERIVATIVES: SYNTHESIS, CHARACTERIZATION AND BIOLOGICAL ACTIVITY STUDY

: Our study is included the synthesis of a number of benzamide drivatives through two chemical processes. The first is the benzoylation of some aromatic amines containing a pyrimidine or a pyrazoline ring in their structures (A-G) using benzoyl chloride or p-chloronbenzoyl chloride in the presence of 1,4- dioxan as solvent productive (N1-N6, N13-N16) derivatives. The second is the tosylation of (N2-N6, N15) by p-toluene sulfonyl chloride in the presence of pyridine as catalyst and base at room temperature to produce (B1-B6 ) derivatives . The products have been characterized by IR, 1H-NMR ,13 C-NMR and mass spectroscpies and the physical properties of the products are recorded . The spectral data confirmed the validity of the benzamide derivatives. Also the work is included the study of antimicrobial activity of the synthesized compounds represented by determining the inhibition diameter zone (IZ), minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) given by these compounds against the test organisms Staphylococcus aureas (Gr+ positive) and Escherichia coli (Grnegative). Furthermore, the results of MIC and MBC were compared with those of some common antibiotics such as tetracycline, ampicillin and streptomycin. This comparison showed that it is possible to use the synthesized derivatives as antimicrobials

The effects of Equisetum arvense L. extracts prepared using different solvents and extraction methods for antioxidant and antimicrobial activity

Our study aimed to determine the solvent and extraction method that reveals the biological activities and phenolic contents of the plant Equisetum arvense at the maximum rate. Leaf and stem extracts of Equisetum arvense were prepared using the soxhlet and maceration method in the presence of 5 different solvents. The extracts' total phenolic content (TPC) was determined using the Folin-Ciocalteu method, the antioxidant activity by the DPPH radical scavenging test, and the antimicrobial activity by the disc diffusion method. When the antibacterial activity results were examined, the methanolic leaf extract prepared by the maceration method showed the inhibition zones as 14.5 mm on S. aureus, 14.2 mm on S. epidermidis and 14 mm on E. faecalis. From leaf parts, it was determined that the methanolic extract prepared by the soxhlet method was 85.1%, the acetonic extract 84.5%, the methanolic extract prepared by the maceration method 83%, and the acetonic extract 84.1% scavenged DPPH radical. As a result of the study, it was determined that the maceration method showed better results in evaluating the total phenolic substance amount and antimicrobial activity and the soxhlet method in determining the antioxidant activity. It has been determined that methanol and acetone were the ideal solvents for TPC antioxidant and antimicrobial activity studies to be carried out with E. arvense plant. In this study, plant leaves and stems were studied separately for the first time and their biological activities were compared. In addition, our study provides integrative data investigating and comparing the antioxidant and antimicrobial activities of the E. arvense plant in detail with various solvents and methods.

Antimicrobial activity study of some binuclear complexes with Schiff bases derived from an aromatic dialdehyde and some amino acids

Many metal complexes with amino acid derived Schiff bases have been synthesized and tested for their biological activity. Thus, the aim of the present study was to evaluate the antimicrobial activity of some binuclear complexes with Schiff bases derived from an aromatic dialdehyde and some amino acids by studying the influence of the tested compounds on the development of microbial biofilms on an inert substrate. The biofilms developed on inert substrate by Klebsiella pneumoniae ESBL+, Citrobacter freundii 1748, Bacillus sp., Serratia marcescens 0804, Staphylococcus aureus ATCC 25923 and Escherichia coli 1576 strains were inhibited at concentrations of the tested compounds between 250 μg∙mL-1 and 500 μg∙mL-1. The results of determining the influence of the tested compounds on the development of microbial biofilms showed that they have an inhibitory effect on microbial adhesion.

Solubility enhancement of Cefpodoxime acid by aqueous solution of paracetamol through acoustical, polarizable continuum model and antimicrobial activity studies

The pharmacological response of an antibiotic depends on the optimum concentration of homogenous solution of the drug and deviation from this may result in major problems with generic and formulation developments of new chemical entities (NCE’s). Further, the introduction of additional new drugs with greater pharmacokinetic activity is limited because of their poor aqueous solubility. In the present work, an attempt has been made to explore the enhancement of solubility and hence the bioavailability or antimicrobial activity of a pharmaceutically significant drug Cefpodoxime acid (CA), a metabolite of third generation cephalosporin antibiotic cefpodoxime proxetil (CP), by the addition of aqueous paracetamol (PA) solution. Ultrasonic investigation has been carried out on the aqueous solutions of PA containing different concentration of CA at ambient and physiological temperatures and at pressure 101.3 kPa. The measured values of ultrasonic velocity, density and dynamic viscosity and the computed acoustical parameters at 303.15 K, 310.15 K and 313.15 K reveal significant intermolecular interactions between unlike drug molecules. The polarizable continuum model (PCM) study for the two drugs in four different solvents is applied in the calculation of free energy of solution (ΔGsol) which provide valid information regarding the mutual solubility of the two drugs and possible enhancement of bioavailability of CA in presence of PA. Antimicrobial activity of CA in the presence of PA in aqueous medium confirms the improvisation of solubility of CA drug. The data obtained through antimicrobial activity studies support the increased pharmacokinetic activity of CA in the presence of PA in aqueous environment.

Determination of the Anti-Escherichial Activity of the Pyrimidine Derivative 3-[2-[(4,6-dimethylpyrimidin-2- yl)amino]-2-oxoethyl]quinazolin-4(3H)-one

The aim of this study was to investigate the antimicrobial activity of the pyrimidine derivative 3-[2-[(4,6-dimethylpyrimidin-2-yl)amino]-2-oxoethyl]quinazolin-4(3H)-one against Escherichia coli. The study of antimicrobial activity was carried out in vitro by serial dilutions of the pyrimidine compound, followed by determination of the minimum inhibitory concentration of 3-[2-[(4,6-dimethylpyrimidin-2-yl)amino]-2-oxoethyl]quinazolin-4(3n)-one (VMA-13-14) and in vivo on the model of generalized E.coli infection. The study of antimicrobial activity in vivo was carried out on 40 CBA mice weighing 19–20 g. All manipulations with animals were performed in accordance with the requirements of the regulatory documentation governing the maintenance of laboratory animals and work involving them. The antimicrobial activity of the pyrimidine compound 3-[2-[(4,6-dimethylpyrimidin-2-yl)amino]-2-oxoethyl]quinazolin-4(3H)-one against E.coli in vitro was evaluated in terms of mouse survival, contamination of blood and internal organs (liver, spleen, lungs, brain), as well as the total number of leukocytes and leukograms. The experiment determined that the pyrimidine compound 3-[2-[(4,6-di- methylpyrimidin-2-yl)amino]-2-oxoethyl]quinazolin-4(3n)-one demonstrates antimicrobial activity against E.coli: in vitro, it has a bactericidal effect at a concentration of 128 µg/ml; in vivo, it has an antimicrobial effect in conditions of generalized infection with the introduction of 50 mg/kg/day for 10 days. The antimicrobial effect of 3-[2-[(4,6-dimethylpyrimidin-2- yl)amino]-2-oxoethyl]quinazolin-4(3n)-one is comparable to ceftazidime, which is the drug of choice in the treatment of E.coli infection.

Synthesis, Physiochemical Characterization and Biological Investigation with Quantum Chemical Computations of Benzotriazole Salicylate

In the present work a new organic single crystal Benzotriazole (BTSA) was synthesized and fully characterized by means of single crystal XRD, FT-IR, FT-Raman and UV-visible spectroscopic techniques. Single-crystal X-ray diffraction was applied to the growing crystal to determine the cell dimensions. It has been found that the HOMO and LUMO computed energies accurately depict the characteristics of electron excitation. The TD-DFT approach was used to analyze the UV-visible spectra and study spectroscopic wavenumbers. Analysis using the quantum theory of atoms in molecules has been done to find all potential non-covalent interactions. Multiwfn has been used to visualize Electron Localization Function (ELF) and Localized Orbital Locator (LOL) to examine the molecule’s electrical characteristics. Antimicrobial activity studies indicate the compound good antibacterial and antifungal activity. The docking parameters were studied with Candida tropicalis proteins and the lowest binding energy −5.95 kcal/mol has been achieved for 6ZD2 protein.

NEW SULFONAMIDO-BENZOXAZOLE DERIVATIVES AS ANTIMICROBIAL AGENTS: DESIGN, SYNTHESIS AND BIOLOGICAL EVALUATION

Objective: Many investigations are conducted in the battle against infectious diseases in order to develop new drug-active ingredient candidate compounds and to identify leading compounds. The goal of this study was to synthesis a total of seven compounds, six of which are novel, with the general structure 2-(4-tert-butylphenyl)-5-(4-substitutedphenylsulfonamido)benzoxazole, to elucidate their structures, and to test their antimicrobial activities using the microdilution method. Material and Method: The synthesis of the compounds was carried out in two stages. In the first stage, under PPA catalyst 2,4-diaminophenol and 4-tert-butylbenzoic acid were refluxed, and target compounds were produced in the second step by reacting 4-substitutedbenzenesulfonyl chloride with 5-Amino-2-(4-tert-butylphenyl)benzoxazole. The compounds' antimicrobial activity was determined by using Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, and drug-resistant strains of these microorganisms in vitro antimicrobial activity studies. Furthermore, estimated ADME profiles were calculated using the SwissADME online software. Result and Discussion: The structures of the synthesized compounds were elucidated using 1H-NMR, 13C-NMR and Mass spectroscopy, and also their melting points were determined. The antimicrobial activities of the compounds ranged from 64 µg/ml to ˃512 µg/ml and were weaker than the reference drugs. The best antimicrobial activity was reported against an isolate of E. faecalis, with all compounds having MIC values of 64 µg/ml. The fact that six of the seven synthesized compounds are novel and that their antimicrobial activity will be tested for the first time will make a significant contribution to studies to develop new or alternative antimicrobial agents.

Rhenium (I) tricarbonyl complex with thiosemicarbazone ligand derived from Indole-2-carboxaldehyde: Synthesis, crystal structure, computational investigations, antimicrobial activity, and molecular docking studies

Antibiotic resistance is becoming a cause of serious concern to human health causing a significant impact on the global economy. The demand for novel antimicrobial agents is pressing since drug resistance is spreading and making antibiotics less and less effective. There is unrealized antibacterial potential in metal complexes. Among other compounds, rhenium complexes are particularly appealing because of their strong antibacterial activity and minimal in vivo toxicity. In this study, three Re carbonyl thiosemicarbazone (TSC) complexes were synthesized and characterized and their antibacterial potential was evaluated against various types of gram-positive and gram-negative bacteria. The structure of the ligands and their corresponding Re complexes were optimized at the DFT/B3LYP level of theory employing 6–311++G(d,p) and LANL2DZ basis sets for C, H, N, O, S, and Re atoms respectively. The MS studies performed with time show that [fac-[Re(CO)3Br(HL)] was converted into dimer [Re2(CO)6(L)2] in solution and the crystal structure of the dimer [Re2(CO)6(L)2] obtained as the result of dimerization of the complex was solved. Among the three Re TSC complexes, [fac-[Re(CO)3Br(HL1)] exhibits the greatest antibacterial activity against S.aureus with MIC value 0.5 µg/mL. The data obtained showed that the synthesized complexes were ineffective against gram-negative bacteria but showed excellent antibacterial activity against gram-positive S.aureus. The [fac-[Re(CO)3Br(HL2)] complex derived from isatin-β-thiosemicarbazone showed lesser activity than the other two rhenium TSC complexes which were obtained by condensation of indole-2-carboxaldehyde and thiosemicarbazide. Furthermore, the in-silico molecular docking studies revealed that the binding energy of the docked compound [Re(CO)3Br(HL)] with E. Coli and MRSA targets were extremely favorable (-7.18 and -5.67 kcal/mol, respectively which further demonstrates the potential of the synthesized complexes in the development of new antibacterial drugs. The molecular docking studies as well as experimental investigations demonstrate the effect of substituents on the ligand backbone on the antimicrobial activity of the synthesized rhenium carbonyl complexes. The enhanced antibacterial properties of rhenium carbonyl complexes with the TSC ligands in comparison to the ligand alone also suggest a possible synergistic effect of the metal center and the organic ligand.