Antibacterial Activities of Azole Complexes Combined with Silver Nanoparticles

Biological Activity of Complexes Involving Nitro-Containing Ligands and Crystallographic-Theoretical Description of 3,5-DNB Complexes

Drug resistance in infectious diseases developed by bacteria and fungi is an important issue since it is necessary to further develop novel compounds with biological activity that counteract this problem. In addition, new pharmaceutical compounds with lower secondary effects to treat cancer are needed. Coordination compounds appear to be accessible and promising alternatives aiming to overcome these problems. In this review, we summarize the recent literature on coordination compounds based on nitrobenzoic acid (NBA) as a ligand, its derivatives, and other nitro-containing ligands, which are widely employed owing to their versatility. Additionally, an analysis of crystallographic data is presented, unraveling the coordination preferences and the most effective crystallization methods to grow crystals of good quality. This underscores the significance of elucidating crystalline structures and utilizing computational calculations to deepen the comprehension of the electronic properties of coordination complexes.

Antimicrobial Properties of Azole Functional Silica Nanocomposites

Silica nanoparticles have become more attractive due to their surface characteristics, versatility, biocompatibility, and morphological and physicochemical properties. For this reason, their use in biological applications has been expanding in recent years. In this study, after functionalizing silica nanoparticles with glycidyl methacrylate monomer, nanocomposites were formed by attaching 1,2,4‐Triazole, 3‐Amino‐1,2,4‐Triazole, and 5‐Aminotetrazole particles to the surface. Notably, the thermal degradation temperature of all nanocomposites was determined to surpass 200 °C. However, it is worth mentioning that despite the favorable water uptake rates observed for MT(7.64 %) and M3(5.98 %) nanocomposites, MT did not exhibit resistance against Fenton chemicals and experienced degradation. It is important to note that the material loss in M3 nanocomposites is minimal, measuring less than 1 %. In order to reveal the antifungal and antibacterial activity of the synthesized nanoparticles, Minimum inhibitory concentration(MIC), as well as Minimum Fungicidal Concentration(MFC) against the yeast strain Saccharomyces cerevisiae, and Minimum Bactericidal Concentration(MBC) values against bacteria strains, Staphylococcus aureus, Enterococcus faecalis and Escherichia coli were determined. The findings of the study indicated that MP, M3, and M5 nanocomposites displayed a moderate level of antibacterial activity. It is noteworthy, however, that the antibacterial activity diminished when triazole was combined with MP at concentrations exceeding 100 mg/mL.

Synthesis of 1-(2-Hydroxyphenyl)- and (3,5-Dichloro-2-hydroxyphenyl)-5-oxopyrrolidine-3-carboxylic Acid Derivatives as Promising Scaffolds for the Development of Novel Antimicrobial and Anticancer Agents

Increasing antimicrobial resistance among Gram-positive pathogens and pathogenic fungi remains one of the major public healthcare threats. Therefore, novel antimicrobial candidates and scaffolds are critically needed to overcome resistance in Gram-positive pathogens and drug-resistant fungal pathogens. In this study, we explored 1-(2-hydroxyphenyl)-5-oxopyrrolidine-3-carboxylic acid and its 3,5-dichloro-2-hydroxyphenyl analogue for their in vitro antimicrobial activity against multidrug-resistant pathogens. The compounds showed structure-dependent antimicrobial activity against Gram-positive pathogens (S. aureus, E. faecalis, C. difficile). Compounds 14 and 24b showed promising activity against vancomycin-intermediate S. aureus strains, and favorable cytotoxic profiles in HSAEC-1 cells, making them attractive scaffolds for further development. 5-Fluorobenzimidazole, having a 3,5-dichloro-2-hydroxyphenyl substituent, was found to be four-fold, and hydrazone, with a thien-2-yl fragment, was two-fold stronger than clindamycin against methicillin resistant S. aureus TCH 1516. Moreover, hydrazone, bearing a 5-nitrothien-2-yl moiety, showed promising activity against three tested multidrug-resistant C. auris isolates representing major genetic lineages (MIC 16 µg/mL) and azole-resistant A. fumigatus strains harboring TR34/L98H mutations in the CYP51A gene. The anticancer activity characterization demonstrated that the 5-fluorobenzimidazole derivative with a 3,5-dichloro-2-hydroxyphenyl substituent showed the highest anticancer activity in an A549 human pulmonary cancer cell culture model. Collectively these results demonstrate that 1-(2-hydroxyphenyl)-5-oxopyrrolidine-3-carboxylic acid derivatives could be further explored for the development of novel candidates targeting Gram-positive pathogens and drug-resistant fungi.

Preparation, Characterization of New Antimicrobial Antitumor Hybrid Semi-Organic Single Crystals of Proline Amino Acid Doped by Silver Nanoparticles

Proline is water soluble amino acid extensively used in drug delivery systems. Compounds of cobalt (Co) transition metal have potent antimicrobial and anticancer activities. However, a drug delivery system combining proline cobalt is not reported yet. For the first time, new hybrid semi-organic single crystals of proline cobalt chloride (PCC) are prepared. The novelty of the article is also that single crystal proline cobalt chloride showed potent antimicrobial and antitumor activity. Doping of PCC by Ag⁰NPs significantly increased these biological activities. The anisotropic magnetic properties of single crystals can mitigate the cytotoxicity of Ag⁰NPs on normal cells. Silver nanoparticles (Ag⁰NPs) improved the crystal habits and physicochemical properties. Ag⁰NPs showed the best performance, paramagnetic materials n-type semiconductors due to delocalized excess electrons of Ag⁰NPs incorporated in the crystal lattice interstitially. Crystals have high absorptivity for UV-radiation electromagnetic radiation. Ag⁰NPs enhanced AC electrical conductivity up to 2.3 × 10⁴ Ω cm^-1 due to high electron density. Proline doped crystals are obtained in good purity as triclinic unit cell with having anisotropic magnetism. PCCAg⁰NPs crystal exhibited: high antimicrobial activities to various bacterial and fungal species, inhibition zone (mm): 21, 25, 24, 26, 30, 28, 12, and 46 for S. aureus, E. faecalis, S. typhi, E. coli, P. aerugino, K. pneumoniae, A. braselienses, and C. albicans, respectively, in comparison to ciprofloxacin antibiotic (23, 0, 26, 26, 25, 0, 0, 0) for the same tested species, respectively; higher cytotoxicity against breast cancer cells (IC₅₀ 22.1 μM) than the reference drug cisplatin (IC₅₀ 11.7 μM); and lower cytotoxicity to normal healthy lung cells MRC-5, (IC₅₀ 145.5 μM) than cisplatin (IC₅₀ 30.2 μM). Hence, this crystal is a candidate for chemotherapy of breast cancer.

What are the prospects for using complexes of copper(ii) and zinc(ii) to suppress the vital activity of Mycolicibacterium smegmatis?

New complexes of zinc(ii) and copper(ii) with 2-furoic acid (Hfur), acetic acids and N-donor ligands with the compositions [Zn2(fur)4] n (1), [Zn2(fur)4(NH2py)2] (2, NH2py = 3-aminopyridine), [Zn(fur)2(neoc)] (3, neoc = 2,9-dimethyl-1,10-phenantroline), [Zn(OAc)2(neoc)] (4, OAc = acetat-anion), and [Cu(fur)2(neoc)(H2O)] (5) were synthesized. The structures of the compounds were established by single crystal X-ray diffraction analysis. Complexes 1 and 2 are binuclear; whereas 3-5 are mononuclear. The stabilization of supramolecular architectures in crystals for compounds 1-5 occurs due to π-π-bonding between heterocycles and hydrogen interactions that provide good solubility in aqueous solutions. The stability of the complexes upon dissolution in 5% dextrose and 0.9% NaCl was confirmed by UV-vis spectroscopic and NMR (1H) data. The study of in vitro biological activity was carried out against the non-pathogenic strain of Mycolicibacterium smegmatis that is a model for M. tuberculosis. The synergistic effect of ligands is observed for complexes 3-5 and is characterized by an increase in the biological activity values. On passage from Zn2+ to Cu2+ complexes, the biological activity increases and the maximum effect is observed for compound [Cu(fur)2(phen)]. Analysis of the transcriptomic profiles of the M. smegmatis mc 2 155 strain under the pressure of the copper complex [Cu(fur)2(phen)] made it possible to isolate 185 genes, one quarter of which are associated with the compensation of iron deficiency in the bacterial strain. Genes associated with the transport and metabolism of heavy metals, biosynthesis of fatty and amino acids, biodegradation and transport of urea were also isolated.

Synthesis of Novel Thiazole Derivatives Bearing β-Amino Acid and Aromatic Moieties as Promising Scaffolds for the Development of New Antibacterial and Antifungal Candidates Targeting Multidrug-Resistant Pathogens

Rapidly growing antimicrobial resistance among clinically important bacterial and fungal pathogens accounts for high morbidity and mortality worldwide. Therefore, it is critical to look for new small molecules targeting multidrug-resistant pathogens. Herein, in this paper we report a synthesis, ADME properties, and in vitro antimicrobial activity characterization of novel thiazole derivatives bearing β-amino acid, azole, and aromatic moieties. The in silico ADME characterization revealed that compounds 1-9 meet at least 2 Lipinski drug-like properties while cytotoxicity studies demonstrated low cytotoxicity to Vero cells. Further in vitro antimicrobial activity characterization showed the selective and potent bactericidal activity of 2a-c against Gram-positive pathogens (MIC 1-64 µg/mL) with profound activity against S. aureus (MIC 1-2 µg/mL) harboring genetically defined resistance mechanisms. Furthermore, the compounds 2a-c exhibited antifungal activity against azole resistant A. fumigatus, while only 2b and 5a showed antifungal activity against multidrug resistant yeasts including Candida auris. Collectively, these results demonstrate that thiazole derivatives 2a-c and 5a could be further explored as a promising scaffold for future development of antifungal and antibacterial agents targeting highly resistant pathogenic microorganisms.

Synthesis of novel pyrroles and fused pyrroles as antifungal and antibacterial agents

Pyrroles and its fused forms possess antimicrobial activities, they can easily interact with biomolecules of living systems. A series of substituted pyrroles, and its fused pyrimidines and triazines forms have been synthesised, all newly synthesised compound structures were confirmed by spectroscopic analysis. Generally, the compounds inhibited growth of some important human pathogens, the best effect was given by: 2a, 3c, 4d on Gram-positive bacteria and was higher on yeast (C. albicans), by 5c on Gram-negative bacteria and by 5a then 3c on filamentous fungi (A. fumigatus and F. oxysporum). Such results present good antibacterial and antifungal potential candidates to help overcome the global problem of antibiotic resistance and opportunistic infections outbreak. Compound 3c gave the best anti-phytopathogenic effect at a 50-fold lower concentration than Kocide 2000, introducing a safe commercial candidate for agricultural use. The effect of the compounds on DNA was monitored to detect the mode of action.

Metal and Metal Oxide Nanoparticle as a Novel Antibiotic Carrier for the Direct Delivery of Antibiotics

In addition to the benefits, increasing the constant need for antibiotics has resulted in the development of antibiotic bacterial resistance over time. Antibiotic tolerance mainly evolves in these bacteria through efflux pumps and biofilms. Leading to its modern and profitable uses, emerging nanotechnology is a significant field of research that is considered as the most important scientific breakthrough in recent years. Metal nanoparticles as nanocarriers are currently attracting a lot of interest from scientists, because of their wide range of applications and higher compatibility with bioactive components. As a consequence of their ability to inhibit the growth of bacteria, nanoparticles have been shown to have significant antibacterial, antifungal, antiviral, and antiparasitic efficacy in the battle against antibiotic resistance in microorganisms. As a result, this study covers bacterial tolerance to antibiotics, the antibacterial properties of various metal nanoparticles, their mechanisms, and the use of various metal and metal oxide nanoparticles as novel antibiotic carriers for direct antibiotic delivery.

Preparation of a Hybrid Membrane from Whey Protein Fibrils and Activated Carbon to Remove Mercury and Chromium from Water

Water contamination by mercury and chromium has a direct effect in human health. A promising technology to remove heavy metals by membrane filtration is the use of hybrid membranes produced with whey protein fibrils (WPF) and activated carbon (AC). In this study, the best conditions to produce WPF by heat treatment were determined to maximize the removal of mercury and chromium from water using a central composed design. The results indicated that the best conditions to prepare WPF were 74 °C, 7 h and 3.8% of whey protein with adsorption capacities of 25 and 18 mg/g and removal efficiencies of 81 and 57% for mercury and chromium, respectively. WPF and AC were used to prepare a hybrid membrane that was characterized using transmission electron microscopy, atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller surface area measurements. Batch filtration experiments were performed with the hybrid membrane for chromium and mercury removal at 25, 50 and 100 mg/L to determine its adsorption capacities. A high performance of the hybrid membrane was demonstrated removing efficiently mercury and chromium from water, thus supporting more than ten filtration cycles.

Synthesis and Characterization of Novel Azole Functionalized Poly(glycidyl methacrylate)s for Antibacterial and Anticandidal Activity

BACKGROUND

Presently, rise in the infectious diseases and subsequent development of drug resistance, is a global threat to human health. However, much efforts are being made by scientists, to develop novel antimicrobials, and also to improve the efficacy of available drugs, in order to combat the lifethreatening infections.

OBJECTIVE

Synthesis and characterization of azole functional polymer systems for antimicrobial applications.

MATERIALS AND METHODS

Poly(glycidyl methacrylate) (PGMA), was produced by free radical polymerization of the monomer, glycidyl methacrylate (GMA). Different azole functional PGMAs were produced, through chemical modification with imidazole (Im), 1H-1,2,4-triazole (Tri) and 3-amino-1,2,4-triazole (ATri), to get PGMA-Imi, PGMA-Tri and PGMA-ATri, respectively. The structure was confirmed by Fourier transform infrared spectroscopy (FT-IR), thermal properties were investigated by Thermogravimetric Analysis (TGA), and surface morphology was studied by scanning electron microscopy (SEM). Newly synthesized derivatives were further explored, for their antibacterial and anticandidal activities.

RESULTS

All the three synthesized and characterized derivatives, displayed a significant activity against the tested microorganisms. The minimum inhibitory concentration (MIC) and minimum bactericidal/fungicidal concentration (MBC/MFC), recorded against Staphylococcus aureus (S. aureus), was 0.5 &1mg/ml for PGMA-Imi, followed by PGMA-ATri & PGMA-Tri, respectively, followed by E. coli with, 1 & 2 mg/ml, 4 & 8 mg/ml, 4& 8 mg/ml, respectively, whereas the maximum MIC & MFC was recorded against C. albicans i.e., 8 & 16 mg/ml, 4 & 8 mg/ml ,4 & 8 mg/ml for PGMA-ATri, PGMA-Tri, PGMA-Imi, respectively.

CONCLUSION

In the present work, we report on the state-of-the-art, azole functional polymer systems for antimicrobial applications. These findings suggest that the synthesized azole functional polymer films have antimicrobial properties, which could be potential candidates for coating applications in the biomedical and wastewater treatment field.

Antiamoebic activity of synthetic tetrazoles against Acanthamoeba castellanii belonging to T4 genotype and effects of conjugation with silver nanoparticles

Acanthamoeba causes diseases such as Acanthamoeba keratitis (AK) which leads to permanent blindness and granulomatous Acanthamoeba encephalitis (GAE) where there is formation of granulomas in the brain. Current treatments such as chlorhexidine, diamidines, and azoles either exhibit undesirable side effects or require immediate and prolonged treatment for the drug to be effective or prevent relapse. Previously, antifungal drugs amphotericin B, nystatin, and fluconazole-conjugated silver with nanoparticles have shown significantly increased activity against Acanthamoeba castellanii. In this study, two functionally diverse tetrazoles were synthesized, namely 5-(3-4-dimethoxyphenyl)-1H-tetrazole and 1-(3-methoxyphenyl)-5-phenoxy-1H-tetrazole, denoted by T1 and T2 respectively. These compounds were evaluated for anti-Acanthamoeba effects at different concentrations ranging from 5 to 50 μM. Furthermore, these compounds were conjugated with silver nanoparticles (AgNPs) to enhance their efficacy. Particle size analysis showed that T1-AgNPs and T2-AgNPs had an average size of 52 and 70 nm respectively. After the successful synthesis and characterization of tetrazoles and tetrazole-conjugated AgNPs, they were subjected to anti-Acanthamoeba studies. Amoebicidal assay showed that at concentration 10 μM and above, T2 showed promising antiamoebic activities between the two compounds while encystation and excystation assays reveal that both T1 and T2 have inhibited differentiation activity against Acanthamoeba castellanii. Conjugation of T1 and T2 to AgNP also increased efficacy of tetrazoles as anti-Acanthamoeba agents. This may be due to the increased bioavailability as AgNP allows better delivery of treatment compounds to A. castellanii. Human cell cytotoxicity assay revealed that tetrazoles and AgNPs are significantly less toxic towards human cells compared with chlorhexidine which is known to cause undesirable side effects. Cytopathogenicity assay also revealed that T2 conjugated with AgNPs significantly reduced cytopathogenicity of A. castellanii compared with T2 alone, suggesting that T2-conjugated AgNP is an effective and safe anti-Acanthamoeba agent. The use of a synthetic azole compound conjugated with AgNPs can be an alternative strategy for drug development against A. castellanii. However, mechanistic and in vivo studies are needed to explore further translational values.

Co(ii) and Zn(ii) pyrazolyl-benzimidazole complexes with remarkable antibacterial activity

Three pseudopolymorphs based on a coordination complex of a pyrazolyl-benzimidazole ligand have been synthesized and characterized by single crystal X-diffraction, and showed remarkable antibacterial properties.

Inhibition of C. albicans Dimorphic Switch by Cobalt(II) Complexes with Ligands Derived from Pyrazoles and Dinitrobenzoate: Synthesis, Characterization and Biological Activity

Seven cobalt(II) complexes of pyrazole derivatives and dinitrobenzoate ligands were synthesized and characterized. The single-crystal X-ray diffraction structure was determined for one of the ligands and one of the complexes. The analysis and spectral data showed that all the cobalt complexes had octahedral geometries, which was supported by DFT calculations. The complexes and their free ligands were evaluated against fungal strains of Candida albicans and emerging non-albicans species and epimastigotes of Trypanosoma cruzi. We obtained antifungal activity with a minimum inhibitory concentration (MIC) ranging from 31.3 to 250 µg mL-1. The complexes were more active against C. krusei, showing MIC values between 31.25 and 62.5 µg mL-1. In addition, some ligands (L1-L6) and complexes (5 and Co(OAc)2 · 4H2O) significantly reduced the yeast to hypha transition of C. albicans at 500 µg mL-1 (inhibition ranging from 30 to 54%). Finally, the complexes and ligands did not present trypanocidal activity and were not toxic to Vero cells. Our results suggest that complexes of cobalt(II) with ligands derived from pyrazoles and dinitrobenzoate may be an attractive alternative for the treatment of diseases caused by fungi, especially because they target one of the most important virulence factors of C. albicans.

Development of Antibacterial and Antifungal Triazole Chromium(III) and Cobalt(II) Complexes: Synthesis and Biological Activity Evaluations

In this work, six complexes (2⁻7) of Cr(III) and Co(II) transition metals with triazole ligands were synthesized and characterized. In addition, a new ligand, 3,5-bis(1,2,4-triazol-1-ylmethyl)toluene (1), was synthesized and full characterized. The complexes were obtained as air-stable solids and characterized by melting point, electrical conductivity, thermogravimetric analysis, and Raman, infrared and ultraviolet/visible spectroscopy. The analyses and spectral data showed that complexes 3⁻7 had 1:1 (M:L) stoichiometries and octahedral geometries, while 2 had a 1:2 (M:L) ratio, which was supported by DFT calculations. The complexes and their respective ligands were evaluated against bacterial and fungal strains with clinical relevance. All the complexes showed higher antibacterial and antifungal activities than the free ligands. The complexes were more active against fungi than against bacteria. The activities of the chromium complexes against Candida tropicalis are of great interest, as they showed minimum inhibitory concentration 50 (MIC₅₀) values between 7.8 and 15.6 μg mL^-1. Complexes 5 and 6 showed little effect on Vero cells, indicating that they are not cytotoxic. These results can provide an important platform for the design of new compounds with antibacterial and antifungal activities.