Synthesis, Structure, and Anticancer Activity of Symmetrical and Non-symmetrical Silver(I)-N-Heterocyclic Carbene Complexes

The first evaluation of the in vitro effects of silver(I)-N-heterocyclic carbene complexes on Encephalitozoon intestinalis and Leishmania major promastigotes

Encephalitozoon intestinalis is an opportunistic microsporidian parasite that primarily infects immunocompromised individuals, such as those with HIV/AIDS or undergoing organ transplantation. Leishmaniasis is responsible for parasitic infections, particularly in developing countries. The disease has not been effectively controlled due to the lack of an effective vaccine and affordable treatment options. Current treatment options for E. intestinalis infection and leishmaniasis are limited and often associated with adverse side effects. There is no previous study in the literature on the antimicrosporidial activities of Ag(I)-N-heterocyclic carbene compounds. In this study, the in vitro antimicrosporidial activities of previously synthesized Ag(I)-N-heterocyclic carbene complexes were evaluated using E. intestinalis spores cultured in human renal epithelial cell lines (HEK-293). Inhibition of microsporidian replication was determined by spore counting. In addition, the effects of the compounds on Leishmania major promastigotes were assessed by measuring metabolic activity or cell viability using a tetrazolium reaction. Statistical analysis was performed to determine significant differences between treated and control groups. Our results showed that the growth of E. intestinalis and L. major promastigotes was inhibited by the tested compounds in a concentration-dependent manner. A significant decrease in parasite viability was observed at the highest concentrations. These results suggest that the compounds have potential anti-microsporidial and anti-leishmanial activity. Further research is required to elucidate the underlying mechanisms of action and to evaluate the efficacy of the compounds in animal models or clinical trials.

Antiultraviolet, Antioxidant, and Antimicrobial Properties and Anticancer Potential of Novel Environmentally Friendly Amide-Modified Gallic Acid Derivatives

Polyphenols and amides isolated from natural products have various biological functions, such as antioxidant, antimicrobial, anticancer, and antiviral activities, and they are widely used in the fields of food and medicine. In this work, four novel and environmentally friendly amide-modified gallic acid derivatives (AMGADs), which were prepared by using different amides to modify gallic acid (GA) from Polygonaceae plants, displayed good antiultraviolet (anti-UV), antioxidant, antimicrobial, and anticancer effects. Significantly, the anti-UV capability of compounds n1 and n2 was notably superior to that of the UV absorber GA. Moreover, compound n2 possessed better 2,2-diphenyl-1-picrylhydrazyl radical (DPPH•) scavenging ability and ferric reducing antioxidant power than vitamin C. The antibacterial activities of all AMGADs, with inhibition rates of more than 96.00 and 79.00% for Escherichia coli and Staphylococcus aureus, respectively, were better than those of GA. Compound n1 had broad-spectrum anticancer activity, and its inhibitory effect on HepG2 cells exceeded that of 5-fluorouracil. The good and rich bioactivities of these AMGADs revealed that combining GA with amides is conducive to improving the activity of GA, and this study laid a good foundation for their scientific application in the fields of food and medicine.

Silver(I) Complexes Based on Oxadiazole-Functionalized α-Aminophosphonate: Synthesis, Structural Study, and Biological Activities

Two silver(I) complexes, bis{diethyl[(5-phenyl-1,3,4-oxadiazol-2-yl-κN3:κN4-amino) (4-trifluoromethylphenyl)methyl]phosphonate-(tetrafluoroborato-κF)}-di-silver(I) and tetrakis-{diethyl[(5-phenyl-1,3,4-oxadiazol-2-yl-κN3-amino)(4-trifluoromethylphenyl)methyl]phosphonate} silver(I) tetrafluoroborate, were prepared starting from the diethyl[(5-phenyl-1,3,4-oxadiazol-2-yl-amino)(4-trifluoromethylphenyl)methyl]phosphonate (1) ligand and AgBF4 salt in Ag/ligand ratios of 1/1 and 1/4, respectively. The structure, stoichiometry, and geometry of the silver complexes were fully characterized by elemental analyses, infrared, single-crystal X-ray diffraction studies, multinuclear NMR, and mass spectroscopies. The binuclear complex ([Ag2(1)2(BF4)2]; 2) crystallizes in the monoclinic asymmetric space group P21/c and contains two silver atoms adopting a {AgN2F} planar trigonal geometry, which are simultaneously bridged by two oxadiazole rings of two ligands, while the mononuclear complex ([Ag(1)4]BF4; 3) crystallizes in the non-usual cubic space group Fd-3c in which the silver atom binds to four distinct electronically enriched nitrogen atoms of the oxadiazole ring, in a slightly distorted {AgN4} tetrahedral geometry. The α-aminophosphonate and the monomeric silver complex were evaluated in vitro against MCF-7 and PANC-1 cell lines. The silver complex is promising as a drug candidate for breast cancer and the pancreatic duct with half-maximal inhibitory concentration (IC50) values of 8.3 ± 1.0 and 14.4 ± 0.6 μM, respectively. Additionally, the interactions of the ligand and the mononuclear complex with Vascular Endothelial Growth Factor Receptor-2 and DNA were evaluated by molecular docking methods.

N-Heterocyclic Carbene (NHC) Silver Complexes as Versatile Chemotherapeutic Agents Targeting Human Topoisomerases and Actin

In recent years, the number of people suffering from cancer has risen rapidly and the World Health Organization and U.S. and European governments have identified this pathology as a priority issue. It is known that most bioactive anticancer molecules do not target a single protein but exert pleiotropic effects, simultaneously affecting multiple pathways. In our study, we designed and synthesized a new series of silver N-heterocyclic carbene (NHC) complexes [(NHC)2 Ag]+ [AgX2 ]- (X=iodide or acetate). The new complexes were active against two human breast cancer cell lines, MCF-7 and MDA-MB-231. These compounds showed multiple target actions as anticancer, by inhibiting in vitro the activity of the human topoisomerases I and II and interfering with the cytoskeleton dynamic, as also confirmed by in silico studies. Moreover, the antimicrobial activity of these silver complexes was studied against Gram-positive/negative bacteria. These dual properties provide a two-tiered approach, making these compounds of interest to be further deepened for the development of new chemotherapeutic agents.

Zinc Coordination Compounds with Benzimidazole Derivatives: Synthesis, Structure, Antimicrobial Activity and Potential Anticancer Application

Developing new, smart drugs with the anticancer activity is crucial, especially for cancers, which cause the highest mortality in humans. In this paper we describe a series of coordination compounds with the element of health, zinc, and bioactive ligands, benzimidazole derivatives. By way of synthesis we have obtained four compounds named C1, C2, C4 and C4. Analytical analyses (elemental analysis (EA), flame atomic absorption spectrometry (FAAS)), spectroscopic (Fourier transform infrared spectroscopy (FT-IR), mass spectrometry (MS)) and thermogravimetric (TG) methods and the definition of crystal structures were used to explore the nature of bonding and to elucidate the chemical structures. The collected analytical data allowed the determination of the stoichiometry in coordination compounds, thermal stability, crystal structure and way of bonding. The cytotoxicity effect of the new compounds as a potential antitumor agent on the glioblastoma (T98G), neuroblastoma (SK-N-AS) and lung adenocarcinoma (A549) cell lines and human normal skin fibroblasts (CCD-1059Sk) was also determined. Cell viability was determined by the MTT assay. The results obtained confirmed that conversion of ligands into the respective metal complexes significantly improved their anticancer properties. The complexes were screened for antibacterial and antifungal activities. The ADME technique was used to determine the physicochemical and biological properties.

Design, DFT studies, antimicrobial and antioxidant potential of Binuclear N-heterocyclic Carbene (NHCs) complexes, Probing the aspect of DNA interaction through In-vitro and In-silico approach

N-heterocyclic carbene (NHC) adducts have shown remarkable biological potential for numerous medical applications. With an aim to improve biological potential of benzimidazolium salts, newer analogues of benzimidazole and their silver complexes were synthesized and characterized. Synthesized salts (L₁-L₂) and silver complexes (C₁-C₂) were confirmed through elemental analysis, UV-visible spectroscopy, FTIR, ¹H NMR & ¹³C NMR spectroscopy. The compounds C1 & C2 were found stable in solution form for studied time period when examined spectroscopically and showed optimum lipophilicity when measured for their partition coefficient through flask shake method. Synthesized compounds showed good antimicrobial potential against gram positive bacterial strain S. Aureus with IC₅₀ 2.02±0.12 and 2.11±0.13 µM respectively while 2.11±0.1 and 2.28±0.17 µM against gram negative bacterial strain E. Coli for C1 and C2 respectively. The interaction study of the related compounds with DNA was predicted by molecular docking study, which confirmed that the studied compound C1 (-8.04 kcal/mol) has a higher binding energy than compound C2 (-4.23 kcal/mol); Also, the compound C1 exhibits a better affinity against to DNA than Ethidium bromide (-7.68 kcal/mol) and cisplatin (-6.21 kcal/mol).The claim was practically assured through spectroscopic and viscometeric method which confirmed that compounds have good affinity for DNA with binding constant kb, 5.78×10⁴ M^-1 and 6.84×10⁴ M^-1 for C1 and C2 respectively.

Novel Ag(I)-NHC complex: synthesis, in vitro cytotoxic activity, molecular docking, and quantum chemical studies

The importance of organometallic complexes in cancer biology has attracted attention in recent years. In this paper, we look for the in vitro cytotoxic capability of novel benzimidazole-based N-heterocyclic carbene (NHC) precursor (1) and its Ag(I)-NHC complex (2). For this purpose, these novel Ag(I)-NHC complex (2) was characterized by spectroscopic techniques (¹H, ¹³C{¹H} nuclear magnetic resonance (NMR), and Fourier-transform infrared spectroscopy (FT-IR)). Then, in vitro cytotoxic activities of NHC precursor (1) and Ag(I)-NHC complex (2) were investigated against MCF-7, MDA-MB-231 human breast, DU-145 prostate cancer cells, and L-929 healthy cells using MTT assay for 24, 48, and 72 h incubation times. Ag(I)-NHC complex (2) showed promising in vitro cytotoxic activity against all cell lines for three incubation times, with IC₅₀ values lower than 5 µM. It was also determined that (NHC) precursor (1) were lower in vitro cytotoxic activity than Ag(I)-NHC complex (2) against all cell lines. Selectivity indexes (SI_s) of Ag(I)-NHC complex (2) against cancer cells were found higher than 2 for 24 and 48 h incubation time. Besides, the electronic structure and spectroscopic data of the newly synthesized precursor and its Ag-complex have been supported by density functional theory (DFT) calculations and molecular docking analysis. After, the anticancer activity of these compounds has been discussed considering the results of the frontier molecular orbital analysis. We hope that the obtained results from the experiments and computational tools will bring a new perspective to cancer research in terms of supported by quantum chemical calculations.

Synthesis, characterization and catalytic properties of cationic N-heterocyclic carbene silver complexes

Three new dibenzimidazolium salts bridged by 2-methylenepropane-1,3-diyl group were synthesized. Their dinuclear N-heterocyclic carbene Ag(I) complexes were prepared by the reactions of these salts with Ag2O. The structures of the synthesized compounds were defined by nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FT-IR), elemental analysis, and LC-MSMS (for complexes) techniques. Stability of the silver complexes was confirmed by 1H NMR spectroscopy. Catalytic activities of Ag(I) compounds were tested for three-component coupling reaction of some aldehydes, amines, and phenylacetylene.

Silver(I)-N-heterocyclic carbene complexes challenge cancer; evaluation of their anticancer properties and in silico studies

Because of the continuous need for efficient therapeutic agents against various kinds of cancers and infectious diseases, the pharmaceutical industry has to find new candidates and strategies to develop novel and efficient drugs. They increasingly use computational tools in R&D stages for screening extensive sets of drug candidates before starting pre-clinical and clinical trials. N-Heterocyclic carbenes (NHCs) can be evaluated as good drug candidates because they offer both anti-cancer and anti-inflammatory features with their general low-toxicity profiles. To date, different kinds of NHCs (Cu, Co, Ni, Au, Ag, Ru, etc.) have been synthesized and their therapeutic uses has been shown. Here, we have reviewed the recent studies focused on Ag(I)-NHC complexes and their anti-cancer activities. Also, existing examples of the usage of density functional theory and structure-activity relationship have been evaluated.

Organometallic complexes of neodymium: an overview of synthetic methodologies based on coordinating elements

Organometallic complexes of neodymium have unique coordinating ability to form both micro and macromolecules as well as metal-based polymers. These complexes have been reported in different fields and play a tremendous role in luminescence, catalytic, biological and magnetic applications. So, the current study will comprise all possible routes for the synthesis of organometallic complexes of neodymium. Neodymium complexes have been synthesized of single, double, triple and tetra linkages with H, C, N, O as well as S, B, and X. The detailed synthetic routes have been classified into four categories but in brief, neodymium forms complexes by reacting metal chloride, nitrate or oxide (hydrated or dehydrated) as precursor along with appropriate ligand. Most applied solvents for neodymium complexes were Toluene and THF. These complexes required a range of temperature based on the nature of complexes as well as linkages. The authors have surveyed the research work published through 2011–2020 and provide a comprehensive overview to understand the synthetic routes of organometallic complexes of neodymium.

N-heterocyclic carbene-metal complexes as bio-organometallic antimicrobial and anticancer drugs, an update (2015–2020)

N-heterocyclic carbenes (NHCs) are organic compounds that typically mimic the chemical properties of phosphines. NHCs have made a significant impact on the field of coordination and organometallic chemistry because they are easy to prepare and handle and because of their versatility and stability. Importantly, the physicochemical properties of NHCs can be easily fine-tuned by simple variation of substituents on the nitrogen atoms. Over the past few years, various NHC–metal complexes have been extensively used as metal-based drug candidates and catalysts (homogeneous or heterogeneous) for various applications. To help assist future work with these compounds, this review provides a thorough review on the latest information involving some biomedical applications of NHC–metal complexes. Specifically, this article focuses on recent advances in the design, synthesis, characterization and biomedical applications (e.g., antimicrobial and anticancer activity) of various NHC–metal complexes (metal: silver, gold, palladium, rhodium, ruthenium, iridium and platinum) covering work published from 2015 to 2020. It is hoped that the promising discoveries to date will help accelerate studies on the encouraging potential of NHC–metal complexes as a class of effective therapeutic agents.