Synthesis of Ni(II) complexes bearing indole-based thiosemicarbazone ligands for interaction with biomolecules and some biological applications

Synthesis, DFT, Molecular Docking, and Antimicrobial Studies of New Indole-Thiosemicarbazone Ligand and Their Complexes with Fe(III), Co(II), Ni(II), Cu(II)

Indole-3-carbaldehyde based novel ligand (E)-2-((1-benzyl-1H-indol-3-yl)methylene)-N-methylhydrazine-1-carbothioamide (MBIHC) and its metal complexes [(MBIHC)2FeCl2]Cl(C1), [(MBIHC-)2Co] (C2), [(MBIHC-)2Ni] (C3), and [(MBIHC-)2Cu] (C4) have been synthesized. All synthesized compounds have been characterized by various spectroanalytical techniques. The structure of MBIHC was confirmed by single-crystal X-ray data. The geometry of metal complexes was determined by spectroscopic and computational studies. In the case of iron complex, ligand MBIHC coordinated to the metal ion in bidentate mode (via nitrogen, sulphur donor atoms) while in the case of cobalt, nickel, and copper complexes ligand act as a tridentate ligand (via nitrogen, sulphur, carbene donor atoms). In vitro, antifungal and antibacterial studies of ligand and metal complexes were assayed against C. albicans, C. glabrata, E. coli, and K. pneumoniae pathogens. In antifungal activity, complex C1 exhibited a greater inhibition zone than the other compounds for the both examined fungi C. albicans (24±0.32 mm) and C. glabrata (20±0.16 mm). However, the antifungal activities of complex C2 has shown better activity against both E. coli (25±0.24 mm) and K. pneumoniae (16±0.80 mm) pathogens than the other examined compound. Complex C2 has found even better than the benchmark drug Ampiciline in case of E. coli. Further, the DFT calculations and molecular docking studies also validate the experimental bioactivity results of examined compounds.

Rh-Catalyzed C-H Alkynylation of Indole Derivatives with Silver(I)-Controlled Regiodivergence

We have disclosed silver(I)-induced switching of regioselectivity in rhodium-catalyzed C-H alkynylation of indole derivatives with the help of a pivaloyl directing group by tuning C-H metalation modes. The judicious choice of AgOAc, Ag2O, and Ag2CO3 affords an array of C2-alkynylated indoles, C4-alkynylated indoles, and C2,C4-dialkynylated indoles, respectively. The synthetic utility of the alkyne fragment is demonstrated by derivatization into valuable indole-based compounds.

Binuclear palladacycles with ionisable and non-ionisable tethers as anticancer agents

The search for novel anticancer agents to replace the current platinum-based treatments remains an ongoing process. Palladacycles have shown excellent promise as demonstrated by our previous work which yielded BTC2, a binuclear palladadycle with a non-ionisable polyethylene glycol (PEG) tether. Here, we explore the importance of the PEG-tether length on the anticancer activity of the binuclear palladacycles by comparing three analogous binuclear palladacycles, BTC2, BTC5 and BTC6, in the oestrogen receptor positive MCF7 and triple-negative MDA-MB-231 breast cancer cell lines. In addition, these are compared to another analogue with an ionisable morpholine tether, BTC7. Potent anticancer activity was revealed through cell viability studies (MTT assays) revealed that while BTC6 showed similar potent anticancer activity as BTC2, it was less toxic towards non-cancerous cell lines. Interestingly, BTC7 and BTCF were less potent than the PEGylated palladacycles but showed significantly improved selectivity towards the triple-negative breast cancer cells. Cell death analysis showed that BTC7 and BTCF significantly induced apoptosis in both the cancer cell lines while the PEGylated complexes induced both apoptosis and secondary necrosis. Furthermore, experimental and computational DNA binding studies indicated partial intercalation and groove binding as the modes of action for the PEGylated palladacycles. Similarly, experimental and computational BSA binding studies indicated and specific binding sites in BSA dependent on the nature of the tethers on the complexes.

Synthesis of substituted terpyridine nickel nitrate complexes and their inhibitory selectivity against cancer cell lines

Six terpyridine‑nickel complexes 1-6 were formed by the coordination of 4'-(4-R-phenyl)-2,2':6',2″-terpyridine (R = hydroxyl (L1), methoxyl (L2), methylsulfonyl (L3), fluoro (L4), bromo (L5), iodo (L6)) derivatives to nickel nitrate. The compositions and structures of these complexes were analyzed by Fourier Transform infrared spectroscopy (FT-IR), elemental analyses, electrospray ionization mass spectra (ESI-MS), solid-state ultraviolet-visible (UV-Vis) spectroscopy, and single crystal X-ray diffraction (1, 2 and 4) studies. In vitro anticancer cell proliferation experiments against SiHa (human cervical squamous cancer cell line) cells, Bel-7402 (human hepatoma cancer cell line), Eca-109 (human esophageal cancer cell line) and HL-7702 (human normal hepatocyte cell line) indicate that they have more excellent anti-proliferation effects than the cis-platin against Siha cells, Bel-7402 cells and Eca-109 cells. Especially, complex 5 showed a rather outstanding inhibitory effect against the SiHa cell line and was less toxic than the other compounds to the HL-7702 cell line, implying an obvious specific inhibitory effect. Therefore, complex 5 has the potential value to be developed as an anticancer cell-specific drug against human cervical squamous carcinoma. Molecular docking simulation, UV-vis absorption spectroscopy and circular dichroism experiments show that they prefer to bind to DNA part in an embedded binding manner.

The relationship between plasma nickel concentrations and type 2 diabetes mellitus risk: A protective effect within a specific range

BACKGROUND

Nickel is considered an essential nutrient for certain microbial, plant, and animal species, but its role in human health remains controversial. Some studies have reported the relationship between nickel and type 2 diabetes mellitus (T2DM), but the results are not consistent and the mechanism is not clear, which needs further exploration.

AIM

To investigate the possible correlation between nickel and T2DM.

METHODS

We conducted a case-control study of 192 patients with T2DM and 189 healthy controls at a hospital in central China. Plasma concentrations of nickel and six other trace elements were measured with inductively coupled plasma mass spectrometry. Logistic regression models, restricted cubic spline models (RCS), and Bayesian kernel machine regression (BKMR) were used to evaluate the relationship between plasma nickel and T2DM and its metabolic risk factors, as well as the presence or absence of interactions between nickel and other elements.

RESULTS

The T2DM group exhibited considerably lower plasma nickel levels than the control group (P < 0.001). Whether using a crude or adjusted model, logistic regression analysis finds a negative correlation between nickel levels and the risk of T2DM (P trend < 0.001). According to the RCS, the risk of T2DM reduces with rising nickel levels when the value is below 6.1 μg/L; nickel has a negative linear correlation with fasting plasma glucose (FPG), an inverse U-shaped connection with superoxide dismutase (SOD), and a positive linear correlation with malondialdehyde (MDA) (all P overall < 0.05). The plasma nickel concentration was positively correlated with zinc, vanadium, and chromium (r = 0.23, 0.11, and 0.19, respectively; all P < 0.05) and negatively correlated with copper (r = - 0.11, P < 0.05). In the BKMR model, interactions of nickel with zinc on T2DM and SOD, nickel with chromium on T2DM and homeostasis model assessment of β cell (HOMA-β), and nickel with copper on FPG, homeostasis model assessment of insulin (HOMA-IR), and MDA were observed.

CONCLUSION

Nickel may have a dual effect on the risk of T2DM, with a protective range of less than 6.1 μg/L. Potential interactions between nickel, copper, zinc, and chromium existed in their associations with T2DM and its metabolic risk factors.

Indole-Containing Metal Complexes and Their Medicinal Applications

Indole is an important element of many natural and synthetic molecules with significant biological activity. Nonetheless, the co-presence of transitional metals in organic scaffold may represent an important factor in the development of effective medicinal agents. This review covers some of the latest and most relevant achievements in the biological and pharmacological activity of important indole-containing metal complexes in the area of drug discovery.

Nickel chloride complexes with substituted 4'-phenyl-2',2':6',2″-terpyridine ligands: synthesis, characterization, anti-proliferation activity and biomolecule interactions

A series of Ni(II) sandwich-like coordinated compounds were synthesized by the reaction of nickel dichloride and ten 4'-(4-substituent phenyl)-2',2':6',2″-terpyridine ligands, and their structures were confirmed by elemental analysis, FT-IR, ESI-MS, solid state ultraviolet spectroscopy and X-ray single crystal diffraction analysis. Three human cancer cell lines and a normal human cell line were used for anti-proliferation potential study: human lung cancer cell line (A549), human esophageal cancer cell line (Eca-109), human liver cancer cells (Bel-7402) and normal human liver cells (HL-7702). The results show that these nickel complexes possess good inhibitory effects on the cancer cells, outperforming the commonly used clinical chemotherapy drug cisplatin. Especially, complexes 3 (-methoxyl) and 7 (-fluoro) have strong inhibitory ability against Eca-109 cell line with IC50 values of 0.223 μM and 0.335 μM, complexes 4 and 6 showed certain cell selectivity, and complex 6 can inhibit cancer cells and slightly poison normal cells when the concentration was controlled. The ability of these complexes binding to CT-DNA was studied by UV titration and CD spectroscopy, and CD spectroscopy was also used to study the secondary structural change of BSA under the action of the complexes. The binding of these complexes with DNA, DNA-Topo I and bovine serum protein has been simulated by molecular docking software, and the docking results and optimal binding conformation data showed that they interacted with DNA in the mode of embedded binding, which is consistent with the experimental results. These complexes are more inclined to move to the cleavage site when docking with DNA-Topo I, so as to play a role of enzyme cleavage, while BSA promotes the action of the complexes by binding to effective binding sites.

Biomedical applications of selective metal complexes of indole, benzimidazole, benzothiazole and benzoxazole: A review (From 2015 to 2022)

Indole, benzoxazole benzothiazole and benzimidazole are excellent classes of organic heterocyclic compounds. These compounds show significant application in pharmacy, industries, dyes, medicine, polymers and food packages. These compounds also form metal complexes with copper, zinc, cadmium, nickel, cobalt, platinum, gold, palladium chromium, silver, iron, and other metals that have shown to be significant applications. Recently, researchers have attracted enormous attention toward heterocyclic compounds such as indole, benzimidazole, benzothiazole, benzoxazole, and their complexes due to their excellent medicinal applications such as anti-ulcerogenic, anti-cancer, antihypertensive, antifungal, anti-inflammatory, antitubercular, antiparasitic, anti-obesity, antimalarial, antiglycation, antiviral potency, antineuropathic, analgesic antioxidant, antihistaminic, and antibacterial potentials. In this article, we summarize the medicinal applications of these compounds as well as their metal complexes. We hope this article will help researchers in designing and synthesizing novel and potent compounds with significant applications in various fields.

Synthesis, Structure and Biological Activity of Indole-Imidazole Complexes with ZnCl2: Can Coordination Enhance the Functionality of Bioactive Ligands?

The ability of the indole-imidazole hybrid ligands to coordinate with the Zn(II) ion and the resulting structures of this new class of coordination compounds were analyzed in order to determine their structural properties and biological functionalities. For this purpose, six novel Zn(II) complexes, [Zn(InIm)₂Cl₂] (1), [Zn(InMeIm)₂Cl₂] (2), [Zn(IniPrIm)₂Cl₂] (3), [Zn(InEtMeIm)₂Cl₂] (4), [Zn(InPhIm)₂Cl₂] (5) and [Zn₂(InBzIm)₂Cl₂] (6) (where InIm is 3-((1H-imidazol-1-yl)methyl)-1H-indole), were synthesized by the reactions of ZnCl₂ and the corresponding ligand in a 1:2 molar ratio in methanol solvent at an ambient temperature. The structural and spectral characterization of these complexes was performed using NMR, FT-IR and ESI-MS spectrometry and elemental analysis, and the crystal structures of 1-5 were determined using single-crystal X-ray diffraction. Complexes 1-5 form polar supramolecular aggregates by utilizing, for this purpose, the N-H(indole)∙∙∙Cl(chloride) intermolecular hydrogen bonds. The assemblies thus formed differ depending on the distinctive molecular shape, which can be either compact or extended. All complexes were screened for their hemolytic, cytoprotective, antifungal, and antibacterial activities. The results show that the cytoprotective activity of the indole/imidazole ligand significantly increases upon its complexation with ZnCl₂ up to a value comparable with the standard antioxidant Trolox, while the response of its substituted analogues is diverse and less pronounced.

Nickel ions influence the transepithelial sodium transport in the trachea, intestine and skin

Measurements of transepithelial potential and resistance in tissue and organ model systems enable the evaluation of the Ni2+ effect on the epithelial sodium channels, aquaporin 3, and the sodium-potassium pump in the epithelial cells. The aim of the presented study was to assess the immediate and prolonged effect of nickel ions on the transport of sodium ions in tissues exposed to direct contact with nickel, including airways, digestive tract and the skin. The influence of 0.1 mM nickel solution was performed on the trachea (n = 34), intestine (n = 44), and skin (n = 51) samples descended from 16 New Zealand albino rabbits. The electrophysiological parameters were measured in a modified Ussing chamber in stationary conditions and during a 15-s mechanical-chemical stimulation. A statistically significant decrease in the electric resistance values and the smallest range of the measured potential were observed for the Ni-treated trachea specimens. The use of nickel solution did not affect the sodium transport in the intestine epithelium. The skin fragments showed altered sodium ion transport, as demonstrated by the lower range and intensity of the measured potential. The gastrointestinal tract seems to be an organ best adapted to contact with nickel ions. In airways, nickel ions most likely enter epithelial cells and the space between them, modifying proteins and the airway surface liquid. The skin turned out to be the most sensitive tissue to the intensification of sodium ion transport through nickel ions.

Experimental and theoretical studies of new Co(III) complexes of hydrazide derivatives proposed as multi-target inhibitors of SARS-CoV-2

Cobalt(III) complexes with Schiff base ligands derived from hydrazone, (HL 1  = (E)-N'-(3,5-dichloro-2-hydroxybenzylidene)-4-hydroxybenzohydrazide, HL 2  = (E)-N'-(3,5-dichloro-2-hydroxybenzylidene)-4-hydroxybenzohydrazide (3,5-dibromo-2-hydroxybenzylidene), and HL 3  = (E)-4-hydroxy-N'-(2-hydroxy-3-ethoxybenzylidene)benzohydrazide), were synthesized and characterized by elemental analysis, Fourier transform infrared (FT-IR) spectroscopy, UV-Vis spectroscopy, and cyclic voltammetry. X-ray diffraction was used to determine the single crystal structure of the complex (1). Co(III) was formed in a distorted, very regular octahedral coordination in this complex; three pyridine moieties complete this geometry. Schiff base complexes' redox behaviors are represented by irreversible (1), quasi-reversible (2), and quasi-reversible (3) voltammograms. A density functional theory (DFT)/B3LYP method was used to optimize cobalt complexes with a base set of 6-311G. Furthermore, fragments occupying the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were investigated at the same theoretical level. Quantum theory of atoms in molecules (QTAIM) computations were also done to study the coordination bonds and non-covalent interactions in the investigated structures. Hirshfeld surface analysis was used to investigate the nature and types of intermolecular exchanges in the crystal structure of the complex (1). The capacity of cobalt complexes to bind to the major protease SARS-CoV-2 and the molecular targets of human angiotensin-converting enzyme-2 (ACE-2) was investigated using molecular docking. The molecular simulation methods used to assess the probable binding states of cobalt complexes revealed that all three complexes were stabilized in the active envelope of the enzyme by making distinct interactions with critical amino acid residues. Interestingly, compound (2) performed better with both molecular targets and the total energy of the system than the other complexes.

Advances in thiosemicarbazone metal complexes as anti-lung cancer agents

The great success of cisplatin as a chemotherapeutic agent considerably increased research efforts in inorganic biochemistry to identify more metallic drugs having the potential of treating lung cancer. Metal coordination centres, which exhibit a wide range of coordination numbers and geometries, various oxidised and reduced states and the inherent ligand properties offer pharmaceutical chemists a plethora of drug structures. Owing to the presence of C=N and C=S bonds in a thiosemicarbazone Schiff base, N and S atoms in its hybrid orbital has lone pair of electrons, which can generate metal complexes with different stabilities with most metal elements under certain conditions. Such ligands and complexes play key roles in the treatment of anti-lung cancer. Research regarding metallic anti-lung cancer has advanced considerably, but there remain several challenges. In this review, we discuss the potential of thiosemicarbazone Schiff base complexes as anti-lung cancer drugs, their anti-cancer activities and the most likely action mechanisms involving the recent families of copper, nickel, platinum, ruthenium and other complexes.

Design and synthesis of heterocyclic azole based bioactive compounds: Molecular structures, quantum simulation, and mechanistic studies through docking as multi-target inhibitors of SARS-CoV-2 and cytotoxicity

Two heterocyclic azole compounds, 3-(2,3-dihydrobenzo[d]thiazol-2-yl)-4H-chromen-4-one (SVS1) and 5-(1H-indol-3-yl)-4-methyl-2,4-dihydro-3H-1,2,4-triazole-3-thione (SVS2) were obtained unexpectedly from 2-aminothiophenol and 4-oxo-4H-chromene-3-carbaldehyde (for SVS1), and (E)-2-((1H-indol-3-yl)methylene)-N-methylhydrazine-1-carbothioamide in the presence of anhydrous FeCl₃ (for SVS2), respectively. The compounds were well characterized by analytical and spectroscopic tools. The molecular structures of both the compounds were determined by single crystal X-ray diffraction (XRD) study. The results obtained from density functional theory (DFT) study revealed the molecular geometry and electron distribution of the compounds, which were correlated well with the three-dimensional structures obtained from the single crystal XRD. DMol³ was used to calculate quantum chemical parameters [chemical potential (µ), global hardness (η), global softness (σ), absolute electronegativity (χ) and electrophilicity index (ω)] of SVS1 and SVS2. Molecular docking study was performed to elucidate the binding ability of SVS1 and SVS2 with SARS-CoV-2 main protease and human angiotensin-converting enzyme-2 (ACE-2) molecular targets. Interestingly, the binding efficiency of the compounds with the molecular targets was comparable with that of remdesivir (SARS-CoV-2), chloroquine and hydroxychloroquine. SVS1 showed better docking energy than SVS2. The molecular docking study was complemented by molecular dynamics simulation study of SARS-CoV-2 main protease-SVS1 complex, which further exemplified the binding ability of SVS1 with the target. In addition, SVS1, SVS2 and cisplatin were assessed for their cytotoxicity against a panel of three human cancer cells such as HepG-2 (hepatic carcinoma), T24 (bladder) and EA.hy926 (endothelial), as well as Vero (kidney epithelial cells extracted from an African green monkey) normal cells using MTT assay. The results showed that SVS2 has significant cytotoxicity against HepG-2 and EA.hy926 cells with the IC₅₀ values of 33.8 μM (IC₅₀ = 49.9 μM-cisplatin and 8.6 μM-doxorubicin) and 29.2 (IC₅₀ = 26.6 μM-cisplatin and 3.8 μM-doxorubicin), respectively.

Structural characterization and antileishmanial activity of newly synthesized organo-bismuth(V) carboxylates: experimental and molecular docking studies

In a quest to discover new formulations for the treatment of various parasitic diseases, a series of heteroleptic triorganobismuth(V) biscarboxylates of type [BiR₃(O₂CR')₂], where R=C₆H₅ for 1-4 and p-CH₃C₆H₄ for 5-8, were synthesized, characterized and evaluated for their biological potential against L. tropica. All the synthesized complexes were fully characterized by elemental analysis, FT-IR, multinuclear (¹H and ¹³C) NMR spectroscopy and X-ray crystallography. The crystal structures for [BiPh₃(O₂CC₆H₄(o-Br))₂] (1), [BiPh₃(O₂CC₂H₂C₆H₄)₂] (2), [BiPh₃(O₂CC₆H₄(m-NO₂))₂] (3) and [BiPh₃(O₂CC₆H₄(2-OH,3-CH₃))₂] (4) were determined and found to have a distorted pentagonal bipyramidal molecular geometry with seven coordinated bismuth center for 1-3 and for 4 distorted octahedral geometry, respectively. All the synthesized complexes demonstrated a moderate to significant activity against leishmania parasites. A broad analytical approach was followed to testify the stability for (1-8) in solid state as well as in solution and in leishmanial culture M199, ensuring them to be stable enough to exert a significant antileishmanial effect with promising results. Cytotoxicity profile suggests that tris(tolyl) derivatives show lower toxicity against isolated lymphocytes with higher antileishmanial potential. Molecular docking studies were carried out to reveal the binding modes for (1-8) targeting the active site of trypanothione reductase (TR) (PDB ID: 4APN) and Trypanothione Synthetase-Amidase structure (PDB ID 2vob).

Effective inhibition of insulin amyloid fibril aggregation by nickel(II) complexes containing heterocyclic thiosemicarbazones

The sensitivity of protein molecular structures makes them susceptible to aggregation in conditions unfavorable for the maintenance of their native folds. The aggregation of proteins leads to many disorders, but the inhibition of amyloid fibril formation using metal-containing small molecules is gaining popularity. Herein we report the effect of nickel(II) complexes (N1, N2, N3, and N4) bearing thiosemicarbazones on the inhibition of amyloid fibril formation by insulin. The interactions of the complexes with amyloid fibrils were investigated using various biophysical techniques, including light scattering, intrinsic fluorescence assay, thioflavin T (ThT) assay, and Fourier transform-infrared spectroscopy. The results revealed that the phenyl-substituted N3 was an efficient inhibitor of amyloid fibril formation and maintained the insulin in its native structure despite conditions promoting fibrillation. Nickel(II) complexes containing indole based thiosemicarbazones were efficient in inhibiting the amyloid fibril formation and maintaining the insulin in its native structure in unfavorable conditions.

Binding mode transformation and biological activity on the Ru(II)-DMSO complexes bearing heterocyclic pyrazolyl ligands

Three Ru(II)-DMSO complexes (1-3) containing 2-(3-pyrazolyl)pyridine (PzPy), 2-pyrazol-3-ylfuran (PzO), or 2-pyrazol-3-ylthiophene (PzS) ligand, were synthesized and characterized. The monodentate coordination of the heterocyclic pyrazolyl ligand (Pz^Py) with Ru(II) ion via N atom was confirmed by single crystal X-ray diffraction. Complex 1 could be converted to the known η²-bidentate Pz^Py complex cis(Cl), cis(S)-[RuCl₂(Pz^Py)(DMSO)₂] (4) under reflux conditions. The mechanism underlying binding mode transformation was studied by ¹H NMR spectroscopy and density functional theory (DFT) calculations. The binding abilities of the complexes (1-4) with calf-thymus (CT) DNA and bovine serum albumin (BSA) were investigated using spectroscopic and molecular docking techniques. Among the four Ru(II) complexes, complexes 1 and 3 inhibited the long-term proliferation of human breast cancer cells, whereas complexes 2 and 4 did not inhibit their proliferation to a considerable extent. Interestingly, complexes 1 and 3 did not induce significant cell death but rather attenuated the clonogenicity of breast cancer cells by upregulating reactive oxygen species (ROS), endoplasmic reticulum (ER) and autophagic stress.

Synthesis of indole-substituted thiosemicarbazones as an aldose reductase inhibitor: an in vitro, selectivity and in silico study

Aim: Indole is an important component of many drug molecules, and its conjugation with thiosemicarbazone moiety would be advantageous in finding lead compounds for the development of diabetic complications. Methodology: We have designed, synthesized and evaluated a series of 17 indole-thiosemicarbazones (3a-q) as aldose reductase (ALR2) and aldehyde reductase (ALR1) inhibitors. Results: After in vitro evaluation, all indole-thiosemicarbazones showed significant inhibition against both enzyme ALR1 and ALR2 with IC₅₀ in range of 0.42-20.7 and 1.02-19.1 μM, respectively. The docking study was also carried out to consider the putative binding of molecules with the target enzymes. Conclusion: Compound 3f was found to be most active and selective for ALR2. The indole-thiosemicarbazones series described here has selective hits for diabetes-mellitus-associated complications.

N-substitution in isatin thiosemicarbazones decides nuclearity of Cu(II) complexes - Spectroscopic, molecular docking and cytotoxic studies

The mono- (1) and bi-nuclear (2) copper(II) complexes containing N-substituted isatin thiosemicarbazone(s) were synthesized, and characterized by analytical and spectroscopic (UV-Visible, FT-IR and EPR) techniques. Bimetallic nature of complex 2 was confirmed by single crystal X-ray crystallography. The structures predicted by spectroscopic and crystallographic methods were validated by computational studies. From the spectroscopic, crystallographic and computational data, the structures were found to be distorted square planar for 1 and distorted square pyramidal for 2. Molecular docking studies showed hydrogen bonding and hydrophobic interactions of the complexes with tyrosinase kinase receptors. Complex 1 exhibited promising cytotoxic activity against Jurkat (leukemia) cell line, and complex 2 displayed more activity against HeLa S3 (cervical) and Jurkat cell lines with the IC₅₀ values of 3.53 and 3.70 μM, respectively. Cytotoxicity of 1 (Jurkat) and 2 (Jurkat and HeLa S3) was better than that of cisplatin. Morphological changes in A549 (lung), HeLa S3 and Jurkat cell lines were examined in presence of the active complexes with the co-staining of Hoechst, AO (acridine orange) and EB (ethidium bromide) by fluorescence microscope.

Synthesis of Palladium(II) Complexes via Michael Addition: Antiproliferative Effects through ROS-Mediated Mitochondrial Apoptosis and Docking with SARS-CoV-2

Metal complexes have numerous applications in the current era, particularly in the field of pharmaceutical chemistry and catalysis. A novel synthetic approach for the same is always a beneficial addition to the literature. Henceforth, for the first time, we report the formation of three new Pd(II) complexes through the Michael addition pathway. Three chromone-based thiosemicarbazone ligands (SVSL1-SVSL3) and Pd(II) complexes (1-3) were synthesized and characterized by analytical and spectroscopic tools. The Michael addition pathway for the formation of complexes was confirmed by spectroscopic studies. Distorted square planar structure of complex 2 was confirmed by single-crystal X-ray diffraction. Complexes 1-3 were subjected to DNA- and BSA-binding studies. The complex with cyclohexyl substituent on the terminal N of thiosemicarbazone (3) showed the highest binding efficacy toward these biomolecules, which was further understood through molecular docking studies. The anticancer potential of these complexes was studied preliminarily by using MTT assay in cancer and normal cell lines along with the benchmark drugs (cisplatin, carboplatin, and gemcitabine). It was found that complex 3 was highly toxic toward MDA-MB-231 and AsPC-1 cancer cells with IC50 values of 0.5 and 0.9 μM, respectively, and was more efficient than the standard drugs. The programmed cell death mechanism of the complexes in MDA-MB-231 cancer cells was confirmed. Furthermore, the complexes induced apoptosis via ROS-mediated mitochondrial signaling pathway. Conveniently, all the complexes showed less toxicity (≥50 μM) against MCF-10a normal cell line. Molecular docking studies were performed with VEGFR2, EGFR, and SARS-CoV-2 main protease to illustrate the binding efficiency of the complexes with these receptors. To our surprise, binding potential of the complexes with SARS-CoV-2 main protease was higher than that with chloroquine and hydroxychloroquine.

Investigation of biological activity of nickel (II) complex with naproxen and 1,10-phenanthroline ligands

After the accidental discovery of cis-platinum, extensive attempts have centralized on the rational design of metallic compounds for cancer treatment. Here a solvent-dependent complex of nickel (II) with 1,10-phenanthroline and naproxen, [Ni(1,10-phenanthroline)(naproxen)₂(solvent)], solvent = 83% H₂O and 17% EtOH in the crystal structure, has been synthesized and specified by the X-ray structure analysis. It's in vitro DNA binding was inspected by the multispectroscopic methods and gel electrophoresis. The data of DNA-viscosity and competition fluorimetric test by methylene blue (MB) and Hoechst 33258 confirm groove binding mode of the complex to CT-DNA. Comparison of the results of this binding study with previous work revealed that the mode of binding of small compounds to DNA is highly influenced by the structure of the compounds. The DNA cleavage potency of the complex was appraised by the agarose gel electrophoretic and it was found that the complex does not have any momentous cleavage potency on the pUC18 plasmid DNA. The cytotoxicity of the complex on HT 29, HepG2 and HEK-293 cell lines by MTT method indicates that %inhibition of the complex on HT 29 is better than HepG2, compared with cisplatin drug. On HEK-293 cells, %inhibition growth of normal cells of the complex is less than cisplatin. Flow cytometry analysis of the complex on the HT 29 cells indicated the apoptosis cell death. RT-PCR studies revealed down-regulation of BCL2 expression, while the expression of BAX, caspase 3 and BAX/BCL2 genes was up-regulated in HT 29 cells by the complex. HighlightsA solvent-dependent nickel (II) with naproxen and 1,10-phenanthroline with aqueous solubility was synthesized and characterized.All experimental results indicate a groove mode of binding of the complex to CT-DNA.Potential biological characteristics confirmed that the complex is a promising candidate as anticancer agent.Communicated by Ramaswamy H. Sarma.

Guedes da Silva MF, Marzano C. Synthesis, Characterization and Biological Activity of Novel Cu(II) Complexes of 6-Methyl-2-Oxo-1,2-Dihydroquinoline-3-Carbaldehyde-4n-Substituted Thiosemicarbazones

Three new 6-methyl-2-oxo-1,2-dihydroquinoline-3-carbaldehyde-thiosemicarbazones-N-4-substituted pro-ligands and their Cu(II) complexes (1, -NH2; 2, -NHMe; 3, -NHEt) have been prepared and characterized. In both the X-ray structures of 1 and 3, two crystallographically independent complex molecules were found that differ either in the nature of weakly metal-binding species (water in 1a and nitrate in 1b) or in the co-ligand (water in 3a and methanol in 3b). Electron Paramagnetic Resonance (EPR) measurements carried out on complexes 1 and 3 confirmed the presence of such different species in the solution. The electrochemical behavior of the pro-ligands and of the complexes was investigated, as well as their biological activity. Complexes 2 and 3 exhibited a high cytotoxicity against human tumor cells and 3D spheroids derived from solid tumors, related to the high cellular uptake. Complexes 2 and 3 also showed a high selectivity towards cancerous cell lines with respect to non-cancerous cell lines and were able to circumvent cisplatin resistance. Via the Transmission Electron Microscopy (TEM) imaging technique, preliminary insights into the biological activity of copper complexes were obtained.

Exploring indole derivatives as myeloid cell leukaemia-1 (Mcl-1) inhibitors with multi-QSAR approach: a novel hope in anti-cancer drug discovery

In humans, the over-expression of Mcl-1 protein causes different cancers and it is also responsible for cancer resistance to different cytotoxic agents.

Synthesis, DNA/BSA binding studies and in vitro biological assay of nickel(II) complexes incorporating tridentate aroylhydrazone and triphenylphosphine ligands

Two new nickel (II) triphenylphosphine complexes derived from tridentate aroylhydrazone ligands [H2L1 = 2-hydroxy-3-methoxybenzylidene)benzohydrazone and H2L2 = N'-(2-hydroxy-3-methoxybenzylidene)-2-hydroxybenzoylhydrazone] and triphenylphosphine were prepared and their molecular structures were determined by single crystal X-ray diffraction analysis. Both nickel(II) complexes showed slightly distorted square planar geometry with one tridentate aroylhydrazone ligand coordinated through ONO donor atoms and one triphenylphosphine ligand coordinated to the nickel center through the phosphorus atom. DNA interaction studies indicated that both complexes possessed higher affinity to herring sperm DNA (HS-DNA) than the corresponding free aroylhydrazone ligand. Molecular docking investigations showed that both complexes could bind to DNA through intercalation of the phenyl rings between adjacent base pairs in the double helix. Meanwhile, bovine serum albumin (BSA) binding studies revealed the complexes could effectively interact with BSA and change the secondary structure of BSA. Further pharmacological evaluations of the synthesized complexes by in vitro antioxidant assays demonstrated high antioxidant activity against NO· and O2˙- radicals. The anticancer activity of each complex was assessed through in vitro cytotoxicity assays (CCK-8 kit) toward A549 and MCF-7 cancer cell and normal L-02 cell lines. Significantly, the Ni(II) complex derived from H2L1 ligand was found to be more effective cytotoxic toward MCF-7cancerous cell with the IC50 value equaled 9.7 μM, which showed potent cytotoxic activity over standard drug cisplatin. AbbreviationsA549human lung carcinoma cellBSAbovine serum albuminCCK-8Cell Counting Kit-8DFTdensity functional theoryDNAdeoxyribonucleic acidDPPH˙2,2-diphenyl-1-picrylhydrazylH2L12-hydroxy-3-methoxybenzylidene)benzohydrazone N'-(2-hydroxy-3-methoxybenzylidene)-2-hydroxybenzoylhydrazoneH2L2N'-(2-hydroxy-3-methoxybenzylidene)-2-hydroxybenzoylhydrazoneHOMOhighest occupied molecular orbitalIC50the 50% activityL-02human normal liver cellLOMOlowest unoccupied molecular orbital (LUMO)MCF-7human breast carcinoma cellNO˙nitric oxideO2˙-superoxide anionSODsuperoxide dismutaseCommunicated by Ramaswamy H. Sarma.

para metallation of 3-acetyl-chromen-2-one Schiff bases in tetranuclear palladacycles: focus on their biomolecular interaction and in vitro cytotoxicity

Three tetranuclear (1-3) complexes and a mononuclear (4) palladium(ii) complex were synthesized from 3-acetyl-chromen-2-one Schiff base ligands [H₂-3MAC-Rtsc] (where R = H [H₂-3MAC-tsc]; CH₃[H₂-3MAC-mtsc]; C₂H₅[H₂-3MAC-etsc] or C₆H₅[H₂-3MAC-ptsc]) and potassium tetrachloropalladate. Their formation was confirmed by spectroscopic techniques and X-ray crystallographic analysis. Their ability to bind with DNA and albumin was analysed by using absorption and emission titrations. The MTT assay was carried out to analyze the anticancer potential of the ligands and synthesized complexes against HepG2 (human liver cancer) and HT-29 (human colon cancer) cells. In addition, the compounds were less toxic when tested against the human normal keratinocyte cells (HaCaT). Ligands and complexes displayed better cytotoxicity with lower IC₅₀ values than the standard drug cisplatin. Further AO-EB and DAPI staining assays were carried out to detect the mode of cell death induced by the complexes i.e. apoptosis or necrosis. The complex 3 showed better cytotoxicity and was further subjected to flow cytometric analysis. The results suggested that the complex 3 induced apoptotic cell death.

Highly active copper(i) complexes of aroylthiourea ligands against cancer cells – synthetic and biological studies

Copper(i) complexes containing sulfur donor monodentate aroylthiourea ligands have been synthesized and evaluated for their biological applications.