Synthesis, characterization, and antitumor activity of three ternary dinuclear copper (II) complexes with a reduced Schiff base ligand and diimine coligands in vitro and in vivo

Biological Applications, In Vitro Cytotoxicity, Cellular Uptake, and Apoptotic Pathway Studies Induced by Ternary Cu (II) Complexes Involving Triflupromazine with Biorelevant Ligands

The novel mixed-ligand complexes derived from the parent antidepressant phenothiazine drug triflupromazine (TFP) were synthesized along with the secondary ligands glycine and histidine. [Cu(TFP)(Gly)Cl]·2H2O (1) and [Cu(TFP)(His)Cl]·2H2O (2) were examined for their in vitro biological properties. Cyclic voltammetry was used to study the binding of both complexes to CT-DNA. The two complexes were examined for antiviral, antiparasite, and anti-inflammatory applications. An in vitro cytotoxicity study on two different cancer cell lines, MCF-7, HepG2, and a normal cell line, HSF, shows promising selective cytotoxicity for cancer cells. An investigation of the cell cycle and apoptosis rates was evaluated by flow cytometry with Annexin V-FITC/Propidium Iodide (PI) staining of the treated cells. Gene expression and western blotting were carried out to determine the expression levels of the pro-apoptotic markers and the anti-apoptotic marker Bcl2. The tested complexes decreased cell viability and triggered apoptosis in human tumor cell lines. Molecular docking was also used to simulate Bcl2 inhibition. Finally, complex (2) has potent antitumor effects on human tumor cells, especially against HepG2 cells, as seen in the cellular drug uptake assay. Consequently, complex (2) may prove useful against cancer, especially liver cancer. For further understanding, it needs to be explored in vivo.

Phenanthroline and Schiff Base associated Cu(II)-coordinated compounds containing N, O as donor atoms for potent anticancer activity

As an inherent metal ion, copper has been the subject of investigation for developing a novel antitumoral compound that exhibits fewer adverse effects. Copper serves as a cofactor in multiple enzymes, generates reactive oxygen species (ROS), facilitates tumour evolution, metastasis and angiogenesis and has been detected at elevated concentrations in the serum and tissues of various human cancer types. In the given setting, utilising two methodologies in developing novel Copper-based pharmaceuticals for anti-cancer applications is standard practice. These approaches involve either the sequestration of unbound Copper ions or the synthesis of Copper complexes that induce cellular apoptosis. In the past four decades, the latter system has been used, leading to numerous reviews that have examined the anticancer characteristics of a wide range of Copper complexes. These analyses have consistently demonstrated that multiple factors frequently influence the efficacy of these compounds. This review examines the possible anticancer properties of copper and Cu(II) complexes that incorporate Schiff base ligands containing 1,10-phenanthroline. The present study will comprehensively analyse the examined cell lines and mechanistic research associated with each complex.

A novel water-soluble Cu(II) gluconate complex inhibits cancer cell growth by triggering apoptosis and ferroptosis related mechanisms

Metal copper complexes have attracted extensive attention as potential alternatives to platinum-based anticancer drugs due to their possible different modes of action. Herein, a new copper(II) gluconate complex, namely [Cu(DPQ)(Gluc)]·2H₂O (CuGluc, DPQ = pyrazino[2,3-f][1,10]phenanthroline), with good water-solubility and high anticancer activity was synthesized by using D-gluconic acid (Gluc-2H) as an auxiliary ligand. The complex was well characterized by single-crystal X-ray diffraction analysis, elemental analysis, molar conductivity, and Fourier transform infrared spectroscopy (FTIR). The DNA-binding experiments revealed that CuGluc was bound to DNA by intercalation with end-stacking binding. CuGluc could oxidatively cleave DNA, in which ¹O₂ and H₂O₂ were involved. In addition, CuGluc was bound to the IIA subdomain of human serum albumin (HSA) through hydrophobic interaction and hydrogen bonding, showing a good affinity for HSA. The complex showed superior anticancer activity toward several cancer cells than cisplatin in vitro. Further studies indicated that CuGluc caused apoptotic cell death in human liver cancer (HepG2) cells through elevated intracellular reactive oxygen species (ROS) levels, mitochondrial dysfunction, cell cycle arrest, and caspase activation. Interestingly, CuGluc also triggered the ferroptosis mechanism through lipid peroxide accumulation and inhibition of glutathione peroxidase 4 (GPX4) activity. More importantly, CuGluc significantly inhibited tumor growth in vivo, which may benefit from the combined effects of apoptosis and ferroptosis. This work provides a promising strategy to develop highly effective antitumor copper complexes by coordinating with the glucose metabolite D-gluconic acid and exploiting the synergistic effects of apoptosis and ferroptosis mechanisms.

Self-assembly of new cobalt complexes based on [Co (SCN)4], synthesis, empirical, antioxidant activity, and quantum theory investigations

The cobalt (II) complexes have been synthesized from the reaction of the cationic entities (3,4-dimethylaniline (1) and histamine (2)) with metallic salt CoCl₂⋅6H₂O and thiocyanate ion (SCN⁻) as a ligand in H₂O/ethanolic solution and processing by the evaporation crystal growth method at room temperature to get crystals. The synthesized complex has been fully characterized by single-crystal X-ray diffraction. UV–Visible, FTIR spectroscopy, TGA analysis, and DFT circulations were also performed. The crystal structural analysis reveals that the solid (1) {[Co(SCN)₄] (C₈H₁₂N)₃}·Cl crystallizes in the monoclinic system with the space group P2₁/n and the solid (2) {[Co(SCN)₄](C₅H₁₁N₃)₂}·2Cl crystallizes in the monoclinic space group P2₁/m. Metal cations are joined into corrugated chains parallel to the b-axis direction in (1) and (2) by four thiocyanate anions. The crystal structures of (1) and (2) were calculated using XRPD data, indicating that they are closely connected to the DRX mono-crystal results. Different interactions pack the system into a ring formed by N–H⋯Cl and N–H⋯S hydrogen bonds. C–H⋯π and the π⋯π stacking of anilinuim ring for (1) and N–H⋯S intermolecular interactions for (1) and (2) increase the crystals' robustness. Hirshfeld surface analysis cum 2D fingerprint plots visualize the main intermolecular interactions with their contributions in the solid-state phase. The molecular geometries of both complexes obtained from the crystal structure were used for quantum chemical calculation. Here, frontier orbital analysis and electrostatic potential illustrate the chemical reactivities of metal–organic complexes. QTAIM and NCI analysis reveal the strength of interactions at the electronic level.

Three metal complexes with a pyridyl Schiff base: cytotoxicity, migration and mechanism of apoptosis

Three metal complexes [CuL(NO₃)]_n (1), [Cd(HL)(NO₃)₂]_n (2) and [EuL(HCOOH)(H₂O)(NO₃)₂] (3) were synthesized with a pyridyl Schiff ligand L (N'-[(1E)-pyridin-2-ylmethylidene]pyridine-4-carbohydrazide). A crystallographic study revealed that complexes 1 and 2 have a chain structure, and complex 3 is a zero-dimensional monomer. In vitro cytotoxicity studies showed that complex 2 had the best antiproliferative activity against SMMC-7721 cells and complex 3 had the best antiproliferative activity against MDA-MB-231 cells with single-digit IC₅₀ values, both exceeding those of the control drug cisplatin by far. The cell invasion and migration ability through the transwell assay and wound-healing assay showed that the selected complexes could inhibit the invasion and migration of cancer cells. The Hoechst staining assay and ROS generation assay with SMMC-7721 cells indicated that the cytotoxic effects of complex 2 involved apoptosis induction through ROS accumulation. The apoptosis-inducing and cell cycle arrest effects of complex 2 on SMMC-7721 cells indicated that the antitumor effect was achieved through apoptosis induction and inhibition of DNA synthesis by blocking the G₀/G₁ phase of the cell cycle. In addition, complex 2 showed significant inhibition against B. dysentery with an inhibition circle diameter of 24 mm.

Elaboration of novel urea bearing schiff bases as potent in vitro anticancer candidates with low in vivo acute oral toxicity

A novel series of urea Schiff base derivatives were synthesized via the condensation of o-phenylenediamine, naphthyl isocyanate and appropriate aryl aldehyde. The results of the in vitro cytotoxic activities of compounds 5a–h against cancer cells lines PC3, SKOV-3 and HeLa, revealed that almost all compounds exhibited good to moderate activities Compound 5g owing bromine atom at p-position displayed higher activity compared to homolog 5b possessing chlorine atom due to adequate diameter of bromine which is more favourable than chlorine for the inhibition activity. In addition, compound 5h is the best candidate of this series exhibiting excellent activity for three cancer cells lines. Compound 5h demonstrated also an excellent activity with IC50 value of 0.6±0.3μg/mL for prostate cancer cell line PC3 and it is considered more effective than the standard drug doxorubicin Dox (IC50 = 2.6±0.03μg/mL). The most active compound 5h displayed the best activity against ovarian cancer cell line SKOV3 with IC50 = 1.8±0.2μg/mL. This results are higher than clinically used drug Dox (IC50. 2.2±0.02μg/mL). The results of screening activities cytotoxic effect toward cervix cancer cell line HeLa, affirm that compound 5h manifest an activity with IC50 value of 2.2±0.4μg/mL comparable to Dox (IC50. 1.9±0.04μg/mL). In the current study, in vivo acute oral toxicity assessment of urea Schiff base hybrid compounds 5a – h indicated that there was no mortality on treated female mice during 14 days assessment test compared with the vehicle-treated group confirming the safety with LD50 greater than 2000 mg/kg. In the actual study, the results affirmed that compounds 5a–h manifested in vivo no toxicity to saint cells, the compounds 5b, 5g and 5h presented higher anticancer activities against three cancer cells which authorizes promoters to use them as candidate anticancer agents.

A novel biocompatible formate bridged 1D-Cu(ii) coordination polymer induces apoptosis selectively in human lung adenocarcinoma (A549) cells

Copper compounds are promising candidates for next-generation metal anticancer drugs. Therefore, we synthesized and characterized a formate bridged 1D coordination polymer [Cu(L)(HCOO)₂]_n, (L = 2-methoxy-6-methyl-3-((quinolin-8-ylimino)methyl)chroman-4-ol), PCU1, wherein the Cu(ii) center adopts a square pyramidal coordination environment with adjacent CuCu distances of 5.28 Å. Primarily, in vitro DNA interaction studies revealed a metallopolymer which possesses high DNA binding propensity and cleaves DNA via the oxidative pathway. We further analysed its potential on cancerous cells MCF-7, HeLa, A549, and two non-tumorigenic cells HEK293 and HBE. The selective cytotoxicity potential of PCU1 against A549 cells driven us to examine the mechanistic pathways comprehensively by carrying out various assays viz, cell cycle arrest, Annexin V-FTIC/PI assay, autophagy, intercellular localization, mitochondrial membrane potential 'MMP', antiproliferative assay, and gene expression of TGF-β and MMP-2.

Synthesis and physicochemical, DFT, thermal and DNA-binding analysis of a new pentadentate N3S2 Schiff base ligand and its [CuN3S2]2+ complexes

A new N₃S₂ pentadentate Schiff base ligand derived from 5-bromothiophene-2-carbaldehyde, (E)-N1-((5-bromothiophen-2-yl)methylene)-N2-(2-((E)-((5-bromothiophen-2-yl)-methylene amino) ethyl ethane-1,2-diamine, is prepared. The ligand and its complexes are subjected to extensive physical and theoretical analyses and the results are consistent with their predicted compositions. Dicationic Cu(ii) complexes ([CuN₃S₂]X₂) with a coordination number of 5 are proposed on the basis of the spectral data with N₃S₂ serving as a pentadentate ligand. The prepared complexes display a square pyramidal geometry around the Cu(ii) center. TG shows different thermal behavior for the N₃S₂ ligand and its complexes. Solvatochromism of the complexes is promoted by the polarity of the solvent used. A one-electron transfer Cu(ii)/Cu(i) reversible redox reaction is promoted by CV. SEM and EDS of the free ligand and its complexes support the morphology and composition changes observed upon the complexation of Cu(ii). As an outstanding goal to develop anticancer new metal chemotherapy, preliminary studies of the binding of the desired complexes with DNA were carried out, as it is through judging the strength of interactions that a future drug can be designed and synthesized. The viscosity and absorption results obtained for complex 1 indicated its enhanced CT-DNA binding properties as compared to those of complex 2 with K_b values of 3.2 × 10⁵ and 2.5 × 10⁵ M⁻¹, respectively.

A new N₃S₂ pentadentate Schiff base ligand derived from 5-bromothiophene-2-carbaldehyde, (E)-N1-((5-bromothiophen-2-yl)methylene)-N2-(2-((E)-((5-bromothiophen-2-yl)-methylene amino) ethyl ethane-1,2-diamine, is prepared.

Synthesis and Spectral Identification of Three Schiff Bases with a 2-(Piperazin-1-yl)-N-(thiophen-2-yl methylene)ethanamine Moiety Acting as Novel Pancreatic Lipase Inhibitors: Thermal, DFT, Antioxidant, Antibacterial, and Molecular Docking Investigations

Three new tetradentate NNNS Schiff bases (L1–L3) derived from 2-(piperidin-4-yl)ethanamine were prepared in high yields. UV–Visible and FTIR spectroscopy were used to monitor the dehydration reaction between 2-(piperidin-4-yl)ethanamine and the corresponding aldehydes. Structures of the derived Schiff bases were deduced by ¹H and ¹³C NMR, FTIR, UV–Vis, MS, EA, EDS, and TG-derived physical measurements. DFT/B3LYP theoretical calculations for optimization, TD-DFT, frequency, Molecular Electrostatic Potential (MEP), and highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) / were performed for L2. The in vitro antimicrobial activities of the three Schiff bases were evaluated against several types of bacteria by disk diffusion test using Gentamicin as the standard antibiotic. Schiff bases revealed good antioxidant activity by the DPPH method, and the IC₅₀ values were compared to the Trolox standard. Pancreatic porcine lipase inhibition assay of the synthesized compounds revealed promising activity as compared to the Orlistat reference.

Cu(ii)-TACN complexes selectively induce antitumor activity in HepG-2 cells via DNA damage and mitochondrial-ROS-mediated apoptosis

A novel 1,4,7-triazacyclononane derivative (btacn), and its related copper complexes, Cu(btacn)Cl₂ and [Cu(btacn)₂]·(ClO₄)₂, exhibit potent anti-proliferation activity towards HepG-2 and HeLa cells, but low cytotoxicity towards normal cell lines.

Ternary copper(II) complex: NCI60 screening, toxicity studies, and evaluation of efficacy in xenograft models of nasopharyngeal carcinoma

Copper(II) ternary complex, [Cu(phen)(C-dmg)(H₂O)]NO₃ was evaluated against a panel of cell lines, tested for in vivo efficacy in nasopharyngeal carcinoma xenograft models as well as for toxicity in NOD scid gamma mice. The Cu(II) complex displayed broad spectrum cytotoxicity against multiple cancer types, including lung, colon, central nervous system, melanoma, ovarian, and prostate cancer cell lines in the NCI-60 panel. The Cu(II) complex did not cause significant induction of cytochrome P450 (CYP) 3A and 1A enzymes but moderately inhibited CYP isoforms 1A2, 2C9, 2C19, 2D6, 2B6, 2C8 and 3A4. The complex significantly inhibited tumor growth in nasopharyngeal carcinoma xenograft bearing mice models at doses which were well tolerated without causing significant or permanent toxic side effects. However, higher doses which resulted in better inhibition of tumor growth also resulted in toxicity.

Hybrid pharmacophore approach for bio-relevant di-imines based homobimetallic complexes incorporating functionalized dicarboxylates as co-ligands: Synthesis, spectral and structural activity dependent biological insights (in-vitro DNA and HSA binding, antioxidant and cytotoxicity)

Synthesis of bio-efficient homobimetallic complexes, [Cu₂(L¹)₂(dipic)](NO₃)₂.3H₂O (1), [Zn₂(L¹)₂(dipic)](NO₃)₂.4H₂O (2), [Cu₂(L²)₂(oxa)](NO₃)₂.4H₂O (3) and [Zn₂(L²)₂(oxa)] (NO₃)₂.5H₂O (4) was carried out using Schiff bases [(N¹E,N²E)-N¹,N²-bis(5-chlorothiophen-2-ylmethylene)-4-chlorobenzene-1,2-diamine; L¹] and [(N¹E,N²E)-N¹,N²-bis(5-chlorofuran-2-ylmethylene)-4-chlorobenzene-1,2-diamine; L²] as main ligands and dicarboxylate moieties of 2,6-pyridine dicarboxylic acid (H₂-dipic) and oxalic acid (H₂-oxa) as co-ligands, respectively in order to apprehend their structure activity relationships on the basis of pharmacophore hybrid approach. The stoichiometry, geometry, thermal stability, morphology and crystallite size of the compounds were inferred by analytical, spectral (FT-IR, ¹H NMR and ¹³C NMR and Mass), thermal (TGA/DTA), SEM and XRD studies. In-vitro DNA and HSA binding profiles of complexes were analysed by different biophysical measurements. The absorption study divulged that the observed alterations in the physico-chemical properties of complexes upon binding with DNA connoted their intercalative binding mode while fluorescence quenching mechanism was quantified by using Stern Volmer constant (K_SV)_; 1.73×10⁴ (1), 1.47×10⁴ (2), 5.65×10³ (3) and 3.60×10³M^-1 (4) which discerned that hybrid pharmacophore active metal complexes (1 and 2) exhibited efficient quenching effect with Ct-DNA in comparison to complexes (3 and 4) due to greater planarity and extent of conjugation (π-π interactions). The intercalative binding mode of complexes is further supported by competitive displacement assay by using fluorogenic dyes (EtBr and Hoechst 33258). The results of HSA fluorescence study divulged static quenching of the complexes (1-4) with K_SV values of 7.24×10⁴ (1), 6.03×10⁴ (2), 5.06×10⁴ (3) and 2.85×10⁴ (4) while K_b values; 1.16×10⁵ (1), 2.01×10⁴ (2), 5.84×10³ (3) and 8.60×10² (4) suggested them potent avid binder of HSA. Additionally, comparative estimation of scavenging properties using DPPH, superoxide(O₂^.-), hydroxyl (OH^-) and ABTS method and in-vitro cytotoxicity against different cell lines (MCF-7, HeLa and Hep G2) brought out distinct biopotency of complexes due to diverse structural features and chelation effect.

New amino acid-Schiff base derived from s-allyl cysteine and methionine alleviates carbon tetrachloride-induced liver dysfunction

In spite of the tremendous stride in modern medicine, conventional drugs used in the hepatotoxic management are mostly inadequate. The present study aims in the synthesis of novel Schiff base compound derived using s-allyl cystiene and methionine. The newly synthesized compound, 2-((2-((2-(allylthio)-1-carboxyethyl)imino)ethylidene)amino)-4-(methylthio)butanoic acid (ACEMB) was characterized using UV-visible spectrophotometer, FTIR, ¹HNMR, and GC-MS. ACEMB showed potent in vitro antioxidant property. Chronic administration of ACEMB prior to CCl₄ intoxication: i) attenuated the leakage of liver injury markers, such as, enzymes (AST, ALT, GGT, ALP and LDH) and biomolecules (bilirubin) into the blood circulation; ii) normalized the concentration of total proteins, albumin and globulin to control level; and iii) protected the liver against dyslipidemia. These effects of ACEMB show the preservation of endoplasmic reticulum function against CCl₄ toxicity in the liver. The protective effect of ACEMB was due to its antioxidant property, which was revealed by reduced oxidative stress (TBARS and HP) and enhanced functions of the endogenous antioxidative system (SOD, catalase, GPx, GST, GSH, vitamin E and C) against CCl₄ intoxication. Also, ACEMB protected the functional activities of the various mitochondrial tricarboxylic acid cycle and oxidative phosphorylation enzymes. The biochemical alterations are in concurrence with the histological observations, wherein ACEMB pretreatment prevented the vacuolation, degeneration of nuclei and necrosis of hepatocytes. In addition, in silico analysis reveals the interaction of ACEMB in the active site of cytochrome P450. ACEMB mediates hepatoprotective effect by substituting itself as an antioxidant and decreasing oxidative stress, thereby diminishing the intracellular organelle dysfunction against CCl₄ toxicity in the liver.

Synthesis, characterization and anticancer activities of transition metal complexes with a nicotinohydrazone ligand

The reaction of divalent transition metal salts and (E)-N'-(1-(pyridin-2-yl)ethylidene)nicotinohydrazide (penh) led to the formation of [Mn(penh)₂] (complex 1), [Co(penh)₂] (complex 2), [Cu(penh)₂] (complex 3) and [Cd (penh)₂] (complex 4) complexes. The four complexes were characterized using elemental analyses, infrared spectra and single-crystal X-ray diffraction analyses. Subsequently, the complexes were used for in vitro cell level experiments to determine potential antitumor effects. The results demonstrated that the complexes exhibited a similar structure; however, they were crystallized with distinct space groups. In comparison with the uncomplexed penh ligand, all four complexes were able to markedly decrease the proliferation rate of various types of tumor cell, including the human lung cancer cell line A549, human gastric cancer cell line BGC823 and human esophageal cancer cell line Eca109, in a concentration-dependent manner. Furthermore, the complexes promoted tumor cell apoptosis, as demonstrated in the apoptosis assay, and this was confirmed using electrophoresis.