The cytotoxicity and mechanisms of 1,2-naphthoquinone thiosemicarbazone and its metal derivatives against MCF-7 human breast cancer cells

Bio-molecular Fe(III) and Zn(II) complexes stimulate the interplay between PI3K/AKT1/EGFR inhibition and induce autophagy and apoptosis in epidermal skin cell cancer

This study investigated the effectiveness and safety of a hybrid thiosemicarbazone ligand (HL) and its metal complexes (MnII-L, FeIII-L, NiII-HL, and ZnII-HL) against epidermoid carcinoma (A-431). The results indicated that FeIII-L is the most effective, with a high selectivity index of 8.01 and an IC50 of 17.49 ± 2.12 μM for FeIII-L. The study also revealed that the synthesized complexes effectively inhibited gene expression of the Phosphoinositide 3-kinases (PI3K), alpha serine/threonine-protein kinase (AKT1), epidermal growth factor receptor (EGFR2) axis mechanism (P < 0.0001). Additionally, these complexes trigger a chain of events that include the inhibition of proliferating cell nuclear antigen (PCNA), transforming growth factor β1 (TGF β1), and topoisomerase II, and leading to a decrease in epidermoid cell proliferation. Furthermore, the inhibitory activity also resulted in the upregulation of caspases 3 and 9, indicating the acceleration of apoptotic markers, and the down regulation of miRNA221, suggesting a decrease in epidermoid proliferation. Molecular modeling of FeIII-L revealed that it had the best binding energy -8.02 kcal/mol and interacted with five hydrophobic π-interactions with Val270, Gln79, Leu210, and Trp80 against AKT1. Furthermore, the binding orientation of FeIII-L with Topoisomerase II was found to be the most stable, with a binding energy -8.25 kcal/mol. This stability was attributed to the presence of five hydrophobic π-interactions with His759, Guanin13, Cytosin8, and Ala465, and numerous ionic interactions, which were more favorable than those of doxorubicin and etoposide for new regimens of chemotherapeutic activities against skin cancer.

Inhibition of Topoisomerases by Metal Thiosemicarbazone Complexes

Topoisomerases, common targets for anti-cancer therapeutics, are crucial enzymes for DNA replication, transcription, and many other aspects of DNA metabolism. The potential anti-cancer effects of thiosemicarbazones (TSC) and metal-TSC complexes have been demonstrated to target several biological processes, including DNA metabolism. Human topoisomerases were discovered among the molecular targets for TSCs, and metal-chelated TSCs specifically displayed significant inhibition of topoisomerase II. The processes by which metal-TSCs or TSCs inhibit topoisomerases are still being studied. In this brief review, we summarize the TSCs and metal-TSCs that inhibit various types of human topoisomerases, and we note some of the key unanswered questions regarding this interesting class of diverse compounds.

Metal complexes of thiosemicarbazones derived by 2-quinolones with Cu(I), Cu(II) and Ni(II); Identification by NMR, IR, ESI mass spectra and in silico approach as potential tools against SARS-CoV-2

Substituted thiosemicarbazones derived by 2-quinolone were synthesized to investigate their complexation capability towards Cu(I), Cu(II) and Ni(II) salts. The structure of the complexes was established by ESI, IR and NMR spectra in addition to elemental analyses. Monodetate Cu(I) quinoloyl-substituted ligands were observed, whereas Ni(II) and Cu(II) formed bidentate-thiosemicarbazone derived by 2-quinolones. Subsequently, molecular docking was used to evaluate each analog's binding affinity as well as the inhibition constant (ki) to RdRp complex of SARS-CoV-2. Docking results supported the ability of the tested complexes that potentially inhibit the RdRp of SARSCov-2 show binding energy higher than their corresponding ligands. Additionally, ADMET prediction revealed that some compounds stratify to Lipinski's rule, indicating a good oral absorption, high bioavailability good permeability, and transport via biological membranes. Therefore, these metals-based complexes are suggested to be potentially good candidates as anti-covid agents.

Synthesis, Characterization, X-Ray Single-Crystal Structure, Potentiometric Measurements, Molecular Modeling, and Bioactivity Screening of Some Thiosemicarbazones

A series of thiosemicarbazone (TSCN) compounds including ((E)-2-((E)-1-(2-(p-tolyl)hydrazono)propan-2-ylidene)hydrazine-1-carbothioamide (TSC1), (E)-N-ethyl-2-((E)-1-(2-(p-tolyl)hydrazono)propan-2-ylidene)hydrazine-1-carbothioamide (TSC2), and (E)-N-phenyl-2-((E)-1-(2-(p-tolyl)hydrazono)propan-2-ylidene)hydrazine-1-carbothioamide) (TSC3) were synthesized and fully characterized by diverse spectroscopies, such as X-ray single-crystal, infrared, mass, proton nuclear magnetic resonance, and ultraviolet-visible. Potentiometric measurements, molecular modeling, and biological and antitumor activity screening were studied. The thermodynamics and protonation constants of TSC1 as a representative of the synthesized TSCs were calculated and discussed. The solution speciation of different species was studied with pH. The molecular parameters of the optimized structures were calculated and discussed. The X-ray single crystals of TSC2 and TSC3 were established. Considering the antimicrobial activities and correlating structure-activity relationship of the synthesized compounds, the TSC1 molecule was considered a promising candidate as an antifungal agent against Candida albicans. Thus, it would be extremely helpful in the field of medicinal chemistry, particularly as an antimicrobial agent. The results are of significance to the chemistry of antimicrobial agents.

Molecular Docking, DFT Calculations, Effect of High Energetic Ionizing Radiation, and Biological Evaluation of Some Novel Metal (II) Heteroleptic Complexes Bearing the Thiosemicarbazone Ligand

New Pb(II), Mn(II), Hg(II), and Zn(II) complexes, derived from 4-(4-chlorophenyl)-1-(2-(phenylamino)acetyl)thiosemicarbazone, were synthesized. The compounds with general formulas, [Pb(H₂L)₂(OAc)₂]ETOH.H₂O, [Mn(H₂L)(HL)]Cl, [Hg₂(H₂L)(OH)SO₄], and [Zn(H₂L)(HL)]Cl, were characterized by physicochemical and theoretical studies. X-ray diffraction studies showed a decrease in the crystalline size of compounds that were exposed to gamma irradiation (γ-irradiation). Thermal studies of the synthesized complexes showed thermal stability of the Mn(II) and Pb(II) complexes after γ-irradiation compared to those before γ–irradiation, while no changes in the Zn(II) and Hg(II) complexes were observed. The optimized geometric structures of the ligand and metal complexes are discussed regarding density functional theory calculations (DFT). The antimicrobial activities of the ligand and metal complexes against several bacterial and fungal stains were screened before and after irradiation. The Hg(II) complex has shown excellent antibacterial activity before and after γ-irradiation. In vitro cytotoxicity screening of the ligand and the Mn(II) and Zn(II) complexes before and after γ-irradiation disclosed that both the ligand and Mn(II) complex exhibited higher activity against human liver (Hep-G2) than Zn(II). Molecular docking was performed on the active site of MK-2 and showed good results.

Design, synthesis, and catalytic performance of modified graphene oxide based on a cobalt complex as a heterogenous catalyst for the preparation of aminonaphthoquinone derivatives

We are reporting a functionalized graphene oxide catalyst developed by modifying graphene oxide surface using the covalent attachment of an amino-functionalized SiO2 sphere/cobalt complex. Silica network has special characteristics including mechanical strength, high thermal and chemical stability with good dispersion in solvents. The silica/graphene oxide mixture provides improved properties and extends the scope of application. Graphene oxide was functionalized by spherical silica with the help of hybrid silane-containing nitrogen to coordinate with Co(ii) for increasing the catalytic activity. The catalyst was characterized by Fourier Transform Infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD), Energy Dispersive X-ray (EDX), Scanning Electron Microscopy (SEM), Raman spectroscopy, and Thermal Gravimetric (TGA) analyses. The catalyst showed high catalytic activity for multi-component reactions in the synthesis of aminonaphthoquinones in ethanol solvent. The catalyst's ability to improve the yield (96-98%), reduce the reaction time (5-8 min), and recycling ability are important benefits for the catalyst.

Copper Complexes as Anticancer Agents Targeting Topoisomerases I and II

Organometallics, such as copper compounds, are cancer chemotherapeutics used alone or in combination with other drugs. One small group of copper complexes exerts an effective inhibitory action on topoisomerases, which participate in the regulation of DNA topology. Copper complexes inhibitors of topoisomerases 1 and 2 work by different molecular mechanisms, analyzed herein. They allow genesis of DNA breaks after the formation of a ternary complex, or act in a catalytic mode, often display DNA intercalative properties and ROS production, and sometimes display dual effects. These amplified actions have repercussions on the cell cycle checkpoints and death effectors. Copper complexes of topoisomerase inhibitors are analyzed in a broader synthetic view and in the context of cancer cell mutations. Finally, new emerging treatment aspects are depicted to encourage the expansion of this family of highly active anticancer drugs and to expend their use in clinical trials and future cancer therapy.

Mechanistic insights on the mode of action of an antiproliferative thiosemicarbazone-nickel complex revealed by an integrated chemogenomic profiling study

Thiosemicarbazones (TSC) and their metal complexes display diverse biological activities and are active against multiple pathological conditions ranging from microbial infections to abnormal cell proliferation. Ribonucleotide reductase (RNR) is considered one of the main targets of TSCs, yet, the existence of additional targets, differently responsible for the multifaceted activities of TSCs and their metal complexes has been proposed. To set the basis for a more comprehensive delineation of their mode of action, we chemogenomically profiled the cellular effects of bis(citronellalthiosemicarbazonato)nickel(II) [Ni(S-tcitr)₂] using the unicellular eukaryote Saccharomyces cerevisiae as a model organism. Two complementary genomic phenotyping screens led to the identification of 269 sensitive and 56 tolerant deletion mutant strains and of 14 genes that when overexpressed make yeast cells resistant to an otherwise lethal concentration of Ni(S-tcitr)₂. Chromatin remodeling, cytoskeleton organization, mitochondrial function and iron metabolism were identified as lead cellular processes responsible for Ni(S-tcitr)₂ toxicity. The latter process, and particularly glutaredoxin-mediated iron loading of RNR, was found to be affected by Ni(S-tcitr)₂. Given the multiple pathways regulated by glutaredoxins, targeting of these proteins by Ni(S-tcitr)₂ can negatively affect various core cellular processes that may critically contribute to Ni(S-tcitr)₂ cytotoxicity.

Differential Proliferation Effect of the Newly Synthesized Valine, Tyrosine and Tryptophan-Naphthoquinones in Immortal and Tumorigenic Cervical Cell Lines

We previously showed that microwave assisted synthesis is the best method for the synthesis of naphthoquinone amino acid and chloride-naphthoquinone amino acid derivatives by a complete evaluation of reaction conditions such as stoichiometry, bases, and pH influence. Following the same strategy, we synthesized chloride and non-chloride tyrosine, valine, and tryptophan-naphthoquinones achieving 85–95%, 80–92%, and 91–95% yields, respectively. The cyclic voltammetry profiles showed that both series of naphthoquinone amino acid derivatives mainly display one redox reaction process. Overall, chloride naphthoquinone amino acid derivatives exhibited redox potential values (E_1/2) more positive than non-chloride compounds. The six newly synthesized compounds were tested in HPV positive and negative as well as in immortal and tumorigenic cell lines to observe the effects in different cellular context simulating precancerous and cancerous status. A dose-response was achieved to determine the IC50 of six newly synthesized compounds in SiHa (Tumorigenic and HPV16 positive), CaLo (Tumorigenic and HPV18 positive), C33-A (Tumorigenic and HPV negative) and HaCaT (Keratinocytes immortal HPV negative) cell lines. Non-chloride tryptophan-naphthoquinone (3c) and chloride tyrosine-naphthoquine (4a) effects were more potent in tumorigenic SiHa, CaLo, and C33-A cells with respect to non-tumorigenic HaCaT cells. Interestingly, there seems to be a differential effect in non-chloride and chloride naphthoquinone amino acid derivatives in tumorigenic versus non tumorigenic cells. Considering all naphthoquinone amino acid derivatives that our group synthesized, it seems that hydrophobic and aromatic amino acids have the greatest effect on cell proliferation inhibition. These results show promising compounds for cervical cancer treatment.

Synthesis of Amino Acid-Naphthoquinones and In Vitro Studies on Cervical and Breast Cell Lines

We performed an extensive analysis about the reaction conditions of the 1,4-Michael addition of amino acids to 1,4-naphthoquinone and substitution to 2,3-dichloronaphthoquinone, and a complete evaluation of stoichiometry, use of different bases, and the pH influence was performed. We were able to show that microwave-assisted synthesis is the best method for the synthesis of naphthoquinone–amino acid and chloride–naphthoquinone–amino acid derivatives with 79–91% and 78–91% yields, respectively. The cyclic voltammetry profiles showed that both series of naphthoquinone–amino acid derivatives mainly display one quasi-reversible redox reaction process. Interestingly, it was shown that naphthoquinone derivatives possess a selective antitumorigenic activity against cervix cancer cell lines and chloride–naphthoquinone–amino acid derivatives against breast cancer cell lines. Furthermore, the newly synthetized compounds with asparagine–naphthoquinones (3e and 4e) inhibited ~85% of SiHa cell proliferation. These results show promising compounds for specific cervical and breast cancer treatment.

Clarifying the Mechanism of Copper(II) α-(N)-Heterocyclic Thiosemicarbazone Complexes on DNA Topoisomerase IIα and IIβ

Topoisomerase II is a nuclear enzyme involved in the maintenance of DNA and is an effective anticancer drug target. However, several clinical topoisomerase II-targeted agents display significant off-target toxicities and adverse events. Thus, it is important to continue characterizing compounds with activity against topoisomerase II. We previously analyzed α-(N)-heterocyclic thiosemicarbazone copper(II) complexes against human topoisomerase IIα (TOP2A), but humans also express topoisomerase IIβ (TOP2B), which has distinct functional roles. Therefore, we examined two α-(N)-heterocyclic thiosemicarbazone copper [Cu(II)] complexes for activity against TOP2B in a purified system. The Cu(II) complexes, Cu(APY-ETSC)Cl and Cu(BZP-ETSC)Cl, were examined using plasmid DNA cleavage, supercoiled DNA relaxation, enzyme inactivation, protein cross-linking, DNA ligation, and ATP hydrolysis assays with TOP2B to determine whether these compounds act similarly against both enzymes. Both of the Cu(II) thiosemicarbazone (Cu-TSC) complexes we tested disrupted the function of TOP2B in a way similar to the effect on TOP2A. In particular, TOP2B DNA cleavage activity is increased in the presence of these compounds, while the relaxation and ATPase activities are inhibited. Further, both Cu-TSCs stabilize the N-terminal DNA clamp of TOP2A and TOP2B and rapidly inactivate TOP2B when the compounds are present before DNA. Our data provide evidence that the Cu-TSC complexes we tested utilize a similar mechanism against both isoforms of the enzyme. This mechanism may involve interaction with the ATPase domain of TOP2A and TOP2B outside of the ATP binding pocket. Additionally, these data support a model of TOP2 function where the ATPase domain communicates with the DNA cleavage/ligation domain.

Synthesis and redetermination of the crystal structure of salicyl-aldehyde N(4)-morpholino-thio-semi-carbazone

The structure of the title compound (systematic name: N-{[(2-hy-droxy-phen-yl)methyl-idene]amino}-morpholine-4-carbo-thio-amide), C12H15N3O2S, was prev-iously determined (Koo et al., 1977 ▸) using multiple-film equi-inclination Weissenberg data, but has been redetermined with higher precision to explore its conformation and the hydrogen-bonding patterns and supra-molecular inter-actions. The mol-ecular structure shows intra-molecular O-H⋯N and C-H⋯S inter-actions. The configuration of the C=N bond is E. The mol-ecule is slightly twisted about the central N-N bond. The best planes through the phenyl ring and the morpholino ring make an angle of 43.44 (17)°. In the crystal, the mol-ecules are connected into chains by N-H⋯O and C-H⋯O hydrogen bonds, which combine to generate sheets lying parallel to (002). The most prominent contribution to the surface contacts are H⋯H contacts (51.6%), as concluded from a Hirshfeld surface analysis.

DNA interaction studies of rhenium compounds with Schiff base chelates encompassing biologically relevant moieties

Herein, we report the DNA interaction studies of rhenium(I) and -(V) compounds with Schiff base chelates encompassing biologically relevant moieties. More specifically, the DNA interaction capabilities of these rhenium complexes were probed using Gel Electrophoresis and Calf Thymus-DNA titrations monitored by temperature-controlled electronic spectroscopy. The DNA binding modes of the metal compounds were corroborated by molecular docking simulations. In addition, the synthesis and characterization of a novel facial tricarbonyl rhenium(I) compound, fac-[Re(chrs)(CO)₃Br], (chrs = {3-{[(2-hydroxyphenyl)imino]methyl}-4H-chromen-4-one) are reported.

Design and Synthesis of Novel Thiosemicarbazones as Potent Anti-breast Cancer Agents

Background:

Thiosemicarbazones and its derivatives received a great pharmaceutical importance due to their prominent biological activities.

Methods:

A series of disubstituted thiosemicarbazone derivatives (1-12) were designed and synthesized as pure compounds in good yield. All the synthesized compounds were analyzed by spectral data. The anticancer activity of all the compounds was performed against breast cancer MCF-7 and MDA-MB-231 cell lines.

Results:

Most of the compounds showed activity against breast cancer MCF-7 and MDA-MB-231 cell lines with (IC50 = 12.25 &#181;M ‒ 185.35 &#181;M) and (IC50 = 12.97 &#181;M ‒ 107.33 &#181;M), respectively. Compound 9 presented (IC50 = 12.76 &#181;M and 12.97 &#181;M) against MCF-7 and MDA-MB-231 cell lines, respectively.

Conclusion:

Compound 9, was found to exhibit significant anti-breast cancer activity. This compound was further evaluated for side population percent inhibition assay on the breast cancer cell line MCF-7 at 5 and 10 &#181;M concentration. It showed superiority to block side population by more than 80% at 5 μM concentration compared to the reference drug verapamil.

Induction of Necroptosis in Cancer Stem Cells using a Nickel(II)-Dithiocarbamate Phenanthroline Complex

The cytotoxic properties of a series of nickel(II)-dithiocarbamate phenanthroline complexes is reported. The complexes 1-6 kill bulk cancer cells and cancer stem cells (CSCs) with micromolar potency. Two of the complexes, 2 and 6, kill twice as many breast cancer stem cell (CSC)-enriched HMLER-shEcad cells as compared to breast CSC-depleted HMLER cells. Complex 2 inhibits mammosphere formation to a similar extent as salinomycin (a CSC-specific toxin). Detailed mechanistic studies suggest that 2 induces CSC death by necroptosis, a programmed form of necrosis. Specifically, 2 triggers MLKL phosphorylation, oligomerization, and translocation to the cell membrane. Additionally, 2 induces necrosome-mediated propidium iodide (PI) uptake and mitochondrial membrane depolarisation, as well as morphological changes consistent with necroptotosis. Strikingly, 2 does not evoke necroptosis by intracellular reactive oxygen species (ROS) production or poly(ADP) ribose polymerase (PARP-1) activation.

Substitutional impact on biological activity of new water soluble Ni(II) complexes: Preparation, spectral characterization, X-ray crystallography, DNA/protein binding, antibacterial activity and in vitro cytotoxicity

A series of new water soluble nickel(II) complexes containing triphenylphosphine and 4-methoxysalicylaldehyde-4(N)-substituted thiosemicarbazones were synthesized and characterized. Crystallographic investigations confirmed the structure of the complexes (1-4) having the general structure [Ni(4-Msal-Rtsc)(PPh₃)] (Where R=H (1); CH₃ (2); C₂H₅ (3); C₆H₅ (4)) which showed that thiosemicarbazone ligands coordinated to nickel(II) ion as ONS tridentate bibasic donor. DNA/BSA protein binding ability of the ligands and their new complexes were studied by taking calf-thymus DNA (CT-DNA) and Bovine serum albumin (BSA) through absorption and emission titrations. Ethidium bromide (EB) displacement study showed the intercalative binding trend of the complexes to DNA. From the albumin binding studies, the mechanism of quenching was found as static and the alterations in the secondary structure of BSA by the compounds were confirmed with synchronous spectral studies. The binding affinity of the complexes to CT-DNA and BSA has the order of [Ni(4-Msal-etsc)(PPh₃)] (3) >[Ni(4-Msal-mtsc)(PPh₃)] (2) >[Ni(4-Msal-tsc)(PPh₃)] (1) >[Ni(4-Msal-ptsc)(PPh₃)] (4). In vitro cytotoxicity of the complexes was tested on human lung cancer cells (A549), human cervical cancer cells (HeLa), human liver carcinoma cells (Hep G2). All the complexes exhibited significant activity against three cancer cells. Among them, complex 4 exhibited almost 2.5 fold activity than cisplatin in A549 and HepG2 cell lines. In HeLa cell line, the complexes exhibited significant activity which is less than cisplatin. While comparing the activity of the complexes in A549 and HepG2 cell lines it falls in the order 4>1>2>3>cisplatin. The results obtained from DNA, protein binding and cytotoxicity studies, it is concluded that the cytotoxicity of the complexes as determined by MTT assay were not unduly influenced by the complexes having different binding efficiency with DNA and protein. The complexes exhibited good spectrum of antibacterial activity against four pathogenic bacteria such as E. faecalis (gram +ve), S. aureus (gram +ve), E. coli (gram -ve) and P. aeruginosa (gram -ve).

A novel nickel complex works as a proteasomal deubiquitinase inhibitor for cancer therapy

Based on the central role of the ubiquitin-proteasome system (UPS) in the degradation of cellular proteins, proteasome inhibition has been considered an attractive approach for anticancer therapy. Deubiquitinases (DUBs) remove ubiquitin conjugates from diverse substrates; therefore, they are essential regulators of the UPS. DUB inhibitors, especially the inhibitors of proteasomal DUBs are becoming a research hotspot in targeted cancer therapy. Previous studies have shown that metal complexes, such as copper and zinc complexes, can induce cancer cell apoptosis through inhibiting UPS function. Moreover, we have found that copper pyrithione inhibits both 19S proteasome-associated DUBs and 20S proteasome activity with a mechanism distinct from that of the classical 20S proteasome inhibitor bortezomib. In the present study, we reveal that (i) nickel pyrithione complex (NiPT) potently inhibits the UPS via targeting the 19S proteasome-associated DUBs (UCHL5 and USP14), without effecting on the 20S proteasome; (ii) NiPT selectively induces proteasome inhibition and apoptosis in cultured tumor cells and cancer cells from acute myeloid leukemia human patients; and (iii) NiPT inhibits proteasome function and tumor growth in nude mice. This study, for the first time, uncovers a nickel complex as an effective inhibitor of the 19S proteasomal DUBs and suggests a potentially new strategy for cancer treatment.

Thiosemicarbazone-derived copper(ii), cobalt(ii) and nickel(ii) complexes as potential anticancer agents: nuclease activity, cytotoxicity and apoptosis studies

Cobalt(ii), nickel(ii) and copper(ii) complexes with thiosemicarbazone-derived ligands exhibiting significant cytotoxic activity against cancer cells were synthesized and characterized.

Ni(ii) complex with bishydrazone ligand: synthesis, characterization, DNA binding studies and pro-apoptotic and pro-differentiation induction in human cancerous cell lines

A new Ni(ii) complex, [Ni(L)(H₂O)] (1), with diethyl 3,3′-(2,2′-(1,1′-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene))bis(hydrazin-1-yl-2-ylidene))bis(3-oxopropanoate) ligand (H₂L) was synthesized as a potential chemotherapeutic agent.

Synthesis, X-ray structure and in vitro cytotoxicity studies of Cu(i/ii) complexes of thiosemicarbazone: special emphasis on their interactions with DNA

The interactions of four Cu-TSC complexes with DNA & their cytotoxicity studies against the HeLa cell have been reported.

Structural diversity of copper(II) complexes with N-(2-pyridyl)imidazolidin-2-ones(thiones) and their in vitro antitumor activity

Six series of structurally different mono- and binuclear copper(II) complexes 5-10 were obtained by reacting N-(2-pyridyl)imidazolidin-2-ones (1a-l), N,N'-bis(2-pyridyl)imidazolidin-2-ones (2a,b), N-acyl-N'(2-pyridyl)imidazolodin-2-ones (3a-j) and N-(2-pyridyl)imidazolidine-2-thiones (4a-g) with copper(II) chloride at an ambient temperature. The coordination modes of the complexes obtained were established by elemental analysis, IR spectroscopic data and single crystal X-ray diffraction studies. The in vitro cytotoxic activities of both the free ligands and copper(II) complexes were evaluated using a crystal violet microtiter plate assay on five human tumor cell lines: LCLC-103H, A-427, SISO, RT-4 and DAN-G. The free ligands 1-4 at concentration attainable in cancer cells of 20 μM showed no meaningful cytotoxic effect with cell viability in the range of 88%-100%. The most potent copper(II) complex of 1-(6-ethoxy-2-pyridyl)imidazolidin-2-one (6b) exhibited selective cytotoxicity against A-427 lung cancer cell line, while the complexes of 1-(5-methyl-2-pyridyl)imidazolidine-2-thione (5h) and 1-(4-tert-butyl-2-pyridyl)imidazolidine-2-thione (5j) showed cytostatic effect against a whole panel of five human tumor cell lines. In conclusion, the only complexes that showed remarkably increased activity in comparison to the free ligands were those obtained from N-(2-pyridyl)imidazolidine-2-thiones 4c and 4e substituted with alkyl group at position 4 or 5 of pyridine ring.

Synthesis and cytotoxic evaluation of a series of 2-amino-naphthoquinones against human cancer cells

The cytotoxicity of a series of aminonaphthoquinones resulting from the reaction of suitable aminoacids with 1,4-naphthoquinone was assayed against SF-295 (glioblastoma), MDAMB-435 (breast), HCT-8 (colon), HCT-116 (colon), HL-60 (leukemia), OVCAR-8 (ovarian), NCI-H358M (bronchoalveolar lung carcinoma) and PC3-M (prostate) cancer cells and also against PBMC (peripheral blood mononuclear cells). The results demonstrated that all the synthetic aminonaphthoquinones had relevant cytotoxic activity against all human cancer lines used in this experiment. Five of the compounds showed high cytotoxicity and selectivity against all cancer cell lines tested (IC₅₀ = 0.49 to 3.89 µg·mL⁻¹). The title compounds were less toxic to PBMC, since IC₅₀ was 1.5 to eighteen times higher (IC₅₀ = 5.51 to 17.61 µg·mL⁻¹) than values shown by tumour cell lines. The mechanism of cell growth inhibition and structure–activity relationships remains as a target for future investigations.