Heterocyclic dithiocarbazate iron chelators: Fe coordination chemistry and biological activity

A Series of Non-Oxido VIV Complexes of Dibasic ONS Donor Ligands: Solution Stability, Chemical Transformations, Protein Interactions, and Antiproliferative Activity

A series of mononuclear non-oxido vanadium(IV) complexes, [V^IV(L^1-4)₂] (1-4), featuring tridentate bi-negative ONS chelating S-alkyl/aryl-substituted dithiocarbazate ligands H₂L^1-4, are reported. All the synthesized non-oxido V^IV compounds are characterized by elemental analysis, spectroscopy (IR, UV-vis, and EPR), ESI-MS, as well as electrochemical techniques (cyclic voltammetry). Single-crystal X-ray diffraction studies of 1-3 reveal that the mononuclear non-oxido V^IV complexes show distorted octahedral (1 and 2) or trigonal prismatic (3) arrangement around the non-oxido V^IV center. EPR and DFT data indicate the coexistence of mer and fac isomers in solution, and ESI-MS results suggest a partial oxidation of [V^IV(L^1-4)₂] to [V^V(L^1-4)₂]⁺ and [V^VO₂(L^1-4)]^-; therefore, all these three complexes are plausible active species. Complexes 1-4 interact with bovine serum albumin (BSA) with a moderate binding affinity, and docking calculations reveal non-covalent interactions with different regions of BSA, particularly with Tyr, Lys, Arg, and Thr residues. In vitro cytotoxic activity of all complexes is assayed against the HT-29 (colon cancer) and HeLa (cervical cancer) cells and compared with the NIH-3T3 (mouse embryonic fibroblast) normal cell line by MTT assay and DAPI staining. The results suggest that complexes 1-4 are cytotoxic in nature and induce cell death in the cancer cell lines by apoptosis and that a mixture of V^IV, V^V, and V^VO₂ species could be responsible for the biological activity.

From dithiocarbamates to branched dithiocarbazates: Compounds with potent antischistosomal activity

Schistosomiasis or bilharzia is caused by blood flukes of the genus Schistosoma and represents a considerable health and economic burden in tropical and subtropical regions. The treatment of this infectious disease relies on one single drug: praziquantel (PZQ). Therefore, new and potent antischistosomal compounds need to be developed. In our previous work, starting with the drug disulfiram, we developed dithiocarbamates with in vitro antischistosomal activities in the low micromolar range. Based on these results, we report in this study on the synthesis and biological testing of the structurally related dithiocarbazates against Schistosoma mansoni, one of the major species of schistosomes. In total, three series of dithiocarbazate derivatives were examined, and we found that the antischistosomal activity of N-unbranched dithiocarbazates increased by further N-substitution. Comparable tetra-substituted dithiocarbazates were rarely described in the literature, thus a synthesis route was established. Due to the elaborate synthesis, the branched dithiocarbazates (containing an N-aminopiperazine) were simplified, but the resulting branched dithiocarbamates (containing a 4-aminopiperidine) were considerably less active. Taken together, dithiocarbazate-containing compounds with an in vitro antischistosomal activity of 5 µM were obtained.

Dithiocarbazate-FeIII, -CoIII, -NiII, and -ZnII Complexes: Design, Synthesis, Structure, and Anticancer Evaluation

Non-platinum-metal complexes show great potential as anticancer agents. Herein, a series of dithiocarbazate non-Pt-metal complexes, including [Fe^III(L)₂]·Cl·2H₂O 1, [Co^III(L)₂]·NO₃·2.5H₂O 2, [Ni^II(L)₂] 3, and [Zn^II(L)₂] 4, have been designed and evaluated for their efficacy as antineoplastic agents. Among them, complex 2 exhibited higher anticancer efficacy than complexes 1, 3, 4, and cisplatin against several cancer cell lines. Hemolysis assays revealed that complex 2 showed comparable hemolysis with cisplatin. In vivo anticancer evaluations showed that complex 2 could retard tumor xenograft growth effectively with low systemic toxicity. Further studies revealed that complex 2 suppressed cancer cells by triggering multiple mechanisms involving the simultaneous inhibition of mitochondria and glycolytic bioenergetics. Overall, our study provides new insights into the anticancer mechanism of Co complexes, which can be used as a good strategy to overcome the flexibility of cancer cells to chemotherapy adaptation.

Spectroscopic Insight into Tetrahedrally Distorted Square Planar Copper(II) Complex: XRD/HSA, Physicochemical, DFT, and Thermal Investigations

The reaction of bidentate N-S-thione-Schiff base, (E)-benzyl 2-(1-(4-chlorophenyl)-ethylidene)hydrazinecarbodithioate, with Cu(NO3)2·3H2O produced a cis-Cu(II) complex. The molecular structure was confirmed and characterized by CHN-EA, FAB-MS, IR, and UV-Vis analyses. The XRD supported cis-isomer of the bis anionic bidentate N (azomethine) and S (thiol) ligand coordination mode in tetrahedrally distorted square planar, rarely reported in the literature. The results of the XRD-bond lengths were in perfect agreement with the density functional theory (DFT) calculation. DFT-calculated angles around the Cu(II) center displayed slightly less distortion around the metal center from those of XRD. Additionally, the thermal stability of the complex was evaluated via thermal gravimetric analysis (TGA). Two-dimensional fingerprint (2D-FP), Hirshfeld surface analysis (HSA), and molecular electrostatic potential (MEP) support the XRD-packing results with the existence of the H⸱⸱⸱Cl and CH⸱⸱⸱π bonds as the main interactions in the crystal lattice of the desired complex.

Synthesis, characterization and evaluation of antidengue activity of enantiomeric Schiff bases derived from S-substituted dithiocarbazate

A series of Schiff bases have been successfully synthesized through the acid-catalyzed condensation of S-substituted dithiocarbazates and three enantiomerically pure monoterpenes, (1 R )-(+)-camphor, (1 S )-(-)-camphor, (1 R )-(-)-camphorquinone, (1 S )-(+)-camphorquinone, ( R )-(-)-carvone and ( S )-(+)-carvone. Spectroscopic results revealed that the Schiff bases containing camphor or carvone likely adopted an E -configuration along the characteristic imine bond while those containing camphorquinone assumed a Z -configuration. The antidengue potential of these compounds was evaluated based on DENV 2 caused cytopathic effect (CPE) reduction-based in vitro evaluation. The compounds were validated through secondary foci forming unit reduction assay (FFURA). Compounds were also tested for their cytotoxicity against Vero cells. The compounds showed variable degrees of antiviral activity with the camphor compounds displaying the highest antidengue potential. The enantiomers of the compounds behaved almost similarly during the antiviral evaluation.

Iron Complexes of an Antiproliferative Aroyl Hydrazone: Characterization of Three Protonation States by Electron Paramagnetic Resonance Methods

Tridentate aroyl hydrazones are effective metal chelators in biological settings, and their activity has been investigated extensively for medicinal applications in metal overload, cancer, and neurodegenerative diseases. The aroyl hydrazone motif is found in the recently reported prochelator (AH1-S)2, which has shown antiproliferative proapoptotic activity in mammalian cancer cell lines. Intracellular reduction of this disulfide prochelator leads to the formation of mercaptobenzaldehyde benzoylhydrazone chelator AH1 and to iron sequestration, which in turn impacts cell growth. Herein, we investigate the iron coordination chemistry of AH1 to determine the structural and spectroscopic properties of the iron complexes in the solid state and in solution. A neutral iron(III) complex of 2:1 ligand-to-metal stoichiometry was isolated and characterized fully to reveal two different binding modes for the tridentate AH1 ligand. Specifically, one ligand binds in the monoanionic keto form, whereas the other ligand coordinates as a dianionic enolate. Continuous-wave electron paramagnetic resonance experiments in frozen solutions indicated that this neutral complex is one of three low-spin iron(III) complexes observed depending on the pH of the solution. Electron spin echo envelope modulation (ESEEM) experiments allowed assignment of the three species to different protonation states of the coordinated ligands. Our ESEEM analysis provides a method to distinguish the coordination of aroyl hydrazones in the keto and enolate forms, which influences both the ligand field and overall charge of the complex. As such, this type of analysis could provide valuable information in a variety of studies of iron complexes of aroyl hydrazones, ranging from the investigation of spin-crossover behavior to tracking of their distribution in biological samples.

Synthesis, structure and characterization of new dithiocarbazate-based mixed ligand oxidovanadium(iv) complexes: DNA/HSA interaction, cytotoxic activity and DFT studies

The synthesis, structure and characterization of mixed ligand oxidovanadium(iv) complexes [V^IVOL^1–2(L^N–N)] (1–3) are reported. With a view to evaluating their biological activity, their DNA/HSA interaction and cytotoxicity activity have been explored.

Crystal structure of benzyl N'-[(1E,4E)-1,5-bis-(4-meth-oxy-phen-yl)penta-1,4-dien-3-yl-idene]hydrazine-1-carbodi-thio-ate

In the title hydrazinecarbodi-thio-ate derivative, C27H26N2O2S2, the asymmetric unit is comprised of four mol-ecules (Z = 8 and Z' = 4). The 4-meth-oxy-phenyl rings are slightly twisted away from their attached olefinic double bonds [torsion angles = 5.9 (4)-19.6 (4)°]. The azomethine double bond has an s-trans configuration relative to one of the C=C bonds and an s-cis configuration relative to the other [C=C-C= N = 147.4 (6)-175.7 (2) and 15.3 (3)-37.4 (7)°, respectively]. The torsion angles between the azomethine C=N double bond and hydrazine-1-carbodi-thio-ate moiety indicate only small deviations from planarity, with torsion angles ranging from 0.9 (3) to 6.9 (3)° and from 174.9 (3) to 179.7 (2)°, respectively. The benzyl ring and the methyl-enesulfanyl moiety are almost perpendicular to each other, as indicated by their torsion angles [range 93.7 (3)-114.6 (2)°]. In the crystal, mol-ecules are linked by C-H⋯O, N-H⋯S and C-H⋯π(ring) hydrogen-bonding inter-actions into a three-dimensional network. Structural details of related benzyl hydrazine-1-carbodi-thio-ate are surveyed and compared with those of the title compound.

Phenothiazines and phenoxazines: as electron transfer mediators for ferritin iron release

Redox active phenothiazine and phenoxazine dyes facilitate ferritin iron release by acting as electron transfer (ET) mediators following Marcus theory.

N,N-Dimethyl-2-[(1E)-({[(methylsulfanyl)methanethioyl]amino}imino)methyl]aniline

In the title compound, C11H15N3S2, the dithiocarbazate moiety is rotated by 18.73 (8)° with respect to the benzene ring. The dithiocarbazate group adopts anEconfiguration with respect to the C=N bond of the benzylidene group. Furthermore, in the solid state the compound exists in the thione tautomeric form. In the crystal, molecules are linked by pairs of weak N—H...S hydrogen bonds, forming inversion dimers which are arranged in layers parallel to (010).

S-Benzyl 3-[1-(6-methyl-pyridin-2-yl)ethyl-idene]di-thio-carbazate: crystal structure and Hirshfeld surface analysis

In the title di-thio-carbazate ester, C16H17N3S2 (systematic name: (Z)-{[(benzyl-sulfan-yl)methane-thio-yl]amino}[1-(6-methyl-pyridin-2-yl)ethyl-idene]amine), the central methyl-idenehydrazinecarbodi-thio-ate (C2N2S2) core is almost planar (r.m.s. deviation = 0.0111 Å) and forms dihedral angles of 71.67 (3)° with the approximately orthogonally inclined thio-ester phenyl ring, and 7.16 (7)° with the approximately coplanar substituted pyridyl ring. The latter arrangement and the Z configuration about the imine-C=N bond allows for the formation of an intra-molecular hydrazine-N-H⋯N(pyrid-yl) hydrogen bond that closes an S(6) loop. In the crystal, phenyl-C-H⋯S(thione), methyl-ene-C-H⋯π(pyrid-yl), methyl-ene- and phenyl-C-H⋯π(phen-yl) contacts connect mol-ecules into supra-molecular layers propagating in the bc plane; the layers stack along the a axis with no directional inter-actions between them. The analysis of the Hirshfeld surface indicates the relative importance of an intra-layer phenyl-H⋯H(pyrid-yl) contact upon the mol-ecular packing.

Synergy of Iron Chelators and Therapeutic Peptide Sequences Delivered via a Magnetic Nanocarrier

Here, we report the synthesis, characterization, and efficacy study of Fe/Fe₃O₄-nanoparticles that were co-labeled with a tumor-homing and membrane-disrupting oligopeptide and the iron-chelator Dp44mT, which belongs to the group of the thiosemicarbazones. Dp44mT and the peptide sequence PLFAERL(_D[KLAKLAKKLAKLAK])CGKRK were tethered to the surface of Fe/Fe₃O₄ core/shell nanoparticles by utilizing dopamine-anchors. The 26-mer contains two important sequences, which are the tumor targeting peptide CGKRK, and _D[KLAKLAK]₂, known to disrupt the mitochondrial cell walls and to initiate programmed cell death (apoptosis). It is noteworthy that Fe/Fe₃O₄ nanoparticles can also be used for MRI imaging purposes in live mammals. In a first step of this endeavor, the efficacy of this nanoplatform has been tested on the highly metastatic 4T1 breast cancer cell line. At the optimal ratio of PLFAER_D[KLAKLAK]₂CGKRK to Dp44mT of 1 to 3.2 at the surface of the dopamine-coated Fe/Fe₃O₄-nanocarrier, the IC₅₀ value after 24 h of incubation was found to be 2.2 times lower for murine breast cancer cells (4T1) than for a murine fibroblast cell line used as control. Based on these encouraging results, the reported approach has the potential of leading to a new generation of nanoplatforms for cancer treatment with considerably enhanced selectivity towards tumor cells.

Synthesis, structure, magnetic and biological activity studies of bis-hydrazone derived Cu(ii) and Co(ii) coordination compounds

Four coordination compounds of formulae [Cu(II)2(H2L(1))(HL(1))](ClO4)3·H2O (1), [Cu(II)2(H2L(2))(CH3OH)2](ClO4)2·2CH3OH (2), [Co(II)2(H2L(1))2](ClO4)4 (3) and [Co(II)2(H2L(2))2]·2H2O (4) were synthesized via self-assembly of succinohydrazone derived ligands (H2L(1) = N',N'-4-bis(2-pyridyl)succinohydrazide, H4L(2) = N',N'-4-bis(2-hydroxybenzylidene)succinohydrazide) and Cu(2+) and Co(2+) ions, respectively. The compounds were characterized by crystal structure determination, magnetic measurements and biological activities. Compounds 1, 3 and 4 have discrete double helicate structures, whereas compound 2 is a one-dimensional chain. Magnetic studies show antiferromagnetic exchange interactions in 2 with a J value of -67.1 cm(-1) and antiferromagnetic spin-canting in compound 3 originates through supramolecular H-bonding. For compound 3, a clear bifurcation was observed in zero field cooled (ZFC) and field cooled (FC) measurement at a temperature of 3.5 K and field of 0.1 T, implying long range magnetic ordering below this temperature. Interestingly, all of compounds 1-4 show significant changes in their absorption (hypo- and hyperchromism) in the presence of SS-DNA, inferring interaction between the compounds and DNA. In addition, compounds 1-4 significantly exhibited nuclease activities on both RNA and pUC19 plasmid DNA. Moreover, the nuclease activity was further enhanced in the presence of oxidant (H2O2) and suggests the possible role of reactive oxygen species in DNA nicking ability of compounds 1-4. Furthermore, compounds 1, 2 and 4 exhibited significant cytotoxicity against mammalian cancer cell lines (HeLa, A549 and MDAMB-231). In addition, our results from Annexin/PI staining and DNA fragmentation assays revealed that these compounds are capable of inducing apoptosis and have potential to act as anticancer drugs.

2-[(1E)-({[(Benzyl-sulfan-yl)methane-thio-yl]amino}-imino)-meth-yl]-6-meth-oxy-phenol: crystal structure and Hirshfeld surface analysis

The title di-thio-carbazate ester, C16H16N2O2S2, comprises two almost planar residues, i.e. the phenyl ring and the remaining 14 non-H atoms (r.m.s. deviation = 0.0410 Å). These are orientated perpendicularly, forming a dihedral angle of 82.72 (5)°. An intra-molecular hy-droxy-O-H⋯N(imine) hydrogen bond, leading to an S(6) loop, is noted. An analysis of the geometric parameters is consistent with the mol-ecule existing as the thione tautomer, and the conformation about the C=N bond is E. The thione S and imine H atoms lie to the same side of the mol-ecule, facilitating the formation of inter-molecular N-H⋯S hydrogen bonds leading to eight-membered {⋯HNCS}2 synthons in the crystal. These aggregates are connected by phenyl-C-H⋯O(hy-droxy) inter-actions into a supra-molecular layer in the bc plane; these stack with no directional inter-actions between them. An analysis of the Hirshfeld surface confirms the nature of the inter-molecular inter-actions.

A family of Fe3+ based double-stranded helicates showing a magnetocaloric effect, and Rhodamine B dye and DNA binding activities

A series of Fe³⁺ based double-stranded helicates unveil a significant magnetocaloric effect as well as binding activities with Rhodamine B dye and CT-DNA.