Copper(II) complexes with substituted thiosemicarbazones of thiophene-2-carboxaldehyde: synthesis, characterization and antiamoebic activity against E. histolytica

Synthesis, characterisation, DNA binding, acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) activities and molecular docking studies of metal(II) complexes with 1,10-phenanthroline scaffold

A series of metal complexes containing Phenanthroline scaffold [ML] (L-1,10-Phenanthroline derivative comprises conjugated aromatic core and selenol group); M = Cu(II), Zn(II), Co(II) and Zn(II) ions were designed and synthesised to obtain effective anti-cholinesterase efficiencies of metal chelates. Analytical and spectroscopic studies were used to determine the structural features. An octahedral structure with moderate distortion was attributed to the above metal chelates based on spectroscopic data. The distorted octahedral geometry of copper(II) complex to DNA (K_b = 4.05 × 10⁵ M^-1) is stronger than that of ethidium bromide (EB) to DNA (K_b = 3.2 × 10⁵ M^-1), other metal complexes, respectively. The synthesised 1,10-Phenanthroline derivative had the best inhibitory effects against acetylcholinesterase (AChE) and butyrylcholinesterase, with IC₅₀ values of 0.45 and 3.6 M, respectively, which were lower than the reference molecules. As a result, nitrogen-containing heterocyclic compounds (H₂L) showed significant inhibitory profiles against the metabolic enzymes. Therefore, we believe that these experimental results may contribute to the development of new drug molecules particularly in the treatment of neurological disorders including glaucoma, Alzheimer's disease (AD) and diabetes. Docking, AChE and BuChE inhibition activities results revealed that ligand may be used for AD. The prepared 1,10-phenanthroline analogue, which has a high selectivity for AChE, may be studied further to find potential candidates for treating early-stage Alzheimer's symptoms.Communicated by Ramaswamy H. Sarma.

Exploration of Photophysical and Nonlinear Properties of Salicylaldehyde-Based Functionalized Materials: A Facile Synthetic and DFT Approach

The current research presents the synthesis of novel salicylaldehyde thiosemicarbazones (1-6) and their spectroscopic characterization employing UV-visible, Fourier transform infrared spectroscopy, and NMR techniques. Experimental results are compared and validated with the results obtained theoretically by employing density functional theory at the M06 level with the 6-311G (d,p) basis set. Further, various parameters [natural bond orbital (NBO)], linear and nonlinear optical (NLO) properties, and global reactivity parameters (GRPs) are computationally calculated. The NBO approach has confirmed the stability of compounds on account of charge delocalization and hyper conjugative interaction network. Frontier molecular orbital analysis has explained the charge transfer and chemical reactivity capability, while GRPs have led to the analysis of kinetic stability of the studied molecules. Further, the probability of being NLO-active has been theoretically proved by the HOMO/LUMO energy difference (4.133-4.186 eV) and β values (192.778-501.709 a.u). These findings suggest that the studied compounds possess potential NLO applications as they have shown larger NLO values in comparison with that of the urea molecule, and such distinct properties prove their technological importance.

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.

Tridentate imidazole-based Schiff base metal complexes: molecular docking, structural and biological studies

A novel Schiff base was synthesized by the condensation of imidazole-2-carboxaldehyde with l-histidine in an equimolar ratio. The prepared Schiff base was characterized by elemental analysis and spectral characterization techniques. It was then complexed with a series of 3-d metal(II) ions like manganese, iron, cobalt, nickel, copper and zinc. The coordination properties, nature of bonding and stability of the complexes were deduced from elemental analysis, IR, UV-vis, ¹H NMR, mass, electronic spectra, magnetic, conductivity and thermogravimetric analysis. IR studies support the tridentate behaviour of Schiff base as well as its coordination to the central metal ion through an azomethine nitrogen, deprotonated carboxylic oxygen and imidazole ring nitrogen atoms of histidine. The electronic spectra and magnetic moment data demonstrate that the complexes have an octahedral geometry, except zinc complex, which has a tetrahedral geometry. In vitro antimicrobial activity of the synthesized compounds has been shown to exhibit excellent antibacterial and antifungal activities. The antibacterial property of the prepared Schiff base was further confirmed by conducting a docking study of target proteins involved in the antibacterial mechanism.Communicated by Ramaswamy H. Sarma.

Condensed-phase relative Gibbs free energy and E/Z descriptors for 2-acetylthiophene and 2-acetylthiophene-N1-phenyl thiosemicarbazones

Thiosemicarbazones (TSCs) encompasses a class of compounds relevant in the pharmacological context. Their specific applicability varies in function of the appropriated chemical modification and their binding to different transition metals. In the present work, we apply current standards functionals, B3LYP and B97D, with triple zeta basis set quality, 6-311++G(d,p), to investigate the relative stability of the various possible spatial arrangements for 2-acetylthiophene and 2-acetylthiophene-N1-phenyl thiosemicarbazones, denoted ATTSC and ATTSC-Ph, respectively. The relative stability of neutral and deprotonated species at ethanol described by an implicit solvent model was investigated. For ATTSC, the relative Gibbs energy changed significantly upon deprotonation, and for ATTSC-Ph, a novel global minimum was identified. Based on the present study, deprotonation determines population in condensed-media. Such information, valid for ATTSC and ATTSC-Ph, can be crucial in studying other thiosemicarbazones.

Screening organometallic thiophene containing thiosemicarbazone ruthenium (II/III) complexes as potential anti-tumour agents

The new ruthenium (III) complex has been synthesized and characterized by elemental analysis, FT-IR, UV-Vis, EI-Mass, EPR spectroscopy, and magnetic susceptibility measurement. Cytotoxic effects of organoruthenium (II/III) complexes 1a, 1b, and 2a, and their ligands (TSC¹ and TSC²) in cultured human ovarian (A2780, SKOV-3, and OVCAR-3) and colon (DLD, CCD18Co, and Caco-2) cells have been investigated comparing reactivity of the Ru (II/III) complexes and their free TSC ligands. The complexes exhibit higher cytotoxicity in three cancer cell lines than in normal cells. The binding with CT-DNA and BSA of the all complexes were weak compared with their ligand in spite of the cellular uptake of these complexes into the cytoplasm and then nucleus while their cytotoxic effects were vice versa. All the results showed that Complex 1b has more efficient cytotoxicity on the colon cancer cells than ovarian cancer cells. However, Complex 2a is a better drug candidate especially for antitumor therapy of metastasized ovarian cancer.

Copper-mediated N-Arylation of Methyl 2-Aminothiophene-3-carboxylate with Organoboron Reagents

A practical protocol for the synthesis of N-arylated methyl 2-aminothiophene-3-carboxylate has been developed via Chan-Lam cross-coupling. The desired products were synthesized by cross-coupling of methyl 2-aminothiophene-3-carboxylate with both arylboronic acids and potassium aryltrifluoroborate salts in moderate to good yields. A broad range of functional groups was well tolerated.

Regioselective synthesis of 2-(bromomethyl)-5-aryl-thiophene derivatives via palladium (0) catalyzed suzuki cross-coupling reactions: as antithrombotic and haemolytically active molecules

Background

It is seen that the regioselective functionalizations of halogenated heterocycles play an important role in the synthesis of several types of organic compounds. In this domain, the Suzuki-Miyaura reaction has emerged as a convenient way to build carbon-carbon bonds in synthesizing organic compounds. Some of the most important applications of these reactions can be seen in the synthesis of natural products, and in designing targeted pharmaceutical compounds. Herein, we present the regioselective synthesis of the novel series of 2-(bromomethyl)-5-aryl-thiophenes 3a-i,via Suzuki cross-coupling reactions of various aryl boronic acids with 2-bromo-5-(bromomethyl)thiophene (2).

Results

The synthesized compounds were screened for their haemolytic and antithrombolytic activities. The novel compounds 3f, 3i showed highest 69.7, 33.6% haemolysis of blood cells, respectively. The antithrombolytic activity of the compounds was found to be within low to moderate against human blood clot. The compound 3i showed potent clot lysis (31.5%).

Conclusions

Considering these results, it is concluded that the synthesized compounds can be used as a promising source of therapeutic agents.

In vitro antiamoebic activity evaluation and docking studies of metronidazole-triazole hybrids

An in-house database of 520 compounds was docked against Entamoeba histolytica thioredoxin reductase (EhTrR), a promising target for the treatment of amoebiasis. Amongst these, some metronidazole (MTZ)-triazole hybrids were ranked high, with docking scores from -10.23 to -7.56. Studies of the binding orientations and conformations show that the head groups of MTZ-triazole hybrids interact with the arginine residues within the binding pocket of EhTrR, making it clear that such is the optimal and most reliable orientation for this class of compounds. The top-ten MTZ-triazole hybrids were then selected for evaluation of their activity against the HM1:IMSS strain of amoeba. The most active compound, 2-pyridyl-(1,2,3-triazolyl)metronidazole 10, with an IC50 value of 8.4 nM, was significantly more active than the standard drug MTZ alone. Docking studies revealed that compound 10 may act as an EhTrR inhibitor with activity in the nanomolar range and satisfactory ADME properties; it is a suitable candidate to be carried forward as a potential lead in the discovery of drugs to combat amoebiasis.

Synthesis, spectral characterization and antioxidant activity studies of a bidentate Schiff base, 5-methyl thiophene-2-carboxaldehyde-carbohydrazone and its Cd(II), Cu(II), Ni(II) and Zn(II) complexes

A new Schiff base bidentate ligand (L), 5-methyl thiophene-2-carboxaldehyde-carbohydrazone and its metal (Cu(II), Cd(II), Ni(II) and Zn(II)) complexes with general stoichiometry [M(L)2X2] (where X=Cl) were synthesized. The ligand and its metal complexes were characterized by elemental analyses, IR, 1H NMR, ESR spectral analyses, and molar conductance studies. The molar conductance data revealed that all the metal chelates are non-electrolytes. IR spectra showed that ligand (L) is coordinated to the metal ions in a bidentate manner with N and O donor sites of the azomethine-N, and carbonyl-O. ESR and UV-Vis spectral data showed that the geometrical structure of the complexes are Orthorhombic. Furthermore, the antioxidant activity of the ligand and its complexes was determined by hydroxyl radical scavenging, DPPH, NO, reducing power methods in vitro. The obtained IC50 value of the DPPH activity for the copper complex (IC50=66.4 μm) was higher than other compounds. Microbial assay of the above complexes against Staphylococcus aureus, Escherichia coli, Rhizocotonia bataticola and Alternaria alternata showed that copper complex exhibited higher activity than the other complexes.

Synthesis, Structure and Antioxidant Activity of (Tetra-O-acetyl-β-D-galactopyranosyl)thiosemicarbazones of Substituted Benzaldehydes

Some new substituted benzaldehyde (2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl) thiosemicarbazones were synthesised by reaction of 2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl thiosemicarbazide and different substituted benzaldehydes. The reaction was performed using conventional and microwave-assisted heating methods. The structures of thiosemicarbazones were confirmed by spectroscopic (IR, (1) H NMR, (13) C NMR and MS) method. The antioxidant activity of these thiosemicarbazones was evaluated, in vitro and in vivo, and it's shown that some of these compounds had significant antioxidant activity.

Antioxidant activities of thiosemicarbazones from substituted benzaldehydes and N-(tetra-O-acetyl-β-D-galactopyranosyl)thiosemicarbazide

Reaction of N-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)thiosemicarbazide and different substituted benzaldehydes gave some new substituted benzaldehyde N-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)thiosemicarbazones. The reaction was performed using conventional and microwave-assisted heating methods. The structures of thiosemicarbazones were confirmed by spectroscopic (IR, (1)H NMR, (13)C NMR and ESI-MS) method. The antioxidant activity of these thiosemicarbazones was evaluated in vitro and in vivo, and it's shown that some of these compounds had significant antioxidant activity. Amongst the compounds screened for antioxidant activity, thiosemicarbazones 4a, 4b and 4c showed good antioxidant activity on DPPH. The compounds 4g, 4i, 4l caused significant elevation of SOD activity and 4e, 4g, 4i, 4l had higher catalase activity, and only compounds 4c and 4f expressed the GSH-Px activity.

Copper and its complexes in medicine: a biochemical approach

The fundamental role of copper and the recognition of its complexes as important bioactive compounds in vitro and in vivo aroused an ever-increasing interest in these agents as potential drugs for therapeutic intervention in various diseases. The vast array of information available for their bioinorganic properties and mode of action in several biological systems, combined with the new opportunities offered by the flourishing technologies of medicinal chemistry, is creating an exciting scenario for the development of a novel generation of highly active drugs with minimized side effects which could add significantly to the current clinical research and practice. In this paper we attempt to summarize all the available-to-date information on these issues.

Synthesis and antitumor activity of novel benzimidazole-5-carboxylic acid derivatives and their transition metal complexes as topoisomerease II inhibitors

N-aminomethyl-1H-benzimidazole-5-carboxylic acid derivatives 2-5 and the ligand, 1-(5 (or 6-)-carboxy-1H-benzimidazol-2-ylmethyl)pyridinium chloride (6; H2L1) have been synthesized. New benzimidazole complexes 7-9 of the ligand 6; H2L1 with Cu2+, Co2 and Zn2+ were prepared. The growth-inhibitory against a panel of 21 human cancer cell lines of the synthesized compounds 1-9 was studied. Compounds 6-9 showed potent growth-inhibitory activity against the studied cell lines. The correlation coefficients according to COMPARE analysis of the National Cancer Institute screening protocol showed that the pattern of the growth-inhibitory effect of the compounds 6-9 was similar to that of etoposide and doxorubicin but different from that of SN-38 and cisplatin. The topoisomerase II inhibitory activity of the tested compounds 6-9 was studied. Compounds 6 and 8 inhibited topoisomerase II activity at 10 times lower concentration than etoposide in relaxation assay.