Investigation of DNA binding and bioactivities of thioether containing Schiff base Copper(II), Cobalt(II) and Palladium(II) complexes: Synthesis, characterization, spectrochemical study, viscosity measurement

Quantification of mirtazapine in tablets via DNA binding mechanism; development of a new HPLC method

Atypical antidepressant mirtazapine (MIR) is mostly prescribed for the management of major depressive disorder. The identification of MIR in pharmaceutical dosage forms was made possible by developing a novel, quick, sensitive high-performance liquid chromatography (HPLC) approach that was verified in accordance with ICH recommendations. In the first part of this study, HPLC investigations were optimized with regard to variables including pH, working column, mobile phase, temperature, and flow rate. The limit of detection (LOD) was 0.013 ppm, the limit of quantification (LOQ) was 0.044 ppm, and the linear range was computed as 0.5-15 ppm (R2 = 0.9998). The recovery investigation assessed the method's accuracy, which was shown to range between 98.82 and 100.97 %. In the second part, by using UV-vis spectroscopy, HPLC, thermal denaturation, and viscosity measurements, the mechanism of binding interaction of MIR with double-stranded fish sperm deoxyribonucleic acid (dsDNA) has been thoroughly studied. The DNA binding constants (Kb) were determined using UV-Vis absorption and HPLC methods. To investigate the interactions of MIR with dsDNA, molecular docking calculations and additionally, molecular dynamics simulations were performed. Results showed that MIR is located in the minor groove of dsDNA, and in addition to hydrogen bonding, electrostatic interaction is also formed between the aromatic ring of MIR and phosphate oxygen of dsDNA. Finally, a binding characterization study using MIR tablets was also conducted in order to assess the interaction mechanism of the DNA with the drug using the validated analytical procedure developed for the MIR molecule.

Green Synthesis and Bioactivity of Aliphatic N-Substituted Glycine Derivatives

Standard amino acids have an asymmetric α-carbon atom to which -COOH, -NH2, -H, and -R groups are bonded. Among them, glycine is the simplest (R = -H) with no asymmetric carbon, and other natural amino acids are C-substituted of glycine. Here, we have designed and made a green synthesis of some new N-substituted glycine derivatives with R-(NH)CH2-COOH formula, where R is flexible and hydrophobic with different chain lengths and benches of the type propyl, butyl, sec-butyl, tert-butyl, pentyl, isopentyl, tert-pentyl, hexyl, 2-aminoheptyl, and octyl. These glycine derivatives were characterized by recording their melting points and FT-IR, mass, 1H NMR, and 13C NMR spectra. DFT studies revealed that 2-aminoheptyl glycine had the highest electronegativity value and can thus act as a good bidentate ligand for the metal centers. ADME comparative results and bioavailability radars indicated that both octyl- and 2-aminoheptyl glycine had the most lipophilicity, making them good agents in cell passing. Furthermore, lipophilicity determination showed that octyl glycine was the best and propylgly was more soluble than others. Based on solubility, lipophilicity, and dipole moment values, propyl- and 2-aminoheptyl-glycine were considered for bio-macromolecular interaction studies. Thus, the interaction of these two agents with DNA and HSA was studied using absorption spectroscopy and circular dichroism techniques. Due to the presence of the R-amine group, they can interact with the DNA by H-binding and hydrophobicity, while electrostatic mode could not be ruled out. Meanwhile, molecular docking studies revealed that octyl- and 2-aminoheptyl glycine had the highest negative docking energy, which reflects their higher tendency to interact with DNA. The DNA binding affinity of two candidate AAs was determined by viscosity measurement and fluorescence emission recording, which confirms that groove binding occurs. Also, the toxicity of these synthesized amino acid derivates was tested against the human foreskin fibroblast (HFF) cell line. They showed IC50 values within the range of 127-344 μM after 48 h with the highest toxicity for 2-aminoheptyl glycine.

Thioether-based novel transition metal complexes: Synthesis, DNA interaction, in vitro biological assay, DFT calculations, and molecular docking studies

A novel Schiff base ligand 2-(((2-(benzylthio)phenyl)imino)methyl)-4-chlorophenol and its cobalt, nickel, copper, and zinc metal complexes were prepared. Using B3LYP/6-31++G(d,p) method with LanL2DZ as basis set, the molecular structure of metal complexes has been optimized, and their parameters have been explored. The distorted octahedral geometries have been observed in cobalt, nickel, and copper complexes. In contrast, zinc complex exhibited distorted tetrahedral geometry indicating the coordination of metal ions with ligands through ONS binding sites, which are confirmed by various spectroscopic techniques, magnetic measurements, molar conductivity, elemental analysis, and DFT studies. The intercalative binding mode between CT-DNA and synthesized metal complexes has been determined by absorption and fluorescence spectroscopy. The binding constant values of metal complexes found to be varied from 5.28 × 10³ M^-1 to 9.18 × 10⁴ M^-1. Furthermore, several methods have been used to scrutinize the bioactivities, such as in vitro anti-diabetic, anti-inflammatory, and antioxidant. From the obtained results, it can be concluded that zinc metal complex exhibited excellent anti-inflammatory and anti-diabetic activity compared to others. However, the copper complex has good antioxidant property. Besides deducing the prospective binding energies of inhibitors, molecular docking simulations have also been conducted utilizing the enzyme structures of B-DNA, 6-COX, α-amylase, and α-glucosidase.

Synthetic approach toward spiro quinoxaline-β-lactam based heterocyclic compounds: Spectral characterization, SAR, pharmacokinetic and biomolecular interaction studies

Series of spiro quinoxaline-β-lactam based heterocyclic compounds (QL 1 - QL 21) were synthesized and characterized by spectroscopic techniques like ¹H-NMR, LC-MS, FT-IR spectroscopy and elemental analysis. The binding mode and binding strength between compounds and calf thymus-DNA were estimated by UV-visible spectroscopy, viscosity measurement and molecular docking studies. The compounds bind with the DNA through partial intercalation mode. In the absorption titration experiment, the K_b values for all the synthesized compounds were found in the range of 0.24-0.64 × 10⁵ M^-1. The protein binding studies of all the synthesized compounds were evaluated by absorption titration experiment, and the K_b value for all the compounds was obtained in the range of 0.030-1.571 × 10⁴ M^-1. The compounds were screened against two Gram (+ve) and three Gram (-ve) bacteria for antimicrobial activity. The MIC values for all the synthesized compounds were found in 95-255 µM. The LC₅₀ values (cytotoxicity) of the synthesized compounds (QL 1-QL 21) were found in the range of 4.00-12.89 µg/mL. The ADME study was carried out using the online platform SwissADME and admetSAR to evaluate the pharmacokinetic profile of all the synthesized compounds. All the compounds were screened for anticancer activity against the human osteosarcoma (MG-63) cell line. The result shows that all the compounds exhibit effective anticancer activity.Communicated by Ramaswamy H. Sarma.

Experimental and Molecular Docking Studies on the Interaction of a Water-Soluble Pd(II) Complex Containing β-Amino Alcohol with Calf Thymus DNA

The interaction of water-soluble and fluorescent [Pd (HEAC) Cl₂] complex, in which HEAC is 2-((2-((2-hydroxyethyl)amino)ethyl)amino) cyclohexanol, with calf thymus DNA (ct-DNA) has been studied. This study was performed using electronic absorption and fluorescence emission spectroscopies, cyclic voltammetry and circular dichroism analyses, dynamic viscosity measurements, and molecular docking theory. From hypochromic effect observed in ct-DNA absorption spectra, it was found that the Pd(II) complex could form a conjugate with ct-DNA strands through the groove binding mode. The K_b values obtained from fluorescence measurements clearly assert the Pd(II) complex affinity to ct-DNA. The fluorescence quenching of the DNA-Hoechst compound following the successive additions of the Pd(II) complex to the solution revealed that the Pd(II) complex is located in the ct-DNA grooves, and Hoechst molecules have been released into solution; moreover, the resulting measurements from relative viscosity authenticate the Pd(II) complex binding to the grooves. Negative quantities of thermodynamic parameters imply that the Pd(II) complex binds to ct-DNA mainly by the hydrogen bonds and van der Waals forces; also, the Gibbs-free energy changes show the exothermic and spontaneous formation of the Pd(II) complex-DNA system. The electrochemical behavior of the Pd(II) complex in the attendance of ct-DNA was investigated using the cyclic voltammetry method (CV). Several quasi-reversible redox waves were observed along with increasing the anodic/cathodic peak currents, as well as a shift in anodic/cathodic peak potentials. Circular dichroism (CD) observations suggested that the Pd(II)-DNA interaction could alter ct-DNA conformation. The results of molecular modeling confirmed that groove mechanism is followed by the Pd(II) complex to interact with ct-DNA.

A Treatise on Furan Cored Schiff Base Cu(II), Ni(II) and Co(III) Complexes Accentuating Their Biological Efficacy: Synthesis, Thermal and Spectroscopic Characterization, DNA Interactions, Antioxidant and Antibacterial Activity Studies

Three metal complexes [Cu(FMIMDIP)₂ ] (1), [Ni(FMIMDIP)₂ ] (2) and [Co(FMIMDIP)₃ ] (3) where, FMIMDIP=(((furan-2-yl)methylimino)methyl)-4,6-diiodophenol, were synthesized and characterized by various spectroscopy. The analytical data revealed a square planar geometry for 1 and 2 and an octahedral geometry for 3. The kinetic and thermodynamic parameters of the thermal decomposition steps were calculated from the thermograms. The quantum chemical parameters have been calculated using HOMO-LUMO energies and reveal the stability of the complexes. The DNA interaction of 1-3 towards calf-thymus DNA was investigated by absorption titration, fluorescence spectroscopy and gel electrophoresis. All the complexes bind to DNA via intercalation mode with binding constant (K_b ) values of 4.17×10³  M^-1 to 5.9×10⁴  M^-1 and also effectively cleave pBR322 DNA by oxidative and photolytic techniques. The synergistic action of metal chelates with ascorbic acid induced the generation of free radicals. The antibacterial activity of 1-3 was tested against B. thuringiensis, S. pneumoniae, E. coli, and P. putida. Complex 3 has the best activity among all the complexes.

Design, DFT studies, antimicrobial and antioxidant potential of Binuclear N-heterocyclic Carbene (NHCs) complexes, Probing the aspect of DNA interaction through In-vitro and In-silico approach

N-heterocyclic carbene (NHC) adducts have shown remarkable biological potential for numerous medical applications. With an aim to improve biological potential of benzimidazolium salts, newer analogues of benzimidazole and their silver complexes were synthesized and characterized. Synthesized salts (L₁-L₂) and silver complexes (C₁-C₂) were confirmed through elemental analysis, UV-visible spectroscopy, FTIR, ¹H NMR & ¹³C NMR spectroscopy. The compounds C1 & C2 were found stable in solution form for studied time period when examined spectroscopically and showed optimum lipophilicity when measured for their partition coefficient through flask shake method. Synthesized compounds showed good antimicrobial potential against gram positive bacterial strain S. Aureus with IC₅₀ 2.02±0.12 and 2.11±0.13 µM respectively while 2.11±0.1 and 2.28±0.17 µM against gram negative bacterial strain E. Coli for C1 and C2 respectively. The interaction study of the related compounds with DNA was predicted by molecular docking study, which confirmed that the studied compound C1 (-8.04 kcal/mol) has a higher binding energy than compound C2 (-4.23 kcal/mol); Also, the compound C1 exhibits a better affinity against to DNA than Ethidium bromide (-7.68 kcal/mol) and cisplatin (-6.21 kcal/mol).The claim was practically assured through spectroscopic and viscometeric method which confirmed that compounds have good affinity for DNA with binding constant kb, 5.78×10⁴ M^-1 and 6.84×10⁴ M^-1 for C1 and C2 respectively.

Synthesis, characterization of ruthenium(II), nickel(II), palladium(II), and platinum(II) triphenylphosphine-based complexes bearing an ONS-donor chelating agent: Interaction with biomolecules, antioxidant, in vitro cytotoxic, apoptotic activity and cell cycle analysis

Four new transition metal complexes, [M(PPh₃)(L)]^.CH₃OH (M = Ni(II) (1), Pd(II) (2)) [Pt (PPh₃)₂(HL)]Cl (3) and [Ru(CO)(PPh₃)₂(L)] (4) (H₂L = 2,4-dihydroxybenzaldehyde-S-methyldithiocarbazate, PPh₃ = triphenylphosphine) have been synthesized and characterized by elemental analyses (C, H, N), FTIR, NMR (¹H, ³¹P), ESI-MS and UV-visible spectroscopy. The molecular structure of (1) and (2) complexes was confirmed by single-crystal X-ray crystallography. It showed a distorted square planar geometry for both complexes around the metal center, and the H₂L adopt a bi-negative tridentate chelating mode. The interaction with biomolecules viz., calf thymus DNA (ct DNA), yeast RNA (tRNA), and BSA (bovine serum albumin) was examined by both UV-visible and fluorescence spectroscopies. The antioxidant activity of all compounds is discussed on basis of DPPH^• (2,2-diphenyl-1-picrylhydrazyl) scavenging activity and showed better antioxidant activity for complexes compared to the ligand. The in vitro cytotoxicity of the compounds was tested on human (breast cancer (MCF7), colon cancer (HCT116), liver cancer (HepG2), and normal lung fibroblast (WI38)) cell lines, showing that complex (1) the most potent against MCF7 and complex (4) against HCT116 cell lines based on IC₅₀ and selective indices (SI) values. So, both complexes were chosen for further studies such as DNA fragmentation, cell apoptosis, and cell cycle analyses. Complex (1) induced MCF7 cell death by cellular apoptosis and arrest cells at S phase. Complex (4) induced HCT116 cell death predominantly by cellular necrosis and arrested cell division at G2/M phase due to DNA damage.

Arene Ruthenium(II) Complexes Bearing the κ-P or κ-P,κ-S Ph2P(CH2)3SPh Ligand

Neutral [Ru(η⁶-arene)Cl₂{Ph₂P(CH₂)₃SPh-κP}] (arene = benzene, indane, 1,2,3,4-tetrahydronaphthalene: 2a, 2c and 2d) and cationic [Ru(η⁶-arene)Cl(Ph₂P(CH₂)₃SPh-κP,κS)]X complexes (arene = mesitylene, 1,4-dihydronaphthalene; X = Cl: 3b, 3e; arene = benzene, mesitylene, indane, 1,2,3,4-tetrahydronaphthalene, and 1,4-dihydronaphthalene; X = PF₆: 4a-4e) complexes were prepared and characterized by elemental analysis, IR, ¹H, ¹³C and ³¹P NMR spectroscopy and also by single-crystal X-ray diffraction analyses. The stability of the complexes has been investigated in DMSO. Complexes have been assessed for their cytotoxic activity against 518A2, 8505C, A253, MCF-7 and SW480 cell lines. Generally, complexes exhibited activity in the lower micromolar range; moreover, they are found to be more active than cisplatin. For the most active ruthenium(II) complex, 4b, bearing mesitylene as ligand, the mechanism of action against 8505C cisplatin resistant cell line was determined. Complex 4b induced apoptosis accompanied by caspase activation.

Synthesis, characterization and in vitro cytotoxicity studies of novel Cu(II) complex containing zonisamide drug: DNA interaction by multi spectroscopic and molecular docking methods

In this study, the Cu(II) complex with Zonisamide (ZNS) and 1, 10-Phenanthroline (Phen) ligands as an anticancer metallodrug was synthesized and characterized successfully by FT-IR, mass spectrometry, TGA, XPS, AAS, CHNSO, magnetic susceptibility and electrical conductivity. The interaction of Cu(II) complex with DNA was explored through a multi-spectroscopic approach such as fluorescence, UV-vis spectrophotometry, CD spectroscopy, and viscosity measurements. Molecular docking simulation was carried out to gain a deeper insight into the target site of DNA which interacted with the mentioned complex. The competitive binding tests with Hoechst 33258 showed that [CuCl₂(ZNS)(Phen)EtOH].H₂O can bind to the groove site of DNA. The calculated thermodynamic parameters, ΔS° = +201.15 J mol^-1K^-1 and ΔH° = +41.32 kJ mol^-1 confirm that the hydrophobic forces and hydrogen bonding play an essential role in the binding process. The experimental and molecular modeling results demonstrate that the Cu(II) complex binds to DNA through major groove binding. Moreover, the in vitro cytotoxic effects of [CuCl₂(ZNS)(Phen)EtOH].H₂O against B92 cancer cell lines showed better activity in Cu(II) complex in comparison to free ZNS. Therefore, [CuCl₂(ZNS)(Phen)EtOH].H₂O can open a new horizon in the treatment of glioma cancer by ZNS metallodrugs.Communicated by Ramaswamy H. Sarma.

Antimicrobial, cytotoxicity, molecular modeling and DNA cleavage/binding studies of zinc-naproxen complex: switching DNA binding mode of naproxen by coordination to zinc ion

The intercalation DNA binding mode of the naproxen, a non-steroidal anti-inflammatory drug, has been reported previously. In this study, calf thymus deoxyribonucleic acid (CT-DNA) binding of zinc-naproxen complex, [Zn(naproxen)₂(MeOH)₂], at physiological pH has been investigated by multi-spectroscopic techniques and molecular docking. Zinc-naproxen complex displays significant binding property to the CT-DNA (K_b = 0.2 × 10⁵ L.mol^-1). All of the experimental results; relative increasing in viscosity of CT-DNA and fluorimetric studies using ethidium bromide (EB) and Hoechst 33258 probes, are indicative of groove binding mode of zinc-naproxen complex to CT-DNA. These results show that the coordination of naproxen to zinc metal switches the mode of binding from intercalation to groove. The molecular modeling also shows that the complex binds to the AT-rich region of minor groove of DNA. Structural and topography changes of DNA in interaction with the complex by atomic force microscopy (AFM) indicated that CT-DNA becomes swollen after interaction. The pUC18 plasmid DNA cleavage ability of zinc-naproxen complex by gel electrophoresis experiments revealed that zinc-naproxen complex cleaved supercoiled pUC18 plasmid DNA to nicked DNA. The cytotoxicity of the zinc complex performed by MTT method on HT29 and MCF7 cancer cell lines and on HEK 293 normal cell lines indicates that zinc complex has no cytotoxic effect on both HT29 and MCF7 cell lines but has better cytotoxicity effect on HEK 293 cell lines compared to cisplatin standard drug. The antimicrobial activity of the complex against Staphylococcus aureus and Escherichia coli bacteria revealed the high antimicrobial activity of the complex.Communicated by Ramaswamy H. Sarma.

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.