Comparative study of structure–activity relationship of di- and tri-organotin(IV) derivatives of amino acid and peptides

Anticancer Behavior of Pyrrolidine-Based Palladium(II) Complexes and Biophysical Approach on Their DNA, BSA Binding Activity, Molecular Docking, and DFT Study

A series of pyrrolidine-based Pd(II) complexes, [Pd(AEP)Cl2] (C-1), [Pd(AEP)(OH2)2]2+(C-2), [Pd(AEP)(L-cys)]+ (C-3), [Pd(AEP)(N-ac-L-cys)] (C-4), [Pd(AEP)(GSH)] (C-5), and [Pd(AEP)(DL-meth)]2+ (C-6) (where, AEP = 1-(2-aminoethyl)pyrrolidine, L-cys = l-cysteine, N-ac-L-cys = N-acetyl-l-cysteine, GSH = glutathione, and DL-meth = dl-methionine), as anticancer drug candidates have been synthesized and characterized. The DNA binding property of the complexes was executed by gel electrophoresis and spectrophotometric and viscometric methods, and their interaction with BSA was also investigated by various spectroscopic methodologies. The binding activity of the Pd(II) complexes with DNA and BSA were assessed to evaluate their binding mode and binding constants. Molecular docking was performed to correlate with the experimental results on the interaction of the complexes with DNA and BSA. The changes in the microenvironmental and structural properties of BSA are monitored by a synchronous and 3D fluorescence study. The structural properties were evaluated by DFT and TD-DFT studies. The anticarcinogenic activity of the Pd(II) complexes was assessed by PASS prediction software to corroborate with the experimental results of the anticancer activity of the complexes. The ROS generation in cancer cell lines has been investigated, and the cell death mechanism through apoptosis was confirmed by measuring the protein expression. All these complexes have excellent anticancer activity compared to ancillary ligands. The cancer cell line (HCT116) shows almost similar or better cell inhibition activity when treated with the Pd(II) complexes compared to cisplatin, whereas the adverse effect is minimum on a normal cell (NKE). Both the Pd(II) and Pt(II) complexes carrying the same ligands reveal almost similar antiproliferative activity.

Bioactivity, molecular docking and anticancer behavior of pyrrolidine based Pt(II) complexes: Their kinetics, DNA and BSA binding study by spectroscopic methods

The complex [Pt(AEP)Cl₂]; C-1 (where, AEP = 1-(2-Aminoethyl) pyrrolidine) and its hydrolyzed diaqua form cis-[Pt(AEP)(H₂O)₂]²⁺; C-2 were synthesized for their bioactivity and in vitro kinetic study with bioactive thiol group (-SH) containing ligands (like; L- cysteine and N-ac-L- cysteine) for their biological importance for 'drug reservoir' activity. The Thermal Gravimetric Analysis (TGA) was executed to confirm about the weight loss due to coordinated water molecules at high temperature range. At pH 4.0, the substitution behavior of C-2 with the thiols was studied in pseudo-first order reaction condition. The interaction mechanism of thiols with complex C-2 to their corresponding thiol substituted C-3 [Pt(AEP)(L-cys)] and C-4 [Pt(AEP)(N-ac-L-cys)] (where L-cys = L-cysteine and N-ac-L-cys = N-ac-L- cysteine) were proposed from their thermodynamical activation parameters (ΔH^≠ and ΔS^≠), which were obtained from Eyring equation. DNA and BSA binding activity of the complexes C-1 to C-4 were investigated by gel electrophoresis technique, spectroscopic titration and viscosity methods. The binding activity of the complexes with DNA and BSA was evaluated using a theoretical approach molecular docking study. The drug-like nature of the complexes is supported by the prediction of activity spectra for substance (PASS) from 2D structure of the Pt(II) complexes. Structural optimization, HOMO-LUMO energy calculation, Molecular electrostatic potential surface, NBO and TD-DFT calculation were executed by using density functional theory (DFT) with Gaussian 09 software package to pre-assessment of biological activity of the complexes. DFT-based descriptors were determined from the HOMO-LUMA energy to be related with the ability of binding affinity of Pt(II) complexes towards DNA and BSA to the formation of their corresponding adducts. The anticancer property of the design complexes were examined on HCT116 (colorectal carcinoma) cancer cell lines and as well as human normal cell NKE (Normal Kidney Epithelial) and compared with the recognised anticancer drug cisplatin. The Reactive Oxygen Species (ROS) production was assessed by DCFDA assay in presence of the Pt(II) complexes.

Cytotoxic effects of Pd(II) complexes on cancer and normal cells: Their DNA & BSA adduct formation and theoretical approaches

Herein, we report the synthesis and characterisation of a series of Pd(II) complexes: Pd(TEEDA)Cl₂, C-1; [Pd(TEEDA)(OH₂)₂](NO₃)₂, C-2; [Pd(TEEDA)(l-cys)](NO₃)₂, C-3; [Pd(TEEDA)(NALC)], C-4; [Pd(TEEDA)(Meth)](NO₃)₂, C-5; and [Pd(TEEDA)(GSH)], C-6 (where TEEDA = N,N,N'-Triethylenediamine, l-cys = l-cysteine, NALC = N-acetyl-l-cysteine, Meth = dl-methionine and GSH = glutathione). UV-Vis spectroscopic characterisation was supported by TD-DFT theoretical simulation using Gaussian09 software. Different reactivity parameters were calculated from the energy difference between HOMO and LUMO of the complexes by DFT. The bonding mode of the labile ligands was confirmed by NBO analysis. Interaction of the complexes with DNA has been observed by gel electrophoresis experiment. DNA binding nature as well as binding constants of the complexes were measured with UV-Vis and fluorescence spectroscopic method. The binding nature of the complexes with DNA was confirmed by viscometric titration. Interaction of the complexes with BSA was investigated by UV-Vis and fluorescence titration method. Cytotoxic activity of the Pd(II) complexes was evaluated on A549 (lung carcinoma epithelial cells), HCT116(Colorectal Carcinoma) and HEK293 (Human embryonic kidney cells) cell lines. The ROS generation in the presence of the complexes was tested both on cancer cell lines A549 and HCT116 as well as human normal cell HEK293.

New triorganotin(iv) compounds with aromatic carboxylate ligands: synthesis and evaluation of the pro-apoptotic mechanism

Three new organotin(iv) carboxylate compounds were synthesized and structurally characterized by elemental analysis and FT-IR and multinuclear NMR (1H, 13C, 119Sn) spectroscopy. Single X-ray crystallography reveals that compound C2 has a monoclinic crystal system with space group P21/c having distorted bipyramidal geometry defined by C3SnO2. The synthesized compounds were screened for drug-DNA interactions via UV-Vis spectroscopy and cyclic voltammetry showing good activity with high binding constants. Theoretical investigations also support the reactivity of the compounds as depicted from natural bond orbital (NBO) analysis using Gaussian 09. Synthesized compounds were initially evaluated on two cancer (HeLa and MCF-7) cell lines and cytotoxicity to normal cells was evaluated using a non-cancerous (BHK-21) cell line. All the compounds were found to be active, with IC50 values less than that of the standard drug i.e. cisplatin. The cytotoxic effect of the most potent compound C2 was confirmed by LDH cytotoxicity assay and fluorescence imaging after PI staining. Apoptotic features in compound C2 treated cancer cells were visualized after DAPI staining while regulation of apoptosis was observed by reactive oxygen species generation, binding of C2 with DNA, a change in mitochondrial membrane potential and expression of activated caspase-9 and caspase-3 in cancer cells. Results are indicative of activation of the intrinsic pathway of apoptosis in C2 treated cancer cells.

Fluorescent organotin compounds as dyes in silk fibroin (Bombyx mori): ultrasound-assisted synthesis, chemo-optical characterization, cytotoxicity, and confocal fluorescence microscopy

The fluorescent silk fibroin (FSF) is useful in a number of biomedical applications.

Synthesis of chiral R/S-pseudopeptide-based Cu(ii) & Zn(ii) complexes for use in targeted delivery for antitumor therapy: enantiomeric discrimination with CT-DNA and pBR322 DNA hydrolytic cleavage mechanism

The detailed mechanism of the hydrolytic cleavage pathway of 1S with pBR322 d DNA and the molecular docked model with DNA are shown below.

Variation of the Molecular Conformation, Shape, and Cavity Size in Dinuclear Metalla-Macrocycles Containing Hetero-Ditopic Dithiocarbamate-Carboxylate Ligands from a Homologous Series of N-Substituted Amino Acids

A homologous series of dithiocarbamate ligands derived from N-substituted amino acids was reacted with different diorganotin dichlorides to give 18 diorganotin complexes. Spectroscopic and mass spectrometric analysis evidenced the formation of assemblies with six-coordinate tin atoms embedded in skewed-trapezoidal bipyramidal coordination environments of composition C₂SnS₂O₂. Single-crystal X-ray diffraction analysis for three of the compounds revealed a one-dimensional polymeric structure for the complex with the ligand derived from 5-aminopentanoic acid, which through further intermolecular Sn···O interactions generated an overall two-dimensional coordination polymer containing 40-membered hexanuclear tin macrocycles. On the contrary, the ligands derived from 6-aminohexanoic and 8-aminooctanoic acid provided the expected 22- and 26-membered dinuclear macrocyclic structures. Density functional theory calculations for a representative series of macrocyclic complexes of composition [Me₂SnLx]₂ with Lx = ¯S₂CN(Me)-(CH₂)_x-COO¯ (x = 3-12) enabled a detailed analysis of the variations in the molecular conformation, shape, and cavity size of the macrocycles in dependence of the aliphatic spacer. Because of odd-even effects, the difunctional ligands can adopt either a curved or a twisted-pincer shape, while the SnS_xO_4-x (x = 0-4) moieties can act either as linear or angular tectons with varying connectivity angles.

Diorganotin(IV) complexes of flexible N-protected amino acids and ketoximes: preparation and structure – antimicrobial activity relationship

Diorganotin(IV) complexes of flexible N-protected amino acids and ketoximes having the compositions Me2Sn [[Formula: see text]CHRCOO][ON = C6H10] (where R = –CH2CH(CH3)2, –CH(CH3)C2H5,–CH2C6H5, –CH(CH3)2) and Me2Sn[[Formula: see text]CHRCOO][ON=CR′R″] (where R = –CH2CH(CH3)2, –CH(CH3)C2H5, –CH2C6H5, R′ = R″ = CH3; R = –CH(CH3)C2H5, –CH2C6H5, –CH(CH3)2, R′ = CH3, R″ = C6H5) were prepared by the reaction of dimethyltin(IV) dichloride with sodium salts of flexible N-protected amino acids and ketoximes in 1:1:1 molar ratio in refluxing dry benzene. The synthesized complexes were characterized by elemental analyses and IR, multinuclear NMR (1H, 13C, and 119Sn), and mass spectral studies. Plausible structures of these complexes have been suggested on the basis of molecular weight measurements and spectral data. 119Sn NMR spectral data indicate the presence of pentacoordinated tin centres in these complexes. Some of the synthesized complexes and their ligands were also screened for their in vitro antimicrobial activity.

Synthetic, Spectroscopic, Crystallographic, and Biological Studies of Seven-Coordinated Diorganotin(IV) Complexes Derived from Schiff Bases and Pyridinic Carboxylic Acids

The synthesis and characterisation of diorganotin(iv) monomeric derivatives of pyridine Schiff bases and pyridinic carboxylic acids are reported. All complexes were characterised by mass spectrometry, elemental analyses, IR spectra, and multinuclear NMR analyses. Among them, complexes 5a, 5d, 5e, 5g, and 6a were also confirmed by X-ray crystallography diffraction analyses, which led to establishing that the tin atom is seven-coordinated and has a distorted pentagonal–bipyramidal coordination environment in the solid state and also revealed that both ligands occupy the equatorial positions and the organic substituents the axial positions. The antioxidant activity of the synthetic derivatives towards 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) as well as the thiobarbituric acid reactive substances (TBARS) assay were determined, and were compared with standard antioxidants, showing a dose-dependent activity in both cases. A prominent response was obtained depending on the substituent. The anti-inflammatory activity was also evaluated on a 12-O-tetradecanoylphorbol-13-acetate (TPA) model of induced acute inflammation. The results of the biological tests are discussed in terms of structural characteristics.

Synthesis and spectroscopic characterization of diorganotin(iv) complexes of N′-(4-hydroxypent-3-en-2-ylidene)isonicotinohydrazide: chemotherapeutic potential validation by in vitro interaction studies with DNA/HSA, DFT, molecular docking and cytotoxic activity

A diorganotin(iv) hydrazide complex as a potential cancer chemotherapeutic agent targeting DNA using the carrier protein HSA.

Potentially bioactive organotin(IV) compounds: synthesis, characterization, in vitro bioactivities and interaction with SS-DNA

Fourteen new organotin(IV) complexes with general formula R2SnL2 or R3SnL where R = CH3, C2H5, C4H9, C6H5, C6H11, CH2-C6H5, C(CH3)3, C8H17 and L = N-[(2-methoxyphenyl)]-4-oxo-4-[oxy]butanamide were synthesized and characterized by elemental analyses, FT-IR, NMR ((1)H, (13)C and (119)Sn), mass spectrometry and single crystal X-ray structural analysis. Crystallographic data for four triorganotin(IV) complexes (R3SnL, R = CH3, C2H5, C4H9, CH2-C6H5) showed the tin has approximate trigonal bipyramidal geometry with the R groups in the trigonal plane. The carboxylate groups of ligands L bridge adjacent tin atoms, resulting in polymeric chains. In case of the diorganotin(IV) derivatives a six-coordinate geometry at the tin atom is proposed from spectroscopic evidence. The Me-Sn-Me bond angle in complex 7 was determined from the (2)J[(119)Sn-(1)H] value as 166.3° that falls in the range of six-coordinate geometry. The ligand and its complexes (1-14) were screened for their antimicrobial, antitumor, cytotoxic and antileishmanial activities and found to be biologically active. The ligand and its complexes bind to DNA via intercalative interactions resulting in hypochromism and minor bathochromic shifts as confirmed by UV-visible spectroscopy. Based on in vitro studies such as the potato disc method, the synthesized compounds were found to possess significant antitumor activity. Also, from cytotoxicity and DNA interaction studies, these compounds can also be used for the prevention and treatment of cancer. Gel electrophoresis assay was used to investigate the damage to double stranded super coiled plasmid pBR322 DNA by the synthesized compounds and compounds 1 and 7 were found to cause the maximum damage. All the synthesized compounds exhibit strong antileishmanial activity that was even higher than that of Amphotericin B, with significant cytotoxicity. This study, therefore, demonstrated the potential use of these compounds as source of novel agents for the treatment of leishmaniasis.

Zinc(II) complexes of Pro-Gly and Pro-Leu dipeptides: synthesis, characterization, in vitro DNA binding and cleavage studies

Dipeptide (Pro-Gly and Pro-Leu) Zinc(II) complexes 1 and 2 were designed and synthesized for potential use as cancer chemotherapeutic agents. In order to augment the DNA recognition of metallonuclease activity, zinc metal ion was tethered to peptide motif to carry out DNA site specific hydrolytic cleavage. The structural formulation of the complexes 1 and 2 was done by elemental analysis, spectroscopic methods (IR, NMR, electronic) and molar conductance measurements. Their in vitro DNA binding profile was investigated by UV-vis titrations, fluorescence titrations and circular dichroism which revealed that these complexes bind to CT DNA by electrostatic interactions via groove binding mode. Zn(II) Pro-Gly complex 1 showed greater binding affinity to CT DNA as compared to the Zn(II) Pro-Leu complex 2 due to steric constraints in the latter. The supercoiled pBR322 DNA cleavage activity of complex 1, ascertained by gel electrophoresis demonstrated efficient DNA cleaving ability via hydrolytic mechanistic pathway. Further, the molecular docking studies confirmed that complex 1 bind to the minor groove of DNA having AT-rich sequences with relative binding energy of -196.72kJmol(-1).

Synthesis, Structural, and Antimicrobial Studies of Some New Coordination Compounds of Palladium(II) with Azomethines Derived from Amino Acids

Some new coordination compounds of palladium(II) have been synthesized by the reaction of palladium(II) acetate with azomethines in a 1 : 2 molar ratio using acetonitrile as a reaction medium. Azomethines used in these studies have been prepared by the condensation of 2-acetyl fluorene and 4-acetyl biphenyl with glycine, alanine, valine, and leucine in methanol. An attempt has been made to probe their bonding and structures on the basis of elemental analyses and IR,1H, and13C NMR spectral studies. Pd(II) compounds have been found to be more active than their uncomplexed ligands as both of them were screened for antibacterial, antifungal, and insecticidal activities.

Interaction of 5'-Guanosine Monophosphate with Organotin(IV) Moieties: Synthesis, Structural Characterization, and Anti-Inflammatory Activity

Reaction(s) of 5'-guanosine monophosphate (5'GMP) with di- and triorganotin(IV) chloride(s) led to formation of organotin(IV) derivatives of general formulae, [R2Sn(5'-GMP)·H2O] n and [(R'3Sn)2(5'-GMP)·H2O] n , where R = Me, n-Bu, and Ph; R' = Me, i-Pr, n-Bu, and Ph; (5'-GMP)(2-) = 5'-guanosine monophosphate. An attempt has been made to prove the structures of the resulting derivatives on the basis of FT-IR, multinuclear (1)H, (13)C, and (119)Sn NMR and (119)Sn Mössbauer spectroscopic studies. These investigations suggest that both di- and triorganotin(IV)-5'-guanosine monophosphates are polymeric in which (5'-GMP)(2-) is bonded through phosphate group resulting in a distorted trigonal bipyramidal geometry around tin. The ribose conformation in all of the derivatives is C3'-endo, except diphenyltin(IV) and tri-i-propyltin(IV) derivatives where it is C2'-endo. All of the studied derivatives exhibited mild-to-moderate anti-inflammatory activity (~15.64-20.63% inhibition) at 40 mg kg(-1) dose and LD50 values > 400 mg kg(-1) in albino rats.