DNA interaction studies of a platinum(II) complex, PtCl(2)(NN) (NN=4,7-dimethyl-1,10-phenanthroline), using different instrumental methods

Selective Recognition of Oncogene Promoter C-Myc G-Quadruplex: Design, Synthesis, and In Vitro Evaluation of Naphthalimide and Imidazo[1,2-a]pyrazines for Their Anticancer Activity

c-Myc is a transcription factor that is overexpressed in most human cancers. Despite its challenging nature, we have developed a series of naphthalimide-imidazopyrazine conjugates to target c-Myc. The library of synthesized derivatives was tested for their anticancer activity against a nine-panel of cancer cell lines. Compound 8eb showed excellent cytotoxicity against all the tested cancer cell lines, with the range of growth inhibition from -98.79% to 96.62% at a single-dose concentration of 10-5 M. Further, 8eb was employed for a 5-dose assay against the same cancer cell lines, which showed efficacy at varying concentrations with an MG-MID GI50 value of 2.61 μM. Biophysical studies were performed to explore the interaction of 8eb with c-Myc Pu27 over ct-DNA, oncogene promotor Pu22, and human telomere, with a binding constant value of 1.3 × 107 M-1. Additionally, experiments were performed to get insights into the interaction mechanism between 8eb and the c-Myc oncogene promoter. A molecular docking study unveiled the stacking of the compound with G4 DNA through groove binding, where very few reports are available, with a favorable binding energy of -9.2 kcal/mol. Moreover, the pharmacokinetic study and HOMO-LUMO energy gap analysis underscored the potency of the active candidate. The compound's binding ability toward HSA was also assessed, where results suggested effective binding of the compound to HSA, revealing its potential for easy delivery to the target site. The above findings suggested that these newly synthesized candidates with potent anticancer activity offer a promising avenue as G4 DNA c-Myc stabilizers.

Synthesis and biological evaluation of 1-phenyl-4,6-dihydrobenzo[b]pyrazolo[3,4-d]azepin-5(1H)-one/thiones as anticancer agents

Cancer is associated with uncontrolled cell proliferation invading adjoining tissues and organs. Despite the availability of several chemotherapeutic agents, the constant search for newer approaches and drugs is necessitated owing to the ever-growing challenge of resistance. Over the years, DNA has emerged as an important druggable therapeutic drug due to its role in critical cellular processes such as cell division and maintenance. Further, evading apoptosis stands out as a hallmark of cancer. Hence, designing new compounds that would target DNA and induce apoptosis plays an important role in cancer therapy. In the current work, we carried out the synthesis and anticancer evaluation of 1-aryl-4,6-dihydrobenzo[b]pyrazolo[3,4-d]azepin-5(1H)-ones/thiones (26 compounds) against selected human cancer cell lines. Among these, compounds 8ae, 8ad, 8cf, 10ad and Kenpaullone have shown good inhibitory properties against HeLa cells (IC₅₀ < 2 µM) with good selectivity over the non-cancerous human embryonic kidney (Hek293T) cells. In cell cycle analysis, the compounds 8ad and 8cf have exhibited G₂/M cell cycle arrest in HeLa cells. In addition, the compounds 8ad and 8cf induced apoptosis in a dose-dependent manner in the Annexin-V FITC staining assay. The DAPI staining clearly demonstrated the condensed and fragmented nuclei in 8ad, 8cf, 8ae and Kenpaullone-treated HeLa cells. In addition, these compounds strongly suppressed the healing after 48 h in in vitro cell migration assay. The DNA binding experiments indicated that compounds 8ae, 8cf, and 8ad as well as Kenpaullone interact with double-stranded DNA by binding in grooves which may interrupt the DNA replication and kill fast-growing cells. Molecular docking studies revealed the binding pose of 8ad and Kenpaullone at HT1 binding pocket of double-stranded DNA. Compounds 8ad and 8cf demonstrated moderate topo II inhibition which could be a possible reason for their anticancer properties. Compounds 8ad and 8cf may cause the topo II and DNA covalent complex, which leads to the inhibition of DNA replication and transcription. This eventually increases the DNA damage in cells and promotes cell apoptosis. With the above interesting biological profile, the new 1-aryl-2,6-dihydrobenzo[b]pyrazolo[3,4-d]azepin-5(4H)-one/thione derivatives have emerged as promising leads for the discovery of new anticancer agents.

Triazolo-linked benzimidazoles as tubulin polymerization inhibitors and DNA intercalators: Design, synthesis, cytotoxicity, and docking studies

A simple "click" protocol was employed in the quest of synthesizing 1,2,3-triazole-linked benzimidazoles as promising anticancer agents on various human cancer cell lines such as A549, HCT116, SK-Mel-28, HT-29, and MCF-7. Compound 12j demonstrated significant cytotoxic potential towards SK-Mel-28 cancer cells (IC₅₀ : 4.17 ± 0.09 µM) and displayed no cytotoxicity (IC₅₀ : > 100 µM) against normal human BEAS-2B cells inferring its safety towards normal healthy cells. Further to comprehend the underlying apoptosis mechanisms, AO/EB, dichlorodihydrofluorescein diacetate (DCFDA), and 4',6-diamidino-2-phenylindole (DAPI) staining were performed, which revealed the nuclear and morphological alterations. Compound 12j displayed impairment in cellular migration and inhibited colony formation. The annexin V binding assay and JC-1 were implemented to evaluate the scope of apoptosis and the loss of the mitochondrial transmembrane potential in SK-Mel-28 cells. Cell-cycle analysis revealed that compound 12j arrested the cells at the G2/M phase in a dose-dependent manner. Target-based assays established the inhibition of tubulin polymerization by 12j at an IC₅₀ value of 5.65  ± 0.05 μM and its effective binding with circulating tumor DNA as a DNA intercalator. The detailed binding interactions of 12j with tubulin and DNA were examined by docking studies on PDB ID: 3E22 and DNA hexamer (PDB ID: 1NAB), respectively.

Antibacterial Activity of Co(III) Complexes with Diamine Chelate Ligands against a Broad Spectrum of Bacteria with a DNA Interaction Mechanism

Cobalt coordination complexes are very attractive compounds for their therapeutic uses as antiviral, antibacterial, antifungal, antiparasitic, or antitumor agents. Two Co(III) complexes with diamine chelate ligands ([CoCl₂(dap)₂]Cl (1) and [CoCl₂(en)₂]Cl (2)) (where dap = 1,3-diaminopropane, en = ethylenediamine) were synthesized and characterized by elemental analysis, an ATR technique, and a scan method and sequentially tested against Gram-positive and Gram-negative bacteria. The minimum inhibitory concentration results revealed that anaerobic and microaerophilic bacteria were found to be the most sensitive; the serial passages assay presented insignificant increases in bacterial resistance to both compounds after 20 passages. The synergy assay showed a significant reduction in the MIC values of nalidixic acid when combined with Compounds (1) or (2). The assessment of cell damage by the complexes was performed using scanning electron microscopy, transmission electron microscopy, and confocal microscopy, which indicated cell membrane permeability, deformation, and altered cell morphology. DNA interaction studies of the Co(III) complexes with plasmid pBR322 using spectrophotometric titration methods revealed that the interaction between Complex (1) or (2) and DNA suggested an electrostatic and intercalative mode of binding, respectively. Furthermore, the DNA cleavage ability of compounds by agarose gel electrophoresis showed nuclease activity for both complexes. The results suggest that the effect of the tested compounds against bacteria can be complex.

Synthesis and biological evaluation of novel imidazo[1,2-a]pyridine-oxadiazole hybrids as anti-proliferative agents: Study of microtubule polymerization inhibition and DNA binding

Efforts towards the development of potential anticancer agents, a new series of imidazo[1,2-a]pyridine-oxadiazole hybrids were synthesized and evaluated for their in vitro anticancer activity against lung cancer (A549) and prostate cancer (PC-3, DU-145) cell lines. Amongst the compounds tested, 6d showed the highest potency on A549 cells with an IC₅₀ value of 2.8 ± 0.02 μM. Flow cytometric analysis of compound 6d treated A549 cells showed apoptosis induction by annexin-v/PI dual staining assay and the effect of 6d on different phases of cell cycle was also analyzed. Target based studies demonstrated the inhibition of tubulin polymerization by 6d at an IC₅₀ value of 3.45 ± 0.51 μM and its effective binding with CT-DNA. Further, the molecular modelling studies revealed that 6d has a prominent binding affinity towards α/β-tubulin receptor with admirable physico-chemical properties.

Benzimidazole-1,2,3-triazole hybrid molecules: synthesis and study of their interaction with G-quadruplex DNA

A series of new benzimidazole-1,2,3-triazole hybrid derivatives have been synthesized via 'click' reaction and evaluated for their in vitro cytotoxicity as well as DNA binding affinity. MTT assay showed that all the six compounds are cytotoxic to PC3 and B16-F10 cancer cell lines. Though all the compounds showed moderate interaction with G4, c-Myc promoter DNA and dsDNA, 4f exhibited selective interaction with G-quadruplex DNA over duplex DNA as demonstrated by spectroscopic experiments like UV-vis spectroscopy, fluorescence spectroscopy, CD spectroscopy, thermal melting and fluorescence lifetime experiments. They also confirm the G-quadruplex DNA stabilizing potential of 4f. Viscosity measurements also confirm that 4f exhibits high G-quadruplex DNA selectivity over duplex DNA. Docking studies supported the spectroscopic observations. Cell cycle analysis showed that 4f induces G₂/M phase arrest and induces apoptosis. Hence, from these experimental results it is evident that compound 4f may be a G-quadruplex DNA groove binding molecule with anticancer activity.

Targeting tubulin polymerization and DNA binding of 4-thiazolidinone–umbelliferone hybrids: synthesis and cytotoxicity evaluation

The discovery of a series of combretastatin A-4 inspired novel molecular hybrids of 4-thiazolidinone–umbelliferone as prominent cytotoxic agents was reported.

Development of β-carboline-benzothiazole hybrids via carboxamide formation as cytotoxic agents: DNA intercalative topoisomerase IIα inhibition and apoptosis induction

In quest of promising anticancer agents, the pharmacophores of natural (β-carboline) and synthetic origin (benzothiazole) were adjoined by a carboxamide bridge and three-point diversification was accomplished. The in vitro cytotoxic ability of the compounds was established on adherent and suspension human cancer cell lines and compounds 8u and 8f advanced as pre-eminent molecules with IC₅₀ values of 1.46 and 1.81 μM respectively in A549 cell line. The cytospecificity was entrenched for potent compounds 8u and 8f by evaluating against normal human lung epithelial cells and selectivity index was calculated. Furthermore, EtBr displacement, relative viscosity and gel-based topoisomerase II target assays unveiled the intercalative topo-II inhibitory capability and DNA binding studies (absorbance) revealed the dissociation constant (K_d) for compounds 8u and 8f as 98 and 103 μM respectively. Additionally, cell-based flow cytometric assays like Annexin-V/PI dual staining aids in the quantification of apoptosis induced and JC-1 staining disclosed the depolarization of mitochondrial membrane potential by compound 8u in A549 cells in a dose-dependent manner. Moreover, wound healing assay established the inhibition of in vitro cell migration by compound 8u on A549 cells. In addition, molecular docking studies proved the binding of compounds 8u and 8f in the active site of DNA complexed with topo IIα and stabilized by interactions with DNA base pairs and amino acid residues. Remarkably, the compounds 8u and 8f follow Lipinski's rule of five and are in the recommended range for Jorgensen's rule of three with a minimal violation and other pharmacokinetic parameters revealing druggability of the synthesized hybrids.

Spectroscopic and In Silico DNA Binding Studies on the Interaction of Some New N-Substituted Rhodanines with Calf-thymus DNA: In Vitro Anticancer Activities

BACKGROUND

In this era of science, cancer is a black dot on the face of humankind. Consequently, the search of promising anticancer agents continues.

AIMS

Here we designed and synthesized new N-substituted rhodanines (RD1-7), evaluated their multispectroscopic interaction with calf thymus DNA, in silico and anticancer studies against MDA-MB-231cancer cell line.

METHODS

By MTT assay rhodanine RD1 was found to be the most potent with IC50 value of 72.61 μM. In addition, DNA binding studies (UV-vis and fluorescence) revealed strong binding affinity of RD1-7 with DNA (Kb in the range of 1.5-7.4 × 105 M-1). Moreover, molecular docking study, experimental DNA binding and anticancer studies are all well agreed to each other.

RESULTS

It was observed that H-bonding and hydrophobic attractions were responsible for stability of DNAcompound adducts. Besides, the reported rhodanines (RD1-7) were found as minor groove binders of DNA. Concisely, RD1-7 indicated promising pharmacological properties and hence, shows auspicious future for the development of novel anticancer agents.

CONCLUSION

The reported rhodanines showed excellent anticancer properties. Therefore, the described rhodanines may be used as potential anticancer agents in the future.

Studies on the Interaction of [SnMe2Cl2(bu2bpy)] Complex with ct-DNA Using Multispectroscopic, Atomic Force Microscopy (AFM) and Molecular Docking

The interaction of SnMe₂Cl₂(bu₂bpy)complex with calf thymus DNA (ct-DNA) has been explored following, using spectroscopic methods, viscosity measurements, Atomic force microscopy, Thermal denaturation and Molecular docking. It was found that Sn(IV) complex could bind with DNA via intercalation mode as evidenced by hyperchromism and bathochromic in UV-Vis spectrum; these spectral characteristics suggest that the Sn(IV) complex interacts with DNA most likely through a mode that involves a stacking interaction between the aromatic chromophore and the base pairs of DNA. In addition, the fluorescence emission spectra of intercalated methylene blue (MB) with increasing concentrations of SnMe₂Cl₂(bu₂bpy) represented a significant increase of MB intensity as to release MB from MB-DNA system. Positive values of ΔH and ΔS imply that the complex is bound to ct-DNA mainly via the hydrophobic attraction. Large complexes contain the DNA chains with an average size of 859 nm were observed by using AFM for Sn(IV) Complex-DNA. The Fourier transform infrared study showed a major interaction of Sn(IV) complex with G-C and A-T base pairs and a minor perturbation of the backbone PO₂ group. Addition of the Sn(IV)complex results in a noticeable rise in the Tm of DNA. In addition, the results of viscosity measurements suggest that SnMe₂Cl₂(bu₂bpy) complex may bind with the classical intercalative mode. From spectroscopic and hydrodynamic studies, it has been found that Sn(IV)complex interacts with DNA by intercalation mode. Optimized docked model of DNA-complex mixture confirmed the experimental results.

Synthesis and biological evaluation of pyrazole linked benzothiazole-β-naphthol derivatives as topoisomerase I inhibitors with DNA binding ability

A series of new pyrazole linked benzothiazole-β-naphthol derivatives were designed and synthesized using a simple, efficient and ecofriendly route under catalyst-free conditions in good to excellent yields. These derivatives were evaluated for their cytotoxicity on selected human cancer cell lines. Among those, the derivatives 4j, 4k and 4l exhibited considerable cytotoxicity with IC₅₀ values ranging between 4.63 and 5.54 µM against human cervical cancer cells (HeLa). Structure activity relationship was elucidated by varying different substituents on benzothiazoles and pyrazoles. Further, flow cytometric analysis revealed that these derivatives induced cell cycle arrest in G2/M phase and spectroscopic studies such as UV-visible, fluorescence and circular dichroism studies showed that these derivatives exhibited good DNA binding affinity. Additionally, these derivatives can effectively inhibit the topoisomerase I activity. Viscosity studies and molecular docking studies demonstrated that the derivatives bind with the minor groove of the DNA.

Design and synthesis of DNA-intercalative naphthalimide-benzothiazole/cinnamide derivatives: cytotoxicity evaluation and topoisomerase-IIα inhibition

A new series of different naphthalimide-benzothiazole/cinnamide derivatives were designed, synthesized and tested for their in vitro cytotoxicity on selected human cancer cell lines. Among them, derivatives 4a and 4b with the 6-aminobenzothiazole ring and 5g with the cinnamide ring displayed potent cytotoxic activity against colon (IC₅₀: 3.715 and 3.467 μM) and lung cancer (IC₅₀: 4.074 and 3.890 μM) cell lines when compared to amonafide (IC₅₀: 5.459 and 7.762 μM). Later, the DNA binding studies for these selected derivatives (by CD, UV/vis, fluorescence spectroscopy, DNA viscosity, and molecular docking) suggested that these new derivatives significantly intercalate between two strands of DNA. In addition, the most potent derivatives 4a and 4b were also found to inhibit DNA topoisomerase-II.

Drug Effect of Thulium(III)-Arsenazo III Complex on Herring Sperm DNA

To assess the potential cytostatic properties of the thulium(III)-arsenazo III complex as a probe of rare earth complex antitumor drugs, the interaction information of the thulium(III)-arsenazo III complex with DNA was obtained by using spectroscopy, viscosity measurements, and voltammetric methods. The thermodynamic functions demonstrated that the binding constants of the thulium(III)-arsenazo III complex with DNA were Kθ298.15K = 4.84 × 106 L·mol−1 and Kθ308.15K = 4.48 × 106 L·mol−1, and the binding process was enthalpy driven. The increase in relative viscosity of DNA with the addition of the thulium(III)-arsenazo III complex and the results from Scatchard and voltammetric methods showed that the interaction mode between the thulium(III)-arsenazo III complex and DNA was groove binding along with weak intercalative binding.

Synthesis of DNA interactive C3-trans-cinnamide linked β-carboline conjugates as potential cytotoxic and DNA topoisomerase I inhibitors

A series of new C3-trans-cinnamide linked β-carboline conjugates has been synthesized by coupling between various β-carboline amines and substituted cinnamic acids. Evaluation of their anti-proliferative activity against a panel of selected human cancer cell lines such as A549 (lung cancer), MCF-7 (breast cancer), B16 (melanoma), HeLa (cervical cancer) and a normal cell line NIH3T3 (mouse embryonic fibroblast cell line), suggested that the newly designed conjugates are considerably active against all the tested cancer cell lines with IC₅₀ values 13-45 nM. Moreover, the conjugates 8v and 8x were the most active against MCF-7 cells (14.05 nM and 13.84 nM respectively) and also even potent on other cell lines tested. Further, detailed investigations such as cell cycle analysis, apoptosis induction study, topoisomerase I inhibition assay, DNA binding affinity and docking studies revealed that these new conjugates are DNA interactive topoisomerase I inhibitors.

Synthesis and characterization of new unsymmetrical Schiff base Zn (II) and Co (II) complexes and study of their interactions with bovin serum albumin and DNA by spectroscopic techniques

Two novel tetra-coordinated Cobalt(II) and Zinc (II) chelate series with the general formula of [Co (L)·2H₂O] (1) and [Zn (L)] (2) [L=N-2-hydroxyacetophenon-N'-2-hydroxynaphthaldehyde-1,2 phenylenediimine)] with biologically active Schiff base ligands were synthesized and recognized by elemental analysis and multi-nuclear spectroscopy (IR and ¹H and ¹³C NMR); then, their biological activities including DNA and protein interactions were studied. The interaction of the synthesized compounds with bovine serum albumin (BSA) was investigated via fluorescence spectroscopy, showing the affinity of the complexes for these proteins with relatively high binding constant values and the changed secondary BSA structure in the presence of the complexes. The interaction of these compounds with CT-DNA was considered by UV-Vis technique, emission titration, viscosity measurements, helix melting methods, and circular dichroism (CD) spectroscopy, confirming that the complexes were bound to CT-DNA by the intercalation binding mode. Furthermore, the complexes had the capability to displace the DNA-bound MB, as shown by the competitive studies of these complexes with methylene blue (MB), thereby suggesting the intercalation mode for the competition. Finally, the theoretical studies carried out by the docking method were performed to calculate the binding constants and recognize the binding site of the BSA and DNA by the complexes. In addition, in vitro and in silico studies showed that the compounds were degradable by bacterial and fungal biodegradation activities.

Intercalation of a Zn(II) complex containing ciprofloxacin drug between DNA base pairs

In this study, an attempt has been made to study the interaction of a Zn(II) complex containing an antibiotic drug, ciprofloxacin, with calf thymus DNA using spectroscopic methods. It was found that Zn(II) complex could bind with DNA via intercalation mode as evidenced by: hyperchromism in UV-Vis spectrum; these spectral characteristics suggest that the Zn(II) complex interacts with DNA most likely through a mode that involves a stacking interaction between the aromatic chromophore and the base pairs of DNA. DNA binding constant (K_b = 1.4 × 10⁴ M^-1) from spectrophotometric studies of the interaction of Zn(II) complex with DNA is comparable to those of some DNA intercalative polypyridyl Ru(II) complexes 1.0 -4.8 × 10⁴ M^-1. CD study showed stabilization of the right-handed B form of DNA in the presence of Zn(II) complex as observed for the classical intercalator methylene blue. Thermodynamic parameters (ΔH < 0 and ΔS < 0) indicated that hydrogen bond and Van der Waals play main roles in this binding prose. Competitive fluorimetric studies with methylene blue (MB) dye have shown that Zn(II) complex exhibits the ability of this complex to displace with DNA-MB, indicating that it binds to DNA in strong competition with MB for the intercalation.

Synthesis and spectroscopic characterization study of new palladium complexes containing bioactive O,O-chelated ligands: evaluation of the DNA/protein BSA interaction, in vitro antitumoural activity and molecular docking

[Pd{(C,N)-C₆H₄CH₂NH(Et) (Qu)] (2) and [Pd{(C,N)-C₆H₄CH₂NH(Et) (Nar)] (3) (Qu = Quercetin, Nar = Naringin) mononuclear palladium (II) complexes have been synthesized and characterized using elemental analysis, IR and electronic spectroscopy. The interaction of the prepared complexes with calf thymus DNA and bovine serum albumin (BSA), monitored by UV-visible and fluorescence titrations, respectively, have been carried out to better understand the mode of their action under biological conditions. Intercalative binding mode between the complexes and DNA is suggested by the binding constant (K_b) values of 2.5 × 10⁶ and 3.2 × 10⁶ for complexes 2 and 3, respectively. In particular, the in vitro cytotoxicity of the complexes on two cancer cells lines (bladder carcinoma TCC and breast cancer MCF7) showed that the compounds had broad spectrum, anti-cancer activity with low IC₅₀ values and the order of in vitro anticancer activities is consistent with the DNA-binding affinities. In the meantime, the quenching of tryptophan emission with the addition of complexes using BSA as a model protein indicated the protein binding ability. The quenching mechanisms of BSA by the complexes were static processes, according to the results obtained. The competitive binding using Warfarin, Digoxin and Ibuprofen site markers, which contain definite biding sites, demonstrated that the complexes bind to site I on BSA. Ultimately, the binding sites of DNA and BSA with the complexes have been determined by molecular modelling studies.

Forced degradation studies of lansoprazole using LC-ESI HRMS and 1 H-NMR experiments: in vitro toxicity evaluation of major degradation products

Regulatory agencies from all over the world have set up stringent guidelines with regard to drug degradation products due to their toxic effects or carcinogenicity. Lansoprazole, a proton-pump inhibitor, was subjected to forced degradation studies as per ICH guidelines Q1A (R2). The drug was found to degrade under acidic, basic, neutral hydrolysis and oxidative stress conditions, whereas it was found to be stable under thermal and photolytic conditions. The chromatographic separation of the drug and its degradation products were achieved on a Hiber Purospher, C18 (250 × 4.6 mm, 5 μ) column using 10 mM ammonium acetate and acetonitrile as a mobile phase in a gradient elution mode at a flow rate of 1.0 ml/min. The eight degradation products (DP1-8) were identified and characterized by UPLC/ESI/HRMS with in-source CID experiments combined with accurate mass measurements. DP-1, DP-2 and DP-3 were formed in acidic, DP-4 in basic, DP-5 in neutral and DP-1, DP-6, DP-7 and DP-8 were in oxidation stress condition Among eight degradation products, five were hitherto unknown degradation products. In addition, one of the major degradation products, DP-2, was isolated by using semi preparative HPLC and other two, DP-6 and DP-7 were synthesized. The cytotoxic effect of these degradation products (DP-2, DP-6 and DP-7) were tested on normal human cells such as HEK 293 (embryonic kidney cells) and RWPE-1(normal prostate epithelial cells) by MTT assay. From the results of cytotoxicity, it was found that lansoprazole as well as its degradation products (DP-2, DP-6 and DP-7) were nontoxic up to 50-μM concentrations, and the latter showed slightly higher cytotoxicity when compared with that of lansoprazole. DNA binding studies using spectroscopic techniques indicate that DP-2, DP-6 and DP-7 molecules interact with ctDNA and may bind to its surface. Copyright © 2017 John Wiley & Sons, Ltd.

Exploring the binding mechanism of paraquat to DNA by a combination of spectroscopic, cellular uptake, molecular docking and molecular dynamics simulation methods

The possibility that paraquat may exert its toxicity also by interaction with DNA is studied using a combination of different computational and experimental techniques.

Experimental and computational studies on the effects of valganciclovir as an antiviral drug on calf thymus DNA

DNA-binding properties of an antiviral drug, valganciclovir (valcyte) was studied by using emission, absorption, circular dichroism, viscosity, differential pulse voltammetry, fluorescence techniques, and computational studies. The drug bound to calf thymus DNA (ct-DNA) in a groove-binding mode. The calculated binding constant of UV-vis, K_a, is comparable to groove-binding drugs. Competitive fluorimetric studies with Hoechst 33258 showed that valcyte could displace the DNA-bound Hoechst 33258. The drug could not displace intercalated methylene blue from DNA double helix. Furthermore, the induced detectable changes in the CD spectrum of ct-DNA as well as changes in its viscosity confirm the groove-binding mode. In addition, an integrated molecular docking was employed to further investigate the binding interactions between valcyte and calf thymus DNA.

Synthesis, DNA binding affinity and anticancer activity of novel 4H-benzo[g][1,2,3]triazolo[5,1-c][1,4]oxazocines

A new class of tricyclic heterocycles 4H-benzo[g][1,2,3]triazolo[5,1-c][1,4]oxazocines was synthesized through a Knoevenagel condensation/azide-alkyne cycloaddition reaction cascade in one-pot operation. These eight membered ring containing heterocycles exhibited moderately high anticancer activity against four cancer cell lines; human cervix cancer cell line (HeLa), human prostate cancer cell line (DU145), human breast cancer cell line (MCF-7) and human breast adenocarcinoma epithelial cell line (MDA-MB-231). Our results indicate that these compounds have a weak cytotoxic effect on normal human mammary epithelial cell line (MCF-10A). Cell cycle and apoptosis assay indicate that they inhibit the cell cycle at the G2/M phase and induce apoptosis. Through the RED₁₀₀ assay, it is evident that they have potential to inhibit pBR 322 plasmid DNA cleavage by BamH1. UV-visible, fluorescence titration and viscosity studies suggested that these compounds possess DNA binding affinity.

Development of viscometric methods for studying the interaction of various porphyrins with DNA. Part II: Meso-tetra-(3N-hydroxyethylpyridyl) porphyrin and its Ni-, Cu-, Co- and Zn- containing derivatives

The influence of porphyrin molecules configuration on their ability to affect on DNA structure were investigated for water-soluble cationic meso-tetra-(3N-hydroxyethylpyridyl) porphyrin (H2THOEtPyP3) and its metal complexes with Cu, Ni, Co, Zn using viscometry and UV-vis absorption spectroscopy. A comparative analysis was performed with the results of previously conducted similar studies of meso-tetra-(4N-hydroxyethylpyridyl) porphyrin (H2THOEtPyP4). Viscosity measurements show that the change in position of peripheral radicals on pyridylic ring has absolutely no effect on the laws of interaction of investigated porphyrins with DNA in case of outside binders such as CoTHOEPyP3 and ZnTHOEPyP3. In the presence of planar porphyrins, such as CuTHOEPyP3 and NiTHOEPyP3 the laws of structural changes of DNA are the same as in the case of H2THOEtPyP3, with some differences. Comparison of different locations of peripheral radicals on pyridylic rings leads to the conclusion that H2THOEtPyP3 and its metal complexes bind to DNA preferably more than H2THOEtPyP4 and its metal complexes. This fact may be explained only suggesting that porphyrins with hydroxyethyl groups at 3N-position are favorably located relative to the DNA helix axis than at 4N-position.

Biological Impact of Pd (II) Complexes: Synthesis, Spectral Characterization, In Vitro Anticancer, CT-DNA Binding, and Antioxidant Activities

A new series of Pd (II) complexes of methyl substituted benzylamine ligands (BLs) has been synthesized and characterized via spectroscopic techniques such as UV/Vis. FTIR, LCMS, ¹H, and ¹³C NMR. The UV/Vis study in DMSO, DMSO + water, and DMSO + PBS buffer (pH = 7.2) confirmed their molecular sustainability in liquids. Their in vitro anticancer activity against breast cancer cell lines such as MCF-7 and MDA-MB-231 makes them interesting for in vivo analysis. Their stronger DNA binding activity (DBA) compared with free ligand suggested them as a good DNA binder. DBA was further confirmed by physicochemical studies such as surface tension and viscosity of complex + DNA which inferred the disruption of DNA and intercalation of complexes, respectively. Their % binding activity, % disruption of DNA base pairs (DNABP), and % intercalating strength are reported in this paper for the first time for better understanding of DNA binding mechanism. Along with this, their scavenging activity (SA) determined through DPPH free radical and the results indicate good antioxidant behaviour of complexes.

Sugar-boronate ester scaffold tethered pyridyl-imine palladium(II) complexes: synthesis and their in vitro anticancer evaluation

A series of five palladium(ii) pyridyl-imine Schiff base complexes 5a-e containing boronate esters with protected sugar diols derived from d-xylose, l-sorbose and d-mannitol were designed and synthesized starting from pyridyl-imines generated in situ from 3-aminophenyl boronate ester of sugars 3a-e and 2-pyridinecarboxaldehyde, followed by the addition of Pd(cod)Cl2 in dichloromethane solvent. All the complexes are remarkably stable orange/yellow crystalline solids and were obtained in good yields. The complexes were fully characterized by FT-IR, multinuclear NMR ((1)H, (13)C and (11)B), UV-visible spectroscopy, and elemental analysis. The solid state structures of 3a and 5a were established by single crystal X-ray diffraction analysis. The complexes have been tested for their in vitro anticancer activities against human colon cancer (HT-29) and breast cancer (MDA-MB-231) cell lines. All the complexes have shown moderate to good cytotoxicity in both the cancer cell lines with IC50 values ranging from 4.27 to 34.76 μM. Strikingly, 5a displayed selective anticancer activity against both HT-29 and MDA-MB-231 cells with low IC50 values 6.71 and 8.58 μM respectively. Results also demonstrate that some of these complexes are highly potent against HT-29 cells as compared to the other cancer cell lines. In particular, 1,2:5,6-di-O-isopropylidene-d-mannitol complex 5d showed a two-fold higher toxicity against HT-29 cells in comparison with that of cisplatin. In addition, these complexes are less toxic to model non-tumorigenic human embryonic kidney cells (HEK-293T). Furthermore, the interaction of the complexes with calf thymus DNA (CT-DNA) was investigated using spectroscopy and viscosity measurements. It was found that they intercalate with DNA.

DNA binding studies of hematoxylin-Dy(ш) complex by spectrometry using acridine orange as a probe

The interaction of a hematoxylin(HE)-Dy(Ш) complex with herring sperm DNA(hsDNA) was studied using acridine orange(AO) as a probe by UV-vis absorption, circular dichroism(CD), fluorescence spectroscopy and viscosity measurements. From the results of the probe experiment, we found that the HE-Dy(Ш) complex could compete with AO for intercalating into hsDNA. The binding constants of the HE-Dy(Ш) complex to hsDNA was obtained by the double reciprocal method and indicated that the affinity between hsDNA and the complex is weaker than that between hsDNA and classical intercalators. The thermodynamic parameters(ΔH°, ΔG°, ΔS°) were calculated from the UV-vis absorption data measured at two different temperatures. Further experimental results suggested that there exist groove binding and partial intercalation binding between hsDNA and HE-Dy(Ш) complex.