Nasima Arshad

A thermal analysis study of 1,2-dipiperidinoethane complexes of cobalt, nickel, copper, zinc and cadmium by TG-DTG-DTA techniques

A number of complexes of the general formula ML(NO3)2, (M=Co(II), Ni(II), Cu(II), Zn(II) and Cd(II); L=1,2-dipiperidinoethane (DPE)) were prepared and studied by means of TG–DTG–DTA techniques. Their compositions were investigated by elemental analysis in order to ensure their purity and structural elucidations were based on conductivity measurements. room temperature magnetic measurement, proton NMR, and IR spectra. Thermal decomposition of these distorted tetrahedral complexes and their ligand took place in two distinct steps upon heating up to 720°C with the loss of inorganic and organic fragments and show almost the same mode of decomposition. The thermal degradation of all the complexes in static air atmosphere starts at temperature lower than observed for free ligand degradation. The composition of intermediates formed during degradation was confirmed by microanalysis and IR spectroscopy. The residues after heating above 600°C correspond to metal oxide. It follows from the results that thermal stability of the complexes increases in the following sequence: Ni(II)

Electrochemical and spectroscopic investigations of carboxylic acid ligand and its triorganotin complexes for their binding with ds.DNA: in vitro biological studies.

A carboxylic acid ligand, (Z)-4-(4-acetylphenylamino)-4-oxobut-2-enoic acid (APA-1), and its triphenyl-(APA-2) and tributyl-tin(IV) (APA-3) compounds have been synthesized and investigated for their binding with ds.DNA using UV-visible spectroscopy, fluorescence spectroscopy, cyclic voltammetry, and viscosity measurements under physiological conditions of pH and temperature. The experimental results from all techniques i.e. binding constant (Kb), binding site size (n) and free energy change (ΔG) were in good agreement and inferred spontaneous compound-DNA complexes formation via intercalation. Among all the compounds APA-3 showed comparatively greater binding at pH 4.7 as evident from its greater Kb values {APA-3: Kb: 5.63×10(4)M(-1) (UV); 7.94×10(4)M(-1) (fluorescence); 9.91×10(4)M(-1) (CV)}. Electrochemical processes of compounds before and after the addition of DNA were found diffusion controlled. Among all compounds, APA-3 exhibited best antitumor activity.

Triazolothiadiazine derivatives as corrosion inhibitors for copper, mild steel and aluminum surfaces: Electrochemical and quantum investigations

The corrosion inhibition activity of triazolothiadiazine derivatives namely 1-(6-(4-nitrophenyl)-7H[1,2,4]triazolo[3,4-b],[1,3,4]thiadiazine3-yl)ethanol (NTTD) and 6-phenyl-3-(triflouromethyl)-7H-[1,2,4]triazole[3,4-b]thiadiazine (FTTD) was examined on copper (Cu), mild steel (MS) and aluminum (Al) in different aggressive media (borate buffers of pH 10.4 and 8.4 for Cu; 1.0 M HCl and 1.0 M NaOH for MS; 1.0 M NaCl for Al). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used and results obtained from both techniques complement each other. CV results showed that the compounds act as mixed type inhibitors for Cu-surface. Impedance spectra of Cu, MS and Al-surfaces in the presence of NTTD and FTTD were characterized as charge transfer controlled. Different parameters obtained from potentiodynamic polarization and impedance data revealed increase in the corrosion protection with inhibitor’s concentration and followed a stable and spontaneous chemisorption mechanism in all aggressive media. Adsorption data from both CV and EIS fitted well to the Langmuir adsorption isotherm. Among both compounds; FTTD has shown better corrosion protection activity in all aggressive media. In general, compound FTTD showed better inhibition efficiency at pH 8.4 among all aggressive media. Different quantum chemical parameters were calculated from DFT/B3LYP based on 3-21G by using Gaussview 03 which further supported the experimental results.

UV-absorption studies of interaction of karanjin and karanjachromene with ds. DNA: Evaluation of binding and antioxidant activity

AbstractTwo flavonoids, karanjin (Kj) and karanjachromene (Kc) have been investigated spectrophotometrically for their mode of interactions with double stranded (ds)-DNA at blood (7.4) and stomach (4.7) pH and at human body temperature (37°C). Benesi-Hildebrand equation was used to evaluate the binding constants, Kb. Binding constants at both pH values and at body temperature showed stronger binding of both the flavonoids and formation of 1:1 flavonoid-DNA complex via intercalative mode. However, Kb values for karanjin were evaluated to be comparatively greater than karanjachromene at both pH values. The highest value of binding constant (1.32×105 M−1) for karanjin at blood pH (7.4) demonstrated its comparatively stronger binding and greater effectiveness at this pH. Standard Gibbs free energy changes (ΔG) of flavonoid-DNA complexes were calculated as negative values and indicative of spontaneity of their binding. Both flavonoids showed significant DNA protection activity.

Electrochemical studies of the interactional mechanism and scavenging activity of antioxidants towards dinitroaromatics

In the work discussed in this paper, cyclic voltammetric results obtained for the interaction of ascorbic acid, β-carotene, and three structurally related flavonoids (quercetin, rutin, and morin) with the anion radical of 1,3-dinitrobenzene were used to determine their antioxidant activity. The extent of the antioxidant–anion radical interactions was measured as the antioxidant activity coefficient. Higher values of this coefficient obtained for the three flavonoids in DMF are indicative of their greater antioxidant activity than ascorbic acid and β-carotene in this solvent. On the basis of cyclic voltammetric responses, a possible mechanism of the reaction of the reduction product of 1,3-dinitrobenzene with the antioxidants is proposed. Hyperchem PM3 quantum mechanical semi-empirical calculations of charges on reactive sites of the antioxidants and the 1,3-dinitrobenzene anion radical were also carried out; the results obtained supported the proposed mechanism of interaction.Graphical abstract

Synthesis, characterization of amide substituted dexibuprofen derivatives and their spectral, voltammetric and docking investigations for DNA binding interactions

Three amide derivatives - methyl-2-[2-(4-isobutylphenyl)propanamido]propanoate (Dex-2), methyl 2-[2-(4-isobutylphenyl) propanamido]-3-phenylpropanoate (Dex-3) and methyl 2-[2-(4-isobutylphenyl)-propanamido]-4-methylpentanoate (Dex-4) of dexibuprofen (Dex-1) 2-(4-isobutylphenyl)propanoic acid were synthesized and conformed for structures by physical data and spectral analysis. Further, all the compounds were studied for their binding with ds.DNA through experimental (UV-visible/and fluorescence spectroscopy, cyclic voltammetry) and theoretical (molecular docking) techniques. Spectral and voltammetric responses as well as kinetic and thermodynamic data interpretations at stomach (4.7) and blood (7.4) pH and at human body temperature (37°C) indicated spontaneous interaction of all the compounds with DNA via intercalation and external bindings. The binding constants (Kb) and Gibbs free energy changes (-ΔG) were evaluated greater at pH7.4 attributing comparatively more significant binding of all the compounds with DNA at blood pH. Among all compounds, Dex-4 showed greater binding with DNA at both pH with greater Kb values i.e., {UV-visible: pH 4.7 (2.36×104M-1); pH7.4 (2.42×104M-1), fluorescence: pH4.7 (2.24×104M-1); pH7.4 (2.56×104M-1) and CV: pH4.7 (4.06×104M-1); pH7.4 (4.89×104M-1)}. Binding site size (n) at both pH values was evaluated n≥1 for Dex-2 and Dex-4 which assured intercalation as a major mode of interaction between compounds and DNA. For Dex-1 and Dex-3 (n) was evaluated n≤1 at both pH values and the values n<1 indicated the possibility of binding via groove or electrostatic interactions. Electrochemical processes were found diffusion controlled and diffusion coefficients (Do) for all the compounds - DNA adducts were evaluated lesser than unbound compounds. Docking studies further supported DNA binding evidences obtained from spectral and electrochemical investigations.

Synthesis, theoretical, spectroscopic and electrochemical DNA binding investigations of 1, 3, 4-thiadiazole derivatives of ibuprofen and ciprofloxacin: Cancer cell line studies

Two new 1,3,4-thiadiazole derivatives of ibuprofen and ciprofloxacin namely {(5-(1-(4-isobutylphenyl)ethyl)-1,3,4-thiadiazol-2-amine)} 1 and {(3-(5-amino-1,3,4-thiadiazol-2-yl)-1-cyclopropyl-6-fluoro-7-(piperazin-1-yl)quinolin-4(1H)-one)} 2 were synthesized and characterized by spectroscopic and elemental analysis. DFT and molecular docking were done initially for theoretical binding possibilities of the investigated compounds. In vitro DNA binding investigations were carried out with UV-visible spectroscopic, fluorescence spectroscopic, cyclic voltammetric (CV) experiments under physiological conditions of the stomach (4.7) and blood (7.4) pH and at normal body temperature (37 °C). Both theoretical and experimental results suggested spontaneous and significant intercalative binding of the compounds with DNA. Kinetic and thermodynamic parameters (Kb, ΔG) were evaluated greater for compound 2 which showed comparatively more binding and more spontaneity of 2 than 1 to bind with DNA at both pH values. Binding site sizes were found greater (n > 1) and revealed the possibility of other sites for interactions along with intercalation. Overall results for DNA binding were found more significant for 2 at Stomach (4.7) pH. Viscometric studies further verified intercalation as a prominent binding mode for both compounds. IC50 values obtained from human hepatocellular carcinoma (Huh-7) cell line studies revealed 2 as potent anticancer agent than 1 as value found 25.75 μM (lesser than 50 μM). Theoretical and experimental DNA binding studies showed good correlation with cancer cell (Huh-7) line activity of 1 and 2 and further suggested that these compounds could act as potential anti-cancer drug candidates.

Cyclic Voltammetric DNA Binding Investigations on Some Anticancer Potential Metal Complexes: a Review

Cancer is developed by rapid, uncontrolled, and abnormal cell proliferation and one of the leading causes of deaths worldwide in human beings. For the remedial measures of preventing different types of cancers, one of the research domains that have gained substantial importance in medical science is the development of new metallo-drugs and their investigations as potential anticancer drug agents by using various analytical techniques. Since metal-based complexes show weak absorption bands, electrochemical methods are considered more feasible and preferable over spectroscopic methods for easy characterization. Due to closer resemblance of electrochemical and biological processes, cyclic voltammetry among different electrochemical methods is considered the most versatile for the study of in-vitro metal-based drug–DNA interactions in terms of changes in the redox activities. Current potential data of a metal complex leads to determine binding kinetics in terms of binding constant and binding site size that involve determining the binding mode of drug with DNA, i.e., electrostatic interactions, intercalation, or minor-major groove binding. Binding parameters and modes of interactions, further, help to develop the mechanism of action of drug with the DNA. In this review, we emphasize on cyclic voltammetric DNA binding studies on some metal complexes that have been carried out in the last three decades for the investigation of their anticancer potentials.