Spectral Studies and Bactericidal, Fungicidal, Insecticidal and Parasitological Activities of Organotin(IV) Complexes of Thio Schiff Bases Having no Donor Atoms

Twelve new organotin(IV) complexes of the type RnSnLm [where n = 3, m = 1, R = CH3 or C6H5; n = 2, m = 2, R = C6H5 or C4H9 ; L = anion of Schiff bases derived from the condensation of 2-amino-5-(o-anisyl)-l,3,4-thiadiazole with salicylaldehyde (HL-1), 2- hydroxynaphthaldehyde (HL-2) and 2-hydroxyacetophenone (HL-3)] have been synthesized and characterized by elemental analysis, molar conductances, electronic, infrared, far-infrared, 1H NMR and 119Sn Mössbauer spectral studies. Thermal studies of two complexes, viz., Ph3Sn (L-1) and Ph2Sn(L-2)2 have been carried out in the temperature range 25-1000∘C using TG, DTG and DTA techniques. All these complexes decompose gradually with the formation of SnO2 as an end product. In vitro antimicrobial activity of the Schiff bases and their complexes has also been determined against Streptococcus faecalis, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus Penicillin resistance (2500 units), Candida albicans, Cryptococcus neoformans, Sporotrichum schenckii, Trichophyton mentagrophytes and Aspergillus fumigatus. The Schiff bases (HL-1), (HL-2) and the organotin(IV) compounds have also been tested against various important herbicidal, fungicidal, insecticidal species and also for parasitological activity against freeliving nematode

Organotin(IV) triazolates as molecular precursors for pure-phase, nanosized SnS/SnO₂ through pyrolysis

510-516The thermal decomposition of organotin(IV) triazolates of general formula R₂SnL₂ (R = methyl (1), n-butyl (2), n-octyl (3) and phenyl (4)) and R₃SnL (R = Me (5); and L = anion of 3-amino-5-mercapto-1,2,4-triazole) provides a simple route to prepare nanosized semiconductors, SnS and SnO₂ in nitrogen and air atmosphere, respectively, at low temperature 600-700ºC. The crystallite average size of the residues determined by X-ray diffraction line broadening is found in the range of 6-63 nm. The particle size of the residues obtained by the pyrolysis of 2 and 4 (in nitrogen) has also been determined by tunneling electron microscope and found to be in the range 2-55 nm. The surface morphology of these residues has been determined by scanning electron microscopy. The thermogravimetric analysis shows that the weight loss observed in nitrogen is higher than that expected for the formation of SnS as end-product. This indicates the partial loss of the residue to the gas phase due to sublimation at higher temperature. Kinetic studies of 2 and 4 in air indicate the first order kinetics for the decomposition process. The X-ray diffraction, SEM and TEM results of the residues along with kinetic parameters show that 5 and 2 are the best precursors for production of pure phase nanosized SnO₂ followed by 3 in air whereas 4 is the best precursor for SnS followed by 2 in nitrogen. These compounds are much better precursors for production of pure phase nanosized SnO₂/SnS as compared to diorganotin(IV) thiadiazolates

Copper(II) complexes of (salicylidene)amino acid schiff bases as models: Peroxidase and catalase

108-113Activity of copper(II) complexes of (salicylidene)amino acid Schiff bases have been tested towards the decomposition of hydrogen peroxide at 40° and over a wide range of pH 6.0-11.0. Detailed kinetic investigations for the disproportionation of hydrogen peroxide catalysed by the complexes of the general formula, Cu[(sal:aa)H2O] nH2O (where sal:aa = salicylideneamino acid schiff base derived from the condensation of salicylaldehyde and glycine/– valine/-methionine; n =0 or 2) at 40°C and at pH 9.0 are discussed. The decomposition of hydrogen peroxide catalysed by the above complexes conforms to Michaelis-Menten type kinetics

Metal-Based Anticancer Agents: In vitro DNA Binding, Cleavage and Cytotoxicity

Two new metal-based anticancer chemotherapeutic agents, [(Ph2Sn)2(HGuO)2(phen)Cl2] 1 and [(Ph3Sn)(HGuO)(phen)]- Cl.CH3OH.H2O 2, were designed, prepared and characterized by analytical and spectral (IR, ESI-Mass, 1H, 13C and 119Sn NMR) techniques. The proposed geometry of Sn(IV) in 1 and 2 is distorted octahedral and distorted trigonal-bipyramidal, respectively. Both 1 and 2 exhibit potential cytotoxicity in vitro against MCF-7, HepG-2 and DU-145 cell lines. The intrinsic binding constant (Kb) values of 1 (2.33 × 105 M-1) and 2 (2.46 × 105 M-1) evaluated from UV-Visible absorption studies suggest non-classical electrostatic mode of interaction via phosphate backbone of DNA double helix. The Stern-Volmer quenching constant (Ksv) of 1 (9.74 × 105 M-1) and 2 (2.9 × 106 M-1) determined by fluorescence studies suggests the groove binding and intercalation mode for 1 and 2, respectively. Effective cleavage of pBR322 DNA is induced by 1. Their interaction with DNA of cancer cells may account for potency

Cellular uptake of metal oxide-based nanocomposites and targeting of chikungunya virus replication protein nsP3

BACKGROUND: Emergence of new pathogenic viruses along with adaptive potential of RNA viruses has become a major public health concern. Hence it becomes even more important to explore and evaluate the antiviral properties of nanocomposites which is an ever-evolving field of medical biology. METHODS: In this study, series of metal/metal oxide (Ag/NiO : NiO, AN-5%, AN-10% and AN-15%) and ternary metal oxide nanocomposites (Ag2O/NiO/ZnO : N/Z, A/N/Z-1, A/N/Z-2 and A/N/Z-3) have been synthesized and characterized. Cellular uptake of nanocomposites was confirmed by ICP-MS. RESULTS: Intriguingly, molecular docking of metal oxides in the active site of nsP3 validated the binding of nanocomposites to chikungunya virus replication protein nsP3. In-vitro antiviral potential of nanocomposites were tested by performing plaque reduction assay, cytopathic effect (CPE) analysis and qRT-PCR. The nanocomposites showed significant reduction in virus titre. Half-maximal inhibitory concentration (IC50) for A/N/Z-3 and AN-5% were determined to be 2.828 and 3.277 g/mL, respectively. CPE observation and qRT-PCR results were consistent with the data obtained from plaque reduction assay for A/N/Z-3 and AN-5%. CONCLUSION: These results, have opened new avenues for development of nanocomposites based antiviral therapies

Spectroscopy evidence of interaction of 1,5 disubstituted piperidino-amido anthraquinone derivative with human telomeric G-quadruplex DNA: Basis of anticancer action

The binding of ligands to G-quadruplex (G4) structures at the ends of human telomeric DNA induces thermal stabilization, which interferes with telomere maintenance by disrupting the association of telomeres with the telomerase enzyme—an important marker for cancer. Understanding the binding mode of the ligand-G quadruplex DNA complex is imperative for evaluating the relative efficacy and specificity of their interaction. We focused on the interaction of 1,5-Bis(3-piperidino propionamido) anthracene-9,10-dione with human telomeric DNA sequences using surface plasmon resonance, absorbance, fluorescence (steady-state and lifetime), and circular dichroism spectroscopy techniques. The ligand binding with HTel22 (Kb = 8.4 × 105 M−1) induced cell toxicity with an IC50 value of ∼ 8.64 µM in MCF-7 cancer cell lines. Significant hypochromism (59 %), fluorescence quenching (97 %), no change in fluorescence lifetime and absence of induced Circular Dichroism (CD) band upon addition of G4 DNA to ligand, suggest a groove/external binding mode. CD spectral changes reflect rearrangement in parallel and antiparallel strands to accommodate the ligand. Docking results reveal specific short contacts of the ligand's side chain, including 9CO, 13N, 14NH, and 11CO, with the grooves of the G4 DNA, without making any contact with the loops, favoring an energetically more favorable conformation. Thermal denaturation profiles, obtained by Differential Scanning Calorimetry and CD, show the stabilization of wHTel26 and HTel22 G4 DNA in K+ and Na+ rich solutions by 21.2 and 17.6 °C, respectively, which may restrict the access of telomerase to telomeres. The findings indicate the potential of modifying anthraquinone substituent groups for therapeutic applications