Variation in the Biomolecular Interactions of Nickel(Ii) Hydrazone Complexes Upon Tuning the Hydrazide Fragment

Three new bivalent nickel hydrazone complexes have been synthesised from the reactions of [NiCl2(PPh3)(2)] with H2L {L = dianion of the hydrazones derived from the condensation of o-hydroxynaphthaldehyde with furoic acid hydrazide (H2L1) (1)/thiophene-2-acid hydrazide (H2L2) (2)/isonicotinic acid hydrazide (H2L3) (3)} and formulated as [Ni(L-1)(PPh3)] (4), [Ni(L-2)(PPh3)] (5) and [Ni(L-3)(PPh3)] (6). Structural characterization of these compounds 4-6 were accomplished by using various physico-chemical techniques. Single crystal X-ray diffraction data of complexes 4 and 5 proved their distorted square planar geometry. In order to ascertain the potential of the above synthesised compounds towards biomolecular interactions, additional experiments involving interaction with calf thymus DNA (CT DNA) and bovine serum albumin (BSA) were carried out. All the ligands and corresponding nickel(II) chelates have been screened for their scavenging effect towards O-2(-), OH and NO radicals. The efficiency of complexes 4-6 to arrest the growth of HeLa, HepG-2 and A431 tumour cell lines has been studied along with the cell viability test against the non-cancerous NIH 3T3 cells under in vitro conditions.University Grants Commission, New Delhi under the UGC-SAP-DRSRobert A. Welch Foundation F-0003Chemistr

Assessment of a diketopiperazine, cyclo(Trp-Phe) from Streptomyces griseoplanus SAI-25 against cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae)

Microorganisms produce a range of metabolites with varying pest control properties. With this concept, we earlier identified 15 Streptomyces spp. strains with insecticidal activity against Helicoverpa armigera (Hübner), Spodoptera litura (Fabricius), and Chilo partellus (Swinhoe). In recent studies, we evaluated an insecticidal compound purified from the extracellular extract of S. griseoplanus SAI-25 by bioactivity-guided fractionation against H. armigera. Spectral studies by infrared (IR), nuclear magnetic resonance (NMR), and electron spray ionization mass spectroscopy (ESI-MS) confirmed that the purified compound was cyclo(Trp-Phe) of the diketopiperazines class. Cyclo(Trp-Phe) exhibited antifeedant (70 %), larvicidal (67 %), and pupicidal (59 %) action against H. armigera in a dose-dependent manner. The lethal dose for 50 % of the group (LD50) and LD90 values for larvicidal effect were 619 and 2750 ppm, respectively. In addition, the purified compound prolonged larval (10.3–11.1 days) and pupal (10.9–11.8 days) periods compared with the untreated control (larval duration 9.8 days, pupal duration 10.6 days). This is the first report on the presence and biological activity of cyclo(Trp-Phe) isolated from the genus Streptomyces

Effect of Substitution and Planarity of the Ligand On DNA/BSA interaction, Free Radical Scavenging and Cytotoxicity of Diamagnetic Ni(II) Complexes: A Systematic Investigation

Four new bivalent nickel hydrazone complexes have been synthesised from the reactions of [NiCl2(PPh3)(2)] with H2L {L = dianion of the hydrazones derived from the condensation of salicylaldehyde or o-hydroxy acetophenone with p-toluic acid hydrazide (H2L1) (1), (H2L2) (2) and o-hydroxy acetophenone or o-hydroxy naphthaldehyde with benzhydrazide (H2L3) (3) and (H2L4) (4)} and formulated as [Ni(L-1)(PPh3)] (5), [Ni(L-2)(PPh3)] (6), [Ni(L-3)(PPh3)] (7) and [Ni(L-4)(PPh3)] (8). Structural characterization of complexes 5-8 were accomplished by using various physico-chemical techniques. In order to study the influence of substitution in the ligand and its planarity on the biological activity of complexes 5-8 containing them, suitable hydrazone ligands 1-4 have been selected in this study. Single crystal diffraction data of complexes 5, 7 and 8 proved the geometry of the complexes to be distorted square planar with a 1 : 1 ratio between the metal ion and the coordinated hydrazones. To provide more insight on the mode of action of complexes 5-8 under biological conditions, additional experiments involving their interaction with calf thymus DNA (CT DNA) and bovine serum albumin (BSA) were monitored by UV-visible and fluorescence titrations respectively. Further, the ligands 1-4 and corresponding nickel(II) chelates 5-8 have been tested for their scavenging effect towards OH and O-2(-) radicals. The effect of complexes 5-8 to arrest the growth of HeLa and Hep-2 tumour cell lines has been studied along with the cell viability against the non-cancerous NIH 3T3 cells under in vitro conditions.University Grants Commission, New Delhi, IndiaRobert A. Welch Foundation F-0003Chemistr

Copper(I) and Nickel(II) Complexes with 1:1 Vs. 1:2 Coordination of Ferrocenyl Hydrazone Ligands: Do the Geometry and Composition of Complexes Affect DNA Binding/Cleavage, Protein Binding, Antioxidant and Cytotoxic Activities?

A new series of geometrically different complexes containing ferrocenyl hydrazone ligands were synthesised by reacting suitable precursor complex [MCl2(PPh3)(2)] with the ligands HL1 or HL2 (where M = Cu(II) or Ni(II); HL1 = [Cp2Fe(CH=N-NH -CO-C6H5)] (1) and HL2 = [Cp2Fe(CH=N-NH-CO-C5H4N)]) (2). The new complexes of the composition [Cu(L-1)(PPh3)(2)], (3) [Cu(L-2)(PPh3)(2)] (4), [Ni(L-1)(2)] (5) and [Ni(L-2)(2)] (6) were characterised by various spectral studies. Among them, complexes 3 and 5 characterised by single crystal X-ray diffraction showed a distorted tetrahedral structure for the former with 1 : 1 metal-ligand stoichiometry, but a distorted square planar geometry with 1 : 2 metal-ligand stoichiometry in the case of the latter. Systematic biological investigations like DNA binding, DNA cleavage, protein binding, free radical scavenging and cytotoxicity activities were carried out using all the synthesised compounds and the results obtained were explained on the basis of structure-activity relationships. The binding constant (K-b) values of the synthesised compounds are found to be in the order of magnitude 10(3)-10(5) M-1 and also they exhibit significant cleavage of supercoiled (SC) pUC19 DNA in the presence of H2O2 as co-oxidant. The conformational changes of bovine serum albumin (BSA) upon binding with the above complexes were also studied. In addition, concentration dependent free radical scavenging potential of all the synthesised compounds (1-6) was also carried out under in vitro conditions. Assays on the cytotoxicity of the above complexes against HeLa and A431 tumor cells and NIH 3T3 normal cells were also carried out.University Grants Commission, New Delhi, IndiaDepartment of Science and Technology, Government of India, New DelhiRobert A. Welch Foundation F-0003Chemistr