Glucose-lowering Activity of Amino Acid-N-phosphonic Acid Oxovanadium Complexes and Its Interaction with DNA

Vanadium has well-documented lowering glucose properties both in vitro and in vivo.The design of newoxovanadium(IV) coordination compounds,intended for use as insulin-enhancing agents in the treatment of diabe-tes mellitus,can potentially benefit from a synergistic approach,in which the whole complex has more than an ad-ditive effect from its component parts.Biological testing with oxovanadium(IV) organic phosphonic acid,for insu-lin-enhancing potential included acute administration,by oral garage in streptozotocin (STZ) diabetic rats.Thecomplexes of oxovanadium(IV) amino acid-N-phosphonic acid exhibit higher lowering glucose activity in vivo.Theinteraction of the complexes of oxovanadium(IV) amino acid-N-phosphonic acid with DNA was investigated byagarose gel electrophoresis.The results indicated that these complexes have strong interaction with DNA.     

Synthesis, Characterization and the Effect of Glucose-lowering of Guanidino Acid Oxovanadium（Ⅳ） Complexes

Two guanidino acid oxovanadium(Ⅳ) complexes have been synthesized. Preliminary tests in vivo have shown that the two title complexes all display lowering glucose activity in vivo to STZ-rats. The effect of glucose-lowering of guanidino acetic acid oxovanadium(Ⅳ) complex in vivo is higher than that of guanidino propanoic acid oxovanadium(Ⅳ) complex.     

A study on the glucose lowering effects of ester-based oxovanadium complexes

The ester-based vanadium complexes, bis(methylacetoacetato) oxovanadium (IV), bis(ethylacetoacetato) oxovanadium(IV) and bis(ethylbenzoylacetato) oxovanadium(IV), have been prepared and characterized by physicochemical and spectroscopic methods. The biological efficacies of the complexes were investigated. These complexes possess substantial glucose lowering ability and also show improved glucose tolerance effect.     

Molecular Dynamics Simulation of Interaction between Calcite Crystal and Phosphonic Acid Molecules

The interactions between calcite crystal and seven kinds of phosphonic acids, nitrilotris(methylphosphonic acid) (NTMP), nitrilo‐methyl‐bis(methylphosphonic acid) (NMBMP), N,N‐glycine‐bis(methylphosphonic acid) (GBMP), 1‐ hydroxy‐1,1‐ethylenebis(phosphonic acid) (HEBP), 1‐amino‐1,1‐ethylenebis(phosphonic acid) (AEBP), 1,2‐ethylenediamine‐N,N,N′,N′‐tetrakis(methylphosphonic acid) (EDATMP), and 1,6‐hexylenediamine‐N,N,N′,N′‐tetrakis‐ (methylphosphonic acid) (HDATMP) have been simulated by a molecular dynamics method. The results showed that the binding energy of each scale inhibitor with the (1l?0) (1l?0) face of calcite crystal was higher than that with (104) face, which has been approved by the analysis of pair correlation functions. The sequence of scale inhibition efficiencies for phosphonic acids against calcite scale is as follows: EDATMP>HDATMP>HEBP>NTMP>GBMP>HEBP>NMBMP, and the growth inhibition on the (1l?0) face of calcite was at the leading status. Phosphonic acids deformed during the binding process, and electrovalent bonds formed between the phosphoryl oxygen atoms in phosphonic acids and the calcium ions on calcite crystal.     

Synthesis,characterization and biological studies of oxovanadium(IV) complexes with triazole‐derived Schiff bases

A series of triazole‐derived Schiff bases (L¹–L⁵) and their oxovanadium(IV) complexes have been synthesized. The chemical structures of Schiff bases were characterized by their analytical (CHN analysis) and spectral (IR, ¹H and ¹³C NMR and mass spectrometry) data, and oxovanadium(IV) complexes were elucidated by their physical (magnetic susceptibility and conductivity), analytical (CHN analysis), conductance measurements and electronic spectral data. The molar conductivity data indicate the oxovanadium(IV) complexes to be non‐electrolyte. The Schiff bases act as bidentate and coordinate with the oxovanadium(IV)‐forming stoichiometry of a complex as [M (L‐H)₂] where M = VO and L = L¹–L⁵ in a square‐pyramidal geometry. The agar well diffusion method was used for in vitro antibacterial screening against E. coli, S. flexenari, P. aeruginosa, S. typhi, S. aureus and B. subtilis and for antifungal activity against T. longifucus, C. albican, A. flavus, M. canis, F. solani and C. glaberata. The biological activity data show the oxovanadium(IV) complexes to be more antibacterial and antifungal than the parent Schiff bases against one or more bacterial and fungal strains. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis,spectral characterization,and antidiabetic study of new furan-based vanadium(IV) complexes

We have synthesized furan-based vanadium complexes, bis(5-nitrofuran-2-carboxylato)oxovanadium(IV) – [VO(5NF)₂], bis(1-furan-2-yl-ethanonato)oxovanadium(IV) sulfate – [VO(2AF)₂]SO₄, and bis(5-methyl-2-furalato)oxovanadium(IV) sulfate – [VO(MFFA)₂]SO₄ possessing [VO(O₄)] coordination mode. These complexes are characterized by physico-chemical and spectroscopic methods. Based on electron paramagnetic resonance parameters, the proposed geometry is close to a distorted square pyramid. Animal study was carried out using standard protocol and the complete profile of glucose, protein, and total cholesterol levels were analyzed followed by an oral glucose tolerance test.     

Donor property of cobalt(II) Schiff base complexes toward triphenyltin(IV)‐chloride: A kinetic study

In this study, some cobalt(II)tetraaza Schiff base complexes were used as donors in coordinating to triphenyltin(IV)chloride as acceptors; the kinetics and mechanism of the adduct formation were studied spectrophotometrically. Co(II)tetraaza Schiff base complexes used were [Co(amaen)][N,N′‐ethylene‐bis‐(o‐amino‐α‐methylbenzylideneiminato)cobalt(II)] ( 1 ), [Co(appn)] [N,N′‐1,2‐propylene‐bis‐(o‐amino‐α‐phenylbenzylideneiminato)cobalt(II)] ( 2 ), [Co(ampen)] [N,N′‐ethylene‐bis‐(o‐amino‐α‐phenylbenzylideneiminato)cobalt‐(II)] ( 3 ), [Co(cappn)][N,N′‐1,2‐proylene‐bis‐(5‐chloro‐o‐amino‐α‐phenylbenzylideneiminato)cobalt(II)] ( 4 ), and [Co(campen)] [N,N′‐ethylene‐bis‐(5‐chloro‐o‐amino‐α‐phenylbenzylid‐eneiminato)cobalt(II)] ( 5 ). The reactivity trend of the complexes in interaction with triphenyltin(IV)chloride was Co(amaen) > Co(appn) > Co(ampen) > Co(cappn) > Co(campen). The linear plots of k_obs versus the molar concentration of the triphenyltin(IV)chloride, a high span of the second‐order rate constant k₂ values, and large negative values of ΔS^≠ and low ΔH^≠ values suggest an associative (A) mechanism for the acceptor–donor adduct formation. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 635–640, 2012     

Synthesis of crab type Aminomethyldiphosphine‐Oxovanadium(IV) complexes supported on magnetic Nano particles: Selective and recoverable catalysts in vitamin K3 synthesis

Nano Fe₃O₄ particles were obtained in microvawe oven using closed system. Oxovanadium(IV) complexes of Fe₃O₄@SiO₂@(aminomethylphosphine) type ligands were synthesized and characterized using SEM, EDX, TEM, UV‐Visible, XRD, FT‐IR and TG/DTA techniques. Catalytic properties of the synthesized pincer type oxovanadium(IV)‐aminomethylphosphine complexes supported on magnetic nano structure were investigated in the synthesis of 2‐methyl‐1, 4‐naphthoquinone (Vitamin K₃, menadione, 2MNQ) from 2‐methyl naphthalene (2MN) in hydrogen peroxide, acetic acid and sulfuric acid. Magnetic‐nano particle supported oxovanadium(IV)‐aminomethylphosphine type complexes were very efficient catalysts with the 51.36‐55.20 % selectivities in conversions of 89.78‐95.01 %. Besides, the hetergeneous complexes were very active in five cycling tests on avarage evaluated in the reusability.     

Oxovanadium(IV) and ruthenium(II) carbonyl complexes of ONS‐donor ligands derived from dehydroacetic acid and dithiocarbazate: Synthesis,characterization, antioxidant activity,DNA binding and in vitro cytotoxicity

A series of new complexes of oxovanadium(IV) [VO(L)(B)] and ruthenium(II) [Ru(CO)(PPh₃)₂(L)] ( 1.1- 1.3,  2.1–2.3 ) (H₂L = dehydroacetic acid Schiff base of S‐methyldithiocarbazate, H₂smdha ( 1 ) or S‐benzyldithiocarbazate, H₂sbdha ( 2 ); B = 2,2′‐bipyridine (bpy) or 1,10‐phenanthroline (phen)) have been synthesized. The structure of these complexes was authenticated using elemental analyses and spectroscopic techniques, and their magnetic properties and electrochemical behaviour were studied. The molecular structures of oxovanadium(IV) complexes [VO(smdha)(bpy)]?CH₂Cl₂ ( 1.1 ) and [VO(sbdha)(phen)]?2H₂O ( 2.2 ) were confirmed using single‐crystal X‐ray crystallography. Analytical data showed that the ligands 1 and 2 are chelated to the metal centres in a bi‐negative tridentate fashion through azomethine N, thiol S and deprotonated hydroxyl group. The antioxidant activity of the synthesized compounds was tested against 2,2‐diphenyl‐1‐picrylhydrazyl) radical, which showed that the complexes demonstrate a better scavenging activity than their corresponding ligands. The cupric ion reducing antioxidant capacity method was also employed and the total equivalent antioxidant capacity values were found to be higher for the oxovandium(IV) complexes. DNA binding affinity of the compounds was determined using UV–visible and fluorescence spectra, revealing an intercalation binding mode. Higher cytotoxicity for the complexes compared to their ligands was found against human liver hepatocellular carcinoma (HepG2) and breast adenocarcinoma (MCF7) cell lines using MTT assay.     

Synthesis and characterization of binary and ternary oxovanadium complexes of N,N′‐(2‐pyridyl)thiourea and curcumin: Catalytic oxidation potential,antibacterial, antimicrobial,antioxidant and DNA interaction studies

Two binary and two ternary mono‐oxovanadium (IV) complexes of acetylacetonate, curcumin and N ,N ′‐bis(2‐pyridyl)thiourea were synthesized. They were characterized using elemental analysis, infrared and UV–visible spectroscopies and magnetic and conductivity measurements. The formation constants K _f were determined from spectrophotometric measurements. The catalytic potential of the VO complexes was investigated for the oxidation of 1‐octene by aqueous H₂O₂ in acetonitrile. They display high catalytic potential for the conversion of 1‐octene with low chemoselectivity to the epoxy product. The VO complexes exhibit good antibacterial and antimicrobial activities. The antioxidant activity of the VO complexes and their ligands was investigated. The VO complexes show high DNA affinity and DNA cleavage ability.     

Synthesis and characterization of oxovanadium(IV), vanadium(IV) and oxovanadium(V) complexes of tetradentate Schiff bases. Attempted preparation of vanadium-carbon bonded compounds through desilylation

Condensation of 1,3-diaminopropane-2-ol with diacetylmonoxime, acetylacetone, salicylaldehyde and orthohydroxyacetophenone yielded the tetradentate Schiff bases N,N′-(2-hydroxy)propylenebis{(2-imino-3-oximino)butane} (H₂dampnol), N,N′-(2-hydroxy)propylenebis(acetylacetoneimine) (H₂acacpnol), N,N′-(2-hydroxy)propylenebis-(salicyalaldimine) (H₂salpnol) and N,N′-(2-hydroxy)propylenebis(7-methylsalicylaldimine) (H₂ohacpnol), respectively. The ligands form complexes with oxovanadium(IV), vanadium(IV) and oxovanadium(V) salts. Some mixed ligand complexes involving σ-bonded phenyl and benzyl radical along with tetradentate ligand, H₂L (where, H₂L stands for H₂dampnol, H₂acacpnol, H₂salpnol or H₂ohacpnol) of the types [(L)V(C₆H₅)₂]CH₃OH and [(L)V(CH₂Ph)₂]CH₃OH have been synthesized, characterized and also provide the syntheses of some new organovanadium(IV) complexes. Silylation coupled with desilylation have been employed as a route to new organovanadium(IV) complexes. All the complexes have been characterized with the help of elemental analyses, molar conductance values, molecular weights, magnetic moments and spectroscopic (IR, UV-Vis, ESR) data.     

Study on the Chromatographic Behavior of Bases on Dodecylamine-N,N-dimethylenephosphonic Acid-Modified Zirconia Stationary Phase

A new zirconia-based stationary phase (DPZ) was prepared by modifying zirconia with dodecylamine-N,N-dimethylenephosphonic acid (DDPA). DDPA was adsorbed on zirconia with only one phosphonic group, with the other being free. Besides the hydrophobic interaction provided by nonpolar dodecyl, DPZ also has dipolar interaction, ion-exchange or electrostatic repellent interaction provided by the free phosphonic group and amino group at different conditions. Separation of bases on this stationary phase was achieved with satisfaction owing to the various retention mechanisms. The influence of methanol content, pH value, ion types, and ionic strength of mobile phase are studied in detail. Translated from Chinese Journal of Chromatography, 2005, 23(1) (in Chinese)     

Asymmetric Synthesis of α-Amino Phosphonic Acids using Stable Imino Phosphonate as a Universal Precursor

A practical method for synthesizing chiral α-amino phosphonic acid derivatives was developed. Readily available and stable N-o-nitrophenylsulfenyl (Nps) imino phosphonate was utilized as a substrate for a highly enantioselective Friedel–Crafts-type addition of indole or pyrrole nucleophiles catalyzed by chiral phosphoric acid. The resulting adduct was easily converted into N-9-fluorenylmethyloxycarbonyl (Fmoc) amino phosphonic acid, which is useful for synthesizing peptides containing an amino phosphonic acid.     

Structural models of vanadate-dependent haloperoxidases and their reactivity

Vanadium(V) complexes with hydrazone-based ONO and ONN donor ligands that partly model active-site structures of vanadate-dependent haloperoxidases have been reported. On reaction with [VO(acac)₂] (Hacac = acetylacetone) under nitrogen, these ligands generally provide oxovanadium(IV) complexes [VO(ONO)X] (X = solvent or nothing) and [VO(acac)(ONN)], respectively. Under aerobic conditions, these oxovanadium(IV) species undergo oxidation to give oxovanadium(V), dioxovanadium (V) or μ-oxobisoxovanadium(V) species depending upon the nature of the ligand. Anionic and neutral dioxovanadium(V) complexes slowly deoxygenate in methanol to give monooxo complexes [VO(OMe)(MeOH)(ONO)]. The anionic complexes [VO₂(ONO)]^- can also be convertedin situ on acidification to oxohydroxo complexes [VO(OH)(HONO)]⁺ and to peroxo complexes [VO(O₂)(ONO)]^-, and thus to the species assumed to be intermediates in the haloperoxidases activity of the enzymes. In the presence of catechol (H₂cat) and benzohydroxamic acid (H₂bha), oxovanadium (IV) complexes, [VO (acac)(ONN)] gave mixed-chelate oxovanadium(V) complexes [VO(cat)(ONN)] and [VO(bha)(ONN)] respectively. These complexes are not very stable in solution and slowly convert to the corresponding dioxo species [VO₂(ONN)] as observed by⁵¹V NMR and electronic absorption spectroscopic studies.     

Novel cytotoxic oxovanadium(IV) complexes: Influence of pyrazole‐incorporated heterocyclic scaffolds on their biological response

Homoleptic VO^IV complexes with bidentate heterocycles, namely bipyrazole/pyrimidin‐2‐amine/triazolopyrimidine derivatives, are novel square pyramidal oxovanadium(IV) complexes. Their identities have been established using physicochemical techniques, namely elemental and spectral (ESI‐MS, IR, UV–visible) analyses. The in vitro antibacterial activities against Gram‐negative and Gram‐positive microorganisms have been studied for all compounds, exhibiting good inhibition as compared to the ligands. In addition, all compounds exhibit significant cytotoxicity towards brine shrimp with LD₅₀ values obtained in the range 8–24 μg ml⁻¹. Cellular level cytotoxicity has been investigated using bioassay of Schizosaccharomyces pombe , the complexes showing inevitable viability as concentration increases. Notably, UV absorption spectral titrations of the synthesized complexes with DNA reveal that the complexes bind to calf thymus DNA (CT‐DNA) through intercalation mode (K _b = 10⁴–10⁵ M⁻¹). Molecular docking reveals that the compounds are stacked between the base pairs of DNA. The results suggest that the complexes show promising binding affinity compared to the ligands towards CT‐DNA.     

Sodium and potassium benzeneazophosphonate complexes with crown ethers: Solid-state microwave synthesis, characterization and biological activity

The eco-friendly synthesis, spectroscopic (IR, MS, ¹H and ¹³C NMR) study and biological (cytostatic, antiviral) activity of sodium and potassium benzeneazophosphonate complexes, obtained by reaction in the solid state under microwave irradiation of the alkali salts of ethyl [α-(4-benzeneazoanilino)-N-benzyl]phosphonic acid and [α-(4-benzeneazoanilino)-N-4-methoxybenzyl]phosphonic acid with crown ethers containing 18-membered (dibenzo-18-crown-6 and bis(4′-di-tert-butylbenzo)-18-crown-6), 24-membered (dibenzo-24-crown-8) and 30-membered (dibenzo-30-crown-10) macrocyclic rings, have been described. The simple work-up solvent free reaction is an efficient green procedure for the formation of mononuclear crown ether complexes in which the sodium/potassium ion is bound to oxygen atoms of the macrocycle and the phosphonic acid oxygen. The free crown ethers, alkali benzeneazophosphonate salts and their complexes were evaluated for their cytostatic activity in vitro against murine leukemia L1210, murine mammary carcinoma FM3A and human T-lymphocyte CEM and MT-4 cell lines, as well as for their antiviral activity against a wide variety of DNA and RNA viruses. The investigated compounds showed no specific antiviral activity, whereas all the free crown ethers and their complexes demonstrated cytostatic activity, which was especially pronounced in the case of bis(4′-di-tert-butylbenzo)-18-crown-6 and its complexes.     

Multispectroscopic DNA interaction and Docking studies

Two new water soluble oxovanadium(IV) complexes with formulae Na[VO(his)(met)SO₄] (1) and Na[VO(gly)(met)SO₄] (2), (gly=glycine his=histidine, and met=metformin) were synthesized and characterized by LCMS, UV‐Visible absorption, infrared spectra, magnetic moment, elemental analysis, thermal analysis and electronic spectral studies. The metal center was found in an octahedral geometry. DNA binding interaction of these complexes with CT DNA has been explored by UV‐Visible absorption, fluorescence, viscosity measurements and cleavage studies. Finally the binding of the complexes with CT‐DNA could be surface binding, mainly in the groove binding. The complexes were docked in to B‐DNA sequence, 5’(D*AP*CP*CP*GP*AP*CP*GP*TP*CP*GP*GP*T)‐3’ retrieved from protein data bank (PDB ID: 423D), using Discovery Studio 2.1 software.     

Neutral Penta‐ and Hexacoordinate Silicon(IV) Complexes Containing Two Bidentate Ligands Derived from the α‐Amino Acids (S)‐Alanine, (S)‐Phenylalanine,and (S)‐tert‐Leucine

The neutral hexacoordinate silicon(IV) complex 6 (SiO₂N₄ skeleton) and the neutral pentacoordinate silicon(IV) complexes 7 – 11 (SiO₂N₂C skeletons) were synthesized from Si(NCO)₄ and RSi(NCO)₃ (R=Me, Ph), respectively. The compounds were structurally characterized by solid‐state NMR spectroscopy ( 6 – 11 ), solution NMR spectroscopy ( 6 and 10 ), and single‐crystal X‐ray diffraction ( 8 and 11 were studied as the solvates 8? CH₃CN and 11? C₅H₁₂ ? 0.5 CH₃CN, respectively). The silicon(IV) complexes 6 (octahedral Si‐coordination polyhedron) and 7 – 11 (trigonal‐bipyramidal Si‐coordination polyhedra) each contain two bidentate ligands derived from an α‐amino acid: (S)‐alanine, (S)‐phenylalanine, or (S)‐tert‐leucine. The deprotonated amino acids act as monoanionic ( 6 ) or as mono‐ and dianionic ligands ( 7 – 11 ). The experimental investigations were complemented by computational studies of the stereoisomers of 6 and 7 .     

Oxovanadium(IV)‐Salen Ion Catalyzed H2O2 Oxidation of Tertiary Amines to N‐Oxides– Critical Role of Acetate Ion as External Axial Ligand

The oxovanadium(IV)‐salen ion catalyzed H₂O₂ oxidation of N,N‐dimethylaniline forms N‐oxide as the product of the reaction. The reaction follows Michaelis–Menten kinetics and the rate of the reaction is accelerated by electron donating groups present in the substrate as well as in the salen ligand. This peculiar substituent effect is accounted for in terms of rate determining bond formation between peroxo bond of the oxidant and the N‐atom of the substrate in the transition state. Trichloroacetic acid (TCA) shifts the λ_max value of the oxidant to the red region and catalyzes reaction enormously. The cleavage of N? O bond by vanadium complex leads to moderate yield of the product. But the percentage yield of the product becomes excellent in the presence of TCA.     

exo‐[N,N′‐Bis(3‐tert‐butyl­salicyl­idene)‐1,2‐di­phenyl‐(RS,SR)‐1,2‐ethane­diyl­diaminato]­oxovanadium(IV)

The title mononuclear oxovanadium(IV) complex, [VO(C₃₆H₃₈N₂O₂)], has a distorted square‐pyramidal coordination. The complex was shown to be the exo isomer.