Synthesis, structures, and urease inhibitory activities of oxovanadium(V) complexes with Schiff bases

An overview: metal-based inhibitors of urease

Urease is a kind of nickel-dependent metalloenzyme, which exists in the biological world widely, and can catalyse the hydrolysis of urea into ammonia and carbon dioxide to provide a nitrogen source for organisms. Urease has important uses in agriculture and medicine because it can catalyse the production of ammonia. Therefore, in this review, metal-based inhibitors of urease will be summarised according to different transition metal ions. Including the urease inhibition, structure-activity relationship, and molecular docking. Importantly, among these reviewed effective urease inhibitors, most of copper metal complexes exhibited stronger urease inhibition with IC50 values ranging from 0.46 μM to 41.1 μM. Significantly, the collected comprehensive information looks forward to providing rational guidance and effective strategies for the development of novel, potent, and safe metal-based urease inhibitors, which are better for practical applications in the future.

Medicinal applications of vanadium complexes with Schiff bases

Many transition metal complexes have been explored for their therapeutic properties after the discovery of cisplatin. Schiff bases have an efficient complexation tendency with the transition metals and several medicinal properties have been reported. However, fewer studies have reported the medicinal utility of vanadium and its Schiff base complexes. This paper provides a comprehensive overview of vanadium complexes with Schiff bases along with their mechanistic insight. Vanadium complexes in + 4 and + 5 oxidation states have exhibited well-defined geometry and found to be thermodynamically stable. The studies have reported the G0/G1 phase cell cycle arrest and decreased delta psi m, inducing mitochondrial membrane depolarization in cancer cell lines along with the alterations in the metabolism of the cancer cells upon dosing with the vanadium complexes. Cancer cell invasion and growth are also found to be markedly reduced by peroxo complexes of vanadium. The studies included in the review paper have been taken from leading indexing databases and focus was laid on recent reports in literature. The biological potential of vanadium complexes of Schiff bases opens new horizons for future interdisciplinary studies and investigation focussed on understanding the biochemistry of these complexes, along with designing new complexes which have better bioavailability, solubility and low or non-toxicity.

Mono Versus Dinuclear Vanadium(V) Complexes: Solvent Dependent Structural Versatility and Electro Syntheses of Mixed-Valence Oxovanadium(IV/V) Entities in Solution

Two mononuclear oxidovanadium(V) complexes type of [V^VO(L¹)(OMe)(MeOH)] (1), [V^VO(L²)(OMe)(MeOH)] (2) and two [V₂O₃]⁴⁺ core of μ-oxidodioxidodivanadium(V) complexes (L¹)(O)V^V-O-V^V(O)(L¹) (3) and (L²)(O)V^V-O-V^V(O)(L²) (4) and two complexes [V^VO(L¹)(8-Hq)] (5) and [V^VO(L²)(8-Hq)] (6) incorporating 8-hydroxyquinoline (8-hq) as co-ligand have been reported where L¹ [(E)-N'-(2-hydroxybenzylidene)cinnamohydrazide] and L² [(2E,N'E)-N'-(2-hydroxybenzylidene)-3-(naphthalen-1-yl)acrylohydrazide] are the dianionic forms of the conjugated keto-imine functionalized substituted hydrazone ligands. The μ-oxidodioxidodivanadium complexes are generated upon switching the solvent from methanol to acetonitrile. The X-ray analysis showed octahedral geometry for the mononuclear complexes 1, 2 and 5 but oxido-bridged dinuclear complexes 3 and 4 formed penta-coordinated square-pyramidal geometry about metal atoms. Two mixed-valence species of type II, 3a and 4a, of general formulae (L)(O)V^IV-O-V^V(O)(L), are being generated upon constant potential electrolysis (CPE) of 3 and 4 respectively. Frozen solution EPR spectra have 13 hyperfine lines, revealing the unpaired electron is majorly localized on one of the two vanadium centres. All these complexes have been well characterized by physio-chemical techniques and the density functional theory (DFT) calculations were applied to obtain further insight into the electronic structure of this type of molecule. The oxidomethoxido complexes 1 and 2 were taken to investigate the catechol oxidase mimicking activity following the oxidation of 3,5-di-tert-butyl catechol (3,5-DTBC) to 3,5-di-tert-butyl benzoquinone (3,5-DTBQ).

An overview on the synthetic urease inhibitors with structure-activity relationship and molecular docking

Urease is a kind of enzyme which could be found in various bacteria, fungi, plants, and algae, which can quickly catalyze the hydrolysis of urea into ammonia and carbon dioxide. With the ammonia concentration increasing, the activity of Helicobacter pylori has got an obvious enhancement and leads to mucosal damage in the stomach, gastroduodenal infection, peptic ulcers, and gastric cancer. The infectious diseases caused by Helicobacter pylori can be controlled to a certain extent by inhibiting urease activity with urease inhibitors. Hence, studies of urease inhibitors have attracted great attention all over the world and a variety of effective urease inhibitors have been synthesized in recent years. In this review, we will draw summaries for these inhibitors including urease inhibitory activity, inhibition kinetics, structure-activity relationship, and molecular docking. The collected information is expected to provide rational guidance and effective strategy to develop novel, potent, and safe urease inhibitors for better practical applications in the future.

Potential Medicinal Applications of Vanadium and its Coordination Compounds in Current Research Prospects: A Review

Background:

The variety of biological applications of vanadium impressed researchers to develop vanadium based drugs. The most well-known fact of vanadium is that it is necessary for human beings as an insulin-enhancing agent and herein, we mainly provide an overview of vanadium-based drugs and their applications in the medicinal field for the treatment of diseases such as diabetes and cancer. The first part of this review is focused on mechanistic studies involved in the anti-diabetic activity. The latter part explains the use of vanadium and its related coordination compounds in the treatment of cancer.

Methods:

This review is purely based on literature search available in the database. We focused on the reports available on the recent advancements in the vanadium chemistry and its biological properties, mainly anti-diabetic and anticancer activities of vanadium based compounds.

Results:

The study of clinical trials of vanadium and its drug molecules imposed more demand due to their remarkable activity with less toxicity.

Conclusion:

A brief literature survey was made pertaining to the applications of vanadium compounds/ complexes. Particularly, special attention was paid to explaining mechanistic studies of vanadium based compounds in the treatment of diabetes and cancer.

Lead Molecules for Targeted Urease Inhibition: An Updated Review from 2010 -2018

The field of enzyme inhibition is a tremendous and quickly growing territory of research. Urease a nickel containing metalloenzyme found in bacteria, algae, fungi, and plants brings hydrolysis of urea and plays important role in environmental nitrogen cycle. Apart from this it was found to be responsible for many pathological conditions due to its presence in many microorganisms such as H. Pylori, a ureolytic bacteria having urease which elevates pH of gastric medium by hydrolyzing urea present in alimentary canal and help the bacteria to colonize and spread infection. Due to the infections caused by the various bacterial ureases such as Bacillus pasteurii, Brucella abortus, H. pylori, H. mustelae, Klebsiella aerogenes, Klebsiella tuberculosis, Mycobacterium tuberculosis, Pseudomonas putida, Sporosarcina pasteurii and Yersinia enterocolitica, it has been the current topic of today's research. About a wide range of compounds from the exhaustive literature survey has been discussed in this review which is enveloped into two expansive classes, as Inhibitors from synthetic origin and Inhibitors from natural origin. Moreover active site details of enzyme, mechanism of catalysis of substrate by enzyme, uses of plant urease and its pathogenic behavior has been included in the current review. So, overall, this review article diagrams the current landscape of the developments in the improvements in the thriving field of urease inhibitory movement in medicinal chemistry from year 2010 to 2018, with an emphasis on mechanism of action of inhibitors that may be used for more development of recent and strong urease inhibitors and open up new doors for assist examinations in a standout amongst the most lively and promising regions of research.

Crystal structure of tetramethylammonium (2-(3-ethoxy-2-oxidobenzylidene)-1-(2-hydroxybenzoyl)hydrazin-1-ido-κ3 N,N′,O)cobalt(III), C36H40N5O8Co

C36H40N5O8Co, monoclinic, P21/c (no. 14), a = 17.353(4) Å, b = 11.474(2) Å, c = 18.074(4) Å, β = 101.056(2)°, V = 3532.0(13) Å3, Z = 4, R gt(F) = 0.0464, wR ref(F 2) = 0.1323, T = 296(2) K 1–3.

DFT study on the redox behavior of two dioxovanadium(v) complexes with N2O donor Schiff base ligands and their use in catalytic oxidation ofortho-aminophenol

Solution phase redox behavior of two vanadium(v) Schiff base complexes was checked. The results agree well with DFT calculations. Both complexes exhibited good catalytic efficiency for the conversion ofo-aminophenol to 2-aminophenoxazine-3-one.

Analysis of energies of halogen and hydrogen bonding interactions in the solid state structures of vanadyl Schiff base complexes

Four vanadyl Schiff base complexes have been prepared and characterized. Energies of supramolecular interactions in complexes 1, 2 and 3 were estimated using DFT calculations, and further corroborated with NCI plot index computational tool.

Stabilization of two conformers via intra- or inter-molecular hydrogen bonds in a dinuclear vanadium(v) complex with a pendant Schiff base: theoretical insight

A dinuclear vanadium(v) complex, (μ-O)₂[V(O)(L)]₂, [where HL = 2-methoxy-6-((2-(2-hydroxyethylamino)ethylimino)methyl)phenol] has been synthesized and characterized by spectral and elemental analysis. A single crystal X-ray diffraction study confirms it structure. Two different conformations, stabilized via either intra- or inter-dinuclear hydrogen bonding interactions, co-exist in the solid-state structure. The energies of these intra- or inter-dinuclear hydrogen bonding interactions have been estimated by Density functional theory (DFT) calculations. A ‘Non-covalent interaction’ (NCI) plot has also been used to characterize these interactions.

Two different hydrogen bonded conformers coexist in a synthesized dinuclear oxovanadium(v) Schiff base. Density functional theory (DFT) calculations were utilized to calculate the energies involved in two different conformers.

Developing potential Helicobacter pylori urease inhibitors from novel oxoindoline derivatives: Synthesis, biological evaluation and in silico study

By recruiting the important moiety from Shikonin, a series of novel oxoindoline derivatives S1-S20 have been synthesized for inhibiting H. pylori urease. The most potent compound S18 displayed better activity (IC₅₀ = 0.71 μM; MIC = 0.48 μM) than the positive controls AHA (IC₅₀ = 17.2 μM) and Metronidazole (MIC = 31.3 μM). With low cytotoxicity, it showed considerable potential for further development. Docking simulation revealed the possible binding pattern of this series. 3D QSAR model was built to discuss SAR and give useful hints for future modification.

Heterometallic Octanuclear NiII 4LnIII 4 (Ln = Y, Gd, Tb, Dy, Ho, Er) Complexes Containing NiII 2LnIII 2O4 Distorted Cubane Motifs: Synthesis, Structure, and Magnetic Properties

The reaction of 2-methoxy-6-[{2-(2-hydroxyethylamino)ethylimino}methyl] phenol (LH₃) with lanthanide metal salts followed by the addition of nickel acetate allowed isolation of a family of octanuclear complexes, [Ni₄Ln₄(μ₂-OH)₂(μ₃-OH)₄(μ-OOCCH₃)₈(LH₂)₄]·(OH)₂·xH₂O. Single crystal X-ray diffraction studies of these complexes reveal that their central metallic core consists of two tetranuclear [Ni₂Ln₂O₄] cubane subunits fused together by acetate and hydroxide bridges. The magnetic study of these complexes reveals a ferromagnetic interaction between the Ln^III and the Ni^II center. The magnitude of exchange coupling between the Ni^II and Ln^III center, parametrized from the magnetic data of the Gd analogue, gives J = +0.86 cm^-1. The magneto caloric effect, studied for the Ni^II ₄Gd^III ₄ complex, shows a maximum of magnetic entropy change, -ΔS _m = 22.58 J kg^-1 K^-1 at 3 K for an applied external field of 5 T.

Schiff bases and their metal complexes as urease inhibitors - A brief review

Schiff bases, an aldehyde- or ketone-like compounds in which the carbonyl group is replaced by an imine or azomethine, are some of the most widely used organic compounds. Indeed, they are widely used for industrial purposes and also exhibit a broad range of biological activities, including anti-urease activity. Ureases, enzymes that catalyze urea hydrolysis, have received considerable attention for their impact on living organisms’ health, since the persistence of urease activity in human and animal cells can be the cause of some diseases and pathogen infections. This short review compiles examples of the most antiurease Schiff bases (0.23 μM < IC₅₀ < 37.00 μM) and their metal complexes (0.03 μM < IC₅₀ < 100 μM). Emphasis is given to ureases of Helicobacter pylori and Canavalia ensiformis, although the active site of this class of hydrolases is conserved among living organisms.

[N'-(4-Dec-yloxy-2-oxido-benzyl-idene)-3-hy-droxy-2-naphtho-hydrazidato-κ3N,O,O']di-methyl-tin(IV): crystal structure and Hirshfeld surface analysis

The title diorganotin compound, [Sn(CH3)2(C28H32N2O4)], features a distorted SnC2NO2 coordination geometry almost inter-mediate between ideal trigonal-bipyramidal and square-pyramidal. The dianionic Schiff base ligand coordinates in a tridentate fashion via two alkoxide O and hydrazinyl N atoms; an intra-molecular hy-droxy-O-H⋯N(hydrazin-yl) hydrogen bond is noted. The alk-oxy chain has an all-trans conformation, and to the first approximation, the mol-ecule has local mirror symmetry relating the two Sn-bound methyl groups. Supra-molecular layers sustained by imine-C-H⋯O(hy-droxy), π-π [between dec-yloxy-substituted benzene rings with an inter-centroid separation of 3.7724 (13) Å], C-H⋯π(arene) and C-H⋯π(chelate ring) inter-actions are formed in the crystal; layers stack along the c axis with no directional inter-actions between them. The presence of C-H⋯π(chelate ring) inter-actions in the crystal is clearly evident from an analysis of the calculated Hirshfeld surface.

Antimicrobial activity of aroylhydrazone-based oxido vanadium(v) complexes: in vitro and in silico studies

A series of oxido vanadium(v) complexes have been synthesized and evaluated from the point of experimental and theoretical antimicrobial activity.

Heterometallic trinuclear {CoIII2LnIII} (Ln = Gd, Tb, Ho and Er) complexes in a bent geometry. Field-induced single-ion magnetic behavior of the ErIII and TbIII analogues

In this paper we report the synthesis, structures and detailed magnetic properties of heterometallic trinuclear Co^IIILn^III complexes.

Inhibition studies of Helicobacter pylori urease with Schiff base copper(ii) complexes

Nine new copper(ii) complexes derived from various Schiff bases were prepared. Five complexes show effective urease inhibitory activities. Complex5has the most effective activity against urease, with a mixed competitive inhibition mechanism.

Mechanism, kinetics, and antimicrobial activities of 2-hydroxy-1-naphthaldehyde semicarbazone as a new Jack bean urease inhibitor

A new inhibitor of jack bean urease, 2-hydroxy-1-naphthaldehyde semicarbazone, was synthesized and employed to investigate the inhibitory mechanism of HNDSC on jack bean urease by kinetic and fluorescence titration assay, and its antibacterial activities were also investigated.

Synthesis, structures and urease inhibitory activity of cobalt(III) complexes with Schiff bases

A series of new cobalt(III) complexes were prepared. They are [CoL(1)(py)3]·NO3 (1), [CoL(2)(bipy)(N3)]·CH3OH (2), [CoL(3)(HL(3))(N3)]·NO3 (3), and [CoL(4)(MeOH)(N3)] (4), where L(1), L(2), L(3) and L(4) are the deprotonated form of N'-(2-hydroxy-5-methoxybenzylidene)-3-methylbenzohydrazide, N'-(2-hydroxybenzylidene)-3-hydroxylbenzohydrazide, 2-[(2-dimethylaminoethylimino)methyl]-4-methylphenol, and N,N'-bis(5-methylsalicylidene)-o-phenylenediamine, respectively, py is pyridine, and bipy is 2,2'-bipyridine. The complexes were characterized by infrared and UV-Vis spectra, and single crystal X-ray diffraction. The Co atoms in the complexes are in octahedral coordination. Complexes 1 and 4 show effective urease inhibitory activities, with IC50 values of 4.27 and 0.35 μmol L(-1), respectively. Complex 2 has medium activity against urease, with IC50 value of 68.7 μmol L(-1). While complex 3 has no activity against urease. Molecular docking study of the complexes with Helicobacter pylori urease was performed.