Novel sesquiterpenoids as tyrosine kinase inhibitors produced by Stachybotrys chortarum

In the course of screening for small-molecule inhibitors to Tyrosine kinase receptor seven novel K-76 derivatives (1-7) have been isolated from the fungal culture of Stachybotrys chortarum. The structures were elucidated by extensive mono- and bi- dimensional spectroscopy and mass spectrometry.     

Quantitation of sunitinib,an oral multitarget tyrosine kinase inhibitor,and its metabolite in urine samples by nonaqueous capillary electrophoresis time of flight mass spectrometry

A rapid, sensitive, and specific method was developed and validated using a nonaqueous‐capillary electrophoresis method with TOF‐MS for determination of sunitinib and N‐desethyl sunitinib in human urine. In order to avoid ionic suppression a urine samples dilution with methanol 1:10 previous step was used. This was the only treatment step to urine samples before the injection. Despite this dilution of the urine, the detection limit was as low as 0.07 mg/L for sunitinib and 0.15 mg/L for N‐desethyl sunitinib. Separation of compounds was achieved with a mixture of 5 mM ammonium formate in methanol. The calibration curves were linear over the range of 0.5–50.0 mg/L for the two analyzed compounds. The within‐run and between‐run precisions were within 5%, while the accuracy ranged from 96.0 to 100.4%. This method can be used in routine clinical practice to monitor sunitinib and N‐desethyl sunitinib drugs in the urine of cancer patients treated with once daily administration.     

Experimental and theoretical studies of acridine orange as corrosion inhibitor for copper protection in acidic media

The corrosion process commonly limits the use of copper in practical applications. The use of corrosion inhibitors is one of the effective methods to reduce the corrosion rate of copper. In this research, the inhibition effect of acridine orange (3,6-bis(dimethylamine)acridine) (AcO) for the protection of copper in 0.5 ?M ?H₂SO₄ solution was studied. For this aim, the change of open circuit potential with exposure time (E_ocp-t), electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), anodic and cathodic potentiodynamic polarization measurements (PP) and chronoamperometry (CA) techniques were used. Some quantum chemical parameters (E_HOMO, E_LUMO and dipole moment) were calculated and discussed. The AcO film formed over the copper surface was examined by SEM, EDX, AFM and contact angle measurements. The electrochemical data showed that AcO is an effective corrosion inhibitor even at low concentrations (ranging between 99.1% and %99.4 ?at concentrations from 0.01 ?mM to 1 ?mM). The corrosion rate of copper decreases in the presence of the inhibitor by reducing both anodic and cathodic rates, which is depended on its concentration. This compound behaves as mixed-type corrosion inhibitors with predominantly cathodic type. Its adsorption on the copper surface obeys Langmuir adsorption isotherm. The value of adsorption equilibrium constant (K_ads) and the standard free energy of adsorption were ΔG_ads 1.298 x 10³ ?M^?1 and -27.71 ?kJ/mol in the case of 0.5 ?M ?H₂SO₄ solution containing 1.0 ?mM AcO, which shows the adsorption is high and spontaneous. The adsorbed inhibitor film over the metal increase contact angle of the surface, which suggests the more hydrophobic properties of the surface are increasing coming from the orientation of hydrophobic sites to the electrolyte. The zero charge potential (E_pzc) studies showed that the surface charge of the metal is positive in the corrosive media containing the inhibitor. Quantum chemical calculations showed that the binding of inhibitor molecules to the metal surface takes place through N atoms of the inhibitor.     

Binding energies of tyrosine kinase inhibitors: Error assessment of computational methods for imatinib and nilotinib binding

The binding energies of imatinib and nilotinib to tyrosine kinase have been determined by quantum mechanical (QM) computations, and compared with literature binding energy studies using molecular mechanics (MM). The potential errors in the computational methods include these critical factors:

• •Errors in X-ray structures such as structural distortions and steric clashes give unrealistically high van der Waals energies, and erroneous binding energies.
• •MM optimization gives a very different configuration to the QM optimization for nilotinib, whereas the imatinib ion gives similar configurations
• •Solvation energies are a major component of the overall binding energy. The QM based solvent model (PCM/SMD) gives different values from those used in the implicit PBSA solvent MM models. A major error in inhibitor—kinase binding lies in the non-polar solvation terms.
• •Solvent transfer free energies and the required empirical solvent accessible surface area factors for nilotinib and imatinib ion to give the transfer free energies have been reverse calculated. These values differ from those used in the MM PBSA studies.
• •An intertwined desolvation—conformational binding selectivity process is a balance of thermodynamic desolvation and intramolecular conformational kinetic control.
• •The configurational entropies (TΔS) are minor error sources.

     

Synthesis and biological evaluation of a series of novel salicylanilides as inhibitors of EGFR protein tyrosine kinases

The synthesis and biological evaluation of two series of salicylanilide derivatives on the EGFR and ErbB-2 tyrosine kinases inhibitory activities were conducted.Of the tested compounds those having an additional aryl group substituted on the anilino ring were active on the EGFR tyrosine kinase inhibition(7a-c and 13a,13c,13d,13f).The inhibitory activities were all in the low micromolar or submicromolar range.In addition,compound 13a was found to have dual inhibitory activities both on EGFR and ErbB-2 tyrosine kinases(1.654±1.280 and 7.134±1.265μmol/L).     

Voltammetric Separation and Determination of Glutathione and L‐tyrosine with Chlorogenic Acid as an Electrocatalytic Mediator

A novel and sensitive voltammetric method was proposed for separation and determination of glutathione (GSH) and L‐tyrosine (Tyr) at acetylene black and chitosan modified glassy carbon electrode (AB‐CS/GCE). By introducing chlorogenic acid (CGA) as a new electrocatalytic mediator, GSH could be detected at much lower potential with symmetric peak shape. Acetylene black and chitosan composite served as current signal amplifier for sensitive detection. The electrochemical behavior of GSH and Tyr in the presence of CGA was studied at AB‐CS/GCE and complete separation of anodic peaks was achieved. Under the optimum conditions, the electrocatalytic oxidation peak current of GSH showed a linear dependence on its concentration in the ranges of 2.0×10⁻⁷‐4.0×10⁻⁵ M with the detection limit of 5.8×10⁻⁸ M (S/N=3), while the oxidation peak current of Tyr was linear to its concentration from 2.5×10⁻⁶ to 4.3×10⁻⁴ M with the detection limit of 9.2×10⁻⁷ M (S/N=3) by differential pulse voltammetry (DPV). The established method has been applied to the simultaneous determination of GSH and Tyr in human urine with satisfactory results.     

Design,Synthesis of Novel Thiourea and Pyrimidine Derivatives as Potential Antitumor Agents

1,3‐Bis‐(arylidene)thiourea derivatives ( 11a‐c ) were prepared by reacting thiourea ( 9 ) with bezaldehyde, p‐chlorobenzaldehyde or p‐anisaldehyde ( 10a‐c ) respectively. Further reaction of ( 11b ) with acetyl acetone, ethyl acetoacetate, malononitrile and acetic anhydride gave tetrahydropyrimidine‐2‐thiones ( 12‐14 ) and 1,3‐diacetyl thiourea ( 15 ). Compound ( 11b ) reacted with chloroacetyl chloride to give the corresponding pyrimidin‐4‐one derivative ( 16 ). Reaction of ( 12‐14 ) with acetic acid in aqueous sodium nitrite yielded the corresponding oxime derivatives ( 17‐19 ). The triazole ( 20 ) was achieved via refluxing of ( 19 ) in dimethylformamide. Reaction of ( 16 ) with mercaptoacetyl chloride gave the sulfanyl‐acetic acid ( 21 ) which afforded the dihydrazinyl ( 22 ) up on treatment with hydrazine hydrate. Newly synthesized compounds ware characterized by elemental analyses and spectral data (IR, ¹H‐NMR, ¹³C‐NMR and mass spectra). The investigated compounds were screened for their cytotoxicity, i.e. compounds 19 , 20 and 22 exhibited highly potential antitumor activity.     

Synthesis,characterization, and biological activity of a Cu(I) complex with 2-(9H-carbazol-9-yl) acetic acid

A new dicopper(I) complex with 2-(9H-carbazol-9-yl) acetic acid (HL) of the formula [Cu₂(dppm)₂L(NO₃)(CH₃OH)] [dppm = bis(diphenylphosphino)methane] was prepared. The complex was structurally characterized by IR, ¹H NMR spectra, and elemental analysis. Single crystal X-ray crystallography revealed that this complex is monoclinic, space group P2₁/c, with a = 13.6552(17) Å, b = 23.123(2) Å, c = 19.257(2) Å, α = γ = 90.00°, β = 106.860(2)°, V = 5818.8(11) ų, Z = 4, D _Calcd = 1.386 mg m^?3, F(000) = 2512, goodness-of-fit = 1.015. The complex was also tested in vitro for its cytotoxic activity using human hepatocellular carcinoma cell line (BEL-7402) and human hepatocellular liver carcinoma cell line (Hep-G2); 5-Fluorouracil was used as a positive control substance. The results indicated that the complex exhibited good cytotoxic activity against both human tumor cell lines.     

Molecular drug design, synthesis and structure elucidation of a new specific target peptide based metallo drug for cancer chemotherapy as topoisomerase I inhibitor

To evaluate the biological preference of metallopeptide drugs in cancer cells, a new dinuclear copper(II) complex [Cu(2)(glygly)(2)(ppz)(H(2)O)(4)]·2H(2)O (1) (glygly = glycyl glycine anion and ppz = piperazine), was designed and synthesized as topoisomerase I inhibitor. The structural elucidation of the complex was done by elemental analysis, spectroscopic methods and single crystal X-ray diffraction. The in vitro DNA binding studies of complex 1 with CT DNA were carried out by employing different optical methods viz. UV-vis, fluorescence and circular dichroism. The molecular docking technique was also utilized to ascertain the mechanism and mode of action towards the molecular target DNA and enzymes. Complex 1 cleaves pBR322 DNA via an oxidative mechanism and strongly binds to the DNA minor groove. Furthermore, complex 1 exhibits significant inhibitory effects on the catalytic activity of topoisomerase I at a very low concentration, ~12.5 μM, in addition to its excellent SOD mimics (IC(50)~0.086 μM).     

Europium tetracycline as a luminescent probe for nucleoside phosphates and its application to the determination of kinase activity

The determination of enzyme activities and the screening of enzyme regulators is a major task in clinical chemistry and drug development. A broad variety of enzymatic reactions is associated with the consumption of adenosine triphosphate (ATP), including, in particular, phosphorylation reactions catalyzed by kinases, formation of adenosine cyclic monophosphate (cAMP) by adenylate cyclases, and ATP decomposition by ATPase. We have studied the effect of a series of adenosine (ATP, ADP, AMP, cAMP) and guanosine (GTP, GDP) phosphoric esters, and of pyrophosphate (PP) on the fluorescence emission of the europium tetracycline (EuTC) complex. We found that these compounds have strongly different quenching effects on the luminescence emission of EuTC. The triphosphates ATP and GTP behave as strong quenchers in reducing the fluorescence intensity of EuTC to 25 % of its initial value by formation of a ternary 1:1:1 complex. All other phosphate esters showed a weak quenching effect only. The applicability of this fluorescent probe to the determination of the activity of phosphorylation enzymes is demonstrated by means of creatine kinase as a model for non-membrane-bound kinases. In contrast to other methods, this approach does not require the use of radioactively labeled ATP substrates, additional enzymes, or of rather complex immunoassays.     

A simple spiroepoxide as methionine aminopeptidase-2 inhibitor: synthetic problems and solutions

The preparation of a simple 1-oxa-spiro[2.4]heptane derivative is described. Observations made in the course of the synthesis show again that apparently minor structural modifications of the dienic substrate exert a strong influence on the ring-closing metathesis outcome and that the efficient construction of even simple but highly substituted systems by RCM may constitute a synthetic challenge.     

Novel 1,2,4-oxadiazole/pyrrolidine hybrids as DNA gyrase and topoisomerase IV inhibitors with potential antibacterial activity

DNA gyrase is a promising target for antibacterial agents. Several classes of small-molecule inhibitors have been discovered in recent decades, but none of these have reached the market. We have designed a small library of 1,2,4-oxadiazole/pyrrolidine hybrids with mid nanomolar inhibitory and potent antibacterial activities against DNA gyrase and topoisomerase IV. Compounds 9, 15, 16, 19, and 21 inhibited Escherichia coli DNA gyrase to a similar extent as the reference compound, novobiocin, with inhibitory values ranging from 120 nM to 270 nM. Compound 16 was one of the most potent compounds in the series, with an IC₅₀ value of 120 nM against E. coli gyrase, which is lower than the IC₅₀ value of novobiocin (170 nM). Compound 16 had the highest inhibitory activity, with minimum inhibitory concentrations (MIC) of 24 and 62 ng/mL against Staphylococcus aureus and E. coli, respectively, which compared favorably with ciprofloxacin (30 and 60 ng/mL, respectively). Compounds 9, 15, 19, and 21 were similar to novobiocin in terms of their activity against E. coli and S. aureus topoisomerase IV, while compound 16 was more potent than novobiocin.     

Epothilone B and its Derivatives as Novel Antitumor Drugs: Total and Partial Synthesis and Biological Evaluation

Summary.  Microtubule stabilizing natural products, as exemplified by paclitaxel (taxol^?), are being considered as novel drugs against malignant therapy resistent solid tumors. Among these compounds, epothilone B and some of its derivatives have emerged as particularly promising candidates for industrial development. The total and partial syntheses of these compounds are described in detail, and some of the most important recent results on their biological activity are discussed. Received December 3, 1999. Accepted December 6, 1999     

Sn(I) halides: Novel binary compounds of tin and their application in synthetic chemistry

Metalloid cluster compounds are ideal model compounds for the area between the molecular and solid state, i.e. the nanometer regime. For the synthesis of metalloid cluster compounds, the disproportionation reaction of a metastable subhalide is a fruitful synthetic route. In the case of tin, monohalides are needed for this synthetic route as tin(II) halides are too stable to be used. Due to thermodynamic data, gaseous SnBr should be formed at 1370 °C, and by applying a co-condensation technique it can be trapped at −196 °C and prepared in synthetic scale. Herein first analyses of SnBr are presented, showing that SnBr is more reactive than the corresponding GeBr, already disproportionating quantitatively to elemental tin and SnBr₂ on heating to room temperature. By applying nitrogen-based donor molecules like NnBu₃ or pyridine, the reactivity can be moderated and the solubility is enhanced leading e.g. to an SnBr emulsion, which can be used for the synthesis of metalloid cluster compounds of tin.     

Novel 3',6'-anhydro and N12,N13-bridged glycosylated fluoroindolo[2,3-a]carbazoles as topoisomerase I inhibitors. Fluorine as a leaving group from sp3 carbon

[reaction: see text] Both 6'- and 4'-fluoro-glycosylated indolo[2,3-a]carbazoles are substrates for base-induced loss of fluorine as a leaving group from sp3 carbon. In the case of alpha-N-glycosylated substrate 3, loss of fluorine from the 6'-position leads to 3,6-anhydroglucose analogue 1. A novel N12,N13-bridged sugar analogue 2 results from loss of 4'-fluorine from beta-N-glycosylated analogue 4. Both analogues 1 and 2 display topo I inhibitory potencies similar to camptothecin.     

Novel dialkylaminoalkyl- and dialkylaminoalcoxi-benzophenones as photoinitiators of polymerization. I. Photochemical characteristics and radical efficiencies

The behavior of the nonconjugated aminated benzophenones—4-[2′-N,N-(diethylamino)ethoxy]benzophenone (E4), 2-[2′-N,N-(diethylamino)ethoxy]-4-methoxybenzophenone (E2), and 4-N,N-dimethylaminomethylbenzophenone (DM)—as photoinitiators of MMA polymerization has been studied and the results compared with those obtained with the conjugated aminobenzophenone 4-N,N-dimethylamino-4′-isopropyl-benzophenone (CU—MI). Photoreduction behavior of these compounds in various solvents in the presence and absence of MMA has been also examined. The order of the polymerization reaction with respect to monomer and initiator concentrations has been investigated; values of initiation quantum yield (Φ_i), K_p/K^1/2_t and efficiencies of the different radicals have also been determined. Similar polymerization rates (R_p) of methyl methacrylate (MMA) were found when E4 and CU-MI were used as photoinitiators under the same range of absorbed irradiation intensity. This fact results from a compensation between the higher rate of E4 radical production (n-π* transition type) and the greater reactivity of the radicals generated from CU-MI.     

Design,synthesis and biological evaluation of O-linked indoles as VEGFR-2 kinase inhibitors (I)

Inhibition of VEGFR-2 signaling pathway has already become one of the most promising approaches for the treatment of cancer. In this study, we describe the design, synthesis, and biological evaluation of a series of O-linked indoles as potent inhibitors of VEGFR-2. Among these compounds, 18 showed significant anti-angiogenesis activities via VEGFR-2 in enzymatic proliferation assays, with IC₅₀ value of 3.8 nmol/L. Kinase selectivity profiling revealed that 18 was a multitargeted inhibitor, and it also exhibited good potency against VEGFR-1, PDGFR-α and β.     

Novel and Potential Small Molecule Scaffolds as DYRK1A Inhibitors by Integrated Molecular Docking-Based Virtual Screening and Dynamics Simulation Study

The dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) is a novel, promising and emerging biological target for therapeutic intervention in neurodegenerative diseases, especially in Alzheimer’s disease (AD). The molMall database, comprising rare, diverse and unique compounds, was explored for molecular docking-based virtual screening against the DYRK1A protein, in order to find out potential inhibitors. Ligands exhibiting hydrogen bond interactions with key amino acid residues such as Ile165, Lys188 (catalytic), Glu239 (gk+1), Leu241 (gk+3), Ser242, Asn244, and Asp307, of the target protein, were considered potential ligands. Hydrogen bond interactions with Leu241 (gk+3) were considered key determinants for the selection. High scoring structures were also docked by Glide XP docking in the active sites of twelve DYRK1A related protein kinases, viz. DYRK1B, DYRK2, CDK5/p25, CK1, CLK1, CLK3, GSK3β, MAPK2, MAPK10, PIM1, PKA, and PKCα, in order to find selective DYRK1A inhibitors. MM/GBSA binding free energies of selected ligand–protein complexes were also calculated in order to remove false positive hits. Physicochemical and pharmacokinetic properties of the selected six hit ligands were also computed and related with the proposed limits for orally active CNS drugs. The computational toxicity webserver ProTox-II was used to predict the toxicity profile of selected six hits (molmall IDs 9539, 11352, 15938, 19037, 21830 and 21878). The selected six docked ligand–protein systems were exposed to 100 ns molecular dynamics (MD) simulations to validate their mechanism of interactions and stability in the ATP pocket of human DYRK1A kinase. All six ligands were found to be stable in the ATP binding pocket of DYRK1A kinase.