In vitro study of iron coordination properties,anti-inflammatory potential,and cytotoxic effects of <Emphasis Type="Italic">N</Emphasis>-salicylidene and <Emphasis Type="Italic">N</Emphasis>-vanillidene anil Schiff bases

N-Salicylidene and N-vanillidene anil Schiff bases SB-1–5 were evaluated for their iron-coordinating properties. For this purpose, reactions with Fe(III) chloride were performed. The obtained results showed that salicylaldehyde bases SB-1 and SB-2 are the best coordinating ligands among the investigated SBs. The corresponding complexes are obtained in good yield and investigated using UV–Vis spectrophotometry and IR spectroscopy. The inhibitory potential of SB-1–5 against iron-containing enzyme lipoxygenase (LOX) was also tested. Salicylidene bases exerted better activity then vanilliden. The cytotoxic in vitro activities against human breast carcinoma MDA-MB-231 and human colon carcinoma HCT-116 cell lines were determined. Based on these results, SB-1 and SB-2 can be considered as interesting compounds for further in vivo investigations.     

Strain in strain-free benzenoid hydrocarbons: the case of fibonacenes

In a recent paper (Radenkovic et al. Chem Phys Lett 625:69–72, 2015), a new method for quantifying the strain energy in benzenoid molecules, resulting from the repulsion between the bay H-atoms was elaborated. In this work, we present a modified procedure, capable of estimating the strain energy in a single-step calculation. Strain energies were obtained at the B3LYP/def2-TZVP level of density functional theory. It was found that in benzenoid molecules with a single bay region, the strain energy is essentially constant, equal to around 7.3 kJ/mol. On the other hand, in the case of the first four members of the fibonacene series, the strain energy is found to be linearly proportional to the number of bay regions.     

Cholinesterase inhibition based determination of pancuronium bromide in biological samples

Pancuronium bromide (PCBr) inhibition effect on enzyme cholinesterase from pooled human serum (Che, EC 3.1.1.8 acylcholine acylhydrolase) was used for development of a spectrophotometric kinetic method for PCBr determination in human serum and urine. Optimal conditions for the basic and inhibitor reactions were established: pH=7.7 and substrate concentration c(benzoylcholine chloride)=1.33 mmol/L. Kinetic parameters were also determined: Michaelis-Menten’s constant K_M=0.40 mmol/L, maximal reaction rate V_max=52.2 μmol/L min, inhibition constant K_i=0,56 μmol/L and IC₅₀=1.31 μmol/L. Linear dependence between the reaction rate and inhibitor concentration exists in PCBr concentration range 8.20–68.25 nmol/L, which corresponds to the real sample concentrations from 0.328 to 2.730 μmol/L. The method detection and quantification limits were 2.01 nmol/L and 6.67 nmol/L, respectively. Precision of the method was tested for three pancuronium concentrations (10.70, 29.35 and 51.25 nmol/L). Relative standard deviation (RSD) was in the range 0.15–7.45%. Accuracy was examined by standard addition method. Influence of the substances usually present in serum and urine on the reaction rate was tested. The developed method was applied for PCBr content determination in serum model samples, urine model samples and in urine taken during surgery. The method has good sensitivity, accuracy, precision and it is suitable for clinical practice.      

Spatial and Electronic Structures of BeB8 and MgB8: How far Does the Analogy Go?

Doping boron clusters with Be and its heavier alkaline-earth congener, Mg, usually leads to complexes of different geometry and electronic structure. In this work we show that both neutral BeB₈ and MgB₈ exhibit a singlet ground state umbrella-like form. In addition, the stability, electronic structure, and aromaticity of the target molecules are compared. The magnetically induced current densities show that BeB₈ and MgB₈ are double aromatic systems: π and σ electrons induce strong diatropic currents. The current densities induced in the studied complexes are of very similar intensity, but with a different spatial distribution. The differences in the current density patterns observed for BeB₈ and MgB₈ arise from the very nature of the bonding interactions between the M atom and B₈ fragment, as demonstrated through the energy decomposition analysis.     

Inclusion complexes with cyclodextrin and usnic acid

Molecular inclusion complexes of usnic acid (UA) with β-cyclodextrin (β-CD) and 2-hydroxypropyl β-cyclodextrin (HP β-CD) were prepared by the co-precipitation method in the solid state in the molar ratio of 1:1. Structural complexes characterization was based on different methods, FTIR, ¹H NMR, XRD and DSC. Parallel to the complex by the above methods, corresponding physical mixtures of UA with cyclodextrins and complexing agents (β-CD, HP β-CD and UA) were analyzed. The results of DSC analysis showed that, at around 200 °C, the endothermal peak in the complexes with cyclodextrins originating from the UA melting has disappeared. Complex diffractogram patterns do not contain peaks characteristic for the pure UA. They are more appropriate to cyclodextrin diffractogram. This fact points to the molecular encapsulation of UA in the cyclodextrin cavity. Chemical shifts in ¹H NMR spectra after the inclusion of UA into the cyclodextrin cavity, especially H-3 protons (0.0012 and 0.0102 ppm in the β-CD and HP β-CD, respectively) and H-5 and H-6 (0.0134 ppm) and hydrogen from CH₃ (0.0073 ppm) HP β-CD also points to the formation of molecular inclusion complexes. The improved solubility of UA in water was achieved by molecular incapsulation. In the complex with β-CD the solubility is 0.3 mg/cm³, with HP β-CD 4.2 mg/cm³ while the uncomplexed UA solubility is 0.06 mg/cm³. The microbial activity of UA and both complexes was tested against eight bacteria and two fungi and during the test no reduced activity of UA in the complexes was observed.     

Dithiobiuretes in reactions with electrophilic acetylenes. New derivatives of 1,3,5-dithiazines,-thiadiazines and-triazines as the products of competing reactions of nucleophilic cycloaddition

The nucleophilic addition of 2,4-dithiobiurete, 1- and 1,4-substituted 2,4-dithiobiuretes (2 a-e) with benzoylacetylene (1) has been studied. 2-(Benzoylmethyl)-4-(R¹-imino)-6-(R²-imino)dihydro-4H-1,3,5-dithiazinium perchlorates (3 a-e) are obtained in glacial acetic acid (AcOH) in the presence of equimolar quantities of HClO₄. The reaction of benzoylacetylene with 1,5-diphenyl-2,4-dithiobiurete in either of MeOH, C₆H₆, or MeCN solvents proceeds non-selectively to give a mixture of products such as 2-(benzoylmethyl)-4,6-di(phenylimino)dihydro-4H-1,3,5-dithiazine (5), 2-(benzoylmethyl)-4-(β-benzoylvinyl)thio-3-phenyl-6-(phenylimino)-3,6-dihydro-2H-1,3,5-thiadiazine (8), 2-(benzoylmethyl)-1,3-diphenylhexahydro-1,3,5-triazine-4,6-dithione (7) and N-(β-benzoylvinyl)-N-phenylthioureas (6).     

Photoreaction between benzoylthiophenes and N-BOC-tryptophan methyl ester

Drug-induced photoallergy requires as the first step formation of covalent drug-protein photoadducts. One of the key amino acids involved in this process is tryptophan (Trp). In this context, several diaryl ketones, including 2-benzoylthiophene (BT), [2-(5-benzoyl-5-thienyl)]-2-methylpropanoic methyl ester (TPA methyl ester) and 4-(2-thienylcarbonyl)phenyl]-2-methylpropanoic methyl ester (SUP methyl ester) have been irradiated in the presence of N-BOC-(L)-tryptophan methyl ester. Laser flash photolysis has allowed to detect three neutral radicals (ketyl, indolyl and skatolyl radicals) resulting from formal hydrogen-atom abstraction. This correlates well with the isolation of homodimers, as well as with cross-coupling products, in the preparative irradiation. The main cross-coupling products were in all cases lactones arising from the reaction of the Trp-derived skatolyl radicals with the corresponding ketyl radicals. These lactones were obtained as the (4R) stereoisomers with remarkable diasteroselectivity. No coupling products through the phenyl p-position of BT or TPA methyl ester were found. By contrast, ketone homodimers and cross-coupling products arising from reaction through the thienyl 5-position were obtained when using BT and SUP methyl ester; this is very interesting, because stable LAT-derived products are difficult to isolate.     

Coordination behaviour and two‐dimensional‐network formation in poly[[μ‐aqua‐diaqua(μ5‐propane‐1,3‐diyldinitrilotetraacetato)dilithium(I)cobalt(II)] dihydrate]: the first example of an MII–1,3‐pdta complex with a monovalent metal counter‐ion

The title compound, {[CoLi₂(C₁₁H₁₄N₂O₈)(H₂O)₃]·2H₂O}_n, constitutes the first example of a salt of the [M^II(1,3‐pdta)]²⁻ complex (1,3‐pdta is propane‐1,3‐diyldinitrilotetraacetate) with a monopositive cation as counter‐ion. Insertion of the Li⁺ cation could only be achieved through application of the ion‐exchange column technique which, however, appeared unsuccessful with other alkali metals and the ammonium cation. The structure contains two tetrahedrally coordinated Li⁺ cations, an octahedral [Co(1,3‐pdta)]²⁻ anion and five water molecules, two of which are uncoordinated, and is built of two‐dimensional layers extending parallel to the (010) lattice plane, the constituents of which are connected by the coordinate bonds. O—H_water...O hydrogen bonds operate both within and between these layers. The crystal investigated belongs to the enantiomeric space group P2₁ with only one (Λ) of two possible optical isomers of the [Co(1,3‐pdta)]²⁻ complex. A possible cause of enantiomer separation during crystallization might be the rigidification and polarization of the [M(1,3‐pdta)]²⁻ core, resulting from direct coordination of Li⁺ cations to three out of four carboxylate groups constituting the 1,3‐pdta ligand. The structure of (I) differs considerably from those of the other [M^II(1,3‐pdta)]²⁻ complexes, in which the charge compensation is realized by means of divalent hexaaqua complex cations. This finding demonstrates a significant structure‐determining role of the counter‐ions.