Wiesław Prukała

Spectroscopy and photophysics of flavin-related compounds: 3-benzyl-lumiflavin.

Molecular structure, spectroscopic and photophysical data for the singlet state of 3-benzyl-lumiflavin in different solvents are presented. Theoretical studies concerning singlet–singlet and triplet–triplet excitation energies were carried out using time-dependent density functional theory (TD-DFT) calculations. These predictions are in good agreement with the experimental results, which reflect the solvent interactions. All the observable singlet–singlet transitions have π–π* character. The title compound appears to be an efficient sensitizer of the production of singlet oxygen (ϕΔ = 0.53). The crystal structure of 3-benzyl-lumiflavin is also presented, along with its solid-state photophysical data.

COX-2 inhibitors: a novel strategy in the management of breast cancer.

Cyclooxygenase-2 (COX-2) inhibitors are common anti-inflammatory drugs with pleiotropic, endogenous actions that could be useful in the management of breast cancer. Here, we provide a complete understanding of the biochemistry of COX-2 and discuss the various molecular mechanisms behind its increased expression in breast cancer. We also analyze the possible mechanisms responsible for the anticancer effect of COX-2 inhibitors and provide an overview of the available preclinical and clinical data on the use of COX-2 inhibitors in breast cancer. Finally, we describe a mathematical model of the relation between the structure and biological potency of promising new COX-2 inhibitors (trans-stilbenes) using a 2D quantitative structure-activity relationship (QSAR) technique.

Two-dimensional spectral–spatial EPR imaging with the rapid scan and modulated magnetic field gradient

A new method for fast spectral-spatial electron paramagnetic resonance imaging (EPRI) is presented. To reduce the time of projections acquisition we propose to combine rapid scan of Zeeman magnetic field using high frequency sinusoidal modulation with simultaneously applied magnetic field gradients, whose amplitude is modulated at low frequency. The correctness of the method is confirmed by studies carried out on a phantom consisting of two LiPc samples. The spectral-spatial images from the acquired data are reconstructed using iterative algorithms. The proposed method allows to acquire the spectral-spatial image with 800 projections at 200ms.

Isotachophoresis of Chosen Biologically Active (E)-Azastilbenes

Abstract Biological activity of (E)-azastilbenes and their numerous derivatives appears in antimicrobial and anticancer effects. They also show the behavior of liquid crystals and the ability of formation of complex compounds. In this work are presented the conditions of optimum separation and determination of chosen isomers of (E)-azastilbenes by the isotachophoretic method. In the process of optimization, the length of steps of analysis, intensity (it was justified by the fact of dependence of ion mobility on electric field intensity), and pH of solutions of electrolytes and samples were changed. A new terminating electrolyte was used for the determinations. By a process of trial and error it was proven that optimum pH for analyzed isomers are 3.8. The shortest time of analysis was obtained for individual isomers. However, for mixtures of isomers the optimum time of analysis was twice as long.

Separation of Biologically Active Isomers of (E)‐N‐Meta‐ and Para‐Nitroazastilbenes by the HPLC Technique

Abstract Results of investigations concerning the chromatography of bromides of (E)‐N‐m‐ and p‐nitrobenzyl‐4′‐hydroxy‐3′‐methoxystilbazoles‐4 are presented. Analyzed compounds, similarly to other azastilbene halogenides show antimicrobial activity. Optimal conditions of chromatographic separation and determination of two mentioned isomers have been elaborated. In the investigation three stationary phases (octadecyl, octyl, and naphthylpropyl), two mobile phases (acetonitrile, dichloromethane) and various flow were considered. The best selectivity and the highest separation factor, α=1.74, were obtained using a naphthylpropyl column and 100% acetonitrile, as the mobile phase. An application of an octadecyl phase, recommended by numerous analysts as standard, allowed only the observation of an existence of two compounds, but did not yield satisfactory results.

Electron ionisation and electrospray ionisation mass spectrometric study of a series of isomeric methyl-, dimethyl- and trimethylalloxazines

Electron ionisation (EI) mass spectra and electrospray ionisation (ESI) mass spectra at different cone voltages of a series of isomeric methyl- and dimethylalloxazines are discussed, and compared with those of lumichrome, and 1- and 3-methyllumichrome. Examination of ESI mass spectra taken at a higher cone voltage and the use of isotope-labelled methanol allow us to discuss the fragmentation pathways of [M+H]+ and [M-H](-) ions. The fragmentation pathways of all of the compounds and the characteristic fragment ions formed in EI-MS are compared with published data. The influence of methyl and dimethyl substituents in the benzene ring on the fragmentation pathways leading to the loss of 43 and 45 Da upon both electron and electrospray ionisation is described.

New Generation Terminating Electrolyte for Electrophoretic Analysis of Ionic Substances

This work presents results of research into the usage of a representative of new generation terminating electrolytes in electrophoretic techniques and a newly developed methodology of separation and determination of selected biologically active (E)-azastilbene derivatives as test substances. The terminating electrolyte used was 4,4′-bis{1-(N-perhydro-azepiniomethyl)[spirobi(1-sila-2,5-dioxacyclopentane-3-on)]ate}. Moreover, the literature pertaining to the usage possibilities of the aforementioned electrolyte was reviewed. The development of this terminating solution enables determination within a much wider pH range (3–12) of both cations and anions without the need to change the electrolyte and significantly broadens the existing research possibilities.

NEW METHODOLOGY OF SEPARATION AND DETERMINATION OF BIOLOGICALLY ACTIVE ISOMERS OF NITROBENZYL AZASTILBENE DERIVATIVES

Drivatives of hydroxystilbazole show biological activity in form of antimicrobial and anticancer effect. In this paper are presented optimum conditions of separation and determination of two isomers, derivatives of hydroxystilbazole by a technique of isotachophoresis. Chloride of (E)-N-(o-nitrobenzyl)-4′-hydroxystilbazole-4 and chloride of (E)-N-(o-nitrobenzyl)-2′-hydroxystilbazole-4 were subjected to an optimization process. Lengths of analysis steps, electric current intensity and pH of electrolyte solutions and samples were changed during the optimization of conditions. The shortest time of analysis (at about 170 seconds) was obtained during determination of individual isomers. However, in case of mixtures, the time of analysis was lengthened two-fold. It was proved by a process of trial and error that optimum pH for analyzed isomers is 3.7. Linearity of determination of mentioned isomers is between 2 and 35 mg mL−1.

Chromatography of Biologically Active Chlorides of (E)-N-o-(m- or p-)chlorobenzyl-γ-azastilbenols-2′(3′ or 4′)

Abstract results of investigations concerning optimization of chromatographic separation and determination of (E)-N-o-(m- or p-)chlorobenzyl-γ-azastilbenols-2′(3′ or 4′) are presented. Analyzed isomers show antimicrobial activity. In the investigation, were considered three stationary phases (octadecyl, octyl, and naphthylpropyl), two mobile phases (acetonitrile, dichloromethane), and various intensities of flow. The best selectivity (α1 = 1.34, α2 = 1.47) was obtained using naphthylpropyl column and 100% acetonitrile, as the mobile phase. An application of octadecyl phase, recommended by numerous analysts as standard, did not yield satisfactory results.

Three 9-[(E)-2-(4-halogenophenyl)vinyl]-9H-carbazoles

The crystal structures of 9-[(E)-2-(4-fluorophenyl)vinyl]-9H-carbazole, C20H14FN, (I), 9-[(E)-2-(4-chlorophenyl)vinyl]-9H-carbazole, C20H14ClN, (II), and 9-[(E)-2-(4-bromophenyl)vinyl]-9H-carbazole, C20H14BrN, (III), are determined mainly by van der Waals forces. The chloro and bromo derivatives are highly isomorphous, while the fluoro derivative has a different packing mode. Weak C-H...X interactions are also involved in the crystal packing. The molecular structures of the three compounds are similar, with relatively large twist angles of ca 55 degrees between the carbazole and benzene planes.