Krzysztof Pypowski

A series of 3,4-dihydroisoquinoline-3-carboxylic acid derivatives were synthesised and tested for their free-radical scavenging activity using 2,2-diphenyl-1-picrylhydrazyl radical (DPPH^·), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical (ABTS^·+), superoxide anion radical (O₂^·−) and nitric oxide radical (^·NO) assays. We also studied D-amino acid oxidase (DAAO), acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) inhibitory activity. Almost each of newly synthesised compounds exhibited radical scavenging capabilities. Moreover, several compounds showed moderate inhibitory activities against DAAO, AChE and BuChE. Compounds with significant free-radical scavenging activity may be potential candidates for therapeutics used in oxidative-stress-related diseases.

In the paper are presented results of investigations concerning modification of silica gel by mono-, di-, and tribenzylgermanium during a chromatographic process. These compounds exhibit biological activity and are characterized by low toxicity. Germanium compounds are widely applied in oncological therapy. The investigations unambiguously show that the above mentioned derivatives can modify silica gel surface. These results have been confirmed by FTIR, ¹³ C CP/MAS NMR, ²⁹ Si CP/MAS NMR and scanning microscopy. The strongest bonds are formed by monobenzyl derivative, slightly weaker bonds are formed by dibenzyl and the weakest bonds (because of sterically large group) formed by tribenzyl derivative. The mass ratio of germanium to silica after modification was monobenzyl derivative, for 15.02%, 11.05%, for dibenzyl and 7.10% for tribenzyl.

The paper presents interactions of mono-, di-, tri-, and tetrabenzyl derivatives of germanium with stationary phase surface and results from these processes of determination. As a final result of the work, optimal conditions of chromatographic separation and determination of these compounds by high-performance liquid chromatography (HPLC) method are proposed. During investigations, different types of stationary phase (including octadecyl, octyl, and chemically bonded aryl phases) and mobile phases are considered. As a result of the investigation, the highest selectivity is showed chemically by bonded aryl stationary phase combined with a mobile phase consisting of acetonitrile (capacity factors of di-, tri-, and tetrabenzyl derivatives of germanium k₁ = 0.86, k₂ = 2.53, k₃ = 6.45). However, octadecyl phase, which is considered as reference phase, exhibits the lowest separation factors of determined benzylgermanium compounds (k₁ = 9.12, k₂ = 37.62, k₃ = 70.43).

Results of investigations regarding the difficulties of benzylgermanium determination by high performance liquid chromatography using standard octadecyl stationary phases have been substantiated on the molecular level. The analyzed organogermanium compounds are biologically active and some are used in oncology. Investigations showed modifications of the octadecyl stationary phase caused by the above-mentioned derivatives. These modifications have been confirmed by infrared spectroscopy with Fourier transform (FTIR), ¹³C CP/MAS Nuclear Magnetic Resonance techniques (NMR), ²⁹Si CP/MAS NMR, and scanning microscopy. The strongest bonds are formed by benzyltrichlorogermanium but the tribenzyl derivative with a sterically large group and the long, 18-carbon chains, is bound only weakly. It also interacts to the smallest extent with residual silanols of the octadecyl phase. Mass ratio germanium to silica calculated on the base of scanning display after modification was 12.63% for monobenzyl derivative, 12.49%, for dibenzyl, and 5.6% for tribenzyl.

In the course of our work we have carried out an optimization of conditions for the separation and determination of selected derivatives belonging to the group of Goshchava-Silanates by a capillary isotachophoresis technique. Analyzed heptacoordinated compounds show biological activity. In the investigations, we considered homo{O,O′,O″,O′′′-oxalic acids Si-[N-benzylaminiomethyl]-Si,Si-dihydroxysilanate} and homo{O,O′,O″,O′′′-oxalic acids Si-[N-benzylaminiomethyl]-Si,Si-diethoxysilanate}. A new terminating electrolyte was proposed for determination of these compounds in a form of aqueous solution of 4,4′-bis{1-[(N,N-dimethyl) aminiomethyl]spirobi(1-sila-2,5-dioxacyclopentan-3-on)at}. Optimum time of analysis did not exceed 9 minutes. The newly elaborated method allows for wider research of biological activity of the analyzed compounds and increases the possibilities of their applications. Until now, information concerning the use of above mentioned technique for heptacoordinated organosilanates has not been published.

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.

Optimal conditions of separation and determination of two newly obtained higher coordinated silanates of the group λ⁵ have been performed. The optimization concerned 1-(N-perhydroazepiniomethyl)[spirobi(1-sila-2,5-dioxacyclopentane-3-on)]ate and 1-(N-perhydroazepiniomethyl)[spirobi(1-sila-2,5-dioxa-4,4-dimethyl-cyclopentane-3-on)]ate. Due to low mobility of analyzed ions, elaboration of a new termination electrolyte was necessary. As a main component of this electrolyte, a newly synthesized compound – 4,4′-bis{1-(N-perhydroazepiniomethyl)[spirobi(1-sila-2,5-dioxacyclopentane-3-on)]ate} was used. Separation of analyzed compounds was carried out in a time under 11 minutes. Optimal separation of the analyzed mixture was obtained in five steps under 12000 V voltage with preseparation and analytical columns applications. Voltage decreasing below 10000 V caused a decrease in the difference of analyzed ions mobility.