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1

Research on stability of gomphrenin pigments influenced by Cu2+ ions

Szmyr N., Wybraniec S.

Challenges of Modern Technology

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2017

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Vol. 8, no. 1

13--18

EN

This paper concerns the results of dehydrogenation of gomphrenin pigments isolated from the purple flowers of Gomphrena globosa L. depending on pH and Cu2+ activity. Betalains are the plant dyes divided into red-violet betacyanins and yellow-orange betaxanthins. These compounds show prohealth properties proven by numerous studies [1]. Isolation of gomphrenins from the plant material was performed in the following stages: preparative extraction, filtration on a silica layer, preliminary purification and concentration on a bed of strong anion exchanger, preparative chromatographic fractionation and sample liofilization. The dehydrogenation studies of gomphrenin I and II were carried out in aqueous solutions (pH 3, 5 and 7) catalyzed by Cu2+ ions addition. The resulting product mixtures of dehydrogenated and decarboxylated gomphrenin derivatives were monitored by high-performance liquid chromatography with diode-array and mass spectrometric detection (LC-DAD-ESI-MS). Based on the results, it can be stated that decarboxylated and dehydrogenated gomphrenin II derivatives are more stable than gomphrenin I derivatives, presumably due to acylation of the glucose moiety. The highest levels of gomphrenin I derivatives were observed at pH 7, however, they were mainly monodecarboxylated ones. At pH 3, significant fraction was represented by tridecarboxylated and dehydrogenated derivatives. The lowest yield of the degradation products was indicated at pH 5.

2

Research on dehydrogenation of gomphrenin in heated ammonia solutions of organic solvents

Szmyr N., Wybraniec S.

Challenges of Modern Technology

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2017

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Vol. 8, no. 1

8--12

EN

In this report, the influence of ammonia on dehydrogenation of gomphrenin pigment, isolated from purple inflorescences of Gomphrena globosa L., in selected organic solvents (methanol, ethanol, acetone and acetonitrile) at 40°C is presented. Betacyanins are water-soluble, vacuolar plant pigments. Due to their numerous pro-health properties, they can be applied in the pharmaceutical industry and as food colorants. However, as most of natural products, they are less stable than synthetic dyes, therefore, further studies need to be carried out on their stability, but also on determination of their degradation products as well as degradation mechanisms. For the experiments of the ammonia treatment, prolonged isolation of gomphrenin from the plant material including extraction, preliminary purification, preparative HPLC fractionation, concentration and liofilization were performed. The tested pigment dissolved in organic solvents was treated by ammonia and the samples for analysis were taken during and after reaction. For identification of obtained derivatives of gomphrenin, high-performance liquid chromatography with diode-array and mass spectrometric detection (LC-DAD-ESI-MS) was performed. As a result of heat processing, the mixture of decarboxylated and dehydrogenated gomphrenin derivatives was detected. Based on the experimental results, it can be stated that gomphrenin is characterized by the greatest stability in methanolic solutions while it is the most labile in the acetonitrilic ones.

3

Influence of EDTA on stabilization of decarboxylated betalains

Skopińska A., Starzak K., Wybraniec S.

Challenges of Modern Technology

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2012

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Vol. 3, no. 4

29--33

EN

Betalains are known to be very sensitive to several factors, including higher temperature, therefore, the studies on their stability are essential for the food industry. In order to determine the stability of betanin derivatives during thermal treatment, a set of degradation experiments was performed, including the protective infl uence of EDTA as a chelating agent. The pigments were dissolved in aqueous solutions of acetonitrile, methanol and ethanol. The studies on thermal degradation of the pigments confi rmed their high lability in all investigated solvents. Under the infl uence of protective activity of EDTA, the rate of the degradation of the decarboxylated betalains was substantially decreased. The analysis of obtained absorption spectra of the degradation products indicated that under the infl uence of EDTA, the products retained the basic chromophoric skeleton.

4

Carbon-13 isotope effect for decarboxylation of phenylpropiolic acid (PPA) in orthophosphoric acid

Zielińska A., Zieliński M., Zielińska-Papiernik H.

Nukleonika

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1999

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Vol. 44, nr 3

403-410

EN

The carbon-13 isotope effect accompanying decarboxylation of phenylpropiolic acid in 85% orthophosphoric acid has been studied in the temperature range 323-353 K. The first fraction of CO2 was found to be generated at 323 K in 85% H3PO4 with the carbon-13 isotope effect, k[indeks dolny]12/k[indeks dolny]13, equal to 1.011-1.015. The subsequent fractions of carbon dioxide produced in the temperature range 323-353 K have shown none but about 0.2% per cent kinetic isotope effect (KIE). It has been suggested that the initial larger carbon-13 fractionation, accompanying the decarboxylation of PPA in 85% orthophosphoric acid, is caused by isotopic equilibra linking decarboxylating monomeric species of PPA with dimeric and larger units formed during solvation and dissolving of solid PPA in orthophosphoric acid. The solvated PPA molecules are decarboxylated in the homogeneous solution with a negligible carbon-13 KIE. The triple bond of phenylpropiolic acid is attacked by the hydrated protons, H3O⊕aq, and formation of the Calpha-H bond is the rate determining step. The bond rupture between the alpha carbon and the carboxyl group is the next fast reaction step. The enthalpy of activation, ΔH[indeks górny]≠ = 123.4 kJ/mol, and the positive entropy of activation, ΔS≠ = +30 e.u.(SI), exclude the chelate like structure of the transition state. This suggests a flexible structure of the transition state complex which must be less solvated than in the initial state. Some further studies of the carbon-13 KIEs in phosphoric acid environment are suggested.

PL

Zbadano efekt izotopowy 13C w reakcji dekarboksylacji kwasu fenylopropiolowego (PPA) w 85% H3PO4 w 323-373 K. Delta (PDB) pierwszej porcji dwutlenku węgla, przy stopniach dekarboksylacji około f= 0.1, wskazuje na jej początkowe wzbogacenie w 13C o około 1,0-1,5%. Spowodowane jest to prawdopodobnie procesami równowagowymi, zachodzącymi między ulegającymi dekarboksylacji monomerami PPA a większymi agregatami, powstającymi w wyniku oddziaływania kryształów PPA z uwodnionymi cząsteczkami kwasu ortofosforowego. Dalsza dekarboksylacja PPA przebiega w roztworze homogenicznym bez wyraźnego rozfrakcjonowania izotopów węgla. Przyłączenie protonów do wiązania potrójnego i tworzenie wiązania Calfa-H zachodzi w etapie krytycznym reakcji, poprzedzającym właściwą dekarboksylację, tj. utratę cząsteczki dwutlenku węgla przez kwas fenylopropiolowy. Entalpia aktywacji ΔH[indeks górny]≠ = 123,4 kJ/mol i dodatnia entropia aktywacji ΔS[indeks górny]≠ = +30 e.u.(SI) sugerują niecykliczny, swobodny, stan przejściowy kompleksów reakcji dekarboksylacji PPA w 85% kwasie ortofosforowym. Zaproponowano dalsze badania efektu izotopowego 13C w środowisku kwasów fosforowych.

5

Reaction of benzo[h]naphthyridine N-oxides with phenyl isocyanate

Bachowska B., Zujewska T.

Polish Journal of Chemistry

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1998

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Vol. 72, nr 1

89-92

EN

Benzo[h]naphthyridine N-oxides reacted with phenyl isocyanate in dimethylformamide to give carbamic acid derivative at room temperature or anilino derivatives at 150 degree C. The process proceeded via 1,3-dipolar cycloaddition followed by aromatization with N-O bond cleavage and loss of CO2 at higher temperature.

6

(13)C kinetic isotope effects in the decarboxylation of phenylpropiolic acid (PPA) assisted with formic acid and (13)C KIE in the decarbonylation of formic acid in the presence of PPA

Zieliński M., Zielińska A., Paul H., Papiernik-Zielińska H.

Polish Journal of Chemistry

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1998

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Vol. 72, nr 12

2551-2555

EN

Carbon-13 kinetic isotope effects, (13)C-KIE, in the decarboxylation of phenylpropiolic acid (carboxyl C-13) in formic acid medium and (13)C KIE in the decarbonylation of liquid formic acid assisted with PPA and acetophenone have been studied in the 70-100 degree C temperature interval. The kinetic and isotope results have been discussed and interpreted as indicating that the formation of C alpha-H bond, preceded by the protonation of acetylenic bond of PPA, is the rate determining step followed by carbon dioxide splitting. The (13)CO-KIE in the carbon monoxide generation assisted with PPA is much larger than the (13)CO-KIE observed in the generation of CO in the presence of phenylacetylene. Thus the decaeboxylation of PPA and decarbonylation of formic acid are interrelated processes proceeding in the reaction cage.