Teresa Kowalska

Thin layer chromatography in phytochemistry

Thin layer chromatography in phytochemistry , Thin layer chromatography in phytochemistry , کتابخانه دیجیتال جندی شاپور اهواز

Influence of putrescine, cadaverine, spermidine or spermine on the formation of N-nitrosamine in heated cured pork meat

The influence of biogenic amines (i.e. putrescine, cadaverine, spermidine and spermine) on the N-nitrosamine formation in heated cured lean meat was studied in the presence or absence of sodium nitrite and at different meat processing temperatures. Experimental evidence was produced using gas chromatography with thermal energy analysis detection (GC-TEA). Concentration of N-nitrosamines was modelled as a function of the temperature and the nitrite concentration for two situations, i.e. presence or absence of added biogenic amines to the meat. The significance of the influence of the changing parameters was evaluated by ANOVA (Analysis of Variance). It was found that higher processing temperatures and higher added amounts of sodium nitrite increase the yields of N-nitrosodimethylamine (NDMA) and N-nitrosopiperidine (NPIP). Spermidine and putrescine amplify the formation of NDMA, but spermine and cadeverine do not influence the formation of this N-nitrosamine. Spermidine and cadeverine cause a significant increase of NPIP. Beside N-nitrosopyrrolidine (NPYR) in some rare cases, no other volatile N-nitrosamines are detected.

Experimental and Model Investigation of the Oscillatory Transenantiomerization of L-α-Phenylalanine

Abstract In an earlier study, we obtained experimental evidence of the oscillatory transenantiomerization of selected profen drugs (e.g., S-(+)-ibuprofen, S-(+)-naproxen, and S-(+) and R-(−)-flurbiprofen) dissolved in aqueous, aqueous-organic, and purely organic liquid media. This process was apparently catalyzed by basic or amphiprotic environments and involved keto-enol tautomerism, and the self-organization of molecules in the solution via association of the carboxylic functional group of profens through hydrogen bonding to form mixed H-bonded associates with the remaining constituents of the solution. A model of the oscillatory transenantiomerization of profens was also developed by adapting an earlier oscillatory model, the Templator. Our new model comprises two linked Templators. The essence of the Templator model adapted to the oscillatory transenantiomerization of profens is the assumption that the H-bonded profen homodimer acts as a template, able to generate new dimers having the same steric configuration as their respective monomeric units. As profens belong to the class of 2-arylpropionic acids (2-APAs), we concluded that the phenomenon of oscillatory transenantiomerization may occur in other 2-APAs as well, among them those amino acids whose molecular structure can formally be derived from propionic acid. Thus, in this study, we focus our attention on L-α-phenylalanine (LPA; one of the nine amino acids essential for humans). Using thin layer chromatography (TLC) and polarimetry, we demonstrate the ability of LPA to undergo oscillatory transenantiomerization analogous to that observed with profens. The self-organization of molecules in a 70% ethanol solution of LPA is confirmed with photographs taken in UV light (λ = 254 nm). Finally, we propose a skeleton molecular mechanism for the transenantiomerization of LPA and simulate the oscillatory interconversion of its L and D forms with two linked Templators.

Preparative layer chromatography

SECTION I Introduction Teresa Kowalska and Joseph Sherma Adsorption Planar Chromatography in the Nonlinear Range: Selected Drawbacks and Selected Guidelines Krzysztof Kaczmarski, Wojciech Prus please connect the names of all the authorsMieczyslaw Sajewicz, and Teresa Kowalska Sorbents and Precoated Layers in PLC Heinz E. Hauck and Michael Schulz Selection and Optimization of the Mobile Phase for PLC Virginia Coman Sample Application and Chromatogram Development Gertrud E. Morlock On Methodical Possibilities of the Horizontal Chambers in PLC Tadeusz H. Dzido and Beata Polak Location of Separated Zones by Use of Visualization Reagents, UV Absorbance on Layers Containing a Fluorescent Indicator, and Densitometry Bernd Spangenberg Additional Detection Methods and Removal of Zones from the Layer Joseph Sherma SECTION II Medical Applications of PLC Jan Bladek , and Anna Szymanczyk PLC of Hydrophilic Vitamins Fumio Watanabe and Emi Miyamoto Preparative Layer Chromatography of Natural Mixtures Monika Waksmundzka-Hajnos, Teresa Wawrzynowicz, Michal L. Hajnos, and Grzegorz Jozwiak Application of Preparative Layer Chromatography to Lipids Weerasinghe M. Indrasena The Use of PLC for Separation of Natural Pigments George W. Francis Application of PLC to Inorganics and Organometallics Ali Mohammad PLC in a Cleanup and Group Fractionation of Geochemical Samples: A Review of Commonly Applied Techniques Monika J. Fabianska The Use of PLC for Isolation and Identification of Unknown Compounds from the Frankincense Resin (Olibanum): Strategies for Finding Marker Substances Angelika Koch, Rita Richter, and Simla Basar Index

Thermodynamic properties of alkylbenzenes from retention-boiling point correlations in gas chromatography

SummaryA thermodynamic interpretation of the empirical correlation between retention and boiling point for alkylbenzenes in stationary phases of low and medium polarity has been found. The transfer of molecules between the liquid and mobile phases was assumed to be similar to, although not identical with, vaporization of any given pure liquid and characterized using the Troutons rule.The two equations developed relate relative retentions to solute boiling point and two systems constants under a given set of conditions. The first equation was found to give a better description since it involves fewer assumptions and approximations.Validity of the model was confirmed by agreement between theoretical and experimental values for equation constants although the agreement becomes poorer as the stationary phase polarity increases. The relationships discussed are applicable to all congeneric solutes of low polarity in stationary phases of medium polarity.

Role of proline and hydroxyproline in N-nitrosamine formation during heating in cured meat.

N-Nitrosamines are formed in a multi-step reaction of nitrite with free amino acids and amines in the meat products. The aim of this study was to determine the role of proline and hydroxyproline in N-nitrosamines formation during heating of cured meat. A lean meat model was used with different nitrite concentrations (0, 120, and 480mg/kg), and addition of proline and hydroxyproline (1000mg/kg), followed by heating at different temperatures. Volatile nitrosamines were analyzed with GC-TEA. The nitrosamine content never exceeded 10μg/kg and stayed <LOQ as long as the nitrite level of 120mg/kg was not surpassed. The importance of proline as a precursor for N-nitrosamine formation was confirmed. In contrast, hydroxyproline inhibited NPYR formation (N-nitrosopyrrolidine) because no traces were found after addition of hydroxyproline. NPYR formation was not related to nitrite, but was significantly influenced by temperature (⩾200°C) and proline. NDMA-presence (N-nitrosodimethylamine) in heated meat products was influenced by nitrite and temperatures >120°C.

Quantitative structure-retention relationships VI. Thermodynamics of Kovats retention index-boiling point correlations for alkylbenzenes in gas chromatography

Abstract Empirical equations known from literature have been interpreted thermodynamically and their performance was checked for alkylbenzenes and for stationary phases of low and medium polarity. These equations relate Kovats retention index ( I ) and boiling point ( T B ) in a linear and a reciprocal way: { I = AT B + B and I = C / T B + D }. It was possible to attribute the proper physical meaning to the equation constants: A , B , C , and D with the help of some assumptions [i.e., (i) Troutons rule; (ii) the transfer of molecules between the liquid and mobile phases was assumed to be similar to, although not identical with, vaporization of any given pure liquid]. The thermodynamic meaning of the equation constants involves the average heat of vaporization for the congener set of solutes ( Δ H vap ) , the standard chemical potential of partitioning of one methylene group of n -alkane (Δ μ p(–CH 2 –) ), the Troutons constant (85 J mol −1 K −1 ), and the column temperature ( T ). By using the residual analysis we have found a considerable curvature in the residual plots, both for the linear and the reciprocal model. Despite of the small bias present in the parameters the validity of this thermodynamic model of solute retention was confirmed by a reasonably good agreement between the theoretical and the experimental values for the equation constants. Beside attributing a physical meaning to the Kovats retention index–boiling point correlations, the other descriptive equations were further developed. A statistical analysis has been made to compare the description by all models discussed. High correlation coefficients, values of Fischers statistic and acceptable residual error indicate the goodness of fit. The quadratic model provides the best description, whereas the linear equation is better than the reciprocal. The relationships discussed are applicable to all congener solutes of low or medium polarity analyzed on stationary phases of low or moderate polarity, and the Troutons rule is applicable to all the enumerated cases.

Development of chromatographic and free radical scavenging activity fingerprints by thin-layer chromatography for selected Salvia species.

INTRODUCTION Plant-derived free radical scavengers have become the subject of intensive scientific interest. Recently, the concept of coupling chromatographic fingerprints with biological fingerprinting analysis has gained much attention for the quality control of plant extracts. However, identification of free radical scavenging activity of each single compound in a complex mixture is a difficult task. Thin-layer chromatography with post-chromatographic derivatisation with the methanol solution of DPPH can be a valuable tool in such analyses. OBJECTIVE Development of chromatographic and free radical scavenging fingerprints of nineteen Salvia species grown and cultivated in Poland. METHODOLOGY Chromatography was performed on the silica gel layers with use of two eluents, one for the resolution of the less polar compounds, and the other one for the resolution of the medium and highly polar ones. The plates were sprayed with the vanillin-sulfuric acid reagent to produce chemical fingerprints, and with DPPH solution to generate free radical scavenging fingerprints. RESULTS With four Salvia species, it was revealed that their strong free radical scavenging properties are not only due to the presence of polar flavonoids and phenolic acids, but also due to the presence of several free radical scavengers in the less polar fraction. Because of the similarities in both the chromatographic and the free radical scavenging fingerprints, S. triloba can be introduced as a possible equivalent of the pharmacopoeial species, S. officinalis. CONCLUSION Fingerprints developed in the experiments proved useful for the analysis of complex extracts of the different Salvia species.

Evaluation of the influence of proline, hydroxyproline or pyrrolidine in the presence of sodium nitrite on N-nitrosamine formation when heating cured meat.

N-nitrosamines are meant to be probable or possible carcinogenic components, possibly formed out of a reaction between nitrite and N-containing substances such as amino acids and secondary amines. Nitrite is often used for processing meat products because of its colouring and antimicrobial properties. During this experimental setup, the influence of proline, hydroxyproline or pyrrolidine on N-nitrosamine formation in meat samples was evaluated. The N-nitrosamines concentrations were measured with gas chromatography-thermal energy analyzer. Only the concentrations of N-nitrosodimethylamine and N-nitrosopyrrolidine were found above the limit of detection in a number of tested experimental conditions. The concentration of these two N-nitrosamines was modelled as a function of temperature and nitrite concentration for different situations (presence or absence of added natural N-containing meat components). It could be concluded that proline and pyrrolidine promoted the formation of N-nitrosopyrrolidine. It could also be confirmed that the higher the temperature of the meat processing procedure and the higher the sodium nitrite amounts added, the higher were the yields of the respective N-nitrosamines.

TLC-MS VERSUS TLC-LC-MS FINGERPRINTS OF HERBAL EXTRACTS. PART II. PHENOLIC ACIDS AND FLAVONOIDS

In the previous paper from this series, we proposed mass spectrometric fingerprinting of a complex and volatile botanical sample upon an example of the essential oil derived from Salvia lavandulifolia. In that paper, we compared two variants of fractionation of such a mixture. A simpler one-dimensional variant consisted of the low-temperature thin-layer chromatographic fractionation coupled with mass spectrometric fingerprinting of each separated fraction (1D LT TLC-MS). A more sophisticated variant was the two-dimensional liquid chromatographic system composed of the low-temperature thin-layer chromatography, high-performance liquid chromatography, and mass spectrometric detection (2D LT TLC-LC-MS). In this study, we present an analogous approach to the non-volatile botanical mixtures upon an example of the pharmacologically important phenolic acids and flavonoids selectively extracted from Salvia lavandulifolia. With these non-volatile fractions, the thin-layer chromatographic separations were carried out at ambient temperature (21 ± 0.5°C). Once again, we compared two variants of fractionation. A simpler one-dimensional variant consisted of the thin-layer chromatographic mode coupled with mass spectrometric fingerprinting of each separated fraction (1D TLC-MS). A more sophisticated variant was the two-dimensional liquid chromatographic system composed of the thin-layer chromatography and high-performance liquid chromatography, with mass spectrometric detection (2D TLC-LC-MS). As expected, the two-dimensional mode proved better performing than the one-dimensional mode (1D TLC-MS). It was concluded that thin-layer chromatography directly or indirectly coupled with mass spectrometric detection can prove very useful in the analysis of the phenolic acid and flavonoid fraction selectively extracted from botanical material.