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JPC - Journal of Planar Chromatography - Modern TLC
Authors: Emil Mincsovics, Péter Ott, Ágnes Alberti, Andrea Böszörményi, Éva Héthelyi, Éva Szőke, Ágnes Kéry, Éva Lemberkovics, and Ágnes Móricz

Bioassay-guided isolation of antibacterial components of chamomile flower methanol extract was performed by overpressured layer chromatography (OPLC) with on-line detection, fractionation combined with sample clean-up in-situ in the adsorbent bed after off-line sample application. The antibacterial effect of the eluted fractions and of those compounds remaining on the adsorbent layer after separation was tested with direct bioautography (DB) against the bioluminescent Pseudomonas savastanoi pv. maculicola and Vibrio fischeri. The fractions with high biological activity were analyzed by solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) and liquid chromatography and tandem mass spectrometry (LC-MS/MS). Two active uneluted compounds were characterized by off-line OPLC-MS using a thin-layer chromatography (TLC)-MS interface. Mainly, essential oil components, coumarins, flavonoids, phenolic acids, and fatty acids were identified in the active fractions.

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.M. Siouffi , in: E. Tyihák (Ed.) Proc. Int. Symp. TLC with Special Emphasis on Overpressured-layer Chromatography (OPLC), Szeged, Hungary, 1984, Labor MIM, Budapest, 1986, pp. 251–264. Siouffi A

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141 145 E. Mincsovics, E. Tyihák, A.M. Siouffi , in: E. Tyihák (ed.), Proc. Inst. Symp. TLC with Special Emphasis on Overpressured Layer Chromatography (OPLC

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Overpressured layer chromatography (OPLC), ensuring pumpforced constant mobile phase flow and the possibility of overrun, offers the expanded exploitation of fine-particle adsorbent layers for a longer development distance. Using an infusion—transfusion OPLC method with a 26-cm long development, the separation of clove, rosemary, eucalyptus, tea tree, spearmint, thyme, and cinnamon bark essential oil components was achieved with good resolutions. In the combination of OPLC and Aliivibrio fischeri assay, the main essential oil components eugenol, borneol, (−)-R-carvone, thymol, and trans-cinnamaldehyde exhibited antibacterial effect. The OPLC—2,2-diphenyl-1-picrylhydrazyl (DPPH*) test showed two antioxidant components: eugenol and thymol.

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A simple method is described for separation and determination of the isomers of trans -resveratrol and related compounds from different types of red wine by overpressured layer chromatography (OPLC). Comparison of OPLC with TLC clearly showed the advantages of the forced-flow technique (higher theoretical plate number, good resolution, etc.) over conventional planar layer liquid chromatography. It was established that the glycosides of resveratrol isomers were always present in higher concentrations than free stilbene isomers in red wine samples. This was especially true for the Pinot Noir wine. Exploitation of the advantages of OPLC provides further possibilities of analysis and isolation of stilbene isomers from grapes and wine.

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We report a new combination of overpressured-layer chromatography (OPLC) with near-infrared (NIR) spectroscopy for pharmaceutical analysis. Different pharmaceutical preparations containing caffeine, paracetamol, and acetylsalicylic acid as model compounds were separated by OPLC. The band density in the solid phase after OPLC was suitable for study of the separated components directly on the layer by NIR spectroscopy.We have demonstrated the applicability of rapid OPLC separation combined with UV densitometry and NIR spectroscopy for both qualitative and quantitative analysis. This OPLC-UV-NIR technique is thus suitable for rapid, nondestructive investigation of multicomponent pharmaceutical preparations and enables a different type of pharmaceutical analysis, e.g. starting-material tests, in-process control, end-product control, stability testing, etc. Another benefit of this newly developed combination of rapid off-line techniques is the possibility of simultaneous collection of qualitative and quantitative chromatographic and spectral information.

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The paper reviews the latest achievements in chiral separation by planar chromatography (PC) since 2001. The emphasis is on cellulose derivatives and, especially, microcrystalline cellulose triacetate (MCTA). A comparison is made with HPLC data retrieved from Chirbase. It is shown that TLC has some interesting features compared with HPLC. Some enantiomer separations have been successfully achieved by TLC whereas no data are available for HPLC. For tribenzoyl cellulose derivatives general trends for resolution by both TLC and HPLC are discussed. The last part of the paper discusses reasons for the scarcity of publications on chiral separations by either PC or overpressured layer chromatography (OPLC). The possibilities of PC for chiral separations are rather unexploited.

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Quantification of carbohydrates and metabolites in fermentation processes can be considered as key factor in determining yield and productivity for a better understanding of the microbial behavior under different conditions. The main aim of the present study was to develop and set up analytical methods for detecting complex sugar and/or metabolite mixtures in fermentation broth based on high-performance thin-layer chromatography (HPTLC). HPTLC is a fast and accurate method of separating complex mixtures, based on planar development. The proposed methods involved the separations of a mixture of monosaccharides (glucose, xylose, arabinose, and rhamnose) deriving from delignification and hydrolysis of hazelnut shells and the corresponding sugar alcohols (xylitol, arabitol, and sorbitol) obtained by fermentations of Candida tropicalis spp., a yeast able to ferment aldoses to produce sugar alcohols. HPTLC methods were set up on simple chamber development and using instrumental techniques like overpressured layer chromatography (OPLC). This approach has enabled the simultaneous monitoring of several samples with significant time and money savings. Different multicomponent broths at different times of fermentation were analyzed.

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JPC - Journal of Planar Chromatography - Modern TLC
Authors: Ágnes Móricz, Györgyi Horváth, Péter Molnár, Béla Kocsis, Andrea Böszörményi, Éva Lemberkovics, and Péter Ott

The composition of the essential oil of Thymus vulgaris L. has been determined by GC-FID and GC-MS. Because separation of thymol, carvacrol, and linalool, components of the essential oil, was more efficient by overpressured layer chromatography (OPLC) than by conventional thin-layer chromatography (TLC), the forced flow technique was used before biological detection. All three test compounds had antibacterial effect against the phytopathogenic bacterium Pseudomonas syringae pv. maculicola, in bioautography, although in essential oil thymol was present in sufficient quantity to produce an inhibiting zone in the adsorbent layer. In BioArena investigations, when reduced glutathione as a formaldehyde (HCHO) capturer was dissolved in the cell suspension before bioautographic exposure to the essential oil, the characteristic inhibiting activity of thymol and carvacrol against Bacillus subtilis soil bacteria was reduced, whereas the presence of the HCHO precursors NGmonomethyl-l-arginine or N ɛ-monomethyl-l-lysine enhanced their antibacterial effect. These results suggest that HCHO and its reaction products may be involved in the antibacterial activity of thymol and carvacrol.

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Optimum-performance laminar chromatography (previously known as overpressured-layer chromatography; OPLC) exploits the advantages of the optimum laminar flow of mobile phase obtained by use of pump to introduce the mobile phase to the adsorbent layer in an automated, microprocessor-controlled separation system. The optimized flow profile in OPLC is the basis of the efficiency of this new technique. The attractiveness of OPLC is particularly apparent from the width of the separation surface (large number of samples). OPLC has enabled improvement of the velocity profile with a decrease in eddy diffusion.OPLC can be used for efficient separation of formaldehyde (HCHO) and some betaines, potential HCHO generators, in macroscopic fungi. Endogenous HCHO is determined, after conversion to formaldemethone, and characterized from proton magnetic resonance spectroscopic ( 1 H NMR) and electron-impact mass spectrometric (EIMS) data. The results show that macroscopic fungi contain moderate levels of HCHO compared with, for example, the leaves of certain higher plant species. Among the betaines, l-carnitine and glycinebetaine were identified by matrix-assisted laser-desorption ionization mass spectrometry (MALDI MS), 1 H NMR spectroscopy, and OPLC. Data prove that automated OPLC, a new separation technique, is suitable for efficient separation of natural substances from a large number of samples in one separation; it is, therefore, a prospective complementary methodological direction among separation techniques.

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