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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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E. Tyihák , Overpressured Layer Chromatography. In: J. Sherma and B. Fried (Eds) Handbook of Thin-Layer Chromatography, Marcel Dekker, New York, 1996, Chapter 7, pp. 171–203. Tyihák E

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The retention factor in pure water, log k w , is proposed as a measure of the hydrophobicity of s -triazine derivatives. In these studies two reversed-phase techniques, thin-layer chromatography (TLC) and overpressured-layer chromatography (OPLC), were used. The effects of the chromatographic system, i.e. mobile and stationary phase properties, on log k w were analyzed to select the best system for determination of the hydrophobicity of the compounds. In TLC the chemically bonded phases RP-18 and RP-CN were used as stationary phases and acetone, acetonitrile, tetrahydrofuran, and dioxane as organic modifiers of the mobile phases. In OPLC RP-8 and RP-18 stationary phases and water-acetonitrile mobile phases were used. The values of log k w , determined by linear extrapolation and by the new method based on Ościk’s equation, were compared with log P values calculated by different theoretical methods. In TLC the best linear correlations between log P and log k w were observed for water-dioxane as mobile phase on both RP-18 and RP-CN stationary phases whereas in OPLC very good relationships were obtained for all the systems applied. Better functions for correlation of log P with log k w were obtained for log k w values determined by the method developed from Ościk’s equation.

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In the present work, fruits of Prangos platychlaena Boiss. ex Tchihat. ssp. platychlaena (Apiaceae) collected from eastern (sample A) and central (sample B) parts of Turkey were subjected to hydrodistillation to yield essential oils (EOs). The chemical composition of P. platychlaena ssp. platychlaena fruit oil was analyzed by gas chromatography–flame ionization detector (GC–FID) and gas chromatography–mass spectrometry (GC–MS) techniques. An unknown compound with m/z 178 [M]+ in high percentages was detected in both EOs (45.8% and 11.2% in samples A and B, respectively). Column chromatography on silica gel was subsequently followed by the sample A and yielded a new acetylenic derivative (1), which was characterized by spectroscopic techniques as (2S)- 3,5-nonadiyne-2-yl acetate. Samples A and B oils were characterized by a series of acetylenic derivatives like 3,5-nonadiyne (24.5% and 5.8% in A and B, respectively), (Z)-3,5-nonadiyne-7-ene (0.2% in A), and (E)-3,5-nonadiyne-7-ene (0.5% in A). Monoterpenes α-pinene (6.8% and 12.8%), α-phellandrene (0.1% and 17.1%), and β-phellandrene (4.2% and 22.4%) were found to be the major components in P. platychlaena ssp. platychlaena EOs in samples A and B, respectively. The components of P. platychlaena ssp. platychlaena EOs were separated on the overpressured layer chromatography (OPLC) plates, and the plates were subsequently subjected to direct-bioautography assays using three plant pathogens such as Colletotrichum acutatum, C. fragariae, and C. gloeosporioides; however, no antifungal activity was observed. Due to a high yield, sample A was evaluated for its repellent activity against female mosquito Aedes aegypti and attraction of sterile male Mediterranean fruit fly Ceratitis capitata. Sample A demonstrated good repellency against Ae. aegypti in human-based cloth patch bioassays and no attraction to C. capitata in short range bioassays.

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A method, including solid phase extraction sample preparation, overpressured layer chromatographic separation, and subsequent densitometric evaluation, was developed for measurement of total resveratrol (cis- and trans-isomers) content of wine. The amount of resveratrol was determined in wine samples from different winemaking regions of Hungary. The total resveratrol was high in Hungarian red wines (3.6–11 mg L−1), and much lower in white ones (0.04–1.5 mg L−1).

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It has been established, by use of bioautographic detection with the phytopathogenic bacteria Pseudomonas savastanoi pv. phaseolicola , that the common aflatoxins have antimicrobial activity after OPLC separation. Our preliminary results suggest this antimicrobial activity originates from the activity of formaldehyde formed by the bacterial cells and/or from the methoxy groups of aflatoxin molecules.

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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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293 300 E. Tyihák and E. Mincsovics , Overpressured-Layer Chromatography (Optimum-Performance Laminar Chromatography) (OPLC). In: Sz. Nyiredy (Ed

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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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