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Öğe Characterization of prostaglandin E-like activity isolated from plant source (Allium cepa)(1986) Claeys M.; Üstünes L.; Laekeman G.; Herman A.G.; Vlietinck A.J.; Özer A.[No abstract available]Öğe Chemical characterization and pharmacological activity of nazlinin, a novel indole alkaloid from nitraria schoberi(1991) Üstünes L.; Özer A.; Laekeman G.M.; Corthout J.; Pieters L.A.C.; Baeten W.; Herman A.G.; Claeys M.; Vlietinck A.J.Nazlinin [1], a novel indole alkaloid with serotonergic activity, has been isolated together with serotonin and tryptamine from Nitraria schoberi using a bioassay-guided fractionation, and its structure has been confirmed by eims and nmr techniques. The contractile and relaxing effects of nazlinin on blood vessels are compared with those of the structurally related serotonin. © 1991, American Chemical Society. All rights reserved.Öğe Isolation and identification of two isomeric trihydroxy octadecenoic acids with prostaglandin E-like activity from onion bulbs (Allium cepa)(1985) Üstünes L.; Claeys M.; Laekeman G.; Herman A.G.; Vlietinck A.J.; Özer A.Two fractions with prostaglandin E-like activity were isolated from onion (Allium cepa) by using XAD-2 adsorption, silicic acid column chromatography and thin layer chromatography. The fractions were analyzed by gas chromatography/mass spectrometry and were characterized as isomeric mixtures of 9,10,13-trihydroxy-11-octadecenoic and 9,12,13-trihydroxy-10-octadecenoic acid, which are lipoxygenase metabolites of linoleic acid. Bio-assay, for which cascade superfusion was used and the rabbit coeliac and mesenteric arteries and the rat fundus strip were employed as assay organs, was utilized to monitor the bio-active profile throughout the isolation procedures. The activity of 1 µg of the pharmacologically active fractions T1 and T2 was found to be equivalent to that of respectively 1.33 and 0.63 ng of prostaglandin E2. © 1985.Öğe Mass spectral characterization of two onion constituents with prostaglandin E-like activity as lipoxygenase metabolites of linoleic acid(1984) Claeys M.; Ustünes L.; Laekeman G.; Herman A.G.; Vlietinck A.J.; Üzer A.Onions (Allium cepa have been used in folk medicine for the treatment of hypertension and gastrointestinal ulcers, which are cases where the administration of prostaglandins is considered. Using bioassay guided fractionation and gas chromatography/mass spectrometry (GC/MS) we have isolated two biologically active fractions with PGE-like properties and have characterized these products as lipoxygenase metabolites of linoleic acid. For the isolation of the active principles, onion bulbs were homogenized in phosphate buffer and the PGE-like products were isolated using Amberlite XAD-2 absorption, silicic acid column chromatography and silicagel thin layer chromatography. The PGE-like activity was estimated in a cascade superfusion system in which the isolated rabbit coeliac artery, the rabbit mesenteric artery and the rat fundus were used as assay organs. For the GC/MS characterization, various types of volatile derivatives were prepared in order to facilitate the structure elucidation. Derivatization included hydrogenation, methyl ester formation, n-butyl boronate formation and trimethylsilylation. The active fractions yielded identical electron-impact mass spectra, indicating that they are stereoisomeric, and each fraction was identified as a mixture of two positional isomers, i.e. of 9,12,13-trihydroxy-10-octadecenoic and of 9,10,13-trihydroxy-11-octadecenoic acid. With regard to the structure elucidation of the latter isomers, the mixed hydrogenated, n-butyl boronate, methyl ester, TMS-ether derivatives were shown to be of particular value for the determination of the vicinal diol function. The isomeric trihydroxylated octadecenoic acids have been described for the first time as metabolites of linoleic acid in wheat flour incubates. In this system, the trihydroxylated octadecenoic acids were shown to be formed through a sequence of three reactions, including an initial 9- or 13-lipoxygenation yielding hydroperoxy octadecadienoic acids, followed by rearrangement into unstable allylic epoxy hydroxy octadecenoic acids, which in turn are hydrolyzed to trihydroxy octadecenoic acids. Furthermore, structurally related trihydroxy octadecadienoic acids have also recently been isolated from a plant source, more specifically from the roots of Bryonia Alba, which are used for the same medicinal purposes as onion bulbs. © 1984.
