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  • 1
    ISSN: 0044-264X
    Keywords: Key words Flavonoids – flavonols – flavones – anthocyanins – bioavailability – antioxidative effects – prevention ; Schlüsselwörter Flavonoide – Flavonole – Flavone – Anthocyane – Bioverfügbarkeit – antioxidative Wirkungen – Prävention ; Abkürzungen DNA = Desoxyribonucleinsäure – LDL = Low-density lipoprotein – HPLC = Hochdruckflüssigchromatografie – IC = Inhibitory concentration – ROS = Reaktive Sauerstoffspezies – SD = Standardabweichung
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Zusammenfassung Flavonoide sind nichtnutritive Pflanzenstoffe, deren Eigenschaften in den letzten Jahren hinsichtlich möglicher protektiver Einflüsse auf chronische Erkrankungen intensiv untersucht wurden. So konnte für Flavonole, Flavone und neuerdings auch Anthocyane in vitro eine teilweise erhebliche antioxidative Aktivität, die vor allem im Abfangen freier Sauerstoffradikale besteht, nachgewiesen werden. In europäischem Obst und Gemüse sind besonders Flavonole, aber auch Anthocyane weit verbreitet. Erhebliche Mengen beider Flavonoide können auch in schwarzem Tee und Rotwein enthalten sein. Diese Lebensmittel stellen mit unterschiedlichen Anteilen die wichtigsten Quellen für die Aufnahme von Flavonolen dar. Während die Absorption der Aglykone seit längerem nachgewiesen ist, konnten erst jüngste Untersuchungen die Absorption von Flavonolglykosiden aus dem Dünndarm belegen. Die durchschnittliche Aufnahme von Flavonolen in der bundesdeutschen Bevölkerung wurde anhand der Daten der Nationalen Verzehrsstudie ermittelt. Sie betrug etwa 11,5 mg pro Person und Tag und stammte überwiegend aus Obst und Gemüse, aber auch aus Tee und Rotwein. In epidemiologischen Studien wurde untersucht, ob die Höhe der Flavonolaufnahme mit dem Auftreten bestimmter Erkrankungen assoziiert ist. Es konnte gezeigt werden, daß ein inverses Verhältnis zwischen tödlich verlaufenden Herzinfarkten und dem Umfang der Flavonolaufnahme besteht. Eine inverse Beziehung von Flavonoidaufnahme und dem Risiko von Krebserkrankungen ließ sich bisher in einer von drei Studien nachweisen. Diese Übersicht stellt den aktuellen Wissensstand über Vorkommen, alimentäre Aufnahme, Bioverfügbarkeit und antioxidative Eigenschaften von Flavonolen, Flavonen und Anthocyanen sowie die mit der Flavonoidaufnahme verbundenen Krankheitsrisiken dar. Die möglichen gesundheitlichen Effekte, besonders von Flavonolen, werden vor diesem Hintergrund kritisch beleuchtet und der daraus resultierende Forschungsbedarf genannt.
    Notes: Summary Flavonoids are non-nutritive compounds of plants that have been intensively investigated during the past years due to their possible protective effects against chronic diseases. In vitro studies were able to demonstrate for flavonols, flavones, and most recently also for anthocyanins a considerable antioxidative activity, mainly based on scavenging of oxygen radicals. Flavonols and anthocyanins are commonly found in European fruits and vegetables. In addition, black tea and red wine may have a high content of these compounds. Those food items are the main sources of flavonol consumption each contributing to a different degree to the overall intake. The absorption of a aglycones has been established before. However, only recently could the absorption of flavonolglycosides be demonstrated. The mean intake of flavonols of the German population was calculated using data from the National German Food Consumption Survey. According to this analysis, the daily per capita intake was about 11.5 mg flavonols, mainly derived from fruits and vegetables, but also from black tea and red wine. Epidemiological studies have been directed to investigate the association between flavonol consumption and disease risk. An inverse association between flavonol intake and mortality from myocardial infarction was observed. According to one of three studies, the flavonoid intake can be inversely correlated with cancer risk. This review summarizes the current knowledge on the occurrence, intake, bioavailability, and antioxidative properties of flavonols, flavones, and anthocyanins as well as the associations between flavonol intake and disease risks. Possible health related effects especially of flavonols are critically reflected, and the necessity of further research is outlined.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to investigate conformational preferences of the 21-residue peptide hormone endothelin-1 (ET-1), an extensive conformational search was carried out in vacuo using a combination of high temperature molecular dynamics / annealing and a Monte Carlo / minimization search in torsion angle space. Fully minimized conformations from the search were grouped into families using a clustering technique based on rms fitting over the Cartesian coordinates of the atoms of the peptide backbone of the ring region. A wide range of local energy minima were identified even though two disulfide bridges (Cys1-Cys15 and Cys3-Cys11) constrain the structure of the peptide. Low energy conformers of ET-1 as a nonionized species in vacuo arestabilized by intramolecular interaction of the ring region (residues 1-15) with the tail (residues 16-21). Strained conformations for individual residues are observed. Conformational similarity to protein loops is established by matching to protein crystal structuresIn order to assess the influence of aqueous environment on conformational preference, the electrostatic contribution to the solvation energy was calculated for ET-1 as a fully ionized species (Asp8, Lys9, Glu10, Asp18, N- and C-terminus) using a continuum electrostatics model (DelPhi) for each of the conformed generated in vacuo, and the total solvation free energy was estimated by adding a hydrophobic contribution proportional to solvent accessible surface area. Solvation dramatically alters the relative energetics of ET-1 conformers from that calculated in vacuo. Conformers of ET-1 favored by the electrostatic salvation energy in water include conformers with helical secondary structure in the region of residues 9-15.Perhaps of most importance, it was demonstrated that the contribution tosolvation by an individual charge depends not only on its solvent accessibility but on the proximity of other charges, i.e., it is a cooperative effect. This was shown by the calculation of electrostatic solvation energy as afunction of conformation with individual charges systematically turned “on” and “off”. The cooperative effect of multiple charges on solvation demonstrated in this manner calls into question models that relate solvation energysimply to solvent accessibility by atom or residue alone. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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