Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Plant verdedigt zich vaak te goed tegen lichtstress : vrije radicalen, schadelijk maar ook nuttig
    Kaiser, M.E. ; Heuvelink, E. ; Kierkels, T. - \ 2016
    Onder Glas 13 (2016)3. - p. 12 - 13.
    horticulture - greenhouse horticulture - pot plants - anthurium - light intensity - defence mechanisms - adverse effects - shade plants - antioxidants - tuinbouw - glastuinbouw - potplanten - anthurium - lichtsterkte - verdedigingsmechanismen - nadelige gevolgen - schaduwplanten - antioxidanten
    Een plant heeft te maken met voortdurend wisselende lichtniveaus die soms zodanig hoog kunnen oplopen dat ze schade veroorzaken. Er bestaat een uitgebreid stelsel van verdedigingslinies op alle niveaus: blad, cel, celorganen en moleculair niveau. Soms is de voorbereiding op mogelijke lichtschade zo goed dat het productie kost.
    Gezondheidswaarde van appel en peer
    Vreeburg, R.A.M. ; Sluis, A.A. van der - \ 2009
    De Fruitteelt 99 (2009)19. - ISSN 0016-2302 - p. 14 - 15.
    fruitteelt - fruitgewassen - appels - peren - gezondheidsvoedsel - vitaminen - antioxidanten - fruit growing - fruit crops - apples - pears - health foods - vitamins - antioxidants
    Algemeen wordt aangenomen dat groente en fruit gezond zijn voor de mens. Maar hoe onderbouwd is de gedachte eigenlijk dat appels en peren gezond zijn
    Isolation, identification and activity of natural antioxidants from sweet grass (Hierochloe odorata), costmary (Chhrysanthemum balsamita) and horehound (Marrubium vulgare), cultivated in Lithuania
    Pukalskas, A. - \ 2008
    Wageningen University. Promotor(en): Aede de Groot, co-promotor(en): Teris van Beek; Jozef Linssen. - [S.l.] : S.n. - ISBN 9789085049821 - 137
    antioxidanten - natuurlijke producten - extractie - fysicochemische eigenschappen - litouwen - antioxidants - natural products - extraction - physicochemical properties - lithuania
    Food products are susceptible to oxidation processes. Oxidation of lipids (fat) is the major cause of food deterioration however also proteins and carbohydrates can be affected. To prevent or retard this process, antioxidants are used. With regard to foods, more and more natural products are preferred by consumers so new natural sources of compounds able to retard oxidation processes and prevent spoilage of food products are continuously investigated.
    The research described in this study is aimed at the evaluation of several herbs as possible sources of food antioxidants. An initial screening of extracts from roman camomile, tansy, sweet grass, costmary, sea-buckthorn and sage for antioxidant activity in rapeseed oil has been performed Sweet grass and sage acetone extracts retarded oxidation processes in oil best.
    Sweet grass was chosen for further investigation as the herb having the highest antioxidant activity. Two other herbs, namely horehound and costmary were further selected for the evaluation of their antioxidant activity in different assays. At first preliminary fractionation of the selected herb extracts was performed. Fractions were tested in three different assays: -carotene oxidation, DPPH• reduction and rapeseed oil oxidation. The experiments did not provide any straightforward answers, which fractions contained the most active antioxidants. Different assays gave different results. More polar fractions were more active in model systems like DPPH• while in the edible oil assay these fractions acted as weak antioxidants, or some even exhibited a prooxidation effect. Acetone extracts performed better than methanol-water extracts in retarding oil oxidation probably due to their higher compatibility with the medium or the more non-polar nature of the contained analytes.
    In further steps the structures of the radical scavenging compounds present in extracts of sweet grass, horehound and costmary were elucidated. Two compounds, namely 5,8-dihydroxybenzopyranone and 5-hydroxy-8-O--D-glucopyranosyl benzopyranone were isolated and identified from sweet grass extract. Both compounds were identified for the first time as natural products. Four compounds, namely 5-O-caffeoyl quinic acid (chlorogenic acid), 3,5-dicaffeoyl quinic acid, 5,7,4'-trihydroxy-3',8-dimethoxy flavone and 5,7,3',4'-tetrahydroxy-3,8-dimethoxyflavonol were identified in costmary extracts. These compounds are quite common in plant kingdom. However, they have not previously been isolated from costmary. Five compounds, namely 5,8-dihydroxy-7,4-dimethoxy flavone, 7-O--glucopyranosyl luteolin, 7-O--glucuronyl luteolin, verbascoside and forsythoside B were isolated from horehound extracts. These compounds are common in the Labiatae family. Their radical scavenging activity was measured using DPPH• and ABTS•+ scavenging assays and compared with the activity of rosmarinic acid and Trolox.
    An on-line HPLC-DPPH-DAD-NMR system for the rapid identification of compounds in complex mixtures was developed. The developed system was tested on commercial rosemary extract and six compounds were identified without the need to isolate them. This proved that simultaneous detection and identification of radical scavengers is possible.
    Several solvents, namely hexane, acetone ant ethanol and their combinations were tested for their suitability to extract all known radical scavengers from sweet grass, costmary and horehound. It was found that initial extraction of the plant material with hexane increased the concentrations of radical scavengers in the following extraction stages.
    Antioxidants, oxidative stress, and cardiovascular diseases : cross-cultural comparisons and prospective cohort studies
    Buijsse, B. - \ 2008
    Wageningen University. Promotor(en): Daan Kromhout; Frans Kok, co-promotor(en): Edith Feskens. - [S.l. : S.n. - ISBN 9789085049609 - 135
    antioxidanten - plantaardige producten - groenten - vruchten - hart- en vaatziekten - intercultureel onderzoek - internationale vergelijkingen - epidemiologische onderzoeken - nederland - cacao - oxidatieve stress - kreta - antioxidants - plant products - vegetables - fruits - cardiovascular diseases - cross cultural studies - international comparisons - epidemiological surveys - netherlands - cocoa - oxidative stress - crete
    Background: Antioxidants in plant foods have been proposed to reduce the risk of cardiovascular diseases (CVD) by reducing oxidative stress. The objective was to confirm prospective studies on CVD and traditional antioxidants (beta-carotene, alpha-tocopherol), and to investigate emerging antioxidants (alpha-carotene, gamma-tocopherol, cocoa flavanols), and oxidative stress (enzyme activity of glutathione peroxidase-3) with CVD risk.
    Methods: In cross-cultural studies, the Cretan (Greece) and Zutphen (The Netherlands) cohorts of Seven Countries Study were compared with respect to long-term mortality of coronary heart disease (CHD), diet, and indicators of oxidative stress. In prospective cohort studies, data were used from the Zutphen Elderly Study (~500 men aged 65-84 y), the ‘Survey in Europe on Nutrition and the Elderly: a Concerted Action’ (SENECA, 1168 men and women aged 70-75 y), and the Minnesota Heart Survey (270 men and women aged 26-85 y).
    Results: The comparison between the Cretan and Zutphen cohorts revealed a 3-fold lower 40-year CHD mortality rate in Crete. This lower mortality in Crete was paralleled by a higher consumption of fruit, tomatoes, and olive oil, amongst others, and by a lower consumption of meat, poultry, and dairy. Consequently, the Cretan men had higher intakes of carotenoids, alpha-tocopherol, vitamin C, and dietary fiber, and lower intakes of trans and saturated fatty acids. This was confirmed at the age of ≥80 years, when the Cretan men had higher plasma concentrations of major dietary antioxidants (major carotenoids and alpha-tocopherol), a lower iron status, and a lower level of oxidative stress. In the Zutphen Elderly Study, the relative risk (RR) of 15-y CVD mortality for 1 standard deviation (SD) increase in dietary intake was 0.81 [95% confidence interval (CI): 0.66-0.99] for alpha-carotene and 0.80 (95% CI: 0.66-0.97) for beta-carotene. The intake of tocopherols was not related to CVD death. In SENECA, plasma concentrations of carotene (sum of alpha- and beta-carotene) were inversely related to CVD mortality (RR for 1 SD increase: 0.83; 95% CI: 0.70-1.00), but plasma concentrations of alpha-tocopherol were not. The daily use of 4 grams of cocoa, a rich source of flavanols, was related to a 3.7 mm Hg lower systolic (95% CI: –7.1 to –0.3) and a 2.1 mm Hg lower (95% CI: –4.0 to –0.2) diastolic blood pressure. The same amount of cocoa was also related to a 50% lower risk of 15-year CVD mortality (RR: 0.50; 95% CI: 0.32-0.78). Finally, in the Minnesota Heart Survey, the odds ratio of CVD mortality for the highest vs. the lowest quartile of glutathione peroxidase-3 activity was 0.42 (95% CI: 0.21-0.86). This inverse relation was confined to those with low concentrations of HDL cholesterol (odds ratio highest vs. lowest quartile: 0.17; 95% CI: 0.06-0.47).
    Conclusion: The Cretan Mediterranean diet is rich in antioxidants, which may partly contribute to the low observed CHD mortality. The findings on beta-carotene support previous observational studies suggesting that this carotenoid relates to a lower CVD risk. We showed that alpha-carotene is correlated with beta-carotene in the diet, and alpha-carotene was also related to a lower CVD mortality. The results on alpha-tocopherol are in line with the outcomes of clinical trials and do not indicate a role for this vitamin in lowering CVD mortality in elderly populations.
    Proceedings of the 2nd international symposium on natural preservatives in food, feed, and cosmetics : Amsterdam, the Netherlands, June 7-8, 2006
    Havkin-Frenkel, D. ; Dudai, N. ; Mheen, H.J.C.J. van der - \ 2008
    Leuven : International Society for Horticultural Science (Acta horticulturae 778) - ISBN 9789066057302 - 110
    conserveermiddelen - voedselconserveermiddelen - voer - cosmetica - natuurlijke producten - medicinale planten - antioxidanten - etherische oliën - aromatische gewassen - preservatives - food preservatives - feeds - cosmetics - natural products - medicinal plants - antioxidants - essential oils - aromatic plants
    Verwaarding reststroom uienbewerking
    Meeusen-van Onna, M.J.G. ; Schroot, J.H. ; Mulder, W.J. ; Elbersen, H.W. - \ 2008
    Wageningen : Agrotechnology & Food Sciences Group (ASFG nr. 886) - ISBN 9789085048503 - 155
    uien - oogstresten - verwerking - extractie - industriële toepassingen - compostering - verbranding - fermentatie - kleurstoffen in voedsel - antioxidanten - scheidingstechnologie - bioethanol - biobased economy - onions - crop residues - processing - extraction - industrial applications - composting - combustion - fermentation - food colourants - antioxidants - separation technology - bioethanol - biobased economy
    In opdracht van ZUVER heeft Wageningen Universiteit en Research Centre de mogelijkheden bekeken voor verwaarding van de reststroom die bij de uienbewerking vrijkomt. Tijdens het uienbewerkingsproces komt een continue reststroom vrij. Deze reststroom bedraagt voor alle uienbewerkingsbedrijven tezamen jaarlijks 16.800 tot 18.900 ton. De reststroom komt vrij tijdens drie verschillende deelprocessen: lossen, afstaarten en sorteren/verpakken. De samenstelling van de reststroom is bij ieder proces anders. De drie deelprocessen geven qua omvang de volgende reststromen: ¿ Lossen: 4.800 ton tot 5.400 ton ¿ Afstaarten: 9.600 ton tot 10.800 ton ¿ Sorteren: 2.400 ton tot 2.700 ton Op dit moment 2008 wordt de reststroom gecomposteerd en over het land uitgereden. Tegelijkertijd willen de uienbewerkingsbedrijven ook kijken naar afzetmogelijkheden met meer toegevoegde waarde. De reststroom bevat interessante componenten die mogelijk interessant zijn voor hoogwaardiger toepassingen. De droge bruine pellen zijn rijk aan onoplosbare vezels en ze bevatten relatief veel quercitine. De wortels en bolstoel bevatten relatief veel zwavelcomponenten die als geur- of smaakstof herkenbaar zijn. Mogelijk kan een mengsel van quercitine en de zwavelcomponenten toegepast worden als insecticide of herbicide. Dit zal afhangen van werkzaamheid, dosering en benodigde zuiverheid. Wanneer de reststroom wordt gescheiden in een grondfractie en een overige fractie zijn er meer mogelijkheden voor de reststroom in beeld. Er zijn dus voordelen van scheiding van de grond- en niet-grondfractie. Het scheiden net na het lossen gebeurt al op dit moment: dat is de losstroom. Voor een aanvullende scheidingsstap is vooral de droge scheidingstechnologie in beeld. Het gaat dan bijvoorbeeld om windziften. Immers op elk bedrijf staan al afzuiginstallaties . ZUVER wil via mechanische stappen de scheiding verder optimaliseren . Om deze scheidingstechnieken te implementeren is nog wel een kort onderzoekstraject noodzakelijk waarin de technische en economische haalbaarheid van een scheiding van grond en uienpellen (inclusief staarten) uitgezocht wordt. Op basis van de samenstelling van de reststroom uit de uienbewerking is een groot aantal toepassingen bedacht. Deze toepassingen zijn gegroepeerd Verwaarding reststroom uienbewerking naar toegevoegde waarde, waarbij het onderscheid in fertilizer (compost, bodemverbeteraar), fuel (energie), fibre (vezel), feed (veevoer), food (humane voeding), farma en other (overig) is gehanteerd. De potentiële toepassingen omvatten een groot scala aan producten, die sterk uiteenlopen waar het gaat om de toegevoegde waarde. Daarvan lijkt een aantal toepassingen aantrekkelijk voor de uienbewerkingsbedrijven. Deze opties zijn nader uitgewerkt. Het gaat daarbij om opties die al binnen handbereik liggen, zoals compostering. Daarnaast zijn er toepassingen waar enig aanvullend onderzoek noodzakelijk is zoals verbranding. De meer hoogwaardiger toepassingen als kleurstof, antioxidant fungicide en insecticide vergen ook verdere ontwikkeling (met partners). Voor deze meer hoogwaardiger toepassingen geldt dat bedrijven die actief zijn in deze markt interesse hebben in de producten die de uienbewerkingsbedrijven kunnen aanleveren. In een samenwerkingsverband kunnen de mogelijkheden voor de verdere productontwikkeling worden verkend.
    New methods for the screening of antioxidants in three Sideritis species
    Koleva, I. - \ 2007
    Wageningen University. Promotor(en): Aede de Groot, co-promotor(en): Teris van Beek; Jozef Linssen. - [S.l.] : S.n. - ISBN 9789085046851 - 197
    antioxidanten - sideritis - chemische samenstelling - hplc - gaschromatografie - analytische scheikunde - antioxidants - sideritis - chemical composition - hplc - gas chromatography - analytical chemistry
    This thesis describes the rapid and robust evaluation of antioxidant activity of complex mixtures such as plant extracts. The study was directed to establish the best screening and isolation procedures for components with antioxidative properties to ensure the development of an “algorithm” for studying natural antioxidants. Three different screening methods (the b-carotene bleaching test (BCBT), the headspace GC method (HS-GC) and the off-line radical scavenging assay with the DPPH radical (DPPH method) and various extraction schemes were used. Three plants from the genus Sideritis grown in Bulgaria (S. scardica, S. syriaca and S. montana) served as test species. The strengths and limitations of each method were illustrated by testing a number of extracts of different polarity. A novel HPLC-DPPH method to rapidly and sensitively pinpoint individual antioxidants in complex mixtures with as little as possible fractionation procedures was developed. The use of the alternative ABTS·+ radical cation made the method in most cases even more sensitive. The instrumental set-up and physico-chemical parameters of both methods were studied. The methods were successful for qualitative and semi-quantitative measurements of pure antioxidants and extracts. A review is under preparation on the use of on-line methods. As a result, a range of flavonoid-, phenylpropanoid- and iridoid glycosides were isolated. The radical scavenging activity of the isolated compounds by off- and on-line DPPH methods was studied. Three novel compounds were isolated: flavonoid glycosides luteolin-4'-methylether-7-O-[6'''-O-acetyl-β-D-allopyranosyl-(1-2)-β-D-glucopyranoside and hypolaetin-4'-methylether-7-O-[β-D-allopyranosyl-(1-2)-6''-O-acetyl-β-D-glucopyranoside, and iridoid glycoside 3''-O-p-coumaroyl-6''-O-acetyl melittoside from Sideritis species. Preliminary studies by the HS-GC method were applied to investigate how Sideritis extracts and pure components would behave in real systems: bulk oils and oil-in-water emulsions. Conjugated dienes and hexanal formation were monitored using rosmarinic acid and BHT as standards. They showed good inhibitory effects with regard to dienes and hexanal formation in both test systems.
    Screening, isolation and evaluation of antioxidative compounds from Geranium macrorrhizum, Potentilla fruticosa and Rhaponticum carthamoides
    Miliauskas, G. - \ 2006
    Wageningen University. Promotor(en): Ernst Sudhölter, co-promotor(en): Teris van Beek; Jozef Linssen. - [S.l.] : S.n. - ISBN 9789085044871 - 160
    antioxidanten - extractie - geranium macrorrhizum - potentilla fruticosa - rhaponticum carthamoides - biologische eigenschappen - antioxidants - extraction - geranium macrorrhizum - potentilla fruticosa - rhaponticum carthamoides - biological properties
    Food molecules (lipids, proteins, carbohydrates) can be widely involved in oxidation reactions. These reactions, caused by so called reactive oxygen species (ROS) are a major cause of food deterioration. In the case of lipid containing foods this process is defined as rancidity. Significant changes can occur in product colour, texture and nutritive value. Eventually the oxidation can result in complete spoilage. Oxidation reactions caused by ROS also play an important role in the ageing processes of living organisms and are associated with numerous diseases, like coronary heart disease, cancer, cataracts, ageing. Although protective mechanisms exist both in living cells and in foods, in many cases there is a need to strengthen this mechanism. A daily intake of antioxidants can prevent or delay problems caused by ROS.

    The research described in this study is aimed at the evaluation of several plant extracts as a possible source of food antioxidants.An initial screening for radical scavenging activity of extracts from medicinal and aromatic plants namely Salvia sclarea , Salvia glutinosa , Salvia pratensis , Salvia officinalis, Lavandula angustifolia , Calendula officinalis , Matricaria recutita , Echinacea purpurea , Rhaponticum carthamoides , Juglans regia , Melilotus officinalis , Geranium macrorrhizum and Potentilla fruticosa has been performed using DPPH and ABTS radical scavenging assays. Of these extracts Geranium macrorrhizum and Potentilla fruticosa possessed the highest radical scavenging activity in both assays, higher than that of the Salvia officinalis extract.

    In further steps of this study the structures of the radical scavenging compounds present in leaf extracts ofGeranium macrorrhizum, in blossoms extracts ofPotentilla fruticosaand leaf extracts of Rhaponticum carthamoides were elucidated.

    The radical scavenging activity of the isolated compounds from Geranium macrorrhizum and Potentilla fruticosa was measured using DPPH·and ABTS·+scavenging assays and compared with the activity of rosmarinic acid and Trolox.

    A quantitative comparison of the major antioxidant compounds in different botanical parts of Geranium macrorrhizum and Potentilla fruticosa was also made.

    A hyphenated LC-DAD-SPE-NMR set-up in combination with on-line radical scavenging detection was used for the identification of radical scavenging compounds from Rhaponticum carthamoidesextracts. The technique enabled selective detection and identification of individual radical scavenging compounds without any prior off-line chromatographic steps. One of identified a new natural compound. Its radical scavenging activity was tested against DPPH radical and was found to be weaker than that of the reference antioxidants rosmarinic acid and Trolox.

    Antioxidant activity of all plant fractions from Geranium macrorrhizum and Potentilla fruticosa was assessed by model system assays and in real food systems consisting of edible oil or fermented sausages.

    A preliminary safety evaluation of some plant extracts has been conducted (enzymatic oxidation assay;effects against singlet oxygen caused erythrocyte hemolysis;mutagenicity evaluation) andindicated the plant extracts not to be genotoxic or mutagenic.

    Research on natural products, like plant antioxidants, demands the application of various analytical techniques. Apart from state-of-the-art analytical instruments, a lot of specific techniques needed to be applied at certain stages, e.g. on-line radical scavenging detection of individual plant constituents in complex plant mixtures. These DPPH/ABTS assays coupled on-line to liquid chromatography-diode array detection set-ups have been developed earlier at the Laboratory of Organic Chemistry of Wageningen University. Expansion of these assays by coupling a mass spectrometer to the system was one part of the methodological research.

    The developed system enabled a quick analysis (simultaneous separation, isolation-identification and detection of radical scavenging activity) of complex Ginkgo and rosemary extracts.

    The hyphenated LC-DAD-SPE-NMR system is another powerful technique for compound isolation and structure elucidation in complex mixtures. The investigation of the application of LC-DAD-SPE-NMR with a semi-preparative HPLC column and comparison of the obtained results with those of an analytical column was described in the thesis.

    It is concluded that extracts from Geranium and Potentilla are unlikely to be a new source of antioxidants for lipophilic food products. Extracts proved to be effective in assays with polarmedia,however their application in such products is also unlikely. Reasons are problems, like odour and colour of the extracts, and the complex extraction procedure.
    A chain analysis of the production of 'healthy' apple juice : the case of polyphenolic antioxidants
    Sluis, A.A. van der - \ 2005
    Wageningen University. Promotor(en): Wim Jongen; Tiny van Boekel, co-promotor(en): Matthijs Dekker. - [S.l. ] : S.n. - ISBN 9789085042310 - 184
    appelsap - appels - antioxidanten - polyfenolen - voedselverwerking - kwaliteit voor voedselverwerking - verwerkingsverliezen - agro-industriële ketens - apple juice - apples - antioxidants - polyphenols - food processing - food processing quality - processing losses - agro-industrial chains
    De laatste jaren bestaat er een groeiende interesse voor de mogelijke gezondheidsbeschermende werking van stoffen in ons voedsel. Daarom staan levensmiddelen met hoge gehalten hiervan steeds meer in de belangstelling van de consument. De productie van dergelijke voedingsmiddelen vereist kennis over de invloed van processen in de hele productieketen van een voedingsmiddel: teelt, veredeling, industri¿ verwerking, distributie, opslag en consumentenverwerking. Dit proefschrift beschrijft het proces van kennisverwerving, -verwerking en toepassing vanuit een productgerichte benadering, en wel aan de hand van polyfenolische antioxidanten in appels. De gehalten hiervan vari¿n sterk tussen verschillende appelrassen en met teeltcondities. Bovendien gaat bij de traditionele bereiding van appelsap het grootste gedeelte van deze stoffen verloren in het productieproces. Het is mogelijk een ¿gezonder¿ appelsap te maken met een hogere antioxidantactiviteit door aanpassingen in het productieproces.
    Endogenous phenolics and starch modifying enzymes as determinants of sorghum for food use in Burkina Faso
    Dicko, M.H. - \ 2005
    Wageningen University. Promotor(en): Fons Voragen; Harry Gruppen, co-promotor(en): Willem van Berkel. - Wageningen : Wageningen University - ISBN 9789085041955 - 174
    sorghum - zetmeel - tropisch voedsel - kieming - fenolverbindingen - antioxidanten - enzymen - burkina faso - sorghum - starch - tropical foods - germination - phenolic compounds - antioxidants - enzymes - burkina faso
    The objective of this thesis is to screen for biochemical determinants in sorghum varieties cultivated in Burkina Faso to identify the best sorghum varieties to be used as source of bioactive components or for specific local foods, e.g. "tô", thin porridges for infants, granulated foods "couscous", and local beers "dolo". The results revealed that sorghum varieties have different contents of starch, amylose, amylopectin and that germination decreased more the content of amylose than amylopectin. While on averagea‑amylase activity increased in all varieties by 2-20fold,b‑amylase activity did not uniformly increase after germination and even decreased in some varieties. The majority (82%) of sorghum varieties cultivated inBurkina Fasoare low proanthocyanidins (condensed tannins) containing sorghums. Some varieties had relatively high content(> 0.4%, w/w),of phenolic compounds such as 3-deoxyanthocyanidins and flavan-4-ols, which are of particular interest for food, colorant and pharmaceutical industries. Independent of grain germination, all sorghum varieties are among the most prominent natural sources of antioxidants due essentially to their phenolic contents. Sorghum varieties are highly polymorph in their expression of phenolic biosynthesizing enzymes, e.g. phenylalanine ammonia lyase, and phenolic modifying enzymes, e.g. peroxidases and polyphenol oxidases. Several peroxidase isoenzymes are expressed both before and after germination, and display a high activity in vitro . These enzymes are the main potential oxidases involved in the oxidation of endogenous phenolic compounds in sorghum grain. The major sorghum grain peroxidase isoenzyme representing more than 80% of total peroxidase activity was characterized at the molecular level. The enzyme, localized in chromosome 1 of sorghum, is a monomeric glycoprotein containing a non-covalently bound type-b heme. The catalytic properties and primary structure of the enzyme are similar to cereal peroxidases, in particular to barley peroxidase 1. Agronomic characteristics of grains (presence of absence of pigmented testa layer and color of the glumes) and plants (red or tan) could be linked to sorghum grain contents in phenolics and starch modifying enzymes. On average, varieties resistant to stresses have greater content and diversity in phenolic compounds and higher oxidative enzyme activities than stress susceptible varieties. The screened biochemical parameters could be linked to the preferences of varieties for specific local foods. For instance, among varieties used for "tô", "dolo", couscous and thin porridge preparation, the "dolo" varieties had the highest average content and diversity in phenolics as well as the highest antioxidant activities. Varieties good for infant porridges preparation have low amylose content and higha-amylase activity after germination.
    Studies on the pro-oxidant chemistry of flavonoids
    Awad, H.M. - \ 2002
    Wageningen University. Promotor(en): I.M.C.M. Rietjens; P.J. van Bladeren; J. Vervoort. - S.l. : S.n. - ISBN 9789058085887 - 133
    flavonoïden - oxidatiemiddelen - antioxidanten - quercetine - structuuractiviteitsrelaties - hplc - kernmagnetische resonantiespectroscopie - massaspectrometrie - flavonoids - oxidants - antioxidants - quercetin - structure activity relationships - hplc - nuclear magnetic resonance spectroscopy - mass spectrometry

    There is currently much interest in the development of functional foods aiming at the prevention of the development of some diseases, for example cancer, by the introduction of selected natural substances at elevated levels into the diet. The rationale for this approach is based especially on epidemiological data that indicate that food items containing such chemicals may reduce the risk of these diseases in humans. Epidemiological studies indicate, for example, that diets rich in fruit and vegetables protect against a variety of diseases, including heart diseases and certain forms of cancer. However, identification of the actual ingredient in a specific diet responsible for the beneficial health effects remains an important bottleneck for translating observational epidemiology to development of a functional food ingredient. The protection against cancer afforded by fruit and vegetables has been attributed to antioxidant micronutrients such as vitamin C, beta-carotene and vitamin E, which may act at many sites, including the stomach, intestine, lung and bladder. However, present scientific attention is focusing as well on the significance of other minor dietary components, notably the flavonoids as protectants against disease. Flavonoids are widespread in nature and are found in considerable quantities in fruits, vegetables, seeds, peel and tubers. The average Western diet may provide up to 1 g of flavonoids per day. Numerous in vitro studies show that flavonoids are potent antioxidants and metal chelators. Their potential as anti-inflammatory, antiallergic and antiviral compounds has also attracted attention. These studies provide the basis for the present rapidly increasing interest for the use of flavonoids as functional food ingredients. As a result increased human exposure to flavonoids can be expected in the near future. In shops and at the internet, food and food supplements based on (iso)flavonoids as functional ingredients are marketed. This, although hard scientific data supporting the health claims as well as data allowing a balanced risk-benefit evaluation are lacking. For flavonoids increased future human exposure regimens induce the question on their pro-oxidant chemistry. There is considerable evidence that some flavonoids are mutagenic in both bacterial and mammalian experimental systems. A high incidence of gastric cancer in some human populations has been linked to consumption of wine containing potentially mutagenic flavonoids (Tamura et al. , Proc. Natl. Acad. Sci. USA. 77, 4961-4965, 1980, Hoey et al. , Am. J. Epidemiol., 113, 669-974, 1981). Relatively little is understood about either the toxicity or protection afforded by flavonoids in humans.

    Since flavonoid quinone/quinone methides have been suggested as the major metabolites responsible for the possible pro-oxidant toxicity and mutagenicity of flavonoids, characterisation of flavonoid quinone chemistry is of importance. However, little information is available on the structure and reactivity of these flavonoid oxidation products. Therefore, the objective of this thesis was to investigate the pro-oxidant chemistry of flavonoids and to perform structure activity studies on the chemical behaviour of 3',4'-dihydroxyflavonoids with special emphasis on the nature and reactivity of the quinone/quinone methide type metabolites formed. Using the GSH trapping method, HPLC, LC/MS, MALDI-TOF, 1H NMR, 13C NMR and quantum mechanical computer calculations the quinone/quinone methide chemistry of a series of 3',4'-dihydroxyflavonoids could be characterised.

    The results provide insight in structure-activity-relationships for the pro-oxidant chemistry of these electrophilic quinone/quinone methide flavonoid metabolites. The results obtained also reveal an unexpected pH-dependent electrophilic behaviour of B ring catechol flavonoids. Furthermore the results of this thesis also reveal, for the first time, evidence for the pro-oxidative chemistry of quercetin in a cellular in vitro model. The formation of these glutathionyl-flavonoid adducts provides evidence for the actual pro-oxidative formation of reactive quinone type metabolites from B ring catechol flavonoids in the selected cellular in vitro model using melanoma cells. Oxidation of the catechols to quinones and their isomeric quinone methides generates potent electrophiles that could alkylate DNA. Interestingly, the structural requirements essential for good antioxidant activity match the requirements essential for pro-oxidant action and quinone methide formation. Altogether, the pro-oxidant behaviour of flavonoids and their quinone/quinone methides are far from straight forward and need to be re-evaluated especially in the framework of the risk-benefit evaluation of the use of these flavonoids as functional food ingredients and/or food supplements.

    Samenvatting

    Er is momenteel veel interesse voor de ontwikkeling van functionele voedingsmiddelen (functional foods), met als doel het voorkomen van het ontstaan van ziekten zoals bijvoorbeeld kanker, via het in verhoogde mate introduceren van geselecteerde natuurlijke bestanddelen in het dieet. De basis voor deze aanpak wordt momenteel met name gevonden in epidemiologische studies die laten zien dat diëten rijk aan specifieke voedselcomponenten of ingrediënten de kans op bepaalde ziekten bij de mens verlagen. Zo geven epidemiologische studies bijvoorbeeld aan dat diëten die rijk zijn aan fruit en groenten beschermen tegen een aantal ziekten zoals hartziekten en bepaalde vormen van kanker. Echter, het identificeren van de belangrijke ingrediënten in het betreffende dieet die het gezondheidsbevorderende effect tot stand brengen is een knelpunt voor het vertalen van de resultaten uit de epidemiologie naar de ontwikkeling van een functioneel voedingsingrediënt.

    De bescherming tegen kanker door groenten en fruit is toegeschreven aan antioxidanten zoals vitamine C, beta-caroteen en vitamine E, die op vele plaatsen in het lichaam, zoals de maag, darmen, long en de blaas actief zijn. Wetenschappelijk wordt momenteel veel aandacht besteed aan het mogelijke belang van andere belangrijke dieet componenten, zoals flavonoïden, als beschermende ingrediënten tegen ziekte. Flavonoïden komen in de natuur veel voor, en worden met name in hoge concentraties gevonden in fruit, groenten, knollen en zaden. Het gemiddelde Westerse dieet bevat ongeveer 1 gram aan flavonoïden per dag.

    Vele in vitro studies tonen aan dat flavonoïden goede antioxidanten en metaal chelatoren zijn. Daarnaast hebben ze anti-inflammatoire, anti-allergische en anti-virale eigenschappen die van belang worden geacht. Deze bevindingen verschaffen de basis voor de momenteel snel groeiende interesse om flavonoïden te gebruiken als functionele voedingsingrediënten. Als gevolg hiervan zou er in de nabije toekomst een toename in de opname van flavonoïden via het dieet verwacht kunnen worden. In winkels en via het internet worden voedingsmiddelen en voedingssupplementen gebaseerd op (iso)flavonoïden als functionele voedingsingrediënten verkocht. Dit, terwijl zowel de wetenschappelijke onderbouwing voor de gezondheidsclaims als gegevens die een gebalanceerde "risk-benefit" analyse mogelijk maken, nog ontbreken. In het geval van verhoogde toekomstige blootstelling van mensen aan flavonoïden worden voor de risk-benefit evaluatie vragen van belang rond hun mogelijk pro-oxidatieve chemisch gedrag. Er zijn aanwijzingen dat sommige flavonoïden mutageen zijn in zowel bacteriële als zoogdier in vitro test systemen. Een verhoogde mate aan maagkanker in bepaalde humane populaties is in verband gebracht met de consumptie van wijn met daarin mogelijk mutagene flavonoïden (Tamura et al. , Proc. Natl. Acad. Sci. USA. 77, 4961-4965, 1980, Hoey et al. , Am. J. Epidem., 113, 669-974, 1981). Alles samenvattend is er eigenlijk weinig bekend van de schadelijke maar ook van de gezondheidsbevorderende effecten van flavonoïden.

    Omdat flavonoid chinon/chinon methides genoemd zijn als de belangrijkste metabolieten die verantwoordelijk zouden zijn voor de mogelijke pro-oxidatieve toxiciteit en mutageniteit van flavonoïden, is karakterisering van deze pro-oxidant chemie van flavonoïden van belang. Echter er is weinig bekend over de structuur en de reactiviteit van deze flavonoid oxidatie producten. Daarom was het doel van deze studie de pro-oxidant chemie van flavonoïden te onderzoeken en een structuur-activiteits studie uit te voeren naar het chemische gedrag van 3',4'-dihydroxyflavonoïden. Daarbij werd speciale aandacht besteed aan de aard en reactiviteit van de gevormde chinon/chinon methide metabolieten. Met behulp van de GSH-trapping methode, HPLC, LC/MS, MALDI-TOF, 1H-NMR, 13C-NMR en kwantum-chemische computerberekeningen kon de chinon/chinon methide chemie van een serie 3',4'-dihydroxyflavonoiden gekarakteriseerd worden.

    De verkregen resultaten geven inzicht in de structuur-activteits relaties voor de pro-oxidatieve chemie van de electrofiele chinon /chinon methides metabolieten van de flavonoïden. De resultaten laten ook een onverwacht effect zien van de pH op het electrofiele gedrag van de B-ring catechol flavonoïden. Bovendien laten de resultaten van het proefschrift zien dat zelfs onder reducerende omstandigheden in een cellulair in vitro model (melanoma cellen) de pro-oxidatieve chemie van quercetine van belang kan zijn. Met name de vorming van glutathion-flavonoid conjugaten is een bewijs dat in het gekozen cellulaire model de pro-oxidatieve vorming van reactieve flavonoid chinon/ chinon methide metabolieten is opgetreden. Oxidatie van de catecholen naar chinonen en hun isomere chinon methides genereert electrofielen die DNA kunnen alkyleren. Van belang is dat de structurele randvoorwaarden die een flavonoid een goede antioxidant maken gelijk blijken te zijn aan de structurele kenmerken die essentieel zijn voor pro-oxidant gedrag en chinon methide vorming.

    Al met al is de pro-oxidant chemie van flavonoïden en van hun chinon /chinon methides verre van recht toe recht aan gebleken en zou de pro-oxidatieve chemie en de toxiciteit van de flavonoïden in het kader van hun gebruik als functional food ingredienten beter onderzocht en afgewogen moeten worden, rekening houdend met hun mogelijk gezondheidsbevorderende effecten.

    Antioxidatieve enzymen uit eendekroos
    Merck, K. ; Gerritsen, Y. ; Willemsen, J. - \ 2002
    Voedingsmiddelentechnologie 35 (2002)10. - ISSN 0042-7934 - p. 20 - 21.
    lemna minor - lemnaceae - medicinale planten - chemische samenstelling - enzymen - antioxidanten - vitaminen - essentiële aminozuren - waterplanten - toegepast onderzoek - voedselindustrie - gezondheidsbevordering - lemna minor - lemnaceae - medicinal plants - chemical composition - enzymes - antioxidants - vitamins - essential amino acids - aquatic plants - applied research - food industry - health promotion
    De toegenomen vraag naar gezondheidsbevorderende levensmiddelingrediënten en het enzym superoxide dismutase (SOD) dat als voedingssupplement wordt gebruikt
    Isolation, identification and evaluation of natural antioxidants from aromatic herbs cultivated in Lithuania
    Dapkevicius, A. - \ 2002
    Wageningen University. Promotor(en): Æ. de Groot; T.A. van Beek; J.P.H. Linssen. - S.l. : S.n. - ISBN 9789058085788 - 154
    antioxidanten - keukenkruiden - thymus vulgaris - lipidenperoxidatie - spectroscopie - hplc - antioxidants - culinary herbs - thymus vulgaris - lipid peroxidation - spectroscopy - hplc
    Oxidative spoilage of lipid-rich foods decreases their shelf-life and leads to undesirable chemical and physical changes. Nowadays natural antioxidants are generally preferred. The major part of industrially used antioxidants consists of radical scavengers, which inhibit the oxidative chain reaction by inactivating free radicals formed during peroxidation of lipids. Aromatic and medicinal herbs are rich sources of natural radical scavenging compounds. The research described in this thesis focuses on the evaluation of several aromatic plants grown in Lithuania as a possible source of food antioxidants. Various aspects of lipid oxidation, of antioxidative mechanisms and of natural sources of radical scavenging antioxidants are outlined in Chapter 1.

    Employment of model systems for antioxidant studies is often preferred over lipid stability tests due to their speed and the simplified comparison and interpretation of the obtained results. Preliminary screening of extracts from aromatic plants was carried out using theβ-carotene-linoleic acid model system (β-CLAMS). The method is based on a competition between the plant antioxidant and an oxidisable indicator (β-carotene) for free radicals, which are generated during temperature-accelerated oxidation of linoleic acid. The agar-diffusion and spectrophotometricβ-CLAMS tests singled out thyme ( Thymus vulgaris L.) and sage ( Salvia officinalis L.) as the most promising sources of natural antioxidant compounds (Chapter 2). The screening results also revealed that supercritical fluid extraction (SFE) as well as solvent extraction with acetone and methanol-water were the two most efficient techniques for isolation of antioxidant constituents from sage and thyme (Chapter 2). In further antioxidant activity tests, the spectrophotometricβ-CLAMS technique was adapted to microtiter plates, which gave a better reproducibility and a shorter analysis time. The modified and improved spectrophotometricβ-CLAMS confirmed the preliminary screening results. Sage and thyme acetone extracts again demonstrated the highest radical scavenging activity with relative antioxidant activities similar to those of 2,6-di- tert -butyl-4-methylphenol (BHT) (Chapter 3).

    The activity of primary antioxidants can be evaluated directly by monitoring the reduction of free radicals. Such experiments can be carried out off-line, i.e. by the introduction of previously isolated antioxidant compound(s) into an equilibrated free radical containing model system, or on-line, by adding a solution of a free radical to the eluate of an HPLC column. The on-line techniques allow for a rapid and selective detection of radical scavenging substances in the presence of many inactive constituents with a minimum of preparatory manipulations. Two on-line model systems based on the reduction of radical intermediates of the luminol chemiluminescence (CL) reaction and on the reduction of the stable 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH·) were used for the detection of antioxidant compounds in thyme and sage isolates. Ten compounds in the thyme acetone oleoresin and six in sage gave an inhibition signal on the CL detector (Chapter 4).

    An adequate HPLC separation and a sensitive detection of radical scavenging are two key-elements that determine the success of on-line experiments. Improved separation efficiency especially for polar analytes was observed after an acetonitrile/water gradient program was introduced and after lowering of the pH of the HPLC solvents (Chapter 5). A stable, pulse-free flow, appropriate instrumental set-up and optimised compositions of the CL and the DPPH·reagents improved the sensitivity of the on-line detection. The minimum detectable amounts registered in this study varied from 0.06 ng for rosmarinic acid to 2400 ng for carvacrol (HPLC-CL detection) and from 0.2 ng for eugenol to 19 ng for BHT (HPLC-DPPH·detection) (Chapter 5). It was found that the HPLC-CL system was on average more sensitive, however the HPLC-DPPH·method was more robust.

    The on-line HPLC-DPPH·method as well as TLC plates sprayed with DPPH·solution were used for the activity-guided isolation of radical scavenging compounds from a leaf extract of thyme. Nine active compounds were isolated from the methanolic and the acidic aqueous alcoholic extract by means of solvent partitioning, normal phase chromatography, size exclusion chromatography and reversed phase MPLC or HPLC (Chapter 6). Rosmarinic acid, eriodictyol, taxifolin, luteolin 7-glucuronide, p -cymene 2,3-diol and p -cymene 2,3-diol 6-6´-dimer were identified by a combination of UV, CD, mass spectrometry and 1H and 13C NMR. Two weakly active, volatile compounds, thymol and carvacrol, were identified by GC-MS and their structures confirmed by GC and TLC analysis with reference compounds. The structure of a highly active new phenylpropanoid trimer 3'-O-(8''-Z-caffeoyl)-rosmarinic acid was elucidated from its UV and CD spectra, FD mass spectrum, and 1H-, 13C-, COSY and direct and long range 1H-13C NMR spectra (Chapter 6). In off-line Trolox Equivalent Antioxidant Capacity (TEAC) and DPPH·assays, this compound was a weaker and stronger radical scavenger than rosmarinic acid, respectively.

    The presence in T. vulgaris of radical scavenging compounds of different polarity and with distinctive reactivity to different radicals offers the possibility to use extracts from this plant as natural antioxidants for various lipid-containing food systems.

    Epidemiological studies on the relation between diet and COPD
    Tabak, C. - \ 2000
    Agricultural University. Promotor(en): D. Kromhout; H.A. Smit; D.J.J. Heederik. - S.l. : S.n. - ISBN 9789058082183 - 135
    ademhalingsziekten - voeding - antioxidanten - chronisch ziektebeloop - respiratory diseases - nutrition - antioxidants - chronic course

    Chronic Obstructive Pulmonary Disease (COPD) is an important cause of morbidity and mortality around the world. In the early 1990's several dietary factors were suggested to protect against COPD, based on proposed biological mechanisms and a small number of epidemiological studies. Antioxidants (e.g. vitamin C and E,β-carotene, flavonoids) and foods rich in antioxidants (e.g. fruits, vegetables, whole grains) may protect the airways against oxidant-mediated damage. Alcohol and n-3 fatty acids (mainly present in fish) are thought to have anti-inflammatory effects.

    To gain more insight into the relation between diet and COPD, we analysed data from two large-scale population-based epidemiological studies. Data from the Seven Countries Study (1960-1990) allowed us to study the relation longitudinally in an international setting. However, less sophisticated methods than available today were used to examine mainly ever-smoking middle-aged and older men. In the cross-sectional MORGEN-study (1993-1997), Dutch men and women (20-59 yr.) with a large variation in smoking habits were examined using modern, high-quality methods. All associations were adjusted for age, height (for pulmonary function only), gender, smoking, body mass index and total energy intake.

    In the 16 cohorts of the Seven Countries Study, we observed an inverse ecological association of 25-yr COPD mortality with baseline fruit and fish consumption. At the individual level, not energy-adjusted baseline fruit and vitamin E intake were inversely associated with 20-yr COPD mortality in men from three European countries. Alcohol consumption showed a U-shaped curve with 20-yr COPD mortality, with the lowest rate in light drinkers (>1.4,≤30 g/day). This U-shaped curve was supported by cross-sectional data on alcohol and pulmonary function. In all three countries, men with intake of both fruits and vegetables above the median had a higher pulmonary function (FEV 1 or FEV 0.75 ) than those with a low intake of both foods. Finally, bread intake was positively associated with pulmonary function in the three countries.

    In participants of the MORGEN-study, intake of catechins, flavonols and flavones was positively associated with the FEV 1 and inversely associated with the prevalence of chronic cough and breathlessness. Catechin intake, not derived from tea, was independently associated with both the FEV 1 and all studied COPD symptoms. Flavonol and flavone intake, however, was independently associated with chronic cough only. At the food group level, solid fruit (=apples, pears), but not tea, intake was beneficially associated with COPD. Furthermore, we observed independent beneficial associations of a favourable intake of fruits and whole grains (above the median) and alcohol (1-30 g/day) with COPD. The 2578 subjects with a favourable intake of all three foods had a 139 ml higher FEV 1 and a lower prevalence of COPD symptoms (OR = 0.44) compared to those with unfavourable intakes of the three foods. This was also observed in never smokers.

    The studies described in this thesis mainly suggest a protective effect of a high intake of fruits and whole grains and of light alcohol consumption (up to 3 drinks/day) against COPD. Causality of the observed relations is supported by an apparently temporal relation and by plausible biological mechanisms. Smoking did not seem to explain our findings. Confounding by other health related lifestyle factors can, however, not be excluded. The observed effect of dietary factors was estimated to reduce COPD with 10 to 30% at the population level and is, if causal, certainly of public health relevance.

    Ozonides: intermediates in ozone-induced toxicity : a study on their mechanism of toxic action and detoxification by antioxidants
    Hempenius, R.A. - \ 2000
    Agricultural University. Promotor(en): J.H. Koeman; I.M.C.M. Rietjens; G.M. Alink. - S.l. : S.n. - ISBN 9789058083524 - 123
    ozon - toxiciteit - werkwijze - antioxidanten - ontgifting - longfunctie - ratten - ozone - toxicity - mode of action - antioxidants - detoxification - lung function - rats

    Ozone is a major constituent of photochemical smog. The toxicity of ozone is well documented and has been related to its strong oxidative potential. The principal target organ for ozone toxicity is the respiratory system. Unsaturated fatty acids, which are present in both the lipids of the lung lining fluid and the cell membranes of the cells that line the airways, are thought to be primary target molecules for ozone. Ozone reacts with unsaturated fatty acids via the so-called Criegee mechanism. Along with aldehydes and hydroxyhydroperoxides, Criegee ozonides are the main products of the reaction of ozone with unsaturated fatty acids. It is generally assumed that these lipid ozonation products act as secondary toxins in ozone-induced toxicity. However, very little is known about the reactivity and fate of ozonides and the role they play in ozone toxicity. Therefore, the aim of the present study was to gain insight into the mechanism of the toxic action of ozonides in relation to ozone-induced lung toxicity.For the investigations the ozonide from the polyunsaturated fatty acid methyl linoleate was used. On ozonation of methyl linoleate the major product formed appeared to be the trans -9,10-methyl linoleate ozonide (MLO).It has been suggested that ozonides are a kind of peroxide, and it is, therefore, believed that ozonides are a source of free radicals. This implies that ozonides might be capable of initiating the chain autoxidation of other non-ozonated polyunsaturated fatty acids in the membrane bilayer, and consequently of producing a cascade of damage. This hypothesis was investigated by comparing the in vitro cellular toxic action of MLO with a model peroxidative agent, i.e., cumene hydroperoxide. The ozonide was shown to be three times more toxic towards alveolar macrophages than the peroxide. On the basis of the cellular protection of antioxidants it was clearly shown that the ozonide and the hydroperoxide exert their toxic effects using different mechanisms. Whereas the results with the model hydroperoxide, cumene hydroperoxide, confirmed the mechanism by which peroxides exert their toxic effects, namely by lipid peroxidation and/or depletion of intracellular glutathione (GSH) levels, the investigations regarding the potency of MLO to induce lipid peroxidation revealed that the main toxic mechanism of MLO did not proceed via a radical-mediated mechanism. Nevertheless, suppletion of cells with the lipid-soluble radical scavengerα-tocopherol resulted in a significant protection towards ozonide exposure. In addition, preincubation of MLO withα-tocopherol resulted in a detoxification of the ozonide. This suggests thatα-tocopherol is able to interact directly with the ozonides themselves, thus scavenging these reactive intermediates.Investigations regarding the chemical characteristics of the detoxification of MLO byα-tocopherol revealed that the main products formed were the aldehyde nonanoic 9-oxo methyl ester and the acid nonanedioic acid monomethyl ester. This finding is in agreement with the general opinion that the decomposition of ozonides results in the formation of aldehydes and acids. In general, it is believed that thermal decomposition of ozonides proceeds via homolytic cleavage of the peroxide bond to yield the oxy bi-radical followed by a rearrangement. A modification on this mechanism includes concerted homolysis and intramolecular hydrogen atom abstraction. In contrast to the results obtained at elevated temperatures (≥50 °C), in previous studies ozonides have been shown to be stable compounds at 37 °C. No radical formation could be detected when MLO was incubated for 30 min at 37 °C using spin traps and electron spin resonance (ESR). Taking into account the fact that peroxide bond homolysis is an essential part of ozonide decomposition, one might postulate thatα-tocopherol, being an efficient hydrogen atom donor, facilitates the process of O-O bond homolysis, thereby inducing aldehyde and acid formation already at relatively low (i.e.≤37 °C) temperatures.An additional interesting finding was that the degradation products of MLO, i.e., nonanoic 9-oxo methyl ester and nonanedioic acid monomethyl ester (azelaic acid monomethyl ester), were not toxic towards alveolar macrophages at concentrations where MLO showed complete loss of cell viability. This observation is especially of importance because it is often suggested that Criegee ozonides will be formed in relatively small amounts (ca. 10%) when ozone reacts with unsaturated fatty acids in the lung lining fluids and may, therefore, play a minor role in ozone-induced toxicity. However, the results of the present study clearly indicate that ozonides are far more toxic than their aldehyde and acid type degradation products, which are generally observed as major products resulting from the reaction of ozone with fatty acids under physiological conditions.In addition, the mechanism underlying the reaction of another cellular antioxidant, namely glutathione, with polyunsaturated fatty acid ozonides was investigated. In previous studies it has been shown that preincubation of MLO with glutathione caused a significant detoxification of the ozonide. Furthermore, the detoxification reaction was shown to be catalysed by glutathione S -transferases leading to the formation of oxidised glutathione and aldehydes. The reaction of ozonides and peroxides with glutathione was investigated using molecular orbital calculations and the frontier orbital theory. In addition to the results obtained in the comparative study on the toxicity of ozonides and peroxides, the reaction of ozonides with the nucleophilic agent glutathione appeared also to be different when compared with the reaction with peroxides. On the basis of semi-empirical molecular computer calculations the nucleophilic attack by glutathione on the ozonide is expected to occur at one of the carbon atoms of the ozonide ring instead of at one of the peroxidic oxygen atoms as in the case of peroxides. A mechanism for the glutathione S -transferase-mediated detoxification of ozonides, different from that of the reaction with hydroperoxides has been proposed.Furthermore, the in vivo toxicity of ozonides was investigated. Methyl linoleate ozonide (MLO) (0.07 mmol/100 g body wt) was administered to female Wistar rats either intravenously or intraperitoneally. After 24 h the rats were killed and the effects were examined. MLO was found to be toxic only after intravenous administration. The major effects were observed in the lungs. The lungs became enlarged from edema and showed severe haemorrhages. Furthermore, the total thiol level was depleted in serum and lung tissue, accompanied by a decrease in the activity of thiol-dependent enzymes. The vitamin E levels in serum and lung tissue were also reduced. The malondialdehyde (MDA) concentrations in serum and lung tissue were elevated suggesting that in vivo oxidation had occurred. On intraperitoneal administration of MLO, no effects on enzyme activities, thiol and vitamin E content in lung tissue were observed. In serum, however, as on intravenous administration, an increase in the MDA levels and decreases in total thiol and vitamin E levels were found. In view of the route of administration it is to be expected that the ozonide is partially cleared by the liver, and the ozonide and its potentially toxic products are further detoxicated by vitamin E and thiols in the serum before they reach the lung. The above data show that the main target organ for ozonides is the lung, and that the effects caused by MLO in vivo are in many respects similar to the effects found after acute ozone exposure.In short, the most important conclusions of the present studies are:

  • Ozonides exert their toxic effects by a mechanism different from that from the structurally related peroxides.
  • The protective action ofα-tocopherol against ozonides proceeds via a direct interaction by whichα-tocopherol facilitates ozonide degradation through peroxide bond homolysis already at 37 °C.
  • The involvement of ozonides in ozone-induced toxicity may be more important than currently suggested, since they are far more toxic than their aldehyde-type degradation products, which are generally observed as major products resulting from the reaction of ozone with unsaturated fatty acids under physiological conditions.
  • Overall, the results presented in the thesis provide new insights into the toxic mechanism of ozonides and their implications for ozone-induced lung toxicity.

    Spinach as a source of carotenoids, folate and antioxidant activity
    Castenmiller, J.J.M. - \ 2000
    Agricultural University. Promotor(en): J.G.A.J. Hautvast; C.E. West. - S.l. : S.n. - ISBN 9789058081605 - 183
    spinazie - carotenoïden - foliumzuur - antioxidanten - spinach - carotenoids - folic acid - antioxidants

    Fruits and vegetables are generally considered important contributors to a healthy diet and an increased intake of fruits and vegetables is related to a decreased risk of cancers, cardiovascular disease, and other diseases. In this thesis two aspects of spinach, a dark-green, leafy vegetable, are examined. The first aspect is the bioavailability of the carotenoids and folate present in spinach. The second aspect is the antioxidant activity of spinach consumption in humans and the antioxidant capacity of spinach products. The literature on carotenoid bioavailability and bioconversion was reviewed for each of the SLAMENGHI factors. These factors include: Species of carotenoid; molecular Linkage; Amount of carotenoid consumed in a meal; Matrix in which the carotenoid is incorporated; Effectors of absorption; Nutrient status of the host; Genetic factors; Host related factors; and Interactions.

    A dietary intervention study with 70 healthy human subjects divided over six treatment groups was conducted to examine the effect of the food matrix on the bioavailability of carotenoids and folate and to evaluate the effect of spinach intake on biomarkers of antioxidant activity. Four groups received a basic diet plus a spinach product (whole-leaf, minced, enzymatically liquefied, and liquefied spinach plus added dietary fibre), one group received the basic diet plus a carotenoid supplement ofβ-carotene, lutein and a small amount of zeaxanthin dissolved in oil, and one group received the basic diet only. Consumption of spinach (20 g/MJ), containing the carotenoidsβ-carotene and lutein, increased serum concentrations ofβ-carotene, lutein,α-carotene and retinol and decreased the serum concentration of lycopene compared with the control group. Compared with the synthetic carotenoid supplement, the relative bioavailability ofβ-carotene was low, 5.1-9.5%, but much higher for lutein, 45-55%. Serumβ-carotene responses differed significantly between the whole-leaf and liquefied spinach groups and between the minced and liquefied spinach groups. The plasma folate response was significantly greater in the spinach groups compared with the control group. Intake of minced and liquefied spinach resulted in greater plasma folate responses than consumption of whole-leaf spinach.

    Thus, disruption of the food matrix (cell wall structure) and loss of cellular structure had an effect on the bioavailability ofβ-carotene and folate, whereas the bioavailability of lutein was not affected. Addition of dietary fibre to the liquefied spinach to compensate for the fibre that was broken down during liquefaction had no effect on serum carotenoid or plasma folate responses.

    Consumption of spinach or the carotenoid supplement resulted in an increased erythrocyte glutathione reductase activity, and decreased erythrocyte catalase activity and serumα-tocopherol concentration. These changes were related to serum lutein concentrations. The antioxidant capacity of the differently processed spinach products was determined in different oxidation systems. Corrected for the total phenolics content of the spinach, the whole-leaf spinach extract showed the strongest inhibition of hydroperoxide formation, followed by extracts from liquefied and minced spinach. The calculated amount of lutein in the spinach samples used (amounts were adjusted for the total phenolics content of spinach) was correlated with the inhibition of hydroperoxide formation. In a meat ball model at 100 and 200 g spinach/kg meat, whole-leaf and minced spinach were prooxidative (increased the formation of thiobarbituric acid-reactive substances); the liquefied spinach became antioxidative at 200 g/kg. Minced and liquefied spinach were antioxidatively active with respect to the mean inhibition of hexanal formation, whereas whole-leaf spinach showed prooxidant activity.

    In conclusion, the results of the studies described in this thesis demonstrated an effect of the food matrix onβ-carotene and folate, but not on lutein, bioavailability and support the finding thatβ-carotene is not a good antioxidant in man or in foods, but indicate that lutein may play a role as antioxidant.

    Antioxidanten in de voeding
    Graat, J. - \ 1999
    Voeding Nu 1 (1999)12. - ISSN 1389-7608 - p. 25 - 27.
    antioxidanten - groenten - vruchten - samenstelling - voedingswaarde - ziektepreventie - antioxidants - vegetables - fruits - composition - nutritive value - disease prevention
    Antioxidants and air pollution in relation to indicators of asthma and COPD
    Grievink, L. - \ 1998
    Agricultural University. Promotor(en): B. Brunekreef; D. Kromhout; H.A. Smit. - S.l. : Grievink - ISBN 9789054859499 - 134
    antioxidanten - luchtverontreiniging - astma - ademhalingsziekten - antioxidants - air pollution - asthma - respiratory diseases

    Two main research questions were specified in this thesis. First, whether acute respiratory effects of air pollution can be modulated by antioxidants. Second, whether dietary or plasma antioxidants were associated with indicators of asthma and COPD.

    Two intervention studies investigated a possible modulation of the acute respiratory effects of ozone by antioxidant supplementation. In addition a panel study examined a possible modulation of the acute respiratory effects of winter air pollution by antioxidants in diet and serum.

    The first intervention study in 1994 was a pilot study among 26 cyclists who performed lung function measurements (192 observations) before and after exercise. Half of the group was randomly assigned to the supplementation group and were given a daily antioxidant supplementation of vitamins C, E andβ-carotene. The control group did not receive a placebo. We repeated the study in the summer of 1996 with a similar design but this time the study was placebo-controlled. In this study, 38 subjects (380 lung function measurements) participated until the end of the study and the antioxidant supplementation consisted of a cocktail of vitamins C and E.

    Both intervention studies suggest that there was an effect of ozone on FEV 1 and FVC in the control group. There was no change in lung function when ozone levels were high in the supplementation group. The difference in ozone effect between the groups for both studies was statistically significant for FEV 1 and FVC. In the analysis of the panel study, we included only subjects with chronic respiratory symptoms because these subjects showed clear acute respiratory effects of air pollution. The results suggest that subjects with low levels of plasmaβ-carotene showed an effect of air pollution on large PEF decrements, in particular, for PM10 and black smoke, whereas subjects with high levels of plasmaβ-carotene did not show an effect of air pollution. No difference in acute respiratory effects of air pollution was observed for a high versus a low dietary intake of vitamin C, E andβ-carotene or for plasmaα-tocopherol.

    The second research question was investigated within the MORGEN study. This study is a cross-sectional investigation on the prevalence of risk factors for chronic diseases using self-administered questionnaires and a physical examination in a randomly selected sample of the Dutch population.

    First, we examined the relations between dietary antioxidants (vitamins C, E andβ-carotene) and the prevalence of a number of respiratory symptoms and lung function in a population based sample of 6,555 adults. Our results suggested that a high dietary vitamin C andβ-carotene intake was associated with a higher FEV 1 and FVC. Dietary vitamin E was not associated with lung function. None of the dietary antioxidants were consistently associated with the prevalence of a number of respiratory symptoms.

    Second, we studied the relation between plasma levels ofβ-carotene orα-tocopherol and respiratory symptoms in a case-control sample of never and long-term former smokers. Our results suggested that cases (subjects with one or more chronic respiratory symptoms; n=491) tended to have lower plasmaβ-carotene levels than controls (n=496). Plasmaα-tocopherol was not associated with asthma and chronic bronchitis symptoms but was positively associated with dyspnea. This adverse association of plasmaα-tocopherol could not be explained by adjustment for cardiovascular risk factors and remains puzzling. Third, we evaluated the relation between plasma antioxidants (β-carotene andα-tocopherol) and lung function in a random sample (n=367) of the MORGEN study. We found that subjects with a high plasmaβ-carotene concentration tended to have a higher FVC and FEV 1 than subjects with a low plasmaβ-carotene concentration but this was not statistically significant for FEV 1 . Plasmaα-tocopherol was not associated with lung function.

    Versnelde bewaarproeven met luzernemeel en - brokjes, waaraan palmolie en anti - oxydanten zijn toegevoegd
    Huisman, M.H. - \ 1962
    Wageningen : [s.n.] (Intern rapport / Instituut voor bewaring en verwerking van landbouwprodukten no. 150) - 6
    toevoegingen - antioxidanten - voederpeulvruchten - voederplanten - fabricage - palmoliën - behandeling - macromoleculaire stoffen - additives - antioxidants - fodder legumes - fodder plants - manufacture - palm oils - treatment - macromolecular materials
    Praktijkproeven over het toevoegen van palmolie en anti - oxydanten aan kunstmatig gedroogde luzerne
    Huisman, M.H. - \ 1962
    Wageningen : [s.n.] (Intern rapport / Instituut voor bewaring en verwerking van landbouwprodukten no. 149) - 16
    toevoegingen - antioxidanten - voederpeulvruchten - voederplanten - fabricage - palmoliën - behandeling - macromoleculaire stoffen - additives - antioxidants - fodder legumes - fodder plants - manufacture - palm oils - treatment - macromolecular materials
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