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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Stof tot nadenken : vier manieren om de mode-industrie duurzamer te maken
Louwerens, Tessa ; Poldner, Kim ; Fischer, Arnout ; Broek, Ben van den; Dam, Jan van; Houthoff, Iris - \ 2018
biobased materials - clothing - fibres - algae - biomass - hemp - dyes - pigments - bioplastics - biopolymers - ink - natural products
Mid season sale, twee halen één betalen, op=op. Mode wordt steeds goedkoper en wisselt steeds sneller. Leuk voor het oog, maar achter al die fashion gaat grote milieuschade schuil. WUR-wetenschappers zoeken naar manieren om de kledingindustrie duurzamer te maken. Van hennepstof tot algenverf, van chemisch recyclen tot vintage kleding.
Genome-based exploration of the specialized metabolic capacities of the genus Rhodococcus
Ceniceros, Ana ; Dijkhuizen, Lubbert ; Petrusma, Mirjan ; Medema, M.H. - \ 2017
specialized metabolism - natural products - biosynthetic gene clusters - Rhodococcus - Mycobacterium
Background Bacteria of the genus Rhodococcus are well known for their ability to degrade a large range of organic compounds. Some rhodococci are free-living, saprophytic bacteria; others are animal and plant pathogens. Recently, several studies have shown that their genomes encode putative pathways for the synthesis of a large number of specialized metabolites that are likely to be involved in microbe-microbe and host-microbe interactions. To systematically explore the specialized metabolic potential of this genus, we here performed a comprehensive analysis of the biosynthetic coding capacity across publicly available rhododoccal genomes, and compared these with those of several Mycobacterium strains as well as that of their mutual close relative Amycolicicoccus subflavus. Results Comparative genomic analysis shows that most predicted biosynthetic gene cluster families in these strains are clade-specific and lack any homology with gene clusters encoding the production of known natural products. Interestingly, many of these clusters appear to encode the biosynthesis of lipopeptides, which may play key roles in the diverse environments were rhodococci thrive, by acting as biosurfactants, pathogenicity factors or antimicrobials. We also identified several gene cluster families that are universally shared among all three genera, which therefore may have a more ‘primary’ role in their physiology. Inactivation of these clusters by mutagenesis might help to generate weaker strains that can be used as live vaccines. Conclusions The genus Rhodococcus thus provides an interesting target for natural product discovery, in view of its large and mostly uncharacterized biosynthetic repertoire, its relatively fast growth and the availability of effective genetic tools for its genomic modification.
Gebruik van groene middelen : Inventarisatie laanboomkwekerij
Sluis, B.J. van der; Kuik, A.J. van; Baltissen, A.H.M.C. - \ 2016
Wageningen : Wageningen Plant Research, Bloembollen, Boomkwekerij & Fruit - 22 p.
bos- en haagplantsoen - straatbomen - aantrekkelijke bomen - gelderland - gewasbescherming - geïntegreerde plagenbestrijding - biologische bestrijding - natuurlijke producten - bladvoeding - natuurlijke vijanden - organismen ingezet bij biologische bestrijding - woody nursery stock - street trees - amenity trees - plant protection - integrated pest management - biological control - natural products - foliar nutrition - natural enemies - biological control agents
In de laanboomteelt in de regio Opheusden wordt al jarenlang gewerkt aan verduurzaming van de teeltmethoden. Het verantwoord toepassen van gewasbeschermingsmiddelen is daarvan een belangrijk onderdeel. Door strengere regelgeving wordt het chemische middelenpakket steeds verder beperkt en komen boomkwekers in toenemende mate voor knelpunten te staan. Uit oriënterende gesprekken in de regio blijkt dat een deel van de boomkwekerijbedrijven zich inmiddels toelegt op het gebruik van groene middelen om zo de afhankelijkheid van chemische middelen te verkleinen. Volgens de definitie van het Ctgb zijn dit gewasbeschermingsmiddelen van natuurlijke oorsprong (planten, dieren, microorganismen) met een laag risico voor mens, dier, milieu en niet-doelorganismen. In dit project wordt geïnventariseerd wat de mate van gebruik is van groene middelen door laanboomkwekers in de regio Rivierenland én wat hun ervaringen zijn met deze middelen. De uitkomst kan de sector in de regio benutten om de kennisuitwisseling voor duurzaam telen te bevorderen, zowel tussen kwekers als naar de burgers.
Plants4Cosmetics : perspectives for plant ingredients in cosmetics
Boeriu, C.G. - \ 2015
Wageningen : Wageningen UR - Food & Biobased Research (Report / Wageningen UR Food & Biobased Research 1603) - 38 p.
cosmetics - plants - flavonoids - phenols - pigments - plant pigments - polysaccharides - geranium - hyacinthus - chrysanthemum - orchidaceae - skin - hair - oil plants - medicinal plants - natural products - biobased chemicals - biobased economy - cosmetica - planten - flavonoïden - fenolen - pigmenten - plantenpigmenten - polysacchariden - huid - haar - olieleverende planten - medicinale planten - natuurlijke producten - chemicaliën uit biologische grondstoffen
In opdracht van Bio Base Westland en de TKI Tuinbouw Koepel PPS Plantenstoffen, heeft Wageningen UR – Food & Biobased Research een exploratieve desktop studie uitgevoerd gericht op de identificatie van veelbelovende routes voor de valorisatie van plantinhoudstoffen - waaronder ook reststromen uit de tuinbouw - voor de cosmetische industrie. Een uitgebreide analyse van de beschikbare informatie werd uitgevoerd om de mogelijkheden voor de Nederlandse tuinbouwsector te bepalen. Er is gekeken naar marktkansen in de cosmetische industrie met inbegrip van natuurlijke en biologische ingrediënten.
Serieuze vergroening blijft niet lang meer uit : kenniscentrum Plantenstoffen stimuleert gebruik inhoudsstoffen
Noort, F.R. van - \ 2015
Buitenstebinnen : halfjaarlijkse uitgave van Naktuinbouw (2015)5. - p. 6 - 9.
tuinbouw - natuurlijke producten - glastuinbouw - materialen uit biologische grondstoffen - plantaardige producten - dioscorea - vanilla planifolia - dioscorea opposita - indigofera tinctoria - polygonum tinctorium - horticulture - natural products - greenhouse horticulture - biobased materials - plant products
Gaan we weer natuurlijke indigo gebruiken als kleurstof van spijkerbroeken? Zal de grootste fabrikant van cola straks weer échte vanille gebruiken in plaats van synthetische smaakmakers? Veel consumenten kiezen bewust voor producten op natuurlijke basis. De glastuinbouw kan goed op deze trend inspelen door zich te specialiseren in de teelt van deze bijzondere grondstoffen. We staan aan de vooravond van een innovatieve transitie. Onderzoeker Filip van Noort van Wageningen UR Glastuinbouw doet onderzoek naar de mogelijkheden
The secondary metabolome of the fungal tomato pathogen Cladosporium fulvum
Griffiths, S.A. - \ 2015
Wageningen University. Promotor(en): Pierre de Wit; Pedro Crous, co-promotor(en): Jerome Collemare. - Wageningen : Wageningen University - ISBN 9789462575813 - 167
passalora fulva - secundaire metabolieten - metabolomen - genen - genomica - biologische activiteit - biosynthese - natuurlijke producten - secondary metabolites - metabolomes - genes - genomics - biological activity - biosynthesis - natural products

Secondary metabolites (SMs) are biologically active organic compounds that are biosynthesised
by many plants and microbes. Many SMs that affect the growth, behaviour or survival of other
organsisms have been re-purposed for use as medicinal drugs, agricultural biocides and animal
growth promoters. The majority of our anti-infective and anti-cancer drugs are currently derived
from Streptomyces, bacteria that are free living, filamentous, and ubiquitous in terrestrial habitats.
Genome sequencing and mature in silico approaches to genome mining has revealed that filamentous
fungi contain very large numbers of genes related to SM production. Yet these genes are typically
silent under laboratory conditions. There are now many tools and strategies available to activate
or clone silent SM genes. This thesis details our efforts to apply various methods to define and
then manipulate SM genes in Cladosporium fulvum, a biotrophic pathogenic fungus of tomato
containing many silent SM genes and gene clusters.

In chapter 1, the relevance of SMs to medicine and agriculture is considered. Filamentous fungi
are presented as untapped sources of potential useful SMs, as their genomes are often rich in SM
biosynthetic genes that are silent under most conditions. Methods to activate these silent genes and
increase the chemical diversity of fungi are detailed. These include the deletion or over-expression
of genes encoding regulatory proteins, the use of chemical inhibitors, and the manipulation
of growth conditions. Heterologous expression of silent SM genes in a production host is also
discussed as a tool for bypassing host regulatory mechanisms altogether. C. fulvum is introduced
as an organism that has been intensively studied as a biotrophic plant pathogen. Genomic analysis
showed that this fungus has twenty-three core SM genes, a large catalogue composed of 10
polyketide synthases (PKSs), 10 non-ribosomal peptide synthases (NPS), one PKS-NPS hybrid
and one dimethylallyl tryptophan synthase (DMATS). Transcriptional profiling showed that the
majority was silent during growth on tomato and in vitro. Cladofulvin is introduced as the sole
detectable SM produced by C. fulvum during growth in vitro. This presented an opportunity to
apply the aforementioned strategies to induce these silent genes and obtain new compounds. The
importance of cladofulvin and structurally related anthraquinones are briefly discussed as potential
medicines. The value of the cladofulvin biosynthetic gene cluster is also emphasised as a potential
source of novel biosynthetic enzymes.

In chapter 2 the SM gene catalogue identified during the analysis of the C. fulvum genome was
analysed in further detail. Each locus containing a core SM gene was inspected for other biosynthetic
genes linked to SM production, such as those encoding decorating enzymes and regulators. Products
of these SM genes or gene clusters were speculated, based on their similarity to those characterized
in other fungi. Six gene clusters were located in the genome of C. fulvum that are conserved in other
fungal species. Remarkably, two predicted functional gene clusters were linked to the production
of elsinochrome (PKS1) and cercosporin (PKS7), toxic perylenequinones that generate reactive
oxygen species (ROS). We profiled the expression of core SM genes during the growth of C. fulvum
under several in vitro conditions. Expression of each core SM gene was measured by RT-qrtPCR
and the resulting SM profile was determined by LC-MS and NMR analyses. Confirming previous
findings, the majority of SM genes remained silent and only cladofulvin was detected. During
growth on tomato only two core genes, PKS6 and NPS9, were clearly expressed, but both were
significantly down-regulated during colonization of the mesophyll tissue of tomato leaves. We
confirmed that cladofulvin does not cause necrosis on solanaceous plants when infiltrated into
their leaves. In contrast to other biotrophic fungi that have a reduced SM production capacity, our
studies of C. fulvum suggest that down-regulation of SM biosynthetic pathways might represent
another mechanism associated with a biotrophic lifestyle.

In chapter 3 our efforts to activate cryptic pathways in C. fulvum are described, with the aim
of discovering new compounds. Many Ascomycete-specific global regulators of SM production
and morphological development in other fungi were identified in C. fulvum. We investigated
three intensively studied regulators, VeA, LaeA and HdaA. Deleting or over-expressing the genes
encoding these regulators in C. fulvum yielded no new detectable SMs. Cladofulvin biosynthesis
was strongly affected by each regulator; HdaA is an activator while VeA and LaeA are repressors of
cladofulvin production. Attempts were made to stimulate SM production in the mutants and wild
type strains by growing them on different carbon sources, but only cladofulvin biosynthesis was
affected. Interestingly, cladofulvin production was stimulated by carbon limitation and strongly
repressed in the presence of saccharose. Similar to observations made in other fungi, the deletion of
VeA or LaeA did not affect viability, but maturation and conidiation were affected. Sporulation was
not overtly affected by the loss of HdaA, but Δhdaa deletion mutants did not produce cladofulvin.
This suggests that cladofulvin production is not required for asexual reproduction. The main
finding of this chapter is that global regulator manipulation cannot considered to be a universal
tool to discover new fungal natural products.

In chapter 4, anthraquinones and closely related compounds such as anthrones, anthracyclines
and xanthones are considered. Emodin is perhaps the most well characterised anthraquinone that
is produced by many fungi and plants. Once synonymous only with constipation, this former
laxative has since been investigated for its useful anti-cancer, anti-diabetic, anti-infective and antiinflammatory properties. Cladofulvin is a homodimeric anthraquinone composed of nataloe-emodin joined in a remarkably asymmetrical configuration. Dimeric anthraquinones and xanthones are also bioactive, most commonly tested for anti-infective and anti-cancer activities. Despite the ubiquity and medicinal qualities of anthraquinones and related compounds, very few of their biosynthetic pathways are known. No enzymes capable of dimerizing anthraquinones had yet been identified. In this chapter we demonstrated that cladofulvin was very cytotoxic towards human cancer cell-lines, crucially, up-to 300-fold more than its monomeric precursor nataloe-emodin against certain celllines. This became an added incentive to elucidate the cladofulvin pathway and identify the enzyme responsible for dimerizing nataloe-emodin. We confirmed earlier predictions that PKS6/claG is the core gene which starts cladofulvin biosythesis. Deletion of claG abolished cladofulvin production
and no related metabolites were observed. A route to cladofulvin biosynthesis was proposed, guided
by the work performed on the monodictyphenone biosynthetic pathway in Aspergillus nidulans.

We predicted early acting cladofulvin genes and cloned them for heterologous expression in A.
oryzae strain M-2-3. Using this approach we were able to confirm the first five genes in cladofulvin
biosynthesis, claBCFGH, which yielded a reduced and dehydrated form of emodin. This is the
point at which the pathways to cladofulvin and monodictyphenone production diverge. It was
speculated that this emodin-related intermediate might be converted into nataloe-emodin by claK
and/or claN. Finally, it was confirmed that the final step in the cladofulvin pathway is encoded by
claM. Targeted deletion of claM yielded a mutant that accumulated nataloe-emodin and emodin
but no cladofulvin. We discuss how the sequence of claM and ClaM will accelerate the discovery
of functionally similar genes and enzymes, providing a template to engineer enzymes capable of
forming novel dimers from existing monomers.

In chapter 5 the natural role of cladofulvin was considered. This SM is consistently produced by
C. fulvum and global regulator mutants in vitro. The respective biosynthetic genes appear most
active during early and late stages of infection of tomato, but are down-regulated during biotrophic
growth phase (chapter 2). The Δclag mutants (chapter 3) were not overtly different from the wild
type during growth in vitro. We inoculated tomato plants with this mutant in order to test whether
or not cladofulvin was required for normal infection. Simultaneously, we inoculated a C. fulvum
transformant carrying an extra copy of the cladofulvin pathway-specific relulator, OE.claE, fused
to the promoter region of the Avr9 effector gene. The strain was expected to produce cladofulvin
once the fungal hyphae penetrate host stomata and begin to colonise the apoplastic space. In this
way, we aimed to test the effect of cladofulvin over-production on disease symptom development.
The growth of each strain on tomato plants was monitored by RT-qrtPCR at 4, 8 and 12 days post
inoculation (dpi). At each time point the infections were inspected microscopically to detect any
phenotypic abnormalities. We report that the loss of claG did not result an abnormal infection.
Both wild type and ΔclaG mutants sporulated without causing necrosis or dessication of host leaves.
In distinct contrast, brown spots appeared on leaves infected by the OE.claE transformant between
8 – 12 dpi. This was accompanied by much stronger fungal growth and significant accumulation
of cladofulvin. The leaves became desiccated and brittle before the fungus conidiated. Possible
reasons for this phenotype are discussed. A small suite of in vitro experiments was performed on the
Δclag and wild type strains in order to test the role of cladofulvin in survival. Consistent with the
absence of a photoprotective pigment, Δclag spores were considerably more sensitive to ultraviolet
(UV) radiation. Suggesting a role in protection against low temperatures, Δclag spores were less
resistant to repeated cycles of freezing and thawing. Cladofulvin biosynthesis was stimulated and
repressed by cold and heat shocking mature C. fulvum colonies, respectively. Altogether, these
results suggested that cladofulvin confers resistance to abiotic stress.

In chapter 6 the results obtained in this thesis are discussed in a broader context. Particularly,
the discovery of the cytochrome P450 that is involved in dimerization of anthraquinones might
enable discovery of homologous genes encoding enzymes with different specificities. Combining
bioinformatic and functional analyses should prove to be a powerful strategy for discovering
compounds with new biological activities, or enzymes relevant to metabolic engineering.

Kruiden verdringen antibiotica
Wolkers, H. ; Groot, M.J. ; Kleerebezem, M. ; Rebel, J.M.J. - \ 2015
WageningenWorld (2015)2. - ISSN 2210-7908 - p. 34 - 39.
veehouderij - diergezondheid - geneeskrachtige kruiden - dierziektepreventie - natuurlijke producten - antibiotica - reductie - dierenwelzijn - varkens - pluimvee - rundvee - melkvee - diervoeding - dierlijke productie - livestock farming - animal health - herbal drugs - animal disease prevention - natural products - antibiotics - reduction - animal welfare - pigs - poultry - cattle - dairy cattle - animal nutrition - animal production
Vanwege beperking van het antibioticagebruik vallen veehouders steeds vaker terug op kruiden, bacteriedrankjes en andere natuurlijke middelen om dieren gezond te maken én te houden. Hoewel harde medische claims niet altijd voorhanden zijn, boeken boeren soms spectaculaire resultaten met natuurlijke preparaten.
Phototrophic pigment production with microalgae
Mulders, K.J.M. - \ 2014
Wageningen University. Promotor(en): Rene Wijffels, co-promotor(en): Dirk Martens; Packo Lamers. - Wageningen : Wageningen University - ISBN 9789462571457 - 179
algen - fototropie - pigmenten - natuurlijke producten - metabolisme - carotenoïden - licht - gerichte mutagenese - algae - phototropism - pigments - natural products - metabolism - carotenoids - light - targeted mutagenesis
Abstract

Microalgal pigments are regarded as natural alternatives for food colorants. To facilitate optimization of microalgae-based pigment production, this thesis aimed to obtain key insights in the pigment metabolism of phototrophic microalgae, with the main focus on secondary carotenoids.

Different microalgal groups each possess their own set of primary pigments. Besides, a selected group of green algae (Chlorophytes) accumulate secondary pigments (secondary carotenoids) when exposed to oversaturating light conditions.

In this thesis it was found for the first time that nutrient-depleted Isochrysis. aff. galbana T-ISO (Haptophytes) accumulates 3-hydroxyechinenone, a precursor of astaxanthin. Besides, it was found that nitrogen-depleted Chromochloris (Chlorella) zofingiensis (Chlorophyes) accumulates astaxanthin, presumably synthesised via echinenone, and ketolutein.

Inhibition of production of β-carotene derivatives (e.g. echinenone and astaxanthin) did not lead to increased production of primary carotenoids (e.g. lutein) or ketolutein in this species, suggesting that the regulatory mechanisms controlling the flux towards ketolutein and primary carotenoids are not affected by the decreased levels of β-carotene derivatives.

Besides, optimal yields of secondary carotenoids and triacylglycerol (TAG) on light were reached with C. zofingiensis for a range of biomass concentrations at the moment of nitrogen depletion.

This indicated that the biomass-specific photon absorption rate did not affect the amounts of energy used for secondary carotenoid and TAG production, for the range of biomass concentrations tested.

It was also found that nitrogen-depleted C. zofingiensis resupplied with nitrogen hardly degraded astaxanthin, whereas the other major secondary metabolites were degraded rapidly.

This indicated that the overall carotenoid yield on light as well as its content may possibly be improved by applying a repeated batch instead of a series of single batch cultivations, which are traditionally applied.

Finally, it was discussed that the highest increases in carotenoid yield on light can be reached by optimizing strain performance (using targeted genetic engineering and/or random mutagenesis), rather than by optimizing the cultivation conditions/operation mode or reactor design.

Eikenprocessierups op verkeerde spoor
Bergervoet, J.H.W. ; Raaij, H.M.G. van; Stevens, L.H. - \ 2012
[S.l.] : YouTube
thaumetopoea processionea - quercus - plantenplagen - plagenbestrijding - natuurlijke producten - biologische bestrijding - extracten - gedrag - innovaties - landbouwkundig onderzoek - plant pests - pest control - natural products - biological control - extracts - behaviour - innovations - agricultural research
Eenvoudig, milieuvriendelijk en goedkoop de eikenprocessierups bestrijden. Dat komt dichterbij nu onderzoekers van Plant Research International (PRI), onderdeel van Wageningen UR, een natuurproduct hebben gevonden waarmee de rupsen om de tuin geleid kunnen worden. In samenwerking met gemeenten en groenbeheerders moet verder onderzoek uitwijzen welke stoffen voor deze reactie zorgen en hoe ze geproduceerd kunnen worden. De verwachting is dat dit onderzoek twee jaar zal duren. Deze film is gemaakt doorJan Bergervoet. Deze film hoort bij het persbericht van Wageningen UR die op 13 november 2012 verschenen is onder de titel: Wageningse onderzoekers leiden eikenprocessierups om de tuin. Voor meer informatie zie de website: www.wageningenur.nl/eikenprocessierups
Nieuwe middelen tegen Botrytis in cyclaam
Vries, R.S.M. de; Hofland-Zijlstra, J.D. ; Wensveen, W. van - \ 2012
ziektepreventie - gewasbescherming - botrytis - cyclamen - temperatuur - mest - natuurlijke producten - potplanten - sierteelt - glastuinbouw - disease prevention - plant protection - temperature - manures - natural products - pot plants - ornamental horticulture - greenhouse horticulture
Poster met onderzoeksinformatie. Doel: screening van niet-chemische producten en meststoffen tegen Botrytis in cyclaam, en bepaling van invloed van temperatuur op ontwikkeling Botrytis.
Biologisch melkvee natuurlijk gezond : het stalboekje Melkvee in de praktijk
Groot, M.J. - \ 2011
BioKennis bericht Zuivel & rundvlees 2011 (2011)21. - 4
biologische landbouw - melkveehouderij - handboeken - diergezondheid - natuurlijke producten - geneeskrachtige kruiden - melkvee - dierlijke productie - organic farming - dairy farming - handbooks - animal health - natural products - herbal drugs - dairy cattle - animal production
Biologische (melk)veehouders beschikken sinds begin 2010 over de ‘stalboekjes’ van het project Natuurlijk Gezond. De stalboekjes geven biologische veehouders handvaten voor het gebruik van kruiden en andere natuurlijke producten. Deze producten kunnen de weerstand van dieren verhogen, dierziektes voorkomen en op langere termijn bijdragen aan robuustere dieren in de biologische veehouderij. In dit bioKennisbericht meer over natuurlijke diergezondheid en de ervaringen van veehouders met natuurlijke middelen en de stalboekjes.
Biologische varkens natuurlijk gezond : het stalboekje varkenshouderij in de praktijk
Groot, M.J. - \ 2011
BioKennis bericht Varkensvlees 2011 (2011)15. - 4
biologische landbouw - varkenshouderij - diergezondheid - handboeken - natuurlijke producten - geneeskrachtige kruiden - varkens - dierlijke productie - organic farming - pig farming - animal health - handbooks - natural products - herbal drugs - pigs - animal production
Biologische veehouders beschikken sinds begin 2010 over de ‘stalboekjes’ van het project Natuurlijk Gezond. De stalboekjes geven biologische veehouders handvaten voor het gebruik van kruiden en andere natuurlijke producten. Deze producten kunnen de weerstand van dieren verhogen, dierziektes voorkomen en op langere termijn bijdragen aan robuustere dieren in de biologische veehouderij. In dit bioKennisbericht meer over natuurlijke diergezondheid en de ervaringen van veehouders met natuurlijke middelen en de stalboekjes.
Biologisch pluimvee natuurlijk gezond : het stalboekje pluimvee in de praktijk
Groot, M.J. - \ 2011
BioKennis bericht Pluimveevlees & eieren 10 (2011). - 4
biologische landbouw - pluimveehouderij - diergezondheid - handboeken - natuurlijke producten - geneeskrachtige kruiden - pluimvee - dierlijke productie - organic farming - poultry farming - animal health - handbooks - natural products - herbal drugs - poultry - animal production
Biologische veehouders beschikken sinds begin 2010 over de ‘stalboekjes’ van het project Natuurlijk Gezond. De stalboekjes geven biologische veehouders handvaten voor het gebruik van kruiden en andere natuurlijke producten. Deze producten kunnen de weerstand van dieren verhogen, dierziektes voorkomen en op langere termijn bijdragen aan robuustere dieren in de biologische veehouderij. In dit bioKennisbericht meer over natuurlijke diergezondheid en de ervaringen van veehouders met natuurlijke middelen en de stalboekjes.
Natural products for malaria vector control: flora, fish and fungi
Howard, A.F.V. - \ 2010
Wageningen University. Promotor(en): Willem Takken; Marcel Dicke, co-promotor(en): J.J. Githure. - [S.l. : S.n. - ISBN 9789085857204 - 267
malaria - ziekten overgebracht door muskieten - vectorbestrijding - natuurlijke producten - biologische bestrijding - plantaardige pesticiden - biopesticiden - vis - mosquito-borne diseases - vector control - natural products - biological control - botanical pesticides - microbial pesticides - fish
Introduction
Despite international organisations providing much focus over the past 10 years, malaria is still killing vast numbers of Africans, especially children. It is agreed that malaria can only be successfully controlled by using different control tools simultaneously in the spirit of integrated vector management (IVM), and that African communities will need to become more directly involved in mosquito control (Chapter 2). Using mosquito control tools in a way that requires almost no technical equipment or knowledge will open them up to the rural communities that are best placed to deploy them. In addition, widespread insecticide resistance is reducing the ability of insecticide-based tools to control mosquitoes. For these reasons, biological control and other natural mosquito control methods are being researched by many institutions. Several potential natural control tools are readily available in sub-Saharan Africa. If these tools prove effective and become operational, then it is possible that they will be sustainable because communities can intentionally produce the biological agents themselves, bringing a source of money to rural communities. This would be especially important in areas where infrastructure is poorly developed, and repeat applications of chemical control tools are not easily made. This thesis was designed to test the feasibility and effectiveness of a variety of natural products against both larval and adult malaria vector mosquitoes using low-tech methods in laboratory and field trials.

Part I: Flora
Azadirachta indica A. Juss (Meliaceae) (the neem tree) was chosen due to the already proved mosquitocidal properties, and its ready availability in Africa. We wanted to use neem in a way that could easily be deployed in resource-poor rural areas. Laboratory studies were conducted to examine the larvicidal and pupicidal properties of a crude aqueous extract of neem wood against the principle African malaria vector, Anopheles gambiae Giles s.s. (Diptera: Culicidae) (Chapter 3) [1]. The results indicate that even a relatively low dose of 0.15 grams of dried neem wood in 1 litre of water was able to inhibit the emergence of 90% of mosquito adults when larvae were exposed during their first three larval instars. Even for the fourth (last) larval instar, just 0.6 g/l was required to prevent 90% emergence. Furthermore, neem-exposed larvae exhibited significantly increased development times when compared to the controls. Pupae were also killed by the aqueous neem extracts, and were subject to neem-induced emergence abnormalities, but the concentrations required to kill pupae were much higher than for larvae and not likely to be used operationally. High performance liquid chromatography (HPLC) analysis identified several polar constituents in the aqueous neem extracts including nimbin and salannin. However, azadirachtin was not present in significant amounts. The effect of this extract on the oviposition behaviour of adult female An. gambiae s.s. mosquitoes was then monitored (Chapter 4) [2]. The oviposition results show that when using 0.1 g/l of the crude aqueous neem extract, significantly more mosquitoes laid their eggs when compared to mosquitoes exposed to the control treatment. For the doses 10x and 100x higher, the same proportion of mosquitoes laid their eggs as in the control, indicating that even at much higher doses than required for successful larval control, female oviposition will not be detrimentally affected.

Part II: Fish
Larvivorous fish have previously been shown to effectively control mosquito numbers. Therefore, a census was carried out to examine the current status of fish farming in western Kenya (Chapter 5) [3]. Working with the Kenyan Fisheries Department we found that while fish farming is a favoured activity, 30% of the 261 ponds found did not contain fish. These “abandoned” ponds had significantly more An. gambiae s.l., Anopheles funestus Giles and culicine mosquitoes when compared to the ponds that still contained fish. Furthermore, An. gambiae s.l. was proportionally more abundant in the abandoned ponds when compared to the other mosquito types. Surprisingly, vegetation did not significantly affect mosquito distribution. Following our study, demand for fish to restock abandoned ponds increased by 67% when compared to the previous year. The overwhelming majority of fish being farmed in our census area were fish of the tilapiine subfamily. Given this finding, we set up a small-scale field experiment to study the larvivorous potential of the tilapiine fish Oreochromis niloticus L. (Perciformes: Cichlidae) (Chapter 6) [4]. Taking daily measurements of mosquito numbers, we found that immediately after fish introduction, the density of mosquitoes in the treated ponds dropped in comparison to the increase in the control pond. After 15 weeks, anopheline numbers had decreased by >94% in the ponds containing the fish, and we found that fish were able to sustainably control mosquitoes for at least 6 months, when our study finished. It is concluded that this type of fish could be an effective and sustainable way to control mosquito numbers in rural western Kenya. Furthermore, this fish provides a source of much needed income and protein to rural African communities.

Part III: Fungi
For the control of mosquito adults using natural products, entomopathogenic fungi hold the most promise. In this thesis the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae were separately suspended in mineral oil and applied to polyester netting. A laboratory experiment was then conducted to investigate the fungal susceptibility of insecticide-susceptible and insecticide-resistant strains of An. gambiae s.s.. In addition, fungal conidial viability was tested at various time points after application onto polyester netting (Chapter 7) [5]. Whilst both mosquito strains were susceptible to both species of fungal infection, the pyrethroid-resistant An. gambiae s.s. VKPER strain was significantly more susceptible than the insecticide-susceptible SKK strain, dying more quickly. Conidial viability was significantly lower for both species after application onto the polyester netting when compared to the viability in suspension. However, the ability of the treated netting to infect and kill mosquitoes was not significantly diminished over the one week trial period. Given the finding that fungal-treated polyester netting could infect and kill mosquitoes, an experimental hut field trial was conducted in Benin, West Africa, to investigate the effect of fungal treatment on blood feeding behaviour and survival of wild insecticide-resistant mosquitoes. Benin was chosen due to the presence of multi-insecticide-resistant mosquito populations that are threatening the effectiveness of current vector control. We used fungal-treated netting to infect mosquitoes entering the hut windows, and either an untreated or insecticide-treated bednet was placed into each hut to examine how the entomopathogenic fungi would work with current control tools (Chapter 8) [6]. Only enough Culex quinquefasciatus Say (Diptera: Culicidae) mosquitoes were collected from the huts for accurate analysis. Our study was the first to monitor the effect of entomopathogenic fungi on blood feeding of wild mosquitoes. We found that the B. bassiana treatments caused significant and instantaneous reductions in blood feeding. No significant effect of the fungi on mosquito mortality was found. Conidial viability of B. bassiana and M. anisopliae was found to decrease rapidly under field conditions [7].

Conclusions
This thesis used several different experimental techniques to examine the potential of three natural products to control mosquitoes. For the flora, it was found that even a small amount of neem wood in water would control mosquitoes (Chapter 3), and at this and higher doses, the oviposition behaviour was not adversely affected (Chapter 4). Neem trees are readily available in many areas of Africa, and promising field trials indicate that the use of this tree species should be incorporated into malaria control trials.
This thesis reports that edible native African fish can be effective at controlling mosquitoes (Chapter 6), but if fish farming is abandoned and the ponds not filled in, then they can allow large numbers of the most effective malaria vectors to breed (Chapter 5). Fish have been successfully used for malaria vector control in many countries and this could be rolled out across appropriate areas of Africa, as long as it is accompanied with adequate education about the dangers of abandoned ponds.
We found that insecticide-resistant mosquitoes were more susceptible to fungal infection than the insecticide-susceptible strain. Under field conditions fungi were able to prevent blood feeding but did not cause significant mortality in the wild-caught mosquitoes. Although entomopathogenic fungi produce high levels of mortality in laboratory settings, (Chapter 7), their use under field conditions still has a long way to go and is not yet at the operational stage. Although the results found in this thesis are encouraging for the use of fungi in African situations (Chapter 8), further work should be carried out to maximise fungal persistence under field conditions.
The current emphasis is on IVM for malaria control (Chapter 2), and focus is turning to biological control tools that can help manage insecticide-resistant populations. With this in mind, the natural products investigated in this thesis have produced encouraging results that show they have the potential to be integrated into malaria control strategies. Furthermore, flora and fish are readily available in the areas where they are most required, and could be used almost immediately to help reduce mosquito numbers and correspondingly, malaria disease transmission.

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.
Echt eten behoeft geen krans
Dagevos, H. - \ 2008
Voedingsmiddelentechnologie 41 (2008)13. - ISSN 0042-7934 - p. 12 - 13.
voedingsmiddelen - voedselproducten - voedselverwerking - voedselconsumptie - bewustzijn (awareness) - natuurlijke producten - consumentengedrag - bio-ethiek - foods - food products - food processing - food consumption - awareness - natural products - consumer behaviour - bioethics
Het voedselaanbod in de Westerse wereld krijgt een steeds wetenschappelijker sausje. Maar de verwarring bij de consument wordt er alleen maar groter door. Michael Pollan pleit voor eten dat onbewerkt is, onverpakt en geen lawine van gezondheidsclaims nodig heeft. Zijn laatste boek, In defense of food, verscheen onlangs in Nederlandse vertaling: Een pleidooi voor echt eten
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
Melkveehouderij antibioticumvrij, bijdrage FYTO-V, 18 september
Groot, Maria - \ 2007
veterinary science - dairy cows - antibiotics - herbal drugs - natural products - veterinary products - feed supplements - feed additives - research
BioSupport: op weg naar registratie van GNO's
Köhl, J. - \ 2005
gewasbescherming - biologische bestrijding - plantaardige pesticiden - natuurlijke producten - biopesticiden - registratie - marketing - plant protection - biological control - botanical pesticides - natural products - microbial pesticides - registration
PRI en PPO ontwikkelen biologische bestrijders en GNO’s tegen ziekten en plagen. Ondanks de hoge werkzaamheid zijn tot nu toe weinig nieuwe middelen beschikbaar gekomen voor de praktijk. De marktintroductie van deze gewasbeschermingsmiddelen van natuurlijke oorsprong (GNO’s) verloopt moeizaam. Een van de oorzaken zijn de zeer hoge kosten van registratie. BioSupport helpt bij de registratie van ‘marktrijpe’ GNO’s en biologische bestrijders
Mogelijkheden voor geïntegreerde bestrijding van Botrytis in potplanten : teeltmaatregelen en gewasbeschermingsmiddelen van natuurlijke oorsprong
Wubben, J.P. ; Bosker, A.I. ; Lanser, C.J. ; Dik, A.J. - \ 2004
Aalsmeer : Praktijkonderzoek Plant & Omgeving, Sector Glastuinbouw - 35
geïntegreerde plagenbestrijding - potplanten - botrytis - teelt onder bescherming - gewasbescherming - oorsprong - natuurlijke producten - nederland - integrated pest management - pot plants - protected cultivation - plant protection - origin - natural products - netherlands
In de periode van 1999 tot 2001 werd op het Praktijkonderzoek Plant en Omgeving onderzoek verricht naar de mogelijkheden van geïntegreerde bestrijding van Botrytis cinerea in bloeiende potplanten. Het doel van dit project was het vaststellen van de effectiviteit van met name teeltmaatregelen tegen Botrytis cinerea in potplanten als onderdeel van een geïntegreerde bestrijding. Daarnaast werd de effectiviteit van een aantal gewasbeschermingsmiddelen van natuurlijke oorsprong bepaald. Indien deze maatregelen effectief zijn kan een verminderde afhankelijkheid van chemische bestrijdingsmiddelen gerealiseerd worden. Verdeeld over een aantal proeven werd het onderzoek uitgevoerd met Poinsettia (1999 en 2001), Cyclamen (1999) en Saintpaulia (1999, 2000).
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