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Tabacchi, Raffaele
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Tabacchi, Raffaele
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Professeur.e émérite
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Now showing 1 - 6 of 6
- PublicationMetadata onlyComponents from Sri Lankan Piper betle L. leaf oil and their analogues showing toxicity against the housefly, Musca domestica(2007)
; The essential oil extracted from Piper betle L. leaf using pilot plant steam distillation was tested against the adult housefly, Musca domestica, for insecticidal activity. LC50 values at the end of 24 and 48 h exposure periods were 10.3 and 8.7 mg/dm(3), respectively. Ceylon citronella oil (Cymbopogon nardus) used as a standard showed LC(50)s of 26.5 and 24.2 mg/dm(3) for the same exposure periods. Bioassay-guided fractionation of P. betle leaf oil revealed safrole and eugenol as the active principles against M. domestica, safrole showing LC50 values of 4.8 and 4.7 mg/dm(3), and eugenol 7.3 and 6.2 mg/dm(3) for the 24 and 48 h exposure periods, respectively, while citronellal (synthetic standard) showed equal LC50 values of 14.3 mg/dm(3) for the same exposure periods. Using safrole as the starting compound, eight analogues were prepared to study structure-activity relationships. Among the eight analogues, dihydrosafrole gave almost equal mortality at LC50 4.7 mg/dm(3) as that of the parent compound safrole after 24 and 48 h exposure, but isosafrole was twice as active as safrole, showing LC50 values of 2.3 and 2.2 mg/dm(3) for the 24 and 48 h exposure periods. Our GC-MS studies on Sri Lankan P. betle leaf oil show that it contains safrole (52.7%), allyllpyrocatechol diacetate (15.4%), eugenol (6.4%) and eugenyl acetate (5.8%) as the major components. Here we also present the GC-MS profile of fractions of Sri Lankan P. betle leaf oil. Copyright (c) 2006 John Wiley & Sons, Ltd. - PublicationOpen AccessComponents from Sri Lankan Piper betle L. leaf oil and their analogues showing toxicity against the housefly, Musca domestica(2007)
; The essential oil extracted from Piper betle L. leaf using pilot plant steam distillation was tested against the adult housefly, Musca domestica, for insecticidal activity. LC50 values at the end of 24 and 48 h exposure periods were 10.3 and 8.7 mg/dm3, respectively. Ceylon citronella oil (Cymbopogon nardus) used as a standard showed LC50s of 26.5 and 24.2 mg/dm3 for the same exposure periods. Bioassay-guided fractionation of P. betle leaf oil revealed safrole and eugenol as the active principles against M. domestica, safrole showing LC50 values of 4.8 and 4.7 mg/dm3, and eugenol 7.3 and 6.2 mg/dm3 for the 24 and 48 h exposure periods, respectively, while citronellal (synthetic standard) showed equal LC50 values of 14.3 mg/dm3 for the same exposure periods. Using safrole as the starting compound, eight analogues were prepared to study structure–activity relationships. Among the eight analogues, dihydrosafrole gave almost equal mortality at LC50 4.7 mg/dm3 as that of the parent compound safrole after 24 and 48 h exposure, but isosafrole was twice as active as safrole, showing LC50 values of 2.3 and 2.2 mg/dm3 for the 24 and 48 h exposure periods. Our GC–MS studies on Sri Lankan P. betle leaf oil show that it contains safrole (52.7%), allylpyrocatechol diacetate (15.4%), eugenol (6.4%) and eugenyl acetate (5.8%) as the major components. Here we also present the GC–MS profile of fractions of Sri Lankan P. betle leaf oil. - PublicationOpen AccessWhite lupin has developed a complex strategy to limit microbial degradation of secreted citrate required for phosphate acquisition(2006)
; ; Martinoia, EnricoWhite lupins (Lupinus albus L.) respond to phosphate deficiency by producing special root structures called cluster roots. These cluster roots secrete large amounts of carboxylates into the rhizosphere, mostly citrate and malate, which act as phosphate solubilizers and enable the plant to grow in soils with sparingly available phosphate. The success and efficiency of such a P-acquisition strategy strongly depends on the persistence and stability of the carboxylates in the soil, a parameter that is influenced to a large extent by biodegradation through rhizosphere bacteria and fungi. In this study, we show that white lupin roots use several mechanisms to reduce microbial growth. The abundance of bacteria associated with cluster roots was decreased at the mature state of the cluster roots, where a burst of organic acid excretion and a drastic pH decrease is observed. Excretion of phenolic compounds, mainly isoflavonoids, induced fungal sporulation, indicating that vegetative growth, and thus potential citrate consumption, is reduced. In addition, the activity of two antifungal cell wall-degrading enzymes, chitinase and glucanase, were highest at the stage preceding the citrate excretion. Therefore, our results suggest that white lupin has developed a complex strategy to reduce microbial degradation of the phosphate-solubilizing agents. - PublicationOpen Access(1S,3S,7R)-3-methyl-α-himachalene from the male sandfly Lutzomyia longipalpis (Diptera: Psychodidae) induces neurophysiological responses and attracts both males and females(2005)
; ; ; - PublicationOpen AccessHost-Plant Use in the Specialist Leaf Beetle Oreina gloriosa : the Role of Linear Furanocoumarins(2004)
; ; ; Städler, ErichLa chrysomèle alpine Oreina gloriosa (Coleoptera: Chrysomelidae) est hautement spécialisée sur l'ombellifère Peucedanum ostruthium (Apiaceae), l'impératoire. Dans la nature, adultes et larves sont très sélectifs: les uns et les autres se nourrissent exclusivement de feuilles, mais surtout, ils choisissent certaines plantes et en ignorent complètement d'autres. En outre, des études préliminaires ont suggéré que les larves soient actives la nuit. Comme de nombreuses autres apiacées, P. ostruthium synthétise plusieurs furanocoumarines linéaires, métabolites secondaires décrits pour leur activité antiappétante et/ou toxique à l'égard d'insectes phytophages généralistes. Par ailleurs, les furanocoumarines linéaires sont connues pour leur action phototoxique: le rayonnement ultraviolet proche du spectre visible induit chez ces substances une excitation électronique qui peut déterminer différents processus toxiques au niveau cellulaire. Le but de cette étude a été de vérifier l'hypothèse selon laquelle la chimie secondaire de P. ostruthium constituerait un facteur explicatif de l'utilisation de la plante hôte par la strictement monophage O. gloriosa. Toute la recherche a été menée au sein d'une seule population de la plante et de la population du coléoptère qui lui est inféodée.
Dans un premier temps, nous avons étudié le rythme d'activité de la chrysomèle sur les 24 heures dans son mileu. Ce travail a révélé que les larves se nourrissent exclusivement pendant la nuit et s'enfoncent dans le sol pendant le reste de la journée. Certaines jeunes larves se retirent dans les gaines ou les bourgeons. Au contraire, les adultes ont été observés sur les plantes pendant les 24 heures. Nous avons ensuite vérifié si la croissance larvaire était affectée par la photoactivation des furanocoumarines. Pour cela, les larves ont été placées dans deux environnements lumineux, avec et sans rayonnement ultraviolet. La mortalité a été plus grande dans le deuxième traitement: nous n'avons néanmoins pas pu tirer de conclusions définitives sur l'effet de la photoactivation des furanocoumarines. Dans un travail de terrain, nous avons montré que les invertébrés antagonistes de O. gloriosa sont essentiellement actifs pendant la nuit. Au vu du chevauchement entre les périodes d'activité de la chrysomèle et de ses prédateurs, nous suggérons que les ennemis naturels ne constituent pas la raison d'être du comportement des larves. Nous proposons que l'activité nocturne représente une contre-adaptation à la photoactivité des furanocoumarines. Il s'agirait alors d'un rare exemple d'adaptation comportementale chez un insecte spécialisé sur une plante hôte avec furanocoumarines linéaires. En effet, les insectes avec un régime alimentaire strictement lié à ces métabolites secondaires, disposent en général de moyens de détoxification métaboliques. La différence comportementale entre larves et adultes est probablement liée à l'épaisseur et à la pigmentation de la cuticule imaginale, vraisemblablement opaque à la lumière ultraviolette.
Nous avons également vérifié l'hypothèse selon laquelle O. gloriosa dans la nature sélectionnerait les plantes en fonction de leur attributs chimiques. Nous avons échantillonné des plantes fortement consommées et des plantes libres de toute attaque d'O. gloriosa. Les feuilles ainsi récoltées ont été extraites et analysées par chromatographie liquide pour déterminer la composition qualitative et quantitative en furanocoumarines linéaires. La chimie secondaire a permis de bien discriminer plantes consommées et non consommées. O. gloriosa est probablement à même de reconnaître certaines de ces substances comme signaux ou elle est en mesure de mieux en tolérer certaines plutôt que d'autres dans leur action toxique. De toute façon, la chimie secondaire explique, du moins en partie, l'utilisation de la plante hôte par ce coléoptère strictement monophage au sein d'une population de sa plante nourricière. Cet exemple révèle la nécessité d'approfondir l'investigation, trop souvent négligée, du rôle de la variation chimique intrapopulationnelle dans les études concernant la convenance de l'hôte pour des insectes spécialistes., The alpine leaf beetle Oreina gloriosa (Coleoptera: Chrysomelidae) is highly specialized on the umbelliferous plant Peucedanum ostruthium (Apiaceae). Adults and larvae feed on leaves and clearly discriminate between individual plants in nature. Preliminary studies suggested that the larvae are active at night. Like many other apiaceous plants, P. ostruthium produces several linear furanocoumarins, secondary metabolites shown to be deterrent and/or toxic to generalist herbivorous insects. Moreover, linear furanocoumarins are well known as phototoxins: when irradiated with long-wave ultraviolet light, these compounds enter an excited state which can mediate different within cell toxic processes. The aim of the present thesis was to verify the hypothesis that the secondary chemistry of P. ostruthium is a factor explaining the actual host-plant use by the strictly monophagous O. gloriosa. All of our work concentrated on a single plant population and its affiliated beetle population.
We firstly investigated the daily activity rhythm of the beetles in the field. Larvae have been shown to feed exclusively at night and to burrow into the soil for the remainder of the day. Some young larvae hid within sheaths or buds during daylight. In contrast, adults were found on the plants over the 24 hours. We further verified if the performance of the larvae was affected by the photoactivation of the linear furanocoumarins. Larvae were forced to remain in two different light environments, with and without ultraviolet radiation. O. gloriosa was shown to suffer higher mortality when forced under light with ultraviolet radiation. Nonetheless, we were not able to draw definitive conclusions on the effect of the furanocoumarin photoactivation. In a field study, we showed that invertebrate natural enemies of O. gloriosa are mainly active at night. Because of the congruence in time between the beetle and the predators activities we suggest that natural enemies should not be considered as a driving force for the larval night behaviour. We propose that night activity counteracts the photoactive furanocoumarins and should be considered a rare example of behavioural adaptation in a linear furanocoumarin-specialized insect. In fact, specialists are reported to rely on metabolic detoxification. The difference in the behaviour between larvae and adults may be related to the thick and pigmented cuticle of the latter, probably opaque to ultraviolet light.
Finally we tested the hypothesis that individual plants remain free from O. gloriosa attack due to their chemical attributes. Samples of plants hosting actively feeding O. gloriosa (strongly consumed leaves) and plants exhibiting no damage (unattacked leaves) were collected in the field and examined by HPLC for their qualitative and quantitative linear furanocoumarin composition. The secondary chemistry allowed us to clearly segregate attacked and unattacked plants. We suggest that plant chemistry, relative to the ability of O. gloriosa to tolerate or recognise plant chemicals, can to some extent explain the host use of this monophagous leaf beetle within a population of its host plant. This shows the need for further work on the neglected impact, for specialists, of intrapopulation variation in secondary chemistry on host suitability., Il crisomelide alpino Oreina gloriosa (Coleoptera: Chrysomelidae) è altamente specializzato sull'ombellifera Peucedanum ostruthium (Apiaceae), l'imperatoria vera o erba rena. Adulti e larve in natura sono estremamente selettivi: gli uni e le altre si nutrono solo di foglie, ma distinguono tra le singole piante cibandosi di alcune e trascurandone completamente altre. Inoltre indagini preliminari hanno suggerito che le larve siano attive di notte. Analogamente ad altre ombellifere, P. ostruthium contiene varie furanocumarine lineari, metaboliti secondari con effetto deterrente e/o tossico per insetti fitofagi generalisti. Le furanocumarine lineari sono pure note per la loro fototossicità: la luce ultravioletta di lunghezza d'onda vicina allo spettro visibile induce in queste sostanze un'eccitazione elettronica che può provocare vari processi tossici a livello cellulare. La nostra tesi aveva lo scopo di verificare l'ipotesi secondo cui la chimica secondaria di P. ostruthium spiegherebbe l'utilizzazione della pianta ospite - così come l'osserviamo oggi - da parte dello specialista O. gloriosa. Per l'insieme della ricerca ci siamo concentrati su una singola popolazione della pianta e sulla popolazione dell'insetto ad essa legata.
Per prima cosa abbiamo studiato il ritmo di attività dei coleotteri in natura. Abbiamo mostrato che le larve si nutrono esclusivamente di notte e passano il resto della giornata nel suolo. Alcune giovani larve si ritirano dentro le guaine o i germogli. Gli adulti invece sono presenti sulle piante durante tutte le 24 ore. In una ricerca successiva abbiamo verificato se la crescita larvale sia compromessa dalla fotoattivazione delle furanocumarine lineari. Abbiamo tenuto le larve in due distinti ambienti luminosi, con e senza radiazione ultravioletta. Quest'ultima ha determinato una maggiore mortalità di O. gloriosa, tuttavia non siamo stati in grado di formulare conclusioni definitive sull'effetto della fotoattivazione. Un lavoro sul campo ha mostrato che gli invertebrati antagonisti del crisomelide sono essenzialmente attivi di notte. Dato che i periodi di attività di O. gloriosa e dei suoi predatori si sovrappongono, suggeriamo che i nemici naturali non costituiscano il fattore selettivo all'origine del comportamento notturno delle larve. Proponiamo che questa limitazione notturna nell'attività trofica rappresenti un'acquisizione adattativa contro la fotoattività delle furanocumarine. Si tratterebbe allora di un raro esempio di adattamento comportamentale in un insetto specializzato su una pianta contenente furanocumarine lineari. In effetti, in generale gli insetti con un regime alimentare strettamente legato a queste sostanze dispongono di strumenti di detossificazione metabolici. La differenza comportamentale tra larve e adulti potrebbe essere ricondotta al tegumento spesso, colorato e probabilmente opaco alla luce ultravioletta di questi ultimi.
Abbiamo infine verificato l'ipotesi secondo cui la chimica secondaria determinerebbe l'idoneità delle singole piante per la crescita di O. gloriosa. Abbiamo proceduto ad un campionamento sul campo di piante fortemente consumate e di piante prive di qualsiasi segno d'attacco del crisomelide. Le foglie così raccolte sono state estratte e analizzate con la cromatografia liquida per determinare la composizione qualitativa e quantitativa delle furanocumarine. La chimica secondaria ha permesso di ben caratterizzare le piante consumate rispetto a quelle non utilizzate. O. gloriosa è probabilmente in grado di riconoscere talune di queste sostanze quali segnali o di tollerarne alcune piuttosto di altre nella loro azione di tossine. In ogni caso, la chimica secondaria permette di spiegare perlomeno in parte l'utilizzazione della pianta in seno ad una popolazione da parte di questo coleottero altamente specializzato. Questo risultato rivela l'interesse di ulteriori ricerche su un aspetto spesso ignorato quale è l'impatto, per artropodi specialisti, della variazione intrapopolazionale nella chimica secondaria sull'idoneità della pianta ospite. - PublicationMetadata onlyThe NCCR Plant Survival at the University of Neuchatel - The role of chemistry in an interdisciplinary Swiss research network(2003)
; ; The survival of plants is of fundamental importance to guarantee the biodiversity in natural areas and a sustainable agriculture. The National Centre of Competence in Research 'Plant Survival in Natural and Agricultural Ecosystems' devotes its research efforts to the understanding of mechanisms of plant survival. The mechanisms that plants employ to adapt to their biotic and abiotic environment and to cope with important stress factors are investigated. This is achieved by interdisciplinary interaction of disciplines within the NCCR. The particular role played by natural products and analytical chemistry in seven different projects is summarized.