Résultat de la recherche
Lichen extracts as raw materials in perfumery. Part 2: treemoss
This is a comprehensive review of extracts from the lichen Pseudevernia furfuracea (treemoss) that are used in the fragrance industry. Qualitative and quantitative analytical aspects are critically reviewed and the results are compared to those of the related oakmoss extracts. It is shown that more than 90 constituents have been identified so far in treemoss extracts, including 42 depsides, depsidones or depside-derived compounds, and 42 triterpenes or steroids. Constituents of certain host trees, mainly Pinus species, generate specific analytical and toxicological issues which need to be considered in addition to those related to the known degradation products of lichen compounds. A new classification of lichen extracts used as raw materials in fragrance compounding is proposed.
Components from Sri Lankan Piper betle L. leaf oil and their analogues showing toxicity against the housefly, Musca domestica
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.
Isoflavonoid exudation from white lupin roots is influenced by phosphate supply, root type and cluster-root stage
• The internal concentration of isoflavonoids in white lupin (Lupinus albus) cluster roots and the exudation of isoflavonoids by these roots were investigated with respect to the effects of phosphorus (P) supply, root type and cluster-root developmental stage.
• To identify and quantify the major isoflavonoids exuded by white lupin roots, we used high-pressure liquid chromatography (HPLC) coupled to electrospray ionization (ESI) in mass spectrometry (MS).
• The major exuded isoflavonoids were identified as genistein and hydroxygenistein and their corresponding mono- and diglucoside conjugates. Exudation of isoflavonoids during the incubation period used was higher in P-deficient than in P-sufficient plants and higher in cluster roots than in noncluster roots. The peak of exudation occurred in juvenile and immature cluster roots, while exudation decreased in mature cluster roots.
• Cluster-root exudation activity was characterized by a burst of isoflavonoids at the stage preceding the peak of organic acid exudation. The potential involvement of ATP-citrate lyase in controlling citrate and isoflavonoid exudation is discussed, as well as the possible impact of phenolics in repelling rhizosphere microbial citrate consumers.
Geographic origin of European Emmental. Use of discriminant analysis and artificial neural network for classification purposes
The goal of this work was to classify European Emmental cheeses according to their geographic origin using analytical approaches. Twenty-five analytical parameters (factors) were measured in 183 samples. Results were combined by multivariate statistical analysis. Discriminant analysis (DA) and an artificial neural network (ANN) delivered similar results when all regions and factors were included; 95% and 91%, respectively, of the samples were correctly classified in the validation procedure. To reduce the analytical costs and the risk of overfitting, a DA based on a selection of only 11 factors was calculated. In this case, the Jackknifed validation delivered 95% correct assignments. Finally, a system was optimised to discriminate between the Swiss samples and cheeses from other regions. Building a new model for each of the six pairs, Switzerland vs. another region, 100% correct classification could be achieved for the Swiss samples.
Lichen extracts as raw materials in perfumery. Part 1: oakmoss
A comprehensive review is presented on extracts of a lichen, oakmoss (Evernia prunastri), that are used in the fragrance industry. Analytical aspects are discussed in detail, from both qualitative and quantitative standpoints, mainly in relation to the industrial processing of the lichen. It is shown that more than 170 constituents have been identified so far in oakmoss extracts, including 47 depsides or depside-derived compounds and 25 triterpenes or steroids. A survey of industrially relevant synthetic products with an oakmoss odour is included. Toxicology issues related to the use of oakmoss extracts in cosmetics and fragrance formulations are critically reviewed.
Components from Sri Lankan Piper betle L. leaf oil and their analogues showing toxicity against the housefly, Musca domestica
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.
White lupin has developed a complex strategy to limit microbial degradation of secreted citrate required for phosphate acquisition
White 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.
Stereoselective Synthesis of cis- and trans-3,4-Dihydro-3,4,8-trihydroxynaphthalen-1(2H)-one
A short and efficient protocol for the stereoselective synthesis of racemic trans- and cis-3,4-dihydro-3,4,8-trihydroxynaphthalen-1(2H)-one (1 and 2, resp.), is described, comprising nine and eight steps starting from commercial juglone (=5-hydroxynaphthalene-1,4-dione; 12) (Scheme 4). Furthermore, an attempt to obtain 1 and 2 via phthalide annulation as the key step (Schemes 2 and 3) and a regioselective oxidation of the intermediate 1,2,3,4-tetrahydronaphthalene-1,2,4,5-tetrols 27 and 28 with activated MnO2 were carried out (Scheme 4).
Bafoudiosbulbins A, and B, two anti-salmonellal clerodane diterpenoids from Dioscorea bulbifera L. var sativa
Two clerodane diterpenoids, Bafoudiosbulbins A 1, and B 2, together with five known compounds: tetracosanoic acid, 1-(tetracosanoyl)-glycerol, trans-tetracosanylferulate, β-sitosterol and 3-O-β-d-glucopyranosyl-β-sitosterol were isolated from the tubers of Dioscorea bulbifera L. var sativa. Their structures were established by spectroscopic methods (1D and 2D-NMR, MS) and X-ray crystallographic diffraction analysis of compound 1. The CH2Cl2-soluble portion of the crude extract and the two clerodanes were screened for anti-bacterial activity using both agar diffusion and broth dilution techniques against Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Salmonella typhi, Salmonella paratyphi A and Salmonella paratyphi B. They both showed significant activities against P. aeruginosa, S. typhi, S. paratyphi A and S. paratyphi B.
Synthèse et application de sélecteurs chiraux à base de cyclodextrines en chromatographie gazeuse
Ce travail consiste en la synthèse de cyclodextrines dimères substituées par des entités telles que acétyle, t-butyldiméthylsilyle, alkyles, ... en vue de réaliser des colonnes capillaires destinées à l'analyse chirale en chromatographie gazeuse. L'obtention des composés dimériques a nécessité la réalisation de monomères monosubstitués par recours à des voies sélectives. Un soin particulier a été porté à l'optimisation des différentes réactions. La réaction de métathèse, décrite comme inappropriée par certains auteurs a pu être exploitée après étude approfondie du mécanisme réactionnel. Des rendements élevés ont été obtenus. L'usage en chromatographie gazeuse des cyclodextrines dimères synthétisées révèle un pouvoir séparateur au moins comparable à celui des cyclodextrines monomères substituées de façon identique pour un grand nombre d'énantiomères. Dans certains cas, il est observé un accroissement notable du facteur de séparation s'agissant d'énantiomères de taille conséquente. La littérature enseigne que les dimères de cyclodextrines sont d'un apport appréciable s'agissant de la complexation de différentes catégories de substances. Il peut être déduit de ce fait, une certaine potentialité pour cette sorte de cyclodextrine en ce qui concerne la séparation chirale de solutés volumineux., This study comprised the synthesis of cyclodextrin dimers substituted by entities such as acetyl, t-butyldimethylsilyl or alkyls in order to produce capillary columns for chiral analysis in gas chromatography. Production of dimeric compounds required the fabrication of monosubstituted monomers using selective pathways. Particular care was taken of the optimization of the various reactions. The metathesis reaction, considered inappropriate by certain authors, was successfully employed after a thorough study of the reaction mechanism. High yields were obtained. For a large number of enantiomers, the use of synthetic dimeric cyclodextrins in gas chromatography revealed separating powers at least comparable to those of monomeric cyclodextrins with identical substituents. In certain cases a significant increase in the separation factor was observed for bulky enantiomers. According to the literature, dimeric cyclodextrins contribute favourably to the complexation of different categories of substances. It can thus be deduced that this type of cyclodextrin has a certain potential for the chiral separation of bulky solutes.