Identification of a novel 7-desmethyl-7-acetonyl bacteriophaeophorbide c series in a recent sediment

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A novel symmetrical pyrano-3-deoxyanthocyanidin from a Sorghum species

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Retrodihydrochalcones in Sorghum species: Key intermediates in the biosynthesis of 3-deoxyanthocyanidins?

International audienceTwo new open chain flavonoids were isolated from the butanediol/ethanol extract of Sorghum bicolor (L.) Moench leaf sheaths by fractionation and purification processes. This work led to the structural characterization of the 3-(2,4,6-trihydroxyphenyl)-1-(4-hydroxyphenyl)-propan-1-one (or 2,4,4 ',6-tetrahydroxydihydrochalcone) 1, and 3-(2,6-dihydrox-4-methoxyphenyl)-1-(4-hydroxyphenyl)-propan-1-one (or 2,4 ',6-trihydroxy-4-methoxydihydro-chalcone) 2. The structures of these flavonoids were determined by extensive spectroscopic analyses, including UV, ESIMS, HRESIMS, 1D and 2D NMR. The chemical properties of 1 were similar to those earlier described in literature for apiforol, never fully characterized. These results led us to re-question the real structure of this flavan-4-ol, which is often described to be present in Sorghum and has even been considered as a key intermediate in the formation of Sorghum 3-deoxyanthocyanidins. (C) 2011 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved

Genetic diversity of stilbene metabolism in Vitis sylvestris

Stilbenes, as important secondary metabolites of grapevine, represent central phytoalexins and therefore constitute an important element of basal immunity. In this study, potential genetic variation in Vitis vinifera ssp. sylvestris, the ancestor of cultivated grapevine, was sought with respect to their output of stilbenes and potential use for resistance breeding. Considerable variation in stilbene inducibility was identified in V. vinifera ssp. sylvestris. Genotypic differences in abundance and profiles of stilbenes that are induced in response to a UV-C pulse are shown. Two clusters of stilbene ‘chemovars’ emerged: one cluster showed quick and strong accumulation of stilbenes, almost exclusively in the form of non-glycosylated resveratrol and viniferin, while the second cluster accumulated fewer stilbenes and relatively high proportions of piceatannol and the glycosylated piceid. For all 86 genotypes, a time dependence of the stilbene pattern was observed: piceid, resveratrol, and piceatannol accumulated earlier, whereas the viniferins were found later. It was further observed that the genotypic differences in stilbene accumulation were preceded by differential accumulation of the transcripts for chalcone synthase (CHS) and stilbene-related genes: phenylalanine ammonium lyase (PAL), stilbene synthase (StSy), and resveratrol synthase (RS). A screen of the population with respect to susceptibility to downy mildew of grapevine (Plasmopara viticola) revealed considerable variability. The subpopulation of genotypes with high stilbene inducibility was significantly less susceptible as compared with lowstilbene genotypes, and for representative genotypes it could be shown that the inducibility of stilbene synthase by UV correlated with the inducibility by the pathogen

Anionic RR120 dye adsorption onto raw clay: Surface properties and adsorption mechanism

International audienceClay minerals are efficient adsorbent for dyes due to their colloidal properties. A Tunisian raw clay (Fouchana) composed of different species of clay minerals (kaolinite, smectite and minor illite) has shown efficiency for removal of anionic dye Reactive Red 120 (RR120) from aqueous solutions. In order to provide a better understanding of the role played by the different clay species in Fouchana, as well as the nature of the adsorption processes which are involved, a comparative study was conducted using standard clays, namely kaolinite KGa-2, smectite SWy-1 and illite IMt-2. Batch adsorption experiments were performed at ambient temperature and pH of the dye solutions. Acido-basic properties of the solid surfaces, electrophoretic mobility of particles, cation exchange capacity, amount of exchangeable cations and specific surface were investigated. Principal component analysis was used to highlight the influence of the physicochemical characteristics of the clay minerals in the adsorption behavior. The results show that for the conditions set in this study, kaolinite in the Fouchana raw clay plays a major role in anionic dye adsorption, mainly due to its acidic surface sites, but also to exchangeable aluminum (III) cations acting as bridges between the clay mineral and the dye molecules. Smectite and illite most likely play a secondary role by adsorption on exchangeable calcium (II) and dissociated Al (III)-OH groups. (C) 2012 Elsevier B.V. All rights reserved

Structural, Functional, and Evolutionary Analysis of the Unusually Large Stilbene Synthase Gene Family in Grapevine

International audienceStilbenes are a small family of phenylpropanoids produced in a number of unrelated plant species, including grapevine (Vitis vinifera). In addition to their participation in defense mechanisms in plants, stilbenes, such as resveratrol, display important pharmacological properties and are postulated to be involved in the health benefits associated with a moderate consumption of red wine. Stilbene synthases (STSs), which catalyze the biosynthesis of the stilbene backbone, seem to have evolved from chalcone synthases (CHSs) several times independently in stilbene-producing plants. STS genes usually form small families of two to five closely related paralogs. By contrast, the sequence of grapevine reference genome (cv PN40024) has revealed an unusually large STS gene family. Here, we combine molecular evolution and structural and functional analyses to investigate further the high number of STS genes in grapevine. Our reannotation of the STS and CHS gene families yielded 48 STS genes, including at least 32 potentially functional ones. Functional characterization of nine genes representing most of the STS gene family diversity clearly indicated that these genes do encode for proteins with STS activity. Evolutionary analysis of the STS gene family revealed that both STS and CHS evolution are dominated by purifying selection, with no evidence for strong selection for new functions among STS genes. However, we found a few sites under different selection pressures in CHS and STS sequences, whose potential functional consequences are discussed using a structural model of a typical STS from grapevine that we developed

Structural, Functional, and Evolutionary Analysis of the Unusually Large Stilbene Synthase Gene Family in Grapevine

International audienceStilbenes are a small family of phenylpropanoids produced in a number of unrelated plant species, including grapevine (Vitis vinifera). In addition to their participation in defense mechanisms in plants, stilbenes, such as resveratrol, display important pharmacological properties and are postulated to be involved in the health benefits associated with a moderate consumption of red wine. Stilbene synthases (STSs), which catalyze the biosynthesis of the stilbene backbone, seem to have evolved from chalcone synthases (CHSs) several times independently in stilbene-producing plants. STS genes usually form small families of two to five closely related paralogs. By contrast, the sequence of grapevine reference genome (cv PN40024) has revealed an unusually large STS gene family. Here, we combine molecular evolution and structural and functional analyses to investigate further the high number of STS genes in grapevine. Our reannotation of the STS and CHS gene families yielded 48 STS genes, including at least 32 potentially functional ones. Functional characterization of nine genes representing most of the STS gene family diversity clearly indicated that these genes do encode for proteins with STS activity. Evolutionary analysis of the STS gene family revealed that both STS and CHS evolution are dominated by purifying selection, with no evidence for strong selection for new functions among STS genes. However, we found a few sites under different selection pressures in CHS and STS sequences, whose potential functional consequences are discussed using a structural model of a typical STS from grapevine that we developed