Jean-Marc Nuzillard

Hydrolysis of wheat bran and straw by an endoxylanase: production and structural characterization of cinnamoyl-oligosaccharides

Hydrolysis of wheat bran and wheat straw by a 20.7 kDa thermostable endoxylanase released 35 and 18% of the cell-wall xylan content, respectively. Separation of the cinnamoyl-oligosaccharides (accounting for 6%) from the bulk of total oligosaccharides was achieved by specific anion-exchange chromatography. The cinnamoyl-oligosaccharides were further purified by preparative paper chromatography (PPC) and their molecular weight was determined by MALDI-TOF mass spectrometry. The partially purified hydrolysis end-products contained from 4 to 16 and from 4 to 12 pentose residues for wheat bran and straw, respectively, and only one cinnamic acid per molecule. The primary structure of the new feruloyl arabinoxylopentasaccharide from wheat bran hydrolysis, which has been determined using 2D NMR spectroscopy, is O-beta-D-xylopyranosyl-(1-->4)-O-[5-O- (feruloyl)-alpha-L-arabinofuranosyl-(1-->3)]-O-beta-D-xylopyranosy l-(1-->4) -O-beta-D-xylopyranosyl-(1-->4)-D-xylopyranose.

The Antitumor Properties of the α3(IV)-(185-203) Peptide from the NC1 Domain of Type IV Collagen (Tumstatin) Are Conformation-dependent

Tumor progression may be controlled by various fragments derived from noncollagenous 1 (NC1) C-terminal domains of type IV collagen. We demonstrated previously that a peptide sequence from the NC1 domain of the α3(IV) collagen chain inhibits the in vitro expression of matrix metalloproteinases in human melanoma cells through RGD-independent binding to αvβ3 integrin. In the present paper, we demonstrate that in a mouse melanoma model, the NC1 α3(IV)-(185-203) peptide inhibits in vivo tumor growth in a conformation-dependent manner. The decrease of tumor growth is the result of an inhibition of cell proliferation and a decrease of cell invasive properties by down-regulation of proteolytic cascades, mainly matrix metalloproteinases and the plasminogen activation system. A shorter peptide comprising the seven N-terminal residues 185-191 (CNYYSNS) shares the same inhibitory profile. The three-dimensional structures of the CNYYSNS and NC1 α3(IV)-(185-203) peptides show a β-turn at the YSNS (188-191) sequence level, which is crucial for biological activity. As well, the homologous MNYYSNS heptapeptide keeps the β-turn and the inhibitory activity. In contrast, the DNYYSNS heptapeptide, which does not form the β-turn at the YSNS level, is devoid of inhibitory activity. Structural studies indicate a strong structure-function relationship of the peptides and point to the YSNS turn as necessary for biological activity. These peptides could act as potent and specific antitumor antagonists of αvβ3 integrin in melanoma progression.

Isolation of indole alkaloids from Catharanthus roseus by centrifugal partition chromatography in the pH-zone refining mode

Centrifugal partition chromatography (CPC) in the pH-zone refining mode allowed a preparative and efficient isolation of vindoline, vindolinine, catharanthine and vincaleukoblastine from a crude mixture of Catharanthus roseus alkaloids. The separation protocol was tested with a synthetic mixture of vindoline, catharanthine and vincaleukoblastine. The fraction content was analyzed and the results compared with theoretical chromatograms obtained by numerical simulation. The increase in injected sample mass results in an improvement of the purity of the isolated compounds. This observation, confirmed by theory, is of prime importance for the development of preparative pH-zone refining CPC as a preparative separation method.

Blind source separation of positive and partially correlated data

Blind source separation (BSS) consists of processing a set of observed mixed signals to separate them into a set of unobservable original components. Various approaches have been employed to solve BSS problems using the strong assumption focusing on mutually uncorrelated (or orthogonal) source signals. However, in many real-life problems, signal orthogonality is not guaranteed.This paper introduces a new approach to BSS that can be applied to nonorthogonal signals. The orthogonality requirement is replaced by a partial orthogonality and a nonnegativity constraint which are well-suited for many real-world signals. An algebraic property is then exploited to express BSS problems in terms of constrained optimization. An efficient algorithm implementing the approach is reported and applied to examples from nuclear magnetic resonance spectroscopy.

PROTON NMR SPECTROSCOPY ASSIGNMENT OF D-GLUCOSE RESIDUES IN HIGHLY ACETYLATED STARCH

1H NMR spectroscopy assignments have been obtained for starch acetates using COSY and HOHAHA experiments by comparison with the spectra of amylose triacetate and of peracetylated malto-oligosaccharides (maltotriose, maltotetraose, maltoheptaose). These assignments are valuable for the location and evaluation of the substitution pattern in modified starches. The bulk of the 1H NMR spectra of highly acetylated starch strongly resembles the spectrum of amylose triacetate in which all protons are identified and display distinct chemical shifts. The resolving power of the HOHAHA experiment allowed the distinction of minor spin systems. Beside these strong signals pertaining to an average 2.3.6-tri-O-acetyl-alpha-(1-->4) linked D-glucopyranose unit in an infinite chain, the combination of COSY and HOHAHA experiments allowed the identification of these systems to the terminal, n-1, n-2, and to partially acetylated glucopyranosyl units. As an example, two different preparations of starch acetates with degrees of substitution 2.74 and 2.63 were examined. In one case, NMR demonstrates that the defects of acetylation are random on the polymeric chain (with corresponding signals for unacylated secondary hydroxyl positions at delta 3.61 and 3.40) while in another case, these signals are not detectable, probably due to the presence of clusters of non-acetylated residue forming solid-like zones.

A new synthesis of α,β-unsaturated aldehydes

Abstract The two carbon homologation of carbonyl compounds to α,β-unsaturated aldehydes is achieved by the Wittig-Horner reaction with N-methoxy N-methyl diethylphosphonoacetamide 1 followed by lithium aluminum hydride reduction.

LOGIC FOR STRUCTURE DETERMINATION

Abstract A program for structure elucidation of organic molecules is described. The main source of input data relies on NMR carbon-proton correlation spectra. The methodology is illustrated for two indole alkaloids.

Alkaloids from stem bark and leaves of Peschiera buchtieni

Abstract During an investigation of the stem bark and leaves of Peschiera buchtieni , 34 alkaloids were isolated. Eight new alkaloids were obtained from the stem bark, N -methyl-pericyclivine, 18,19( R )-dihydroxycoronaridine, chloromethylene affinisinium, demethylaccedinisine, 18-hydroxyaffinisine, buchtienine, 3-hydroxytetrahydroolivacine and demethylceridimine. The known alkaloids from the stem bark were coronaridine, voaphylline, coronaridine hydroxyindolenine, heyneanine, eglandine, eglandulosine, 19-epi-heyneanine, voachalotine, ochropamine, olivacine, ibogamine, affinisine, N -oxyaffinisine, vallesamine, ( E )-isositsirikine, voaphylline hydroxyindolenine, normacusine B, janetine, 3,14-dihydroolivacine, 3′( R / S )-hydroxy- N -demethyl-tabernamine, 4′,17β-dihydrotchibangensine, ceridimine and N -demethyltabernamine. Apodine, voacristine, voacristine hydroxyindolenine and olivacine were identified in leaves.

(l)- or (d)-Valine tert-butylamide grafted on permethylated β-cyclodextrin derivatives as new mixed binary chiral selectors: Versatile tools for capillary gas chromatographic enantioseparation

This work deals with the synthesis of two mixed binary chiral selectors prepared by grafting (L)- or (D)-valine tert-butylamide on permethylated cyclodextrin macrocycle. The enantioselective properties of the new chiral selectors diluted in OV11 polysiloxane (35% phenyl- and 65% methylsiloxane) were investigated by means of injections of 117 racemic mixtures. The mixed chiral selectors with (L)-valine and, to a lesser extent with (D)-valine, were found to have an improved enantioselectivity toward amino acid derivatives by comparison to permethylated cyclodextrin. The enantioseparation capability of these new chiral selectors has proven to be slightly less efficient than Chirasil-L-Val (Alltech) for amino acid derivatives, but it has been extended to include terpenes, lactones, esters, aliphatic compounds and aryl alcohols.

Metabolomics reveals simultaneous influences of plant defence system and fungal growth in Botrytis cinerea-infected Vitis vinifera cv. Chardonnay berries

Botrytis cinerea is a fungal plant pathogen of grape berries, leading to economic and quality losses in wine production. The global metabolite changes induced by B. cinerea infection in grape have not been established to date, even though B. cinerea infection is known to cause significant changes in chemicals or metabolites. In order to better understand metabolic mechanisms linked to the infection process and to identify the metabolites associated with B. cinerea infection, (1)H NMR spectroscopy was used in global metabolite profiling and multivariate statistical analysis of berries from healthy and botrytized bunches. Pattern recognition methods, such as principal component analysis, revealed clear metabolic discriminations between healthy and botrytized berries of botrytized bunches and healthy berries of healthy bunches. Significantly high levels of proline, glutamate, arginine, and alanine, which are accumulated upon plant stress, were found in healthy and botrytized berries of botrytized bunches. Moreover, largely degraded phenylpropanoids, flavonoid compounds, and sucrose together with markedly produced glycerol, gluconic acid, and succinate, all being directly associated with B. cinerea growth, were only found in botrytized berries of botrytized bunches. This study reports that B. cinerea infection causes significant metabolic changes in grape berry and highlights that both the metabolic perturbations associated with the plant defence system and those directly derived from fungal pathogen growth should be considered to better understand the interaction between metabolic variation and biotic pathogen stress in plants.