Jean-Pierre Utille

Immunocytochemical localisation of para-coumaric acid and feruloyl-arabinose in the cell walls of maize stem

Two phenolic compounds, p-coumaric acid and feruloyl-arabinose, were localised by immunocytochemistry in the cell walls of the apical internode of two lines of maize (Co125 and W401) of different digestibility. The compounds were detected at two stages of cell maturity in the lignified tissues (sclerenchyma, fibres and xylem) and in the medullary parenchyma, which, in the samples studied, was not lignified. p-Coumaric acid is a phenolic acid associated with lignins, which confer resistance on plant cell walls to microbial degradation in the rumen. Feruloyl-arabinose is a compound associated with xylans, the principal hemicelluloses in Gramineae, which are potentially degradable. Labelling of p-coumaric acid decreased in both maize lines with cell age and as the cell walls became lignified. The mass of lignin deposited in the cell walls masked p-coumaric acid, thereby making it less accessible to the antibodies. There was an inverse relationship in the labelling of p-coumaric acid and feruloyl-arabinose. Feruloyl-arabinose was more heavily labelled as the plant cell walls matured in all the lignified tissues of both maize lines and in the parenchyma of the less digestible line. All tissues except the parenchyma were more heavily labelled with both sera in Co125, the more digestible line.

Synthèse en série d-xylopyranose: Tri-O-acétyl-d-xyloses et dérivés chloroacétylés

Abstract Selective acetylation of d -xylose with acetic anhydride in dry pyridine at −30° gave 1,2,3- and 1,2,4-tri- O -acetyl-α- d -xylopyranose with traces of 2,3,4-tri- O -acetyl- d -xylopyranose. Acetylation of d -xylose under conditions differing from the preceding ones only with respect to an azeotropic distillation of an excess of pyridine before addition of acetic anhydride afforded a mixture of the eight possible triacetates. Unambiguous synthesis of 1,2,3-, 1,2,4-, and 1,3,4-tri- O -acetyl-β- d -xylopyranose was obtained from 3,4-di- O -acetyl-1,2- O -(1-ethoxyethylidene)-α- d -xylopyranose, which also gave 1,3,4-tri- O -acetyl-α- d -xylopyranose. The aforementioned O -acetyl derivatives and the derived monochloroacetyl compounds were analyzed by 13 C- and 1 H-n.m.r. spectroscopy at 62.86 and 250 MHz, respectively.

Monoclonal antibodies to p-coumarate.

p-Coumaric acid is one of the predominant phenolic acids acylating the cell walls of grasses; p-coumarates are mainly esterified by lignins and arabinoxylans. Here we describe the production and characterisation of two monoclonal antibodies against p-coumarates. The 5-O-pCou-Ara(1-->4)Xyl was chemically synthesized and conjugated to a carrier protein. Two interesting antibodies were obtained, hereinafter named INRA-COU1 and INRA-COU2. The specificity of these monoclonal antibodies has been evaluated using competitive-inhibition assays with different oligosaccharides and phenolic compounds. INRA-COU1, recognized free p-coumaric acid or p-coumarate esters. INRA-COU1 did not react with any of the other hydroxycinnamic acids and related compounds found in plants. INRA-COU2, only recognizes esterified p-coumarate. These antibodies were used to study the localization of p-coumarates in the cell walls of grasses. Immunocytochemical analyses indicated noticeable amounts of p-coumarate in the cell walls of the aleurone layer of wheat grain, in the epiderm of cereal straw, and in the exoderm of wheat root. The use of these antibodies will contribute to a better understanding of the organisation and developmental dynamics of cell walls in Graminaceae.

Synthesis of allyl 2-O-(α-l-arabinofuranosyl)-6-O-(α-d-mannopyranosyl)-β-d-mannopyranoside, a unique plant N-glycan motif containing arabinose

Abstract The synthesis of the trisaccharide allyl 2- O -(α- l -arabinofuranosyl)-6- O -(α- d -mannopyranosyl)-β- d -mannopyranoside is reported. Stereoselective glycosylation at C-6 of a non-protected allyl β-mannoside with the acetylated α- d -mannosyl bromide gave the α-(1→6)-disaccharide as the main product and the crystalline 3,6-branched trisaccharide as minor compound. Further glycosylation of the 2,3 diol (1→6) disaccharide with l -arabinofuranosyl bromide furnished a mixture of 3- O - and 2- O -α- l -Ara-trisaccharides from which the title compound was isolated.

1H- and 13C-nuclear magnetic resonance study of reducing disaccharides of d-xylopyranose

Abstract 1 H- and 13 C-n.m.r. data for the six hexa- O -acetyl, reducing disaccharides composed of d -xylopyranose units are reported. The chemical shifts were compared with those of some of the penta- O -acetyl or penta- O -acetyl-mono- O -chloroacetyl derivatives. The effects observed on the chemical shifts due to the absence of one O -acetyl group from the hexa- O -acetyl d -xylobioses are discussed, as well as the effects of the substitution of one O -acetyl by one O -chloroacetyl group on the protons of carbon atoms in a close vicinity to the substituted sites.

Specific reactivity of the O-(β-d-glucopyranosyl-(1→6)-d-glucopyranose) linkage with acetic anhydride in the presence of trimethylsilyl trifluoromethanesulfonate

On obtient un compose O-[acetoxy-«1» penta-O acetyl-2,3,4,5,6 glucityl]-6 tetra-O-acetyl-1,2,3,4 glucopyranose qui reagit ensuite avec le methanolate de sodium et donne le D-glucose penta-O-acetyle

Stereoselective reaction of methyl α- and β-D-glycopyranosides with acetic anhydride in the presence of trimethylsilyl trifluoromethanesulphonate

Treatment of methyl β-D-glycopyranosides with TMSOtf–Ac2O gives acyclic products by selective cleavage of the ring carbon–oxygen bond, whereas methyl α-D-isomers undergo replacement of the anomeric methoxy by an acetoxy group with retention of configuration.

Immunogold labelling of feruloyl-arabinose of maize stem after rumen microbial degradation

Immunogold labelling of feruloyl-arabinose was performed on the base and the top of the apical internode of the stem of Co125 and W401 maize, harvested at anthesis +5 days, after incubation in the rumen in nylon bags for 4, 8 and 24h. The description of labelling evolution during rumen degradation was permitted by the quantification of the intensity of labelling in four tissues: sclerenchyma, fibres, xylem and parenchyma. The results are discussed in relation to maize digestibility.

Dérivés Monotritylés du D-xylose☆

Abstract Monotritylation of O-acetyl derivatives of D -xylopyranose and D -xylofuranose with trityl chloride in acetonitrile-pyridine gave the tri-O-acetyl derivatives of 1-,2-, 3-, and 5-O-trityl- D -xylofuranose and of 1-, 2-, 3-, and 4-O-trityl- D -xylopyranose which were required for the identification of the various monotrityl derivatives obtained in the tritylation at 50° of D -xylose with trityl chloride in pyridine or hexamethylphosphoric triamide-silver acetate.

Synthesis of reducing disaccharides of d-xylopyranose

Abstract Twenty-one derivatives of reducing disaccharides, d -xylopyranosyl-(1→2)-, -(1→3)-, and -(1→4)-α- or -β- d -xylose were synthesized according to the Helferich and Zirner method. Disaccharides having a pyranose reducing unit were prepared by condensation of 2,3,4-tri-O-acetyl-, 2,4-di-O-acetyl-3-O-chloroacetyl-, and 2,3-di-O-acetyl-4-O-chloroacetyl-α- d -xylopyranosyl bromide with tri-O-acetyl-β- d -xylopyranose derivatives; among these, 1,2,4-tri-O-acetyl-3-O-(2,4-di-O-acetyl-β- d -xylopyranosyl)-β- d -xylopyranose and 1,2,3-tri-O-acetyl-4-O-(2,3-di-O-acetyl-β- d -xylopyranosyl)-β- d -xylopyranose having a free hydroxyl group in the nonreducing sugar group were prepared for the synthesis of higher-mol.wt. linear oligomers. Glycosylation of the readily available 5-O-chloroacetyl- or 5-O-acetyl-1,2-O-isopropylidene-α- d -xylofuranose gave 1,2-O-isopropylidene-3-O-β- d -xylopyranosyl- d -xylofuranose derivatives, further transformed into hexa-O-acetyl-β-(1→3)-xylobiose. Some analogs of α- d -linked disaccharides were formed during glycosylation. The location of the acetyl groups in the reducing and nonreducing residues were identified by comparison of the methyl-proton resonances for solutions in (2H6)benzene of 2,3,4-tri-O-acetyl-β- d -xylopyranosyl-(1→3)-1,2,4-tri-O-acetyl-β- d -xylopyranose and of a hexa-O-acetyl disaccharide having deuterated acetyl groups in the reducing residue, obtained by acetylation of 2,3,4-tri-O-acetyl-β- d -xylopyranosyl-(1→3)- d -xylopyranose with (2H6)acetic anhydride.