Elisabeth Besson

C-glycosylflavones from Oryza sativa

Abstract Eight flavone C-glycosides isolated from rice plant were found to act as probing stimulants for planthoppers. They have been identified as the known compounds schaftoside, neoschaftoside, carlinoside, isoorientin 2″-glucoside and the new constituents neocarlinoside (6-C-β- D -glucopyranosyl-8-C-β- L -arabinopyranosylluteolin), isoscoparin 2″-glucoside (chrysoeriol 6-C-β- D -(2-O-β- D -glucopyranosyl)glucopyranoside) and its 6‴-p-coumaric and ferulic acid esters.

C-galactosylflavones from Polygonatum multiflorum

Abstract 8-C-Galactosylapigenin and 6-C-galactosyl-8-C-arabinosylapigenin were isolated from the leaves of Polygonatum multiflorum (L.) All. Structural assignments for the latter compound were made on the basis of mass, CD and 13C-NMR spectra.

C-glycosylflavones from parkinsonia aculeata

Abstract The only C -glycosylflavones isolated from Parkinsonia aculeata leaves were identified as orientin (instead of epiorientin), isoorientin (instead of parkinsonin-A), vitexin and isovitexin (instead of parkinsonin-B). Orientin was definitely present in the laevorotatory form.

Genetically controlled 2″-O-glycosylation of isovitexin in the petals of Melandrium album

Abstract The genetically controlled O -glycosylation of the 6- C -glucosyl residue of isovitexin in the petals of Melandrium album has been shown to take place in the 2″-position, by MS of the corresponding permethylated isovitexin glycosides.

The 2″-O-glucosylation of vitexin and isovitexin in petals of Silene alba is catalysed by two different enzymes

Two separate genes, Fg and Vg, which govern the presence of isovitexin 2″-O-glucoside and vitexin 2″-O-glucoside respectively in the petals of Silene alba control different glucosyltransferases. In Vg/Vg,fg/fg plants no isovitexin 2″-O-glucosyltransferase was present and in vg/vg,Fg/Fg plants no vitexin 2″-O-glucosyltransferase activity could be detected. The Fg-controlled UDP-glucose: isovitexin 2″-O-glucosyltransferase has a pH optimum of8.5, while the Vg-controlled vitexin 2″- O-glucosyltransferase has a pH optimum of7.5. Both glucosyltransferases are stimulated by the divalent cations Ca2+, Co2+, Mn2+ and Mg2+. For isovitexin 2″-O-glucosylation, however, much higher concentrations are needed than for vitexin 2″-O-glucosylation.For UDP-glucose a ‘true Km’ value of0.3 mM with the Fg-controlled and of 0.2 mM with the Vg-controlled enzyme was found. For isovitexin and vitexin these values are respectively 0.09 and 0.01 mM.

Apigenin di-C-glycosylflavones of Angiopteris (Marattiales)

A survey of the flavonoids of four species of Angiopteris indicates that di-C-glycosylflavones and flavone-O-glycosides may be characteristic of this distinct group of eusporangiate ferns. Derivatives of flavonols, which are typical of leptosporangiate ferns and Ophioglossum, or biflavones, which are characteristic of the Psilotaceae, were not detected in Angiopteris.

Structure of a 6,8-di-C-pentosylapigenin from Mollugo pentaphylla

Abstract One of the di-C-pentosylflavones isolated from Mollugo pentaphylla was identified as 6-C-β- d -xylopyranosyl-8-C-α- l -arabinop

Investigations on Hoya Species. III. Leaf Phenolics and Latex Lipids of Hoya lacunosa Bl.

Hoya lacunosa leaves contain some main C-glycosylflavonoids, which were identified as: 6-C- arabinosyl 8-C-glucosylapigenin (isoschaftoside), 6-C-glucosyl 8-C-arabinosylapigenin (schaftosi- de) and 6,8-di-C-arabinosylapigenin. In the latex triterpenols were found, often both free and in ester form, of which β-amyrin, α-amyrin, lupeol, 24-methylenecycloartanol, obtusifoliol and cycloeucalenol were identified in the free alcohol fraction. The esters, forming the major part of the total lipid fraction, were solely acetates of some of the above mentioned alcohols.