title: Triterpene saponin hemi-biosynthesis of a leaf beetle's (Platyphora kollari) defensive secretion.
abstract: The adults of the leaf beetle Platyphora kollari (Chrysomelidae) are able to metabolise the oleanane triterpene beta-amyrin (1) into the glycoside 3-O-beta-D: -glucopyranosyl-(1-->4)-beta-D: -glucuronopyranosyl-hederagenin (2) that is stored in their defensive glands. The aim of this study was to test the hypothesis that oleanolic acid (3) is an intermediate in the conversion of 1 into 2 and to check whether the sequestration of pentacyclic triterpenes is selective in favour of beta-amyrin (1). To this end, adults of P. kollari were fed with Ipomoea batatas leaf disks painted with a solution of [2,2,3-(2)H(3)]oleanolic acid or [2,2,3-(2)H(3)]alpha-amyrin and the secretion of their defensive glands analysed by HPLC-ESIMS. The data presented in this work indicated that the first step of the transformation of beta-amyrin (1) into the sequestered glycoside 2 is its oxidation into oleanolic acid (3) and that this conversion is selective but not specific in favour of beta-amyrin (1).
authors.affiliation: Department of Organic Chemistry, CP 160/06, Faculty of Sciences, University of Brussels, 50 Av. F.D. Roosevelt, 1050, Brussels, Belgium.
authors.forename: Jean
authors.initials: J
authors.lastname: Ghostin
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Habib-Jiwan
authors.forename: Raoul
authors.initials: R
authors.lastname: Rozenberg
authors.forename: Désiré
authors.initials: D
authors.lastname: Daloze
authors.forename: Jacques M
authors.initials: JM
authors.lastname: Pasteels
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Braekman
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D002851:Chromatography, High Pressure Liquid; D001517:Coleoptera / Q000502:physiology*; D003903:Deuterium; D006027:Glycosides / Q000378:metabolism; D010935:Plant Diseases / Q000469:parasitology; D018515:Plant Leaves / Q000469:parasitology*; D012503:Saponins / Q000378:metabolism*; D018629:Spectrometry, Mass, Secondary Ion; D014315:Triterpenes / Q000378:metabolism*
chemical_list: D006027:Glycosides; D012503:Saponins; D014315:Triterpenes; D003903:Deuterium