title: New resistance-correlated saponins from the insect-resistant crucifer Barbarea vulgaris.
abstract: Isolation and characterization of plant constituents responsible for insect resistance are of the utmost importance for better understanding of insect-host plant interactions, for selection and breeding of resistant plant varieties, and for development of natural insecticides to be used in future sustainable agriculture and food production. In this study, 3-O-cellobiosyl-cochalic acid (1), 3-O-cellobiosyl-gypsogenin (3), and 3-O-cellobiosyl-4-epihederagenin (4) were isolated from the glabrous type of Barbarea vulgaris var. arcuata exhibiting resistance to the flea beetle Phyllotreta nemorum. In addition to the new constituents, 3-O-cellobiosyl-hederagenin (2), a known insect repellant, was identified. The structures were established by one- and/or two-dimensional homo- and heteronuclear NMR experiments acquired at 800 MHz and by fragmentation and high-resolution mass spectrometric analysis. Compounds 1, 3, and 4 are glycosides of cochalic acid, gypsogenin, and 4-epihederagenin, respectively, none of which have previously been identified in Brassicaceae. Compounds 3 and 4 have both recently been targeted as unidentified constituents exhibiting correlation with P. nemorum resistance, but this is the first report of their structures.
authors.affiliation: Department of Basic Sciences and Environment, Faculty of Life Sciences, University of Copenhagen, Frederiksberg, Denmark.
authors.forename: Nikoline J
authors.initials: NJ
authors.lastname: Nielsen
authors.forename: John
authors.initials: J
authors.lastname: Nielsen
authors.forename: Dan
authors.initials: D
authors.lastname: Staerk
mesh_terms: D000818:Animals; D031216:Barbarea / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D001517:Coleoptera / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D012503:Saponins / Q000032:analysis*; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D012503:Saponins