Article

Journal of Chemical Ecology

, Volume 28, Issue 3, pp 587-599

First online:

Identification of a Triterpenoid Saponin from a Crucifer, Barbarea vulgaris, as a Feeding Deterrent to the Diamondback Moth, Plutella xylostella

  • Tetsuro ShinodaAffiliated withNational Institute of Vegetable and Tea Science Email author 
  • , Tsuneatsu NagaoAffiliated withFaculty of Pharmaceutical Science, Fukuoka University
  • , Masayoshi NakayamaAffiliated withNational Institute of Floricultural Science
  • , Hiroaki SerizawaAffiliated withNagano Vegetable and Ornamental Crops Experiment Station
  • , Masaji KoshiokaAffiliated withNational Institute of Floricultural Science
  • , Hikaru OkabeAffiliated withFaculty of Pharmaceutical Science, Fukuoka University
  • , Akira KawaiAffiliated withNational Institute of Vegetable and Tea Science

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Abstract

Larvae of the diamondback moth, Plutella xylostella, a crucifer specialist, refuse to feed on a crucifer, Barbarea vulgaris, because of the presence of a feeding deterrent, which is extractable with chloroform. We isolated a feeding deterrent from B. vulgaris leaves, by successive fractionations with silica-gel, ODS, i.e., C18 reversed phase, and Sephadex LH-20 column chromatographies, and ODS-HPLC, guided by a bioassay for feeding deterrent activity. The structure of the compound was determined to be a monodesmosidic triterpenoid saponin, 3-O-[O-β-D-glucopyranosyl-(1→4)-β-D-glucopyranosyl]-hederagenin, based on FAB-MS, 1H- and 13C-NMR spectra, and hydrolysis experiments. When the compound was applied to cabbage leaf disks at greater than 0.18 μg/mm2, consumption of the disks by third instars was less than 11% of control disks treated with the solvent alone. Furthermore, all first instars died on the disks treated with the same concentrations. Because the concentration of the compound in the fresh leaves of B. vulgaris was comparable to the effective dose in the cabbage leaf disk tested, we conclude that the unacceptability of B. vulgaris to P. xylostella larvae is primarily due to this saponin.

Barbarea vulgaris Brassicaceae diamondback moth feeding deterrent 3-O-[O-β-D-glucopyranosyl-(1→4)-β-D-glucopyranosyl]-hederagenin host plant resistance insect-plant interactions Lepidoptera Plutella xylostella triterpenoids saponins