ANTIFEEDANT ACTIVITIES OF SESQUITERPENE LACTONES FROMNEUROLAENA LOBATA
Claus M. Passreiter1 and Murray B. Isman2
1 Institut für Pharmazeutische Biologie, Heinrich-Heine-Universität,D-40225 Düsseldorf, Germany;
2 Department of Plant Science, University of British Columbia,Vancouver, Canada V6T 1Z4
Neurolaena lobata (Asteraceae), a widespread medicinal plantin Central America and the Caribbean, contains a number of sesquiterpenelactones active as antimalarial and anticancer agents in vitro. As sesquiterpenelactones can be active against insects, we tested the main compounds isolatedfrom N. lobata for antifeedant activity using 4th instar larvaeof Spodoptera litura in a non-choice leaf disk bioassay. The mostactive compounds were the germacranolides lobatin A and neurolenin B, with65% feeding deterrence at 0.3 mM/cm2. Furanoheliangolides were generallyless active. Beside the compounds isolated from N. lobata, we alsotested the germacranolide epoxide parthenolide and the furanoheliangolidebuddlein A. Both compounds were found to be the most active compounds foreach group. Sesquiterpene lactones from sunflowers, possessing picrotoxinin-likeGABAA-gated chloride ionophore neurotoxicity, also show antifeedant activityrelated to this mode of action. We therefore tested the activityof neurolenin B in comparison to the known GABA antagonists picrotoxininand strychnine, with and without simultaneous administration of equimolarGABA. Co-adminstration of GABA abolished antifeedant bioactivity, stronglysuggesting that these compounds exert their antifeedant effect throughinteraction with GABAA-receptors.