ANTIFEEDANT BIOACTIVITY OF SESQUITERPENE LACTONES FROM NEUROLAENA-LOBATA AND THEIR ANTAGONISM BY GAMMA-AMINOBUTYRIC-ACID

The germacranolides and furanoheliangolides isolated from aerial parts of Neurolaena lobata (L.) R.Br. are assessed as antifeedants against fifth instar larvae of Spodoptera litura (Noctuidae) using leaf disc b ioassays. In terms of potency, they are less active than parthenolide, more active than picrotoxinin, and comparable to strychnine. The anti feedant effect of neurolenin B, appears to result from interaction wit h GABA(A) receptors in the chemosensilla of S. litura as suggested for the known GABA antagonists strychnine and picrotoxinin. All three com pounds show strong antifeedant activities, which are completely lost a fter simultaneous co-administration of equimolar GABA. (C) 1997 Elsevi er Science Ltd.