Arjunetin from Terminalia arjuna as an insect feeding-deterrent and growth inhibitor

Crude ethanolic extract of the stem bark of Terminalia arjuna (Combretaceae) and its three compounds namely arjunic acid, arjungenin and arjunetin were evaluated for antifeedant, growth inhibitory and oviposition-deterrent activities against a lepidopterous insect Spilarctia obliqua. The compound arjunetin showed highest growth inhibitory and feeding-deterrent properties with a growth inhibition (GI(50)) and feeding-inhibition (FD(50)) of 188.5 and 287.1 micro g/g diet respectively. Oviposition bioassays indicated no oviposition-deterrence in any of the compounds tested. The structure-activity relationship study indicated the importance of a glycosidation linkage in arjunetin.