CYCLOHEXADIENONES-INSECT GROWTH-INHIBITORS FROM THE FOLIAR SURFACE AND TISSUE-EXTRACTS OF SENECIO-CANNABIFOLIUS

Dewaxed leaf surface extracts of 12 plants from Hokkaido, prepared by dipping fresh leaves in chloroform for 3 min, were used in a choice le af-disk bioassay against larvae of the tobacco cutworm Spodoptera litu ra. Activity was found only in the extract of Senecio cannabifolius, a very successful weed in Hokkaido. Individual fractions of the extract , however, were not active. Incorporation of the individual fractions of the surface extracts as well as fractions of the methanolic extract s of the leaf residue into an artificial diet fed to neonate S. litura led to the isolation of ethyl (1-hydroxy-4-oxocyclohexa-2,5-dien-1-yl ) acetate, the major surface compound, as the active principle.;This c ompound was also present in the methanolic extract of the leaf residue together with methyl (1-hydroxy-4-oxocyclohexa-2,5-dien-1-yl) acetate , which had the same growth inhibitory effect on the larvae. The prese nce of these compounds in the foliar surface and tissue suggests a def ensive role against herbivores.