Oviposition stimulants for the cabbage root fly: isolation from cabbage leaves

Two compounds present on the surface of Brassica oleracea cv. botrytis leaves have been isolated and identified which stimulate very effectively oviposition in the cabbage root fly, Delia radicum and which are perceived by a specific receptor neuron in the tarsal sensillum C5 of the female fly. Activity of extracts and chromatographic fractions were bioassayed, using oviposition experiments and mainly electrophysiological recordings from the C5 tarsal contact chemoreceptor sensillum of female flies. Spectroscopic data indicate that the main compound is 1,2-dihydro-3-thia-4,10,10b-triaza-cyclopenta[.a.]fluorene-1-carboxylic acid, a novel compound related to Brassica phytoalexins like brassicanal C. It is accompanied by its glycine conjugate.