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

Two compounds present on the surface of Brassica oleracea cv. botrytis leav es have been isolated and identified which stimulate very effectively ovipo sition in the cabbage root fly, Delia radicum and which are perceived by a specific receptor neuron in the tarsal sensillum C-5 of the female fly. Act ivity of extracts and chromatographic fractions were bioassayed, using ovip osition experiments and mainly electrophysiological recordings from the CS tarsal contact chemoreceptor sensillum of female flies. Spectroscopic data indicate that the main compound is 1,2-dihydro-3-thia-4,10,10b-triaza-cyclo penta[.a.]fluorene-1-carboxylic acid, a novel compound related to Brassica phytoalexins like brassicanal C. It is accompanied by its glycine conjugate . (C) 1999 Elsevier Science Ltd. All rights reserved.