IDENTIFICATION OF COMPOUNDS IN AN HPLC FRACTION FROM FEMALE EXTRACTS THAT ELICIT MATING RESPONSES IN MALE SCREWWORM FLIES, COCHLIOMYIA-HOMINIVORAX

When hexane extracts of mature screwworm females were chromatographed on a silica gel column, mating stimulant activity was concentrated in a fraction that eluted with hexane-ether (94:6, v/v). Separation of th is fraction with HPLC (acetonitrile-acetone; 60:40, isocratic) resulte d in a chromatogram of some 20 peaks. Only peaks 4-11 elicited mating responses. Peaks 5-10 had most of the activity, with peak 8 producing the highest response. Sixteen compounds were characterized from peak 8 by gas chromatography-mass spectrometry: six unbranched secondary ace tates (C31H62O2); seven previously unreported methyl-branched secondar y acetates (C32H64O2); one unbranched ketone (C31H62O); and one methyl -branched ketone (C32H64O). The isomeric acetates were not completely resolved from each other by capillary gas chromatography (CGC) on meth yl silicone columns. The sixteenth compound was an aldehyde (C30H60O) that was present only in occasional peak 8 preparations. These compoun ds and several derivatives were characterized by capillary gas chromat ography-mass spectrometry (CGC-MS). The position of the acetate group was ascertained by conversion to a keto group or by replacement of the acetate with a methyl group. Pheromone activity was not observed in p eaks trapped either from CGC or by recombination of the trapped CGC pe aks from HPLC peak 8. This apparent loss of activity from CGC peaks or from TLC cannot currently be explained.