INHIBITION OF ANTENNAL ESTERASES OF THE EGYPTIAN ARMYWORM SPODOPTERA-LITTORALIS BY TRIFLUOROMETHYL KETONES

A series of aliphatic and aromatic trifluoromethyl ketones has been te sted as inhibitors of the antennal esterases of the Egyptian armyworm Spodoptera littoralis, by evaluation of the extent of hydrolysis of [1 -H-3]-(ZE)-9,11-tetradecadienyl acetate (1), a tritiated analog of the major component of the sex pheromone. The most active compounds with a long chain aliphatic structure were 3-octylthio-1,1,1-trifluoropropa n-2-one (2) (IC50 0.55 muM) and 1,1,1-trifluorotetradecan-2-one(4) (IC 50 1.16 muM). The aromatic compounds were generally less potent inhibi tors than the corresponding aromatic ones, although beta-naphthyltrifl uoromethyl ketone (10) exhibited a remarkable inhibitory activity (IC5 0 7.9 muM). Compounds 2, 4 and 10 exhibit a competitive inhibition wit h K(i) values of 2.51x10(-5) M, 2.98x10(-5) M and 2.49x10(-4) M, respe ctively. Some of the trifluoromethyl ketones tested were slow-binding inhibitors and compounds 2 and 10 are described as inhibitors of the a ntennal esterases of a moth for the first time.