Inhibition of antennal esterases of the egyptian armyworm Spodoptera littoralis by trifluoromethyl ketones

Abstract

A series of aliphatic and aromatic trifluoromethyl ketones has been tested as inhibitors of the antennal esterases of the Egyptian armyworm Spodoptera littoralis, by evaluation of the extent of hydrolysis of [1- 3H]-( Z,E)-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-trifluoropropan-2-one ( 2) (IC 50 0.55 μM) and 1,1,1-trifluorotetradecan-2-one ( 4) (IC 50 1.16 μM). The aromatic compounds were generally less potent inhbitors than the coressponding aromatic ones, although β-naphthyltrifuloromethyl ketone ( 10) exhibited a remarkable inhibitory activity (IC 50 7.9 μM). Compounds 2, 4 and 10 exhibit a competitive inhibition with K i values of 2.51×10 −5 M, 2.98×10 −5 M and 2.49×10 −4 M, respectively. Some of the trifluoromethyl ketones tested were slow-binding inhibitors and compounds 2 and 10 are described as inhibitors of the antennal esterases of a moth for the first time.