Insecticidal toxicity of Eucalyptus cinerea essential oil and 1,8-cineole against Musca domestica and possible uses according to the metabolic response of flies

In a fumigant assay, Musca domestica adults treated with Eucalyptus cinerea EO [LC50 =5.5 mg/dm(3); majority component by SPME-GC: 1,8-cineole (88.5%), alpha-pinene (2%), alpha-terpineol (9%)], died within 15 mm or less. The terpenes absorbed by the flies and their metabolites, analyzed using SPME fiber, were 1,8-cineole (LC50 =3.3 mg/dm(3)), alpha-pinene (LC50 =11.5 mg/dm(3)), alpha-terpineol (LC50 =36.8 mg/dm(3)) and a new component 2,3-dehydro-1,8-cineole, in proportions of 74%, 0.1%, 24.7% and 1.2% respectively. 2,3-Dehydro-1,8-cineole and a-terpineol were formed by oxidation of 1,8-cineole mediated by cytochrome P450, as demonstrated by a fumigation assay on flies previously treated with piperonyl butoxide, a P450 inhibitor, which showed an increase in toxicity of the EO and 1,8-cineole, supporting its participation in the formation of metabolites. We also demonstrated that 1,8-cineole acts as a P450 inhibitor-like compound, improving the toxicity of other xenobiotics such as deltamethrin. (C) 2014 Elsevier B.V. All rights reserved.