ANTICHOLINESTERASE ACTIVITY OF ESSENTIAL OIL COMPONENTS IN PEDICULUS HUMANUS CAPITIS (ANOPLURA:PEDICULIDAE) AND ITS RELATIONSHIP WITH THEIR PEDICULIDAL ACTIVITY

TOLOZA. A.C.; MOUGABURE CUETO G. A.;ZYGADLO, J; ZERBA E. AND PICOLLO M.I.

Buenos Aires, Argentina

Congreso; 3rd International Congress On Phthiraptera; 2006

During past decades, the intensive use of permethrin against populations of Pediculus humanus capitis from Buenos Aires, Argentina has resulted in the development of resistance. Thus, the need of new “environmental friendly” control alternatives has become of great interested. Essential oils (EO) seem to be good candidates because most of them are consider as safe products. However, little is known about their mode of action. According to the signs of toxicity, it has been proposed that some essential oils could posses neurotoxic effects, similar to those produced by such insecticides as organophosphates and carbamates. The aim of this work was to analyze the potential competitive inhibition of acetylcholinesterase by essential oil components and its relation with the toxic effect. Biochemical inhibition of acetylcholinesterase was established by 3 assays: an in vitro method employing cholinesterase isolated from electric eels, an ex vivo method employing homogenate from head lice; and in vivo method employing head lice exposed to vapours of 1.8 cineole. A microplate reader was employed to measure acetylcolinesterese activity in all the cases. Concerning in vitro study, the components that showed high inhibition values were 1.8 cineole, pulegone, thymol and bencyl alcohol. For other studies, 1.8 cineole was chosen. With respect to ex vivo analysis, the inhibition concentration 50% (IC50) of 1.8 cineole was obtained. Finally, in the in vivo assay, no correlation was found between neurotoxic symptoms and the cholinesterase inhibition of exposed head lice to vapors of 1.8 cineole. In the present study, activity in vivo was not correlated with acetylcholinesterase activity ex vivo. Although 1.8 cineole showed anticholinesterase activity, it seems that the mentioned inhibition activity is not the main responsible of the pediculicidal activity of these essential oil component. Another possible mode of action of the essential oils is discussed.