title: Electrophysiological and behavioral characterization of bioactive compounds of the Thymus vulgaris, Cymbopogon winterianus, Cuminum cyminum and Cinnamomum zeylanicum essential oils against Anopheles gambiae and prospects for their use as bednet treatments.
abstract: BACKGROUND
  Laboratory and field studies showed that repellent, irritant and toxic actions of common public health insecticides reduce human-vector contact and thereby interrupt disease transmission. One of the more effective strategies to reduce disease risk involves the use of long-lasting treated bednets. However, development of insecticide resistance in mosquito populations makes it imperative to find alternatives to these insecticides. Our previous study identified four essential oils as alternatives to pyrethroids: Thymus vulgaris, Cymbopogon winterianus, Cuminum cyminum, Cinnamomum zeylanicum. The objectives of this study were to identify active compounds of these essential oils, to characterize their biological activity, and to examine their potential as a treatment for bednets.
  
  
  METHODS
  We evaluated the electrophysiological, behavioural (repellency, irritancy) and toxic effects of the major compounds of these oils against Anopheles gambiae strain 'Kisumu'.
  
  
  RESULTS
  Aldehydes elicited the strongest responses and monoterpenes the weakest responses in electroantennogram (EAG) trials. However, EAG responses did not correlate consistently with results of behavioral assays. In behavioral and toxicity studies, several of the single compounds did exhibit repellency, irritancy or toxicity in An. gambiae; however, the activity of essential oils did not always correlate with activity expected from the major components. On the contrary, the biological activity of essential oils appeared complex, suggesting interactions between individual compounds and the insect under study. Data also indicated that the three effects appeared independent, suggesting that repellency mechanism(s) may differ from mechanisms of irritancy and toxicity.
  
  
  CONCLUSIONS
  Based on the bioassays reported here, some of the compounds merit consideration as alternative bednet treatments.
authors.affiliation: UR Hortsys, Cirad, Campus de Baillarguet, 34980, Montferrier, France. emilie.deletre@cirad.fr.
authors.forename: Emilie
authors.initials: E
authors.lastname: Deletre
authors.affiliation: UMR MiVEGEC, IRD-CNRS-UM1-UM2, 911 Ave Agropolis, 34980, Monferrier, France. Fabrice.Chandre@ird.fr.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Chandre
authors.affiliation: USDA-ARS, European Biological Control Laboratory, Campus de Baillarguet, 34980, Monferrier, France. lwilliams@ars-ebcl.org.
authors.forename: Livy
authors.initials: L
authors.lastname: Williams
authors.affiliation: UR Hortsys, Cirad, Campus de Baillarguet, 34980, Montferrier, France. cnf.dumenil@gmail.com.
authors.forename: Claire
authors.initials: C
authors.lastname: Duménil
authors.affiliation: Institut des Biomolécules Max Mousseron, Faculté de Pharmacie, 15 Av.Charles Flahault, 34000, Montpellier, France. chantal.menut@univ-montp2.fr.
authors.forename: Chantal
authors.initials: C
authors.lastname: Menut
authors.affiliation: UR Hortsys, Cirad, Campus de Baillarguet, 34980, Montferrier, France. thibaud.martin@cirad.fr.|Plant Health Department, ICIPE, P.O. Box 30772-00100, Nairobi, Kenya. thibaud.martin@cirad.fr.
authors.forename: Thibaud
authors.initials: T
authors.lastname: Martin
mesh_terms: D000818:Animals; D000852:Anopheles / Q000187:drug effects* / Q000502:physiology; D001522:Behavior, Animal / Q000187:drug effects; D002935:Cinnamomum zeylanicum / Q000737:chemistry*; D028527:Cuminum / Q000737:chemistry*; D031743:Cymbopogon / Q000737:chemistry*; D007300:Insect Control / Q000295:instrumentation / Q000379:methods; D057148:Insecticide-Treated Bednets; D007306:Insecticides / Q000737:chemistry / Q000494:pharmacology*; D009822:Oils, Volatile / Q000737:chemistry / Q000494:pharmacology*; D010938:Plant Oils / Q000737:chemistry / Q000494:pharmacology*; D046930:Thymus Plant / Q000737:chemistry*
chemical_list: D007306:Insecticides; D009822:Oils, Volatile; D010938:Plant Oils