Terpenoid insecticides based on plant essential oils, including peppermint, thyme, clove, and rosemary, can kill insects rapidly, which suggests a neurotoxic mechanism of action in insects and ticks. We have studied individual monoterpenoids, including camphor, menthol, carvacrol, and eugenol, to determine their effects at three types of receptors in the insect nervous system and one enzyme in the insect nervous system. Certain monoterpenoids have activity at GABA receptors from house fly and American cockroach, as positive or negative modulators, while others have no effect. Some monoterpenoids have activity at an octopamine receptor cloned from American cockroach brain, as positive allosteric modulators or inverse agonists. One monoterpenoid (carvacrol) inhibits binding of 14C-nicotine at the nicotinic acetylcholine receptor from house fly head. Investigation of many monoterpenes in GABA and octopamine in vitro systems is allowing development of quantitative structure-activity relationships and a better understanding of the physicochemical properties required for potency.

Multiple insecticidal mechanisms of action of monoterpenes

244th National Meeting (2012)

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