Acaricidal Activities of Bicyclic Monoterpene Ketones from Artemisia iwayomogi against Dermatophagoides spp.

The acaricidal properties of 1,7,7-trimethylbicyclo[2.2.1]heptan-2-one isolated from Artemisia iwayomogi and its structural analogues were evaluated against Dermatophagoides farinae and D. pteronyssinus, and their effects were compared with that of the commercial acaricide benzyl benzoate. Based on the 50 % lethal dose (LD50) values against D. farinae, 1,7,7-trimethylbicyclo[2.2.1]heptan-2-one (0.82 μg/cm2) was 9.71 times more effective than benzyl benzoate (7.96 μg/cm2), followed by (1R)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-one (1.03 μg/cm2), (1S)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-one (1.58 μg/cm2), and (1R)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-one oxime (3.05 μg/cm2) in a filter paper bioassay. The acaricidal activities of 1,7,7-trimethylbicyclo[2.2.1]heptan-2-one and its structural analogues against D. pteronyssinus were similar to those against D. farinae. These results demonstrate that naturally occurring A. iwayomogi-isolated 1,7,7-trimethylbicyclo[2.2.1]heptan-2-one and its structural analogues are suitable for the production of natural acaricides against house dust mites.