Acaricidal activity of active constituent isolated in Chamaecyparis obtusa leaves against Dermatophagoides spp.

Acaricidal activities of materials derived from Chamaecyparis obtusa leaves against Dermatophagoides farinae and Dermatophagoides pteronyssinus were examined using the dry film method and compared with that of commercial benzyl benzoate and N,N-diethyl-m-toluamide (DEET). The active constituent of the C. obtusa leaves was identified as beta-thujaplicin (C10H12(O2)) by spectroscopic analyses. Responses varied with dose. On the basis of a 24 h LC50 value, acaricidal activity against D. farinaewas more pronounced with beta-thujaplicin (72.2 mg/m2) than benzyl benzoate (89.9 mg/m2) and DEET (377 mg/m2). Acaricidal activity against D. pteronyssinus was more pronounced in beta-thujaplicin (62.1 mg/m2) than benzyl benzoate (72.4 mg/m2) and DEET (193 mg/m2). These results indicate that acaricidal activity of C. obtusa leaves likely results from by beta-thujaplicin. Beta-thujaplicin merits further study as potential house dust mite control agents or lead compounds.