Acaricidal Effects of Thymus vulgaris Leaf-derived Materials and Monoterpene Alcohols against Dermatophagoides spp.

Abstract

Acaricidal activities of Thymus vulgaris leaf-derived materials were examined using a fumigant and filter paper bioassay and compared to those of monoterpene alcohols and the synthetic acaricide, benzyl benzoate. In the fumigant bioassay, the LD50 value of the T. vulgaris oil was 3.1 and 3.7 μg/cm2 against Dermatophagoides farinae and D. pteronyssinus, respectively. Active constituent of T. vulgaris leaves was purified by various chromatographies and identified as carvacrol by various spectra. When the relative toxicity against Dermatophagoides spp. was measured using a fumigant and filter paper bioassay, carvacrol was 4.1 to 8.0-fold more toxic than benzyl benzoate, but less toxic than β-citronellol. Specifically, in case of acaricidal activity of β-citronellol was 32.2 to 63.1-fold higher than that of benzyl benzoate against Dermatophagoides spp. Taken as a whole, the filter paper bioassay with all tested compounds leading to more effective acaricidal activity than the fumigant bioassay. In addition, the results of this study revealed that carvacrol and the two monoterpene alcohols (β-citronellol and borneol) were generally higher than those of commercial acaricides such as benzyl benzoate against the two mite species. These results indicate that carvacrol, β-citronellol, and borneol could be useful as a new preventive agent against damage caused by arthropod pests.