Chi-Hoon Lee

Acaricidal activities of major constituents of essential oil of Juniperus chinensis leaves against house dust and stored food mites.

The acaricidal activities of major constituents from the oil of Juniperus chinensis (var. globosa) leaves were compared with those of DEET (N,N-diethyl-m-toluamide) by using impregnated fabric disk bioassay against Dermatophagoides spp. and Tyrophagus putrescentiae. Toxicity varied with doses as well as chemical composition. The 50% lethal doses (LD50) of J. chinensis oil against Dermatophagoides farinae, Dermatophagoides pteronyssinus, and T. putrescentiae were 21.60, 19.89, and 38.10 microg/cm2, respectively. The active constituent was purified using silica gel chromatography and high-performance liquid chromatography. The acaricidal component was identified as bomyl acetate through gas chromatography-mass spectrometry, 1H nuclear magnetic resonance (NMR), 13C-NMR, 1H-13C shift correlation spectrum-NMR, and distortionless enhancement by polarization transfer-NMR. The LD50 of bornyl acetate (2.94 microg/cm2) against D. farinae was significantly lower than those of DEET (37.13 microg/cm2) and alpha-eudesmol (29.72 microg/cm2). Similar results were observed when bomyl acetate and alpha-eudesmol were tested against D. pteronyssinus and T. putrescentiae. The lower LD50 of bornyl acetate indicates that it may be responsible for the major acaricidal activity against house dust and stored food mites, even though it constitutes only 19.5% of J. chinensis oil. Overall, these findings indicated that bornyl acetate and c-eudesmol have potential for use as control agents against house dust and stored food mites.

Acaricidal properties of piperazine and its derivatives against house-dust and stored-food mites

BACKGROUND Piperazine derivatives possess pharmacological properties, yet the acaricidal activity of these compounds has not been investigated. This study was conducted to evaluate the colour alteration and acaricidal activity of piperazine derivatives against Dermatophagoides spp. and Tyrophagus putrescentiae (Schrank) using filter paper and fumigant methods. RESULTS In a fumigant bioassay, 1-phenylpiperazine (7.83 microg cm(-2)) against D. farinae (Hughes) was found to be 4.7 times more toxic than DEET (36.84 microg cm(-2)), followed by benzyl benzoate (9.72 microg cm(-2)), piperazine (11.41 microg cm(-2)), 1-ethoxycarbonylpiperazine (20.14 microg cm(-2)) and 1-(2-methoxyphenyl)piperazine (22.14 microg cm(-2)). In a filter paper bioassay, 1-(2-methoxyphenyl)piperazine (3.65 microg cm(-2)) was 5.7 times more toxic than DEET (20.64 microg cm(-2)), followed by 1-ethoxycarbonylpiperazine (4.02 microg cm(-2)), 1-phenylpiperazine (4.75 microg cm(-2)), benzyl benzoate (7.83 microg cm(-2)) and piperazine (10.59 microg cm(-2)). Similar results have been exhibited with piperazine derivatives against D. pteronyssinus (Troussart). However, no activity against T. putrescentiae was observed for piperazine derivatives, except for piperazine. CONCLUSIONS These results indicate that piperazine derivatives may be suitable as vapour-phase acaricide fumigants owing to their high volatility, acaricidal activity and safety. 1-Phenylpiperazine was found to be an excellent mite indicator based on the colour change it induced. Taken together, these findings indicate that piperazine derivatives may be used to replace existing problematical acaricides owing to their activity and ability to act as a mite indicator.