Acaricidal activity of triketone analogues derived from Leptospermum scoparium oil against house-dust and stored-food mites.
BACKGROUND
Various attempts to control the populations of house-dust and stored-food mites have been implemented using synthetic chemicals. Although effective, the repeated use of these chemicals has led to resistance owing to the mite's high reproductive potential and short life cycle. Therefore, this study aimed to develop natural acaricides using oils derived from Leptospermum scoparium JR & G Forst., which may affect the overall biological activity of a mite without adverse effects. Results were compared with those from using benzyl benzoate and N,N-diethyl-3-methylbenzamide (DEET).


RESULTS
The LD(50) values of L. scoparium oil were 0.54, 0.67 and 1.12 microg cm(-2) against Dermatophagoides farinae (Hughes), D. pteronyssinus (Troussart) and Tyrophagus putrescentiae (Schrank) respectively. The active constituent isolated from L. scoparium was identified as leptospermone (6-isovaleryl-2,2,4,4-tetramethyl-1,3,5-cyclohexanetrione) by spectroscopic analysis. Based on the LD(50) values of leptospermone and its derivatives, the most toxic compound against D. farinae was leptospermone (0.07 microg cm(-2)), followed by 2,2,4,4,6,6-hexamethyl-1,3,5-cyclohexanetrione (1.21 microg cm(-2)), benzyl benzoate (10.03 microg cm(-2)) and DEET (37.12 microg cm(-2)). Furthermore, similar results were observed when the leptospermone and its derivatives were tested against D. pteronyssinus and T. putrescentiae.


CONCLUSIONS
These results indicate that L. scoparium oil-derived materials, particularly leptospermone and 2,2,4,4,6,6-hexamethyl-1,3,5-cyclohexanetrione, have potential for development as new agents for the control of three species of mite.
Jeong
Eun-Young
EY
Environmental Science Major and Institute of Agricultural Science & Technology, College of Agriculture & Life Science, Chonbuk National University, Chonju 561-756, South Korea.
Kim
Min-Gi
MG
Lee
Hoi-Seon
HS
D000818:Animals; D007306:Insecticides / Q000737:chemistry / Q000494:pharmacology*; D031649:Leptospermum / Q000737:chemistry*; D008925:Mites / Q000187:drug effects*; D009822:Oils, Volatile / Q000737:chemistry / Q000494:pharmacology*; D010696:Phloroglucinol / Q000031:analogs & derivatives; D010938:Plant Oils / Q000737:chemistry / Q000494:pharmacology*
D007306:Insecticides; D009822:Oils, Volatile; D010938:Plant Oils; C508521:leptospermone; D010696:Phloroglucinol