ACTIVITIES OF LEAF OILS AND THEIR COMPONENTS FROM LAURACEAE TREES AGAINST HOUSE-DUST MITES

To investigate the effects of leaf oils from Lauraceae trees on house dust mites, Dermatophagoides pteronyssinus and D. farinae, antimite activity tests were conducted. Of leaf oils from six species obtained by steam distillation, the leaf oil of shirodamo (Neolitsea sericea) had the strongest activity against both species of mites. Antimite-active compounds were found to be present in its high-boiling fraction. Furthermore, from the activity tests using the fractions separated with a silica gel column and from the analyses with gas chromatography-mass spectrometry, nuclear magnetic resonance spectroscopy, and infrared spectroscopy, isosericenine, caryophyllene oxide, and alpha-cadinol were identified as the major components having great antimite activities. In the activity test with the fraction containing isosericenine as a major component, knockdown-style death was observed and such a unique death was never seen in the other fractions. The susceptibility to leaf oils and their fractions was greater in D. farinae than in D. pteronyssinus. In addition, a difference in activities of the components against the mites between the different species was recognized.