The aim of the study is to determine the acaricidal compounds of Inula britanica extracts and its action mechanism. Petroleum ether extract of I. britanica were found to have high acaricidal activity to Tetranychus cinnabarinus with a mortality of 92.05％at the concentration of 2mg/mL. Afterwards, the petroleum ether extracts of I. britanica were further purified using column chromatography, and 38 fractions were got. The toxicities of these 38 fractions to T. cinnabarinus were determined. Fraction-7 was found to have high acaricidal activity to T. cinnabarinus with a mortality of 85.53% at the concentration of 2mg/mL. The main compounds of the high bioactive fraction-7 were identified by GC-MS. Lupeol was identified from fraction-7 of I. britanica by GC-MS, and lupeol was found to have high acarcidal activity to T. cinnabarinus with a mortality of 66.46% at the concentration of 2mg/mL. Lupeol may be main acaricidal compounds of I. britanica extracts. The effects of lupeol on the activities of Glutathione-S-transferase (GSTs),Ca²⁺ -ATPase,SOD and protein content of T. cinnabarinus were assayed by colorimetric method at the 4th, 8th, 12th, 16th, 20th and 24th hour after treated with Lupeol. The results showed that the activities of GSTs at the 4th、12th hour post lupeol treatment were higher than those of the control group. Especially the GSTs activities of the control mites were 82% of the treated group at the 12^th hr post treatment. However, GSTs activities of the lupeol treated mites were restrained at the 8th, 16th, 20th and 24th hr post treatment. As to Ca²⁺-ATPase activity, the change trend of the specific activities of Ca²⁺-ATPase of the treated mites were similar to that of the control group mites. However, the activities of Ca²⁺-ATPase of the lupeol treated mites were lower than the control group all along the 24 h post treatment. Particularly the activities of Ca²⁺-ATPase of the control group were 2.1 times of the treated mites at the 16^th hr post treatment. Similarly, the change trend of the activities of SOD of the treated mites were similar to those of the control group. In addition, the activities of SOD of the treated mites were higher than the control group all along the 24 h post treatment, and the activities of SOD of the treated mites were 1.5 times of the control group at the 8 th hr post treatment. The results showed that the change trend of the total protein content of the treated mites were similar to that of the control group the total protein content of the mites. The total protein content of the treated mites were higher than the control group before 12th hr post treatment, and then the total protein content of the treated mites were lower than the control group after 12th hr post treatment. Prticularly the total protein content of the treated mites were 1.5 times of the control group at 4th hr post treatment.
Furthermore, statistical analysis revealed that the main enzyme activities of the mites were changed by Lupeol, which may finally lead the mites to death. These results suggested that lupeol of the petroleum ether extract of I. britanica had acaricidal activities against T. cinnabarinus. These data provided useful information for the use of I. britanica as a novel resource of botanical acaricides.