Effects of Inula britannica Extracts on Biological Activities Against Tetranychus cinnabarinus and Several Enzyme Systems in Tetranychus cinnabarinus

Acaricidal activities of the extracts from Inula britannica (I. britannica) against Tetranychus cinnabarinus (T. cinnabarinus) and several enzyme systems in T. cinnabarinus treated with I. Britannica extracts were evaluated under laboratory conditions. It was found that crude extracts from I. britannica with petroleum ether exhibited high acaricidal activities against T. cinnabarinus, and the corrected mortality after treatment for 24 h was 92.05 % at the concentration of 2 mg ml(-1). After a liquid-liquid partition from petroleum ether crude extracts with methanol, the resulting petroleum ether extracts were separated into 38 fractions by column chromatography, and further tests for their acaricidal activities were conducted. Fraction 33, the most major component of the resulting extracts, was found to possess the strongest acaricidal activity against T. cinnabarinus in all 38 fractions, and its corrected mortality against T. cinnabarinus was 90.12 % after 24 h. Moreover, GC-MS analysis results determined that chemical composition of fraction 33 was ethyl palmitate. Laboratory bioassay results indicated that the corrected mortality of ethyl palmitate against T. cinnabarinus after treatment for 24 h was 90.61 %, and the mean lethal concentration (LC50) was 1.255 +/- 0.167 mg ml(-1). In order to determine the mechanism of the toxic effect of ethyl palmitate on T. cinnabarinus, several kinds of important enzyme systems including glutathione S-transferase (GSTs), acetylcholinesterase (AChE) and Na+-adenosine triphosphatase (Na+-ATPase) as well as total protein content in T. cinnabarinus were tested by the colorimetric method. The experimental results showed that after treatment with ethyl palmitate, total protein content in T. cinnabarinus obviously increased, and the activities of GSTs and AChE in T. cinnabarinus were strongly induced, while the activities of Na+-ATPase in T. cinnabarinus were restrained. Been restrained of Na+-ATPase could cause the transmit block of nerve, and eventually result in the death of the mite. These results indicated that Inula britannica extracts possessed significantly high acaricidal activity.