Study on Insecticidal Activity Constituents and Mechanism of Artemisia annua Against Mythimna separate
In order to study the insecticidal activity components and preliminary mechanism of the petroleum ether extract from Artemisia annua against Mythimna separata,the insecticidal activity of different fractions and main components were measured by insect immersion method.The petroleum ether extract was separated by column chromatography and analyzed by gas chromatography-mass spectrometry to determine its chemical components,and the target enzyme and metabolic enzyme activities in the body of Mythimna separata were measured for the active components.The results showed that the petroleum ether extract of Artemisia annua was separated by silica gel column chromatography,and 27 fractions were obtained,of which fraction 8 showed the best contact toxicity.According to gas chromatography-mass spectrometry,the main compounds were tridecane,4-quinolinecarboxaldehyde,caryophyllene oxide,linoleic acid ethyl ester,linolenic acid ethyl ester with contents of 7.9%,72.8%,3.6%,2.4%,3.1%,respectively.The lethal concentration of 50%(LC50)of above 5 compounds on the 7th day were 7.9,2.5,3.6,5.4 and 1.5 mg·mL-1,respectively,which indicated that ethyl linolenic acid had significant contact toxicity against M.separata.On the 7th day of treatment with 1.5 mg·mL-1 linolenic acid ethyl ester,the scanning electron microscopy results showed that the wax layer structure in the surface of M.separata were loosely,the wax layer particles disappeared significantly,and the wax flower gap increased.And the acetylcholinesterase(AChE)and carboxylesterase(CarE)of M.separata treated with 1.5 mg·mL-1 linolenic acid ethyl ester showed first activation and then inhibition,Na+-K+-ATPase showed inhibition over time,and catalase(CAT)showed first inhibition and then activation.To sum up,the linolenic acid ethyl ester was the main active compound of A.annua,which provided reference for the development of new plant-based insecticides and biological control of M.separata and the development and utilization of A.annua resources.
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