Studies on the insecticidal constituents and mechanism of Vinca major against Spodoptera frugiperda
In order to search for chemical components with good insecticidal activity against Spodoptera frugiperda,antifeedant activity,the stomach poisoning,and contact toxicity of petroleum ether,chloroform,ethyl acetate,and water extracts from Vinca major were determined by small leaf plate addition,leaf soaking,and insect soaking method.The results showed that the petroleum ether extract of V.major had the best contact activity against the S.frugiperda with LC50 values of 6.11,5.43,5.27,and 4.62 mg/mL respectively at 1 d,3 d,5 d,and 7 d.Component separation of petroleum ether extract from V.major were separated by silica gel column chromatography,22 fractions were obtained,with fractions 5 and 7 having the best contact activity.Fraction 5 were analyzed by GC-MS.The main chemical components were p-xylene(17.56%),n-nonane(20.92%)and tridecane(28.33%).8 fractions were obtained from fraction 7 by microporous resin chromatography.Fraction VI had the best contact activity.According to GC-MS analysis,the main chemical components were n-nonane(19.09%),tridecane(53.19%)and 2,2,4,6,6-pentamethylheptane(5.21%).The LC50 of p-xylene was 10.45,8.87,6.54 and 5.05 mg/mL at 1 d,3 d,5 d and 7 d,respectively.The activities of AChE and Ca2+-Mg2+-ATPase firstly increased and then decreased with the increase of p-xylene concentration.The activities of CarE were firstly inhibited and then activated.
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