Study On The Insecticidal Activities Of The Extracts From Euphorbia Helioscopia

It is an important way for new pesticide discovery nowdays that searchinginsecticidal active substances and exploring botanical insecticides from plants.Euphorbia helioscopia belongs to Euphorbia genus, Euphorbiaceae family, the extractsof its stem and leaf have insecticidal and antibacterial activity. In order to clarify theapplication value of Euphorbia helioscopia in pest control, we collected activesubstances from the stem and leaf powder of the plant with immersion method, andmeasured the toxicity of the extracts to chewing pests Helicoverpa armigera larvae,sucking pests Macrosiphum avenae and Bemisia tabaci, finally analyzed the chemicalcomposition of petroleum ether extract by GC-MS technique. Main results andconclusions were as follows:1) The stem and leaf powder of Euphorbia helioscopia was immersed with95%ethanol,the substance obtained were then extracted with different polar solvents, petroleum ether,chloroform, ethyl acetate and n-butanol, respectively. It showed that the collectionefficiency of ethanol was8.39%, and the extraction efficiency of petroleum ether,chloroform, ethyl acetate and n-butanol from the ethanol extract were38.30%,51.35%,56.50%and82.90%, respectively.2) Contact toxicity of the4extracts to3rd instar larvae of Helicoverpa armigera wasmeasured by immersing method. The results showed that, each treatment revealed lowcontact activity to the larvae, and the highest mortality was only25%after5d treatment.Stomach poison activity of the extracts to3rd instar larvae of Helicoverpa armigera wasmeasured with the method of small leaf disc. All treatment of the test showed lowactivity, and the highest corrected mortality of the larvae was only49.54%after3dtreatment.3) We also determine the contact toxicity of the extracts to Macrosiphum avenae withthe slide-dip immersion method. Contact toxicity of4extracts on the aphid were alllinearly correlated with treatment dose significantly. After24h treatment, the correctedmortality were96.19%,99.07%,79.17%and74.51%respectively when treated bypetroleum ether, chloroform, ethyl acetate and n-butanol extracts at the concentration of16000mg/L. The highest contact toxicity to the aphid was chloroform extract, followedby petroleum ether extract with the LC50of both extracts of439.61mg/L and552.63 mg/L, respectively.Internal absorption activity to Macrosiphum avenae was determined by successiveimmersion. The4extracts showed large differences in internal absorption activity.Chloroform extract possessed the best activity with the corrected mortality of85.23%,83.42%and91.40%after treated for3days at the concentration of4000mg/L,8000mg/L, and16000mg/L, respectively. N-butanol extract ranked second place, petroleumether extract had a relatively poor activity. There is a positive correlation betweeninternal absorption activity and treatment dose as well as the action time.4) Contact activity to Bemisia tabaci on leaves of cucumber, kidney bean and eggplantwas determined by spray method. In laboratory tests, when spraying the detached leaf,all of the doses of extracts, except for1000mg/L, represented toxic activity higher than85%to the nymph on cucumber and kidney bean, and70%on eggplant. In field trials,no significant differences of control effect were obtained to whitefly on cucumber,kidney bean and eggplant. Moreover, after treated for5days at the concentration of16000mg/L, the control effect of the4extracts exceeded97.05%,96.17%,98.17%and97.03%.5) The chemical composition of petroleum ether extract of Euphorbia helioscopia wasanalysed by GC-MS technology. The petroleum ether extraction was separated throughsilica gel column chromatography into9fractions, for which GC-MS analysis wereconducted, and75substances were identified. These substances were mainly alkanes(20kinds), esters (16kinds), olefin (10kinds), carboxylic acids (10kinds), alcohols (7kinds) and ketones (4kinds). In the fraction, the relatively high content compounds areheptacosane, hexadecanoic acid, phytol, linoleic acid, sterols, docosene amide,octadecenoic amide, hexadecanoic acid ethyl ester, linoleic acid methyl ester and9,12,15-octadecatrienoic ethyl. Compared with previous literature reports, we foundlupeol and caryophyllene should have insecticidal activity in these component.