Studies On Separation And Identification Of Larvicidal Constituents From Melia Azedarach L. Against Mosquito

Bontancical insecticides have many characteristics,such as easy decomposing,non-pollution,uneasy to form resistance and no obvious toxic effects on human and animal.Melia azedarach L.as the traditional medicinal plant can be used as medicine,it tasted bittet,quality of cold,toxic and belonged to liver,spleen and stomach.Insecticidal action has been recorded in Chinese famous pharmacopoeia"Compendium of Materia Medica".Kneading M.azedarach nuts to powder as medicine can get rid of intestinal nematodes.Modern pharmacological studies have shown that Mazedarach can kill not only nematode but also platyhelminthes（hirudinea）and arthropod（mosquito,files,moth,libellulidae）in various degrees.Aedes aegypti,the main vector of dengue fever virus,has expanded survival space with the development of human society and threaten human healthy seriously.Therefore,this study selected M.azedarach of Haikou city,Hainan province as subject investigated and A.aegypti as experiment insect for extracting,separating and identifying the larvicidal activity conponents of M.azedarach.The aim of this study is that providing the basis of empolder plant-derived larvicidal drugs.The research results are as follows:1 Larvicidal activity of ethanol extracts from different parts of M.azedarach against larvae of A.aegyptiUsing method of water bath assisted ethanol extraction to roughly extract the leaf,fruit and bark of M.azedarach in absolute ethanol and immersion method to test these three ethanol extractions larvicidal activity againsting A.aegypti.Results showed that all of them exhibited different degrees larvicidal activity.After 24 h treatment of immersion method,the LC₅₀ of ethanol extracts from leaf,fruit and bark of M.azedarach againsting 3rd instar larvae of A.aegypti were 0.590 mg/mL,0.530 mg/mL,0.825 mg/mL.Considering the factors of temperature,yield,this study selected M.azedarach leaf extracts to continue the larvicidal activity of M.azedarach component separation research.2 Larvicidal activity of different polar solvents extracts from M.azedarach ethanol extracts against larvae of A.aegyptiUsing polar extraction method to divided ethanol extracts into petroleum ether,ethyl acctate and n-butanol extracts and immersion method to test these three polar extractions larvicidal activity againsting A.aegyptl.Results showed that all of them ex against exhibited different degrees larvicidal activity.After 24 h treatment of immersion method,the LC₅₀ of petroleum ether,ethyl acctate and n-butanol extracts againsting 3rd instar larvae of A.aegypti were 0.910 mg/mL,0.547 mg/mL,0.992 mg/mL.Thus this study selected the ethyl acctate extracts to continue the larvicidal activity of M.azedarach component separation purification research.3 Isolation,extraction and purification of larvicidal constituents from ethyl acctate extractsWith the bioassay-guided method,the monomer compounds T1、T2、T3 were isolated and purified by the technique of silica gel column chromatography,Sephadex LH-20 column chromatography,crystallization and recrystallization.4 The structural identification of compounds and toxic activity to A.aegypti larvaeBy using the technique of TLC,MS,NMR,comparing spectroscopic data with the reported compound documents and combining with the monomeric compound properties and it’s precipitation solvent inferred that these monomer compounds T2,T3 were Toosendanone A,Toosendanin.The LC₅₀ of Toosendanone A,Toosendanin againsting 3rd instar larvae of A.aegypti were 0.076 mg/mL、0.048 mg/mL.Conclusion:This study used activity tracing method to trace the active ingredient of killing A.aegypti larvae.Two kinds of larvicidal substances Toosendanone A,Toosendanin were isolated from M.azedarach.