Analysis Of Insecticidal Activity And Active Ingredients Derived From Acorus Calamus

Aiming at to clarify the active constituents and their activities of Acorus calamus, the dissertation focused particularlily on the repellency and contact activity of A.calamus rhizome extracts against the main stored-grain insects,the separation and identification of the active constituents against adults of Sitophilus zeamais,the fumigation activity of the active constituent extracted from A.calamus rhizome was studied based upon the fumigation experiments on the stored-grain insects.At the same time,the effects of extracting parameters on SFE-CO₂ extraction of active ingredients from A.calamus were investigated.The results showed as follows:1.The repellency and contact activity of A.calamus rhizome extracts against the 6 kinds of stored-grain insects were studied using drug-film method.The results showed as follows:The ethanol extract of A.calamus had repellecy activities to the 6 kinds of stored-grain insects.Sixty hours after treatment,the repellency of Tribolium castaneum, Tribolium confusum and Cryptolestes pusillus were all above 90%and get to grade V, while the repellency to Rhizopertha dominica,S.zeamais and Oryzaephilus surinamensis ranged from gradeâ… toâ…¤.The response of the repellency activity varied with different insects.The repellency were in the order T.castaneum＞C.pusillus＞T.confusum＞R. dominica＞S.zeamais＞O.surinamensis.Repellency lowered with lower dosage and longer exposure time.The ethanol extract had contact activities to the 6 kinds of stored-grain insects.The mortality of S.zeamais,R.dominica,T.castaneum,T.confusum,C.pusillus and O. surinamensis were 95.56%,74.44%,10.15%,24.44%,100.00%and 100.00%96 h after treatment under 0.31 mg/cm²ã€‚The response of contact activity varied with different insects.The contact activities were in the order C.pusillus＞O.surinamensis＞S.zeamais＞R.dominica＞T.confusum＞T.castaneum.Contact activity became stronger with the exposure time,and lowered with lower dosage.2.In order to clarify the active constituents,the ethanol extrsct of the A.calamus was pretreated by method of organic solvent extraction and the contact activity of the fractions were studied by S.zeamais.The results showed that the petroleum ether extract had highest bioactivity.At 314.54μg/cm² dosage,the mortality of petroleum ether extract against S.zeamais was 100%4 days after treatment.Adopting the silica gel column chromatography,the effective insecticidal ingredients of petroleum ether extract were separated.Two active constituents were obtained.The active constituent was identified by X-ray single crystal diffraction and spectroscopic analysis,including GC-MS,IR and NMR.The analysis showed that the two active xonstituents were cis-1,2,4-trimethoxy-5-(1-propenyl)benzene(β-asarone) and 1-Isopropyl-4,8-dimethyl-spiro[4.5]decane-2,7-dione(acorone).The insecticidal activity tracing agaist S.zeamais showed that LD₅₀ at 96 h was 28.03μg/cm² and 158.00μg/cm² respectively.3.The fumigation activity of the active constituentβ-asarone was studied based upon the fumigation experiments on the stored-grain insects and the effects ofβ-asarone on the behaviour,mortality and reproductive fitness of C.maculates was also studied.When the S.zeamais egg was treated withβ-asarone120 hours at 200μL/L concentration,the inhabitation rate was 99.09%.β-asarone showed little fumigation activity to larva and pupa of S.zeamais.After being treated 24 hours,the KC₅₀ for S. zeamais adult was 49.38μL/L.After being treated 120 hours,the LC₅₀ for S.zeamais adult was 17.82μL/L.After being treated withβ-asarone 24 hours,the KC₅₀ for R.dominica adult was 102.96μL/L.After being treated withβ-asarone 120 hours,the LC₅₀ for R.dominica adult was 4.42μL/L.The fumigant activity ofβ-asarone to T.castaneum younger larva was more significant than to the older lavar.After being treated 120 hours at 200μL/L concentration,34.32%of the T.castaneum pupa were dead.After being treated withβ-asarone 24 hours,the KC₅₀ for T.castaneum adult was 125.04μL/L.After being treated withβ-asarone 120 hours,the LC₅₀ for T.castaneum adult was 116.48μL/L.After being treated withβ-asarone 120 hours at 200μL/L concentration,the hactchbility rate of Plodia interpunctella egg was 13.33%.β-asarone showed some fumigant activity to P.interpunctella larva and little fumigant activity to pupa and adult.After being treated withβ-asarone 120 hours,the LC₅₀ for Callosobruchus maculates egg was 0.95μL/L.The larva mortality was 51.69%when treated with 120 hours at 200μL/Lconcentration.β-asarone showed little fumigant activity to pupa.After being treated withβ-asarone 24 hours,the KC₅₀ for C.maculates adult was 1.07μL/L. After being treated withβ-asarone 120 hours,the LC₅₀ for C.maculates adult was 0.73μL/L.To elucidate the modes and mechanisms of action ofβ-asarone,we studies on the effects ofβ-asarone on the behaviour,mortality and reproductive fitness of C.maculates under ambient laboratory conditions.The contact toxicity symptoms included restlessness, loss of coordination,knock down and eventual death of adult beetles.After 64 h,β-asarone caused 100%mortality.β-asarone could observably reduce the mounting number of C.maculates.The mounting number reduced with the exposure time.β-asarone caused more reduction in male mating competition than females.The egg number significantly reduced when the insect exposed toβ-asarone.The egg number reduced with the exposure time.There were no difference between the male and the female insects.The hactchbility of the egg lowered when the insects treated withβ-asarone,but there were no difference among exposure time and between male and female insect.4.Supercritical fluid CO₂ extraction(SFE-CO₂) were used to study the contact toxicity of the active extracts from Acorus calamus L.to Sitophilus zeamais Motschusky. Using contact toxicity and extraction efficiency as evaluating indicators,the extracting parameters were optimized using orthogonal experiments.The experimental results showed that the optimized extracting parameter of temperature,pressure,extraction time and modifier(alcohol) dosage was 55℃,35 MPa,40 minutes and 150 mL per 200 gram dry powder,respectively.An extraction efficiency of 4.12%and a LD₅₀ of 27.26μg/cm² to S.zeamais after 96 hours treatment were achieved at the optimal extracting parameters. The experimental results indicated the promise of A.calamus extracts as a novel pesticide owing to their significant contact toxicity to S.zeamais.