Study On Structure-activity Relationship Of Antifeedant Activity Of Camphene And Its Ester And Hydrazide Derivatives Against Spodoptera Litura

Mulberry is the material basis of mulberry planting and silkworm industry.In recent years,the harm of Spodoptera litura to mulberry trees is becoming more and more serious.Traditional chemical control has easy caused environmental pollution,and there is an urgent need to develop new green mulberry plant control agents.Structural modification was an important way to develop new pesticides,and the structure-activity relationship was the theoretical basis for guiding the structural modification of lead compounds to achieve targeted pest control.Camphene,a natural active substance,has certain insecticidal activity,and the advantages of abundant content and active reaction,and was Suitable for structural modification.Therefore,this study used camphene as the precursor to prepare a series of derivatives through esterification and acylation reactions to explore the structure-activity relationship of its antifeedant activity against S.litura,and provides a reference for the development of a new type of insecticide for mulberry field.The main findings are as follows:（1）The feasibility of camphene as an antifeedant of S.litura was confirmed for the first time.The leaf disc method was used to detect the antifeedant activity and feeding preference of S.litura,and the continuous feeding to test the growth inhibition.And also detected the activity of detoxification enzymes and digestive enzymes and the relative expression of glutathione S-transferase gene by real-time quantitative（q PCR）.The results showed that the antifeedant medium concentration(AFC₅₀)of camphene against S.litura was 0.20 mg/m L.When the concentration was 1 mg/m L,it would affect its feeding preference,and when the concentration was 4 mg/m L,it would significantly inhibit its growth and development.The concentration of AFC₃₀（0.0106 mg/m L）was used to treat S.litura,glutathione S-transferase was significantly inhibited at 12 to 48 h,while acetylcholinesterase,amylase,protease and lipase were 51.46%,59.12%,59.14%and 61.31%of the control group at 24 h,but there were no difference from the control group at 48 h.It is speculated that the inhibition of glutathione S-transferase is the main cause of S.litura refusal to feed.The expression levels of 15 glutathione S-transferase related genes（Sl GSTs）were detected.Among them,Sl GSTO1,Sl GSTO3 and Sl GSTS4 were the key genes in the defense process of camphene detoxification in S.litura.（2）Eleven ester derivatives of camphene（9 of which are new compounds）were prepared by sodium borohydride oxidation and esterification,and the structure-activity relationship of its antifeedant activity against S.litura was analyzed.The carbon-carbon double bond on camphene was catalyzed to generate hydroxyl group（camperenol 2a）by sodium borohydride and hydrogen peroxide,and then it was esterified with carboxylic acid under N,N’-dicyclohexylcarbimide and dimethylaminopyridine catalytic.The product（3a～3j）was purified by silica gel column chromatography,and used petroleum ether as the developing solvent.The results show that the double bond in camphene plays an important role in the antifeedant activity of camphene against S.litura.The rational introduction of hydroxyl,alkyl chain and other groups into its structure were able to improve the effect of camphene ester derivatives on the S.litura.The production of methyl branch chains,and the substitution of ester groups for hydroxyl groups will reduce the antifeedant activity of derivatives.The increase in antifeedant activity will also cause the decrease of glutathione S-transferase activity.In addition,after the derivative 3c was treated,the activity of glutathione S-transferase was found to be inhibited,which was 62.33%of the control group at 12 h;the activities of acetylcholinesterase,amylase,protease and lipase were not significantly different from those of the control group at 24 h,indicating that glutathione S-transferase is the key enzyme produced by antifeeding behavior.Among the glutathione S-transferase genes,Sl GSTE4 and Sl GSTE7 are involved in the defense process against the derivative 3c.（3）6 hydrazide derivatives（5a～5f）and intermediate product 4a（All are new compounds）were prepared by oxidation of chromium trioxide and acid chlorination.The relationship between structure of these derivatives and their antifeedant activity against S.litura were analyzed.Compound 2a was oxidized with chromium trioxide to form acid 4a,then acylated with oxalyl chloride to form acid chloride,and then reacted with hydrazides with different structures to form hydrazide derivatives（5a～5f）.The results showed that the introduction of N heterocyclic ring,benzene ring and F^-in the hydrazine derivatives could improve the antifeeding activity of the derivatives against S.litura,and at the same time cause the decrease of glutathione S-transferase activity.The hydrazide derivative 5d treatment of S.litura,the activity of glutathione S-transferase at 36 and 48 h was significantly lower than that of the control group,but there was no significant difference in the activities of acetylcholinesterase,amylase,protease and lipase.Glutathione S-transferase genes Sl GSTO1,Sl GSTS2,Sl GSTS4,Sl GSTT1 and Sl GSTZ1 were consistent with the changes of enzyme activity,indicating that all of them were involved in the defense against 5d.In summary,this article successfully synthesized 18 esters or hydrazide derivatives（including 16 new compounds）using camphene as the precursor,and found that the double bond is the key site for Spodoptera litura to produce antifeeding.The introduction of alkyl chains,Groups such as benzene ring,nitrogen-containing benzene ring and F^-are expected to increase the antifeedant activity of their derivatives,and the antifeedant activity is inversely related to the activity of glutathione S-transferase,which provides high-throughput screening of new drugs for target selection It also provides a new idea for the development of a new type of camphene-derived mulberry insecticide.