Extracting And Formulating Of Capsaicin And Its Mechanism Against Plutella Xylostella

Extracting and purifying of capsaicin,formulation preparation and control effect of capsaicin emulsifiable concentrate,the action modes of capsaicin against Plutella xylostella L.,and effect of capsaicin against Plutella xylostella L.on enzymes activity were researched chiefly.The study provides the basis for the development and research thoroughly of capsaicin,and it has theoretical and practical meaning for the IPM.Experiments were conducted to purifying capsaicin with acetone warm soaking method, acid base method,LCC method.The white cream pure capsaicin was obtained.Bioactivity studies showed that it had strong repellent activity and certain contact activity.Experiments were conducted to screening formulation of capsaicin emulsifiable concentrate with conventional formulation preparation methods in laboratory.The screened formulation was,the percentage of active component was 2%capsaicin,the percentage of cosolvent was 20%acetone,the percentage of emulsifier was 10%TW-80,the percentage of wetting agent was 2%JFC,and the rest was xylene.The results of pot trails of 2%capsaicin emulsifiable concentrate showed that it could control Plutella xylostella L.effectively.2% capsaicin emulsifiable concentrate at 40 mg·L^-1,the revised pest individual depress ratio was 81.82%after treatment 9 d,the rate of protecting leaves was 66.67%after treatment 9 d.Bioactivity studies showed that capsaicin possessed strong oviposition deterrence activity and antifeedant activity,and it also had certain contact toxicity and stomach toxicity on Plutella xylostella L..In the test of contact toxicity,the corrected mortality was 51.72%after applying 60 hours at a capsaicin concentration of 1×10⁶ mg·L^-1.In the test of stomach toxicity, the corrected mortality was 44.44%after applying 60 hours at a capsaicin concentration of 6.25×10⁴mg·L^-1.In the test of oviposition deterrence activity,at a capsaicin concentration of 6.25×10⁴mg·L^-1,the nonchoice oviposition deterrence rate was 96.55%after applying 24 hours,the choice oviposition deterrence rate was 84.30%after applying 24 hours.In the test of antifeedant activity,At a capsaicin concentration of 6.25×10⁴mg·L^-1,the nonchoice antifeedant rate was 81.47%after applying 48 hours,the choice antifeedant rate was 69.69% after applying 48 hours.Experiments were conducted to study the effects of capsaicin against Plutella xylostella L. on different enzymes activity with conventional methods in laboratory.The result showed that capsaicin could inhibit the activity of acetylcholinesterase after treated short time,and capsaicin could enhance the activity of Na⁺K⁺-ATPase after treated long time.Compared with the negative control,the activity of glutathione-S-transferase and carboxylesterase were decreased in different extent by capsaicin.And there were two different esterase isozymes in both treated group and control group.