Study On The Bioactivity Of Scutellaria Barbata Extracts Against Pieris Rapae (L.)

This experiment was conducted to study Bioactivity of Scutellaria barbata against larvae of Pieris rapae(L.),to get components of high antifeedant activity.Modes of action such as effectiveness of contact toxicity,stomach toxicity,inhibition for growth and development and oviposition repellent on Pieris rapae(L.) were also researched in this experiment,results are as below:1.Crude ethanol extracts of 14 Chinese herbs were tested for the antifeedant activities against the 3rd inster larvae ofPieris rapae(L.).The results indicated that crude ethanol extracts of 14 Chinese herbs exhibited indifferent antifeedant activity against the 3rd inster larvae ofPieris rapae(L.).Among those herbs,the crude extracts from Scutellaria barbata,Evodia rutaecarpa,Phellodendron amurense Rupr.showed stronger antifeedant activity,in the selecting antifeedant testing,equal antifeedant activity of three herbs were 100%,96.07 %,84.46%;in the non-choice antifeedant testing,equal antifeedant activity of three herbs were 100%,84.01%,76.20%.2.200ml of distilled-water was put into the crude extract of Scutellaria barbata,the mixed liquid was extracted by petroleum ether,ether,ethyl acetate,n-butyl alcohol and water in turn,and the extracts were concentrated to thick paste at last,respectively.At 200mg/L concentration with treatment after 24h,the antifeedant rate of petroleum ether,ether,acetidin,n-butyl alcohol and water against 3^rd-instar larva of Pieris rapae(L.) was 86.48%,96.84%,10.54,1.10%and 2.71%under choice condition,and 80.87%,94.50%, 8.88%,1.11%and 1.09%under non-choice condition,respectively.The antifeedant rate was 74.05%,82.82%,0.01%,0.25%,and 0.73%under choice condition,and 70.31%, 79.24%,2.85%,0.42%,0.32%under non-choice condition after 48h,respectively.Of them,petroleum ether and ether had better antifeedant effects against this pest.3.The extract of ether from Scutellaria barbata was isolated by Column Chromatography(CC).Silica gel was used as stationary phase,petroleum ether and acetone as mobile phase through gradient elution chromatography.After the determination of antifeedant activity,it showed that the active ingredients were found chiefly in eluate D,eluate B,eluate C and eluateE.The antifeedant rate of eluate D,eluate B,eluate C and eluateE(100mg/L)against 3^rd-instar larva of Pieris rapae(L.) was 96.82%,77.42%,67.22%, 71.98%under choice condition,and 94.78%,73.65%,64.59%,67.72%under non-choice condition.4.The active ingredients which were isolated from CC(Big chromatographic colum) were isolated and purified through the gradient elutiony,the stationary phase was silicagel, and the petroleum ether and ethyl acetate were used as mobile phas.The determination of antifeedant activity(Small cchromatographic colum) showed that the active ingredients were found chiefly in eluate D,eluate C and eluateE.The antifeedant rate of eluate D,eluate C and eluateE(100mg/L)against 3^rd-instarlarva of Pieris rapae(L.) was 99.76%, 71.31%and 79.68%under choice condition,and 96.53%,63.71%,72.53%under non-choice condition.So eluate D was seleced to study other action modes of Scutellaria barbata.5.The contact toxicities of each concentration of eluate D(Small chromatographic column) were mensurated against 3^rd-instar larva of Pieris rapae(L.) by drop method. Contact toxicity was not found under concentration of 25mg/L.At 50mg/L,100mg/L,200mg/L,treatment after7d,the correceted mortality was 3.33%,6.67%, 16.7%,respectively.The results indicated that the active ingredients from the CC of Scutellaria barbata had some contact toxicities against 3^rd-instar larva of Pieris rapae(L.),but contact toxicity was slow,obvious activities was not found.So the medicinal value were not high.6.In the stomach poisoning test,each concentration of eluate D(Small chromatographic column) was measured against 3^rd-instar larva of Pieris rapae (L.).When the concentration was lower than 25mg/L,stomach poisoning activity was not found.Under each concentration,the mortality was 0 after 2d.Stomach poisoning happened in the 3^rd day,under the concentration of 200mg/L.On 4^th day,when concentration was above 50mg/L,stomach poisoning was observed from all treatments. Under the concentration of 200mg/L,the mortality was only 16.67%treatment after 7 day.7.The growth inhibition of each concentration of eluate D(Small chromatographic column) were measured against 3^rd-instar larva of Pieris rapae(L.).The results showed that each treatment had poor growth and lost weight compared with CK.The inhibition effect was the strongest at the concentration of 200mg/L,and the growth inhibition ratio was 108.74%on the 12^thd.Meanwhile,the weight of larva had negative increment,and larve rarely feed on,rarely moved,even died.At the same time,with concentration decreased,the inhibition action reduced.8.In the selective oviposition deterrent test against Pieris rapae(L.),each each concentration of eluate D(Small chromatographic column) had strong oviposition inhibition activity against Pieris rapae(L.),and it was enhanced as the concentration increased.The regression equation was y=1.9726x+1.9363(r=0.997).On the basis of the antifeedant activity of ethanol extract of 14 kinds of cultivated traditional Chinese medicinal materials against larva of Pieris rapae(L.),Scutellaria barbata was screened to show high antifeedant activity.In this study bioactive components against Pieris rapae(L.) were extracted and isolated from Scutellaria barbata.The bioactive components had strong antifeedant activity against 3^rd-instar larva of Pieris rapae(L.).The study provided theoretical foundation for the development of new botanical pesticide with safe and effective performance.Moreover,this study had very important reference value both on the development and utilization of Scutellaria barbata.