Study On The Bioactivity Of Cynanchum Sp Extracts (Alkaloid) Against Plutella Xylostella(L.)

In this study, the bioactive components against Plutella xylostella(L.) were extracted and isolated from Cynanchum sp. The bioactivity components which had strong antifeedant activity and should be alkaloid were acquired. The action modes of these components against Plutella xylostella(L.) were also investigated in the laboratory. The results were as follows:1 The air-dried powdered Cynanchum sp was exhaustively extracted with industrial alcohol and gummy residue was obtained. The residue was acidified with HCl, and basified with NaOH, then extracted with several kinds of organic solvent to obtain Cynanchum sp alkaloid and purificatory Cynanchum sp alkaloid. The extracting rate of Cynanchum sp alkaloid and purificatory Cynanchum sp alkaloid were 0.164% and 0.0916%, respectively. Cynanchum sp is an alkaloidal plant. Alkaloid determinant reagent showed that the Cynanchum sp mainly had small and middle polarity alkaloid, the alkaloid extracted by chloroform was the dominating alkaloid. The thin layer chromatography showed that Cynanchum sp had more than 3 kinds of alkaloid. The antifeedant activity of Cynanchum sp alkaloid against Plutella xylostella(L.) enhanced, as the concentration of Cynanchum sp alkaloid increased.The concentration of Cynanchum sp alkaloid was 800mg/L,400mg/L,200mg/L, 100mg/L,50mg/L; and the antifeedant rate against 3-instar larva of Plutella xylostella(L.) was 99.81%,94.42%,82.60%,59.64%,43.18% under choice condition, respectively; 99.25%,92.59%,85.73%,54.79%,46.15% under non-choice condition, respectively. The regression equation was y=2.1206x+1.1145(r=0.9813), and the AFC₅₀(effective conc, causing 50% antifeedant rate) was 67.96±7.92mg/L.2 The Cynanchum sp alkaloid was isolated by Column Chromatography (CC) and Thin Layer Chromatography (TLC). The Cynanchum sp alkaloid was subjected to alumina column chromatography eluting with petroleum ether, petroleum ether:ethyl acetate(1:1),ethyl acetate, ethyl acetate:metnyl alcohol(95:5,90:10,85:15,75:25,73:30, 65:35,60:40;50:50),metnyl alcohol, giving 40 eluates and 8th～11th eluates were combined to eluate C which had strongest antifeedant activity. The antifeedant rate of eluate C (200mg/L) against 3rd-instar larva of Plutella xylostella(L.) was 93.46%,more than 13.16%...