Study on Insecticidal Activity and Effects of7-demethoxtylo-phorine on the Digestive System of Plutella Xylostella
|Keywords||7-demethoxytylophorine Plutella xylostella insecticidal activity midgut tissues growth hormone enzyme activities|
Plutella xylostella is one of main insects against the cruciferous vegetables over the world. Long time and repeated useing of chemical pesticides has resulted in the resistance of the Plutella xylostella to almost all pesticides, so it is urgently needed to develop new pesticides to sove the problem.Cynanchum komarovii is a kind of insecticidal plant. The total alkaloids from Cynanchum Komarovii showed pronounced insecticidal activity against Plutella xylostella.7-demethoxytylo-phorine is one of alkaloids isolated from the total alkaloids of Cynanchum komarovii, It has already been known that the7-demethoxytylophorine possesses excellent antiviral activity against tobacco flower viruses (TMV) and significant cytotoxic to various human cancer cell lines. To the best of our knowledge, there is no research on the insecticidal activity of7-demethoxytylophorine. In order to inspect deeply the bioactivity of this substance as well as screen the active compound against Plutella xylostella, this thesis, with Plutella xylostella as test insect, made a study on the insecticidal activity of7-demethoxytylophorine and its effects on the midgut tissues, growth hormone and enzyme activities of Plutella xylostella, the results are as follows:1Insecticidal activity of the7-demethoxytylophorine against Plutella xylostellaInsecticidal activities of7-demethoxytylophorine against Plutella xylostella were determined by different testing methods. The results indicated that7-demethoxytylophorine displayed obvious antifeeding effect, growth and development inhibition, stomach toxicity activity against3rd-instar larvae of Plutella xylostella. At the concentration of15.00mg/mL. the antifeedant rate was99.15%at24h after treatment; the growth inhibition rates were103.65%at48h after treatment, that is to say that caused a negative body weight gain, the toxicity mortality rates was67.77%at7d after treatment.2Effect of7-demethoxytylophorine on the midgut tissues of Plutella xylostellaElectronic telescopic technology was used to study the effect of7-demethoxytylophorine on the midgut tissues of Plutella xylostella larvae. Distinct pathological changes on the midgut tissues were observed after exposing to7-demethoxytylophorine. Plutella xylostella treated with7-demethoxy-tylophorine appeared more food accumulation in its intestinal canal, along with intestinal wall bending, intestinal wall cells loosen, microtubules melted, cup cavity overloaded, microvilli disappeared. At the same time the peritrophic membrane was damaged seriously, but the epithelial cells remained in good condition. For dead worm, the epithelial cells arranged in messy, and the peritrophic membrane was completely destroyed.3Effect of7-demethoxytylophorine on the molting hormone levels and chitinase activity of Plutella xylostellaEffect of7-demethoxytylophorine on the molting hormone levels and chitinase activity of Plutella xylostella were estimated by HPLC and3,5-dinitrosalicylic acid colorimetric methods. The content of molting hormone in treated insects reduced48.85%after24h of treatment; chitinase activity was1.3927μg/mgpro/min, the inhibition rate was87.35%compared with the controls of 15.183μg/mgpro/min.4Effects of7-demethoxytylophorine on the digestive enzymes of Plutella xylostellaThe effects of7-demethoxytylophorine on the Protease, amylase and lipase activities of Plutella xylostella were determined by3,5-Dinitrosalicylic acid, Folin-Phenol reagent and Olive oil emulsion turbidimetry, respectively. The protein content in enzyme sample was determined by coomassie brilliant blue method. The results showed that the activities of protease, amylase and lipase were significantly inhibited with the inhibition rates of71.60%,93.38%and89.20%, respectively, at48h after treatment; the protein content was83.8138μg/mL, increased by40.60%compared with control group.