鬼臼毒素对小菜蛾的生物活性及对其几种代谢酶系的影响

为进一步揭示鬼臼毒素的杀虫活性及作用机理，本实验采用小叶碟添加法测定了鬼臼毒素对小菜蛾Plutella xylostella的生物活性及对其幼虫体内羧酸酯酶（CarE）、酸性磷酸酯酶（ACP）、碱性磷酸酯酶（AKP）、谷胱甘肽S-转移酶（GSTs）和细胞色素P450酶系活性的影响。结果表明：鬼臼毒素对小菜蛾具有较好的拒食、毒杀及生长发育抑制作用，其AFC₅₀为0.4110 mg/mL（24 h）和0.2617 mg/mL（48 h），LC₅₀为1.9061 mg/mL（72 h）；0.125 mg/mL剂量下相对生长率比对照下降57.56％（24 h）和41.18％（48 h），化蛹率为43.33％，不能正常羽化。同时，鬼臼毒素对小菜蛾幼虫体内各代谢酶存在不同程度的影响：对羧酸酯酶表现为先激活后抑制的作用；对酸性磷酸酯酶表现先抑制后激活的作用； 对碱性磷酸酯酶活性具有明显的抑制作用，且随着处理时间的延长，抑制作用增强；对谷胱甘肽S-转移酶和细胞色素P450酶系表现出先激活后抑制的影响。

Bioactivity of podophyllotoxin against Plutella xylostella and its effect on metabolic enzymes

In order to reveal the insecticidal activity and mechanism of podophyllotoxin,its bioactivity against Plutella xylostella larvae and its effect on their metabolic enzymes were assayed.The results showed that podophyllotoxin had high antifeedant and toxic activity,as well as obvious growth inhibitor activity against the moth.In 24-hour and 48hour treatments,its AFC_50 were 0.4110 mg/mL and 0.2617 mg/mL,respectively. Its LC_50 of 72 h was 1.9061 mg/mL.When the tested insects were treated at the dosage of 0.125 mg/mL,their related growth rate reduced by 57.56%(24 h) and 41.18%(48 h) compared with the control;the pupation rate was only 43.33%,and the pupae did not eclose normally.At the same time,podophyllotoxin had different influence on metabolic enzymes.The activity of carboxyl esterases(CarE) in the tested larvae was first activated,and then inhibited.The activity of acid phosphatase(ACP) was first inhibited,and then activated.The activity of alkaline phosphatase(AKP) was inhibited obviously,and the inhibition became more intensive as the exposure time prolonged.Both glutathione S-transferase(GSTs) and cytochrome P450 were first induced,and then inhibited.