红蓼拒食活性组分的分离及其对小菜蛾幼虫代谢酶活性的影响

为研究红蓼(Polygonum orientale L.)的杀虫活性及作用机理,通过萃取、柱层析方法,测定了红蓼提取物对小菜蛾(Plutella xylostella L.)3龄幼虫拒食活性及对其幼虫体内谷胱甘肽S-转移酶、羧酸酯酶、酸性磷酸酯酶、碱性磷酸酯酶系活性的影响.结果表明,乙酸乙酯萃取物比其他4种萃取物具有更高的拒食活性,在5.0 mg/ml的浓度下,24 h和48 h的拒食率分别为68.42%和62.55%.乙酸乙酯萃取物经硅胶柱层析后,得到13个组分,比较13个组分的拒食活性发现,组分8的活性较高,在浓度为2.5 mg/ml时,24 h和48 h的拒食率分别为77.13%和68.53%.同时,组分8对小菜蛾幼虫体内代谢酶存在不同程度的影响:对谷光肝肽-S-转移酶和碱性磷酸酯酶的活性具有明显的抑制作用;对羧酸酯酶和酸性磷酸酯酶的活性有一定激活作用.活性物质主要集中在组分8中,是进一步研究的重点内容.

Isolation of antifeeding components from Polygonum orientale L. and its effect on digestive enzymes of plutella xylostella larvae

For evaluating the insect resistance property of Polygonum orientale L, five extracts of its with petroleum ether, chloroform, ethyl acetate, n-butanol and water were tested for their antifeedant activity against plutella xylostella larvae. The results showed that ethyl acetate extract was the most effective one among the five extracts. In 24h and 48h of treatment, the antifeedant rate of the ethyl acetate extract against 3rd instar larvae of p.xylostella at 5.0mg/mL was 68.42% and 62.55%, respectively. The ethyl acetate extract was further separated through silica gel column and the fractions were monitored with analytical thin layer chromatography (TLC). Thirteen fractions were obtained and also tested for their antifeedant activity against p.xylostella larvae. The bioassay results showed that fraction 8 at 2.5mg/mL had higher antifeedant activity to 3rd instar larvae of p.xylostella than other fractions. The antifeedant rate of fraction 8 was 77.13% in 24h of treatment and 68.53% in 48h of treatment. The inhibiting activity of the 8 fraction against two digestive enzymes glutathion-s-transferase and alkaline phosphatase from the p.xylostella larvae was tested, but carboxylesterase and acid phosphatase were induced.