红蓼拒食活性组分的分离及其对小菜蛾幼虫消化酶活性的影响

Isolation of the antifeeding components from Polygonum orientale and its effects on the digestive enzymes of Plutella xylostella larvae

为了进一步评价红蓼(Polygonum orientale L.)的抗虫性,采用液-液分配萃取和硅胶柱层析的方法,从红蓼甲醇提取物中分离获得石油醚、氯仿、乙酸乙酯、正丁醇和水的萃取物,测定了其对小菜蛾(Plutella xylostella)3龄幼虫拒食活性。结果显示,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下,24 h和48h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%。组分8对小菜蛾幼虫体内的蛋白酶、脂肪酶和α-淀粉酶的活性具有一定的抑制作用。

To evaluate the resistance property of Polygonum orientale Linn. to insects, five extracts of it with petroleum ether, chloroform, ethyl acetate, n-butanol and water were tested for their antifeeding activity against Plutella xylostella larvae. The results showed that ethyl acetate extract was the most effective one among the five extracts. After 24 h and 48 h of treatment, the antifeeding rate of the ethyl acetate extract against the 3rd instar larvae of P. xylostella at 5.0 mg/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 antifeeding activity against P. xylostella larvae. The bioassay results showed that fraction No. 8 at 2.5 mg/mL had higher antifeeding activity to the 3rd instar larvae of P. xylostella than other fractions. The antifeeding rate of fraction No. 8 was 77.13%/00 after 24 h of treatment and 68.53% after 48 h of treatment. The inhibiting activity of the 8 fractions against the three digestive enzymes proteinase, lipase and a-amylase from P. xylostella larvae was also tested.