In the search for new plant-derived products with antifeedant and insecticidal potential against economically important insects, 11 grindelanes (two as natural acids and nine as methylated derivatives) purified from the foliar tissue of Grindelia chiloensis (Cornel.) Cabrera (Asteraceae) were evaluated against the fall armyworm, Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae). Larvae of this moth are considered to be the main pest of maize that causes severe losses on local agricultural production. Remarkable alterations in feeding behavior, larval weight, larval and pupal stage lengths, and adult fertility, as well as malformations and mortality in specimens during their life cycle were noticed in the feeding preference tests and no-choice diet assays. Antifeedant indexes (AI%) calculated in food preference bioassays reached up to 79% for the lipophilic grindelane 3b, the most potent antifeedant agent. Grindelane 7b showed a better insecticidal activity (median lethal dose, LD₅₀ = 26.49 µg g⁻¹) and 8b was potentially neurotoxic due to acetylcholinesterase inhibition. Ultrastructure of the middle portion of the digestive tract of larvae fed with small amounts of natural grindelane 9a supplemented to the diet revealed cell damage, and thickening of the peritrophic membrane and a striking number of mitochondria, as evident signs of defense against toxic substances ingested by the larvae. Besides, this study demonstrated that these effective insecticides did not have inhibitory effects on beneficial plant and soil bacteria which would allow ecological pest management.

中文翻译：

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甘草对重要玉米害虫草地贪夜蛾的活性及其对非靶标环境细菌的作用选择性

在寻找对经济上重要的昆虫具有拒食和杀虫潜力的新植物衍生产品时，评估了从Grindelia chiloensis (Cornel.) Cabrera (Asteraceae)的叶组织中纯化的 11 种甘草内酯（两种为天然酸，9 种为甲基化衍生物）对抗秋季粘虫，草地贪夜蛾（JE 史密斯）（鳞翅目：夜蛾科）。这种蛾的幼虫被认为是玉米的主要害虫，给当地农业生产造成严重损失。在喂养偏好测试和无选择饮食分析中注意到摄食行为、幼虫体重、幼虫和蛹阶段长度​​以及成虫生育力的显着变化，以及标本在其生命周期中的畸形和死亡率。在食物偏好生物测定中计算的拒食指数 (AI%) 对于亲脂性甘德兰 3b（最有效的拒食剂）高达 79%。Grindelane 7b 显示出更好的杀虫活性（半数致死量，LD ₅₀  = 26.49 µg g ^-1) 和 8b 由于乙酰胆碱酯酶抑制而具有潜在的神经毒性。幼虫消化道中间部分的超微结构显示，在饮食中补充少量天然研磨剂 9a，显示细胞受损、外周膜增厚和数量惊人的线粒体，这些是防御摄入有毒物质的明显迹象。幼虫。此外，这项研究表明，这些有效的杀虫剂对有益的植物和土壤细菌没有抑制作用，从而可以进行生态害虫管理。