Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium.
Pest Manag Sci. 2012 Feb;68(2):164-9. doi: 10.1002/ps.2235. Epub 2011 Jun 29.
Saponins are a class of secondary plant metabolites consisting of a sugar moiety glycosidically linked to a hydrophobic aglycone (sapogenin) that often possess insecticidal activities. Four saponins were selected: two triterpene saponins, Q. saponaria saponins and aescin, and two steroidal saponins, digitonin and diosgenin. Their effects were investigated on an important pest species and a model piercing-sucking insect, the pea aphid Acyrthosiphon pisum. The triterpene Q. saponaria saponins bark saponin received special attention because of its high activity. Aphids were challenged by oral and contact exposure to demonstrate aphicidal activities, and in choice experiments to support use as a natural deterrent.
When aphids were exposed to supplemented artificial diet for 3 days, a strong aphicidal activity was recorded for three of the four saponins, with an LC50 of 0.55 mg mL(-1) for Q. saponaria saponins, 0.62 mg mL(-1) for aescin and 0.45 mg mL(-1) for digitonin. The LT50 values ranged between 1 and 4 days, depending on the dose. For diosgenin, only low toxicity (14%) was scored for concentrations up to 5 mg mL(-1). In choice experiments with treated diet, a deterrence index of 0.97 was scored for Q. saponaria saponins at 1 mg mL(-1). In contrast, direct contact showed no repellent effect. Spraying of faba bean plants with Q. saponaria saponins resulted in an LC50 of 8.2 mg mL(-1). Finally, histological analysis in aphids fed with Q. saponaria saponins demonstrated strong aberrations of the aphid gut epithelium, and exposure of midgut CF-203 cell lines to Q. saponaria saponins in vitro confirmed the cytotoxic effect.
The present insect experiments provide strong evidence that saponins, as tested here with triterpene Q. saponaria saponins, can be useful as natural aphicides and deterrents. Furthermore, the insect midgut epithelium is suggested to be a primary target of saponin activity.
皂素是一类由糖部分通过糖苷键连接到疏水性糖苷配基（皂素）的次生植物代谢物，通常具有杀虫活性。选择了四种皂素：两种三萜皂素，皂角苷和七叶皂苷，以及两种甾体皂素，洋地黄皂素和薯蓣皂素。研究了它们对一种重要的害虫物种和一种模式刺穿式吸食昆虫豌豆蚜 Acyrthosiphon pisum 的影响。由于其高活性，三萜皂角苷树皮皂素受到了特别关注。通过口服和接触暴露来挑战蚜虫，以证明杀虫活性，并在选择实验中支持用作天然驱避剂。
当蚜虫暴露于补充人工饮食 3 天时，四种皂素中的三种显示出强烈的杀虫活性，LC50 分别为 Q. saponaria saponins 为 0.55 mg mL(-1)，七叶皂苷为 0.62 mg mL(-1)，洋地黄皂素为 0.45 mg mL(-1)。LT50 值范围为 1 至 4 天，具体取决于剂量。对于薯蓣皂素，在 5 mg mL(-1)以下浓度下，仅记录到低毒性（14%）。在处理过的饮食的选择实验中，Q. saponaria saponins 在 1 mg mL(-1)时的驱避指数为 0.97。相比之下，直接接触没有显示出驱避作用。向蚕豆植物喷洒皂角苷导致 LC50 为 8.2 mg mL(-1)。最后，在喂食 Q. saponaria saponins 的蚜虫中进行的组织学分析表明，蚜虫肠道上皮细胞出现严重异常，并且在体外将 Q. saponaria saponins 暴露于中肠 CF-203 细胞系证实了细胞毒性作用。
本昆虫实验提供了强有力的证据，证明皂素，如本文中用三萜 Q. saponaria saponins 进行测试，可以作为天然杀虫剂和驱避剂使用。此外，昆虫中肠上皮细胞被认为是皂素活性的主要靶标。
