Shinoda Tetsuro, Nagao Tsuneatsu, Nakayama Masayoshi, Serizawa Hiroaki, Koshioka Masaji, Okabe Hikaru, Kawai Akira
National Institute of Vegetable and Tea Science, Ano, Mie, Japan.
J Chem Ecol. 2002 Mar;28(3):587-99. doi: 10.1023/a:1014500330510.
Larvae of the diamondback moth, Plutella xylostella, a crucifer specialist, refuse to feed on a crucifer, Barbarea vulgaris, because of the presence of a feeding deterrent, which is extractable with chloroform. We isolated a feeding deterrent from B. vulgaris leaves, by successive fractionations with silica-gel, ODS, i.e., C18 reversed phase, and Sephadex LH-20 column chromatographies, and ODS-HPLC, guided by a bioassay for feeding deterrent activity. The structure of the compound was determined to be a monodesmosidic triterpenoid saponin, 3-O-[O-beta-D-glucopyranosyl-(1-->4)-beta-D-glucopyranosyl]-hederagenin, based on FAB-MS, 1H- and 13C-NMR spectra, and hydrolysis experiments. When the compound was applied to cabbage leaf disks at greater than 0.18 microg/mm2, consumption of the disks by third instars was less than 11% of control disks treated with the solvent alone. Furthermore, all first instars died on the disks treated with the same concentrations. Because the concentration of the compound in the fresh leaves of B. vulgaris was comparable to the effective dose in the cabbage leaf disk tested, we conclude that the unacceptability of B. vulgaris to P. xylostella larvae is primarily due to this saponin.
小菜蛾（Plutella xylostella）是一种十字花科专食性害虫，其幼虫因存在一种可被氯仿提取的拒食剂而拒绝取食十字花科植物——野芥菜（Barbarea vulgaris）。我们通过硅胶柱色谱、ODS（即C18反相柱色谱）、葡聚糖凝胶LH - 20柱色谱以及ODS - HPLC等连续分级分离方法，并以拒食活性生物测定为指导，从野芥菜叶片中分离出一种拒食剂。基于快原子轰击质谱（FAB - MS）、1H - 核磁共振（1H - NMR）和13C - 核磁共振（13C - NMR）光谱以及水解实验，确定该化合物的结构为单糖苷三萜皂苷，即3 - O - [O - β - D - 吡喃葡萄糖基 - (1→4) - β - D - 吡喃葡萄糖基] - 常春藤皂苷元。当该化合物以大于0.18微克/平方毫米的浓度施用于甘蓝叶圆片时，三龄幼虫对叶圆片的取食量不到仅用溶剂处理的对照叶圆片的11%。此外，所有一龄幼虫在相同浓度处理的叶圆片上死亡。由于野芥菜新鲜叶片中该化合物的浓度与所测试的甘蓝叶圆片中的有效剂量相当，我们得出结论，野芥菜对小菜蛾幼虫不可接受主要是由于这种皂苷。
