Max Planck Institute for Chemical Ecology, Hans-Knoell-Str. 8, 07745 Jena, Germany.
Insect Biochem Mol Biol. 2012 Mar;42(3):174-82. doi: 10.1016/j.ibmb.2011.12.002. Epub 2011 Dec 13.
The defensive properties of the glucosinolate-myrosinase system in plants of the order Brassicales have been attributed to the formation of toxic isothiocyanates generated upon tissue damage. Lepidopteran herbivores specialised on brassicaceous plants have been shown to possess biochemical mechanisms preventing the formation of isothiocyanates. Yet, no such mechanisms are known for generalist lepidopterans which also occasionally but successfully feed on plants of the Brassicales. After feeding on Arabidopsis thaliana plants, faeces of Spodoptera littoralis larvae contained glutathione conjugate derivatives (cysteinylglycine- and cysteinyl-isothiocyanate-conjugates) of the plant's major glucosinolate hydrolysis product, 4-methylsulfinylbutyl isothiocyanate. When caterpillars fed on leaves of A. thaliana containing [¹⁴C]₄-methylsulfinylbutyl glucosinolate, more than half of the ingested radioactivity was excreted as the unmetabolised corresponding isothiocyanate, and only 11% as glutathione conjugate derivatives. However, these conjugates were demonstrated to be the major metabolites of isothiocyanates in S. littoralis, and their abundance was shown to correlate with the amount of isothiocyanates ingested. Analysis of larval faeces from several species of generalist lepidopterans (Spodoptera exigua, S. littoralis, Mamestra brassicae, Trichoplusia ni and Helicoverpa armigera) fed on different Brassicaceae revealed that glutathione conjugates arise from a variety of aliphatic and aromatic isothiocyanates derived from dietary glucosinolates.
植物中的葡糖苷硫氰酸盐-黑芥子酶系统具有防御属性，这归因于组织损伤时生成的有毒异硫氰酸酯。已证实专门以十字花科植物为食的鳞翅目食草动物具有防止异硫氰酸酯形成的生化机制。然而，对于偶尔也会成功取食十字花科植物的一般性鳞翅目昆虫来说，目前还不知道有这样的机制。在取食拟南芥植物后，棉铃虫幼虫的粪便中含有植物主要葡糖苷水解产物 4-甲基亚磺酰基丁基异硫氰酸酯的谷胱甘肽共轭衍生物（半胱氨酸甘氨酸-和半胱氨酸异硫氰酸酯-共轭物）。当毛毛虫取食含有 [¹⁴C]₄-甲基亚磺酰基丁基葡糖苷硫氰酸盐的拟南芥叶片时，超过一半的摄入放射性物质作为未代谢的相应异硫氰酸酯排泄，只有 11%作为谷胱甘肽共轭衍生物。然而，这些共轭物被证明是棉铃虫中异硫氰酸盐的主要代谢物，其丰度与摄入的异硫氰酸盐量相关。对几种一般性鳞翅目昆虫（斜纹夜蛾、棉铃虫、菜粉蝶、烟青虫和棉铃实夜蛾）幼虫粪便的分析表明，谷胱甘肽共轭物来自饮食中的葡糖苷硫氰酸盐衍生的各种脂肪族和芳香族异硫氰酸酯。
