Alkaloids of Importance in Plant-Insect Interactions

本研究将重点研究玄参科植物的半寄生种。重点介绍了植物的生物碱和环烯醚萜苷的化学性质，这些代谢物如何影响以植物为食的昆虫食草动物，以及一些分离的环烯醚萜苷如何在实验室中作为手性合成子利用。待研究的植物是寄生在含有生物碱的寄主植物根部的植物。这些生物碱被转移到寄生虫体内，并可能影响食草昆虫。寄生虫利用生物碱作为草食防御，以及寄生虫对某些寄主植物的特异性和生物碱从寄主到寄生虫的运输将被研究。由于昆虫食草动物利用含生物碱和环烯醚萜的植物对化合物进行隔离和/或代谢，因此将对昆虫代谢生物碱和环烯醚萜的化学转化进行研究。环烯醚萜苷结构与其转化为吡啶类生物碱的难易程度之间的关系将被研究，因为在一些植物中，环烯醚萜类化合物可转化为吡啶类单萜生物碱，但从几种高浓度环烯醚萜类化合物中提取的吡啶类单萜尚未被分离出来。最后，由于环烯醚萜类化合物很容易从某些正在研究的植物中以数克数量获得，并且可以在一锅反应中高产地转化为手性的五取代环戊烷，将进行一项研究，将这些产物转化为对映体纯碳环核苷。有了这个奖项，化学分部的合成有机项目将支持科罗拉多州立大学化学系Frank R. Stermitz博士的研究。本研究将集中于半寄生的植物种类，其成员寄生在含有生物碱的寄主植物的根上。这些生物碱被转移到寄生虫体内，并可能影响食草昆虫。寄生虫利用生物碱作为草食防御，以及寄生虫对某些寄主植物的特异性和生物碱从寄主到寄生虫的运输将被研究。后两项研究对生物多样性问题具有重要意义。随着地球雨林受到威胁，仅仅保护植物物种的基因库可能是不够的，如果次生代谢物的组成也依赖于宿主物种，生物多样性问题正成为危机的一部分。

This research will focus on hemiparasitic species of the plant family Scrophulariaceae. It will emphasize the alkaloid and iridoid glycoside chemistry of the plants, how these metabolites may affect insect herbivores whose larvae consume the plants, and how some of the isolated iridoid glycosides can be utilized in the laboratory as chiral synthons. The plant species to be studied are parasitic on the roots of host plants which contain alkaloids. These alkaloids are transferred into the parasites and may themselves affect insect herbivores. Utilization of the alkaloids by the parasites as herbivore defenses will be studied as will specificity of the parasites for certain host plants and alkaloid transport from the host into the parasite. Since insect herbivores which utilize alkaloid- and iridoid-containing plants sequester and /or metabolize the compounds, a study of chemical transformations in insect metabolism of alkaloids and iridoids will be made. Relationships between iridoid glycoside structures and their ease of conversion to pyridine alkaloids will be investigated because, in some plants, iridoids are converted to pyridine monoterpene alkaloids, but pyridine monoterpenes expected from several iridoids found in very high plant concentration have never been isolated. Finally, since iridoids are readily available in multigram quantities from some of the plants under investigation and can be converted in high yield in a one-pot reaction to chiral, pentasubstituted cyclopentanes, a study will be carried out to convert these products to enantiomerically-pure carbocyclic nucleosides. %%% With this award the Synthetic Organic Program of the Chemistry Division will support the research of Dr. Frank R. Stermitz of the Department of Chemistry at Colorado State University. This research will focus on hemiparasitic species of the plant family Scrophularicaeae whose members are parasitic on the roots of host plants which contain alkaloids. These alkaloids are transferred into the parasites and may themselves affect insect herbivores. Utilization of the alkaloids by the parasites as herbivore defenses will be studied as will specificity of the parasites for certain host plants and alkaloid transport from the host into the parasites. These latter two studies have important implications for the biodiversity question that is becoming of crisis proportions as the earth's rainforests are being threatened because simply preserving the genetic pool of plant species may not be enough if secondary metabolite composition is also dependant upon host species.