Insect feeding deterrents sesquiterpene lactones

P h y t o c h e m i c a l investigations of plant species of Parthenium, Encelia and Pi coria (Asteraceae) from semi-arid and arid zones of the United States and Mexico has resulted in the isolation and identification of numerous sesquiterpene lactones and benzopyrans that are active insect feeding deterrents. The chemistry, biological effects and possible mode of action of bioactive pseudoguaianolides and chromenes are reviewed. 

One reason that dominant plants are successful in semi-arid and arid ecosystems is due to the high concentration of terpenoids and prenylated phenolics that repel and/or deter feeding by herbivorous insects. Compounds like sesquiterpene lactones and benzopyrans are present in high quantities in the leaves of species of Pjajl t h ij jn, E n c e l i a and D i c o r i a and have been demonstrated to be effective feeding deterrents against known economic insect pests. Ijt vivo experiments are still needed in the field with bioactive constituents to better understand their effects on native phytophagous insects. 

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