Biosynthesis of Quinoline by a Stick Insect.

The Peruvian stick insect is the only known animal source for unsubstituted quinoline in nature. When disturbed, these insects discharge a defensive secretion containing quinoline. Analysis of samples obtained from l-[2',4',5',6,'7'-H]tryptophan-fed stick insects demonstrated that the insects convert it to [5,6,7,8-H]quinoline by removing the 2'-CH moiety in the indole ring of tryptophan.