Biosynthesis of the isoprene units of chamomile sesquiterpenes

Abstract
Chamomile sesquiterpenes were labelled with 13C by injection of an [1-13C]glucose solution into the anthodia of the plant. The sesquiterpenes bisabololoxide A and chamazulene were isolated from the hydrodistillate of the labelled flowers. Analysis of the labelling patterns and absolute 13C abundances using quantitative 13C NMR spectroscopy showed that two of the isoprene building blocks were predominantly formed via the new triose\pyruvate pathway, whereas the third unit was of mixed origin, being derived from both the mevalonic acid pathway and the triose\pyruvate pathway.