Incorporation of 1-[1-13C]Deoxy-d-xylulose in Chamomile Sesquiterpenes

Incorporation of synthetically prepared 1-[1-13C]deoxy-d-xylulose into chamomile sesquiterpenes has been achieved by injecting an aqueous solution into the anthodia of the plant. The analysis of labeling patterns and absolute 13C abundances of the isolated sesquiterpenes bisabololoxide A (1), bisabololoxide B (2), and chamazulene (3) using quantitative 13C NMR spectroscopy showed that 1-[1-13C]deoxy-d-xylulose was efficiently incorporated in all three isoprene building blocks of the sesquiterpenes. A significantly lower 13C abundance of the labeled carbon atom in the biogenetically terminal isoprene unit confirms the mixed biosynthesis of this unit, involving both the mevalonic acid pathway and the methylerythritol phosphate pathway.