Insights into the formation of carlactone from in‐depth analysis of the CCD8‐catalyzed reactions

Strigolactones are a new class of phytohormones synthesized from carotenoids via carlactone. The complex structure of carlactone is not easily deducible from its precursor, a cis‐configured β‐carotene cleavage product, and is thus formed via a poorly understood series of reactions and molecular rearrangements, all catalyzed by only one enzyme, the carotenoid cleavage dioxygenase 8 (CCD8). Moreover, the reactions leading to carlactone are expected to form a second, yet unidentified product. In this study, we used 13C and 18O‐labeling to shed light on the reactions catalyzed by CCD8. The characterization of the resulting carlactone by LC‐MS and NMR, and the identification of the assumed, less accessible second product allowed us to formulate a minimal reaction mechanism for carlactone generation.