The biosynthetic origin of oxygen functions in phenylphenalenones of Anigozanthos preissii inferred from NMR- and HRMS-based isotopologue analysis

► 13C-labelled precursors were administered to root cultures of Anigozanthos preissii, which were simultaneously incubated in an atmosphere of 18O2. ► Incorporated 18O was detected by means of isotope-induced shifts of 13C NMR signals and HREISMS. ► The sensitivity with which NMR spectroscopy detected 18O was dramatically enhanced by O-methylation with 13C-diazomethane. ► The biosynthetic sequence according to which oxygen functionalities are incorporated from the atmosphere into 9-phenylphenalenones was elucidated.