Feeding experiments using root cultures of Anigozanthos preissii and NMR spectroscopical studies revealed reversible interconversion between phenylpropanoids and dihydrophenylpropanoids, and their incorporation into phenylphenalenones. Multiply labelled dihydrocinnamic acid was transformed to coumaric acid and further metabolized to 2-hydroxy-9-(4 hydroxyphenyl)-1H-phenalen-1-one (hydroxyanigorufone). 13C NMR spectroscopy and HPLC-1 H NMR coupling were employed to detect trace amounts of multiply labelled biosynthetic intermediates and further metabolites. The pathway of the phenylphenalenone biosynthesis is discussed.