Stable isotope-labeled precursors were synthesized for an analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to elucidate the biosynthetic flow of capsaicinoids, capsinoids, and capsiconinoids. [1'-(13)C][5-(2)H]-Vanillin was prepared by the condensation of guaiacol with [(13)C]-chloroform and a D(2)O treatment. Labeled vanillylamine, vanillyl alcohol, ferulic acid, and coniferyl alcohol were prepared from the labeled vanillin. The labeled vanillylamine was converted to labeled capsaicinoid in a crude enzyme solution extracted from pungent Capsicum fruits.
