Electrochemical detection of indole alkaloids of Catharanthus roseus in high-performance liquid chromatography

Hydrodynamic voltammograms for indole and five indole alkaloids with different amino functions were obtained in order to evaluate the applicability of high-performance liquid chromatography (HPLC) with coulometric detection to these compounds. With the exception of serpentine, which has a quaternary nitrogen in its structure, all the compounds were oxidised and gave net signals of greater than 25 nA pmol(-1) at potentials of between +0.2 and +0.85 V versus a solid Pd electrode in an acetate-buffered (pH 6.5) water-methanol-acetonitrile system. An HPLC assay for quantifying picomole amounts of catharanthine and ajmalicine in Catharanthus roseus cell culture samples is described.