Structural Elucidation of Unknown Alkaloids Present In Catharanthus Roseus by Precursor Ion Fingerprinting

Alkaloids are a group of pharmacologically active compounds present in the secondary metabolism of different organisms. Two examples are vincristine and vinblastine, two alkaloids extracted from C. roseus and extensively used in cancer therapy. These molecules are characterized by having a complex structure with several chiral centers; this renders their synthetic production impossible. Since secondary metabolites in plants tend to be present in a relatively low concentration, research has been performed on the use of metabolic engineering to increase the yield of these compounds. One limitation of this technology is the lack of complete knowledge of the metabolic pathway that leads to the biosynthesis of these alkaloids. In order to elucidate the pathway, it is necessary to identify the enzymes and intermediates involved in the series of reactions. The focus of this work is to reveal and confirm the structure of some intermediates present downstream of Tabersonine, a precursor for the alkaloids of interests.  The compounds were purified using High Performance Liquid Chromatography and their fragment ions were characterized using Liquid Chromatography/Mass Spectrometry and Fourier Transform Ion Cyclotron Resonance. Among those intermediates verifieded are 16-hydroxytabersonine and 6,7-dehydroechitovenine.