Natural products represent a successful alternative in searching for new drugs. This project was conducted by precursor-directed biosynthesis (BDP) procedures in order to obtain unnatural compounds by manipulating plant original pathways1. The target of this structural diversification is class of alkaloids; spirocyclic oxindole alkaloids which are accumulated in the specie U. guianensis. Previous studies have successfully demonstrated the incorporation of DL-5-fluoro-tryptamine precursor into AOP biosynthesis from U. guianensis plantlets2. However, the incorporation of fluorinated tryptophan precursors seems to be toxic to the plantlets. Furthermore, there are no studies about the influence of fluoro-tryptophan analogues as well as fluoro-tryptamine analogues in U. guianensis precursor-directed biosynthesis. Thus, we propose chemical (HPLC-DAD-MS/MS) and initial molecular (DNA-SRAP) investigations of plantlets incubated with DL-5-fluoro-tryptophan and DL-5-fluoro-tryptamine. Our experiments were conducted in three different times (24, 48 and 96 hours) and HPLC-DAD-MS/MS analyses showed a peak with m/z 402, after 48 hours after of incubation, which was related to fluoro-rhynchophylline. On the other hand, the DL-5-fluoro-tryptophan was not incorporated by U. guianensis and it seems to be toxic for the plant after 24 hours of incubation. We also demonstrate by DNA-SRAP and cDNA-SRAP that the fed with DL-5-fluoro-tryptophan precursor could start a degradation process in the U. guianensis primary metabolism.