Instrumentation dereplication

The research group of Hostettmann significantly contributed to the current widespread use of LC-MS in the analysis, characterization, and dereplication of plant phenols including flavonoids. Initially, thermospray and continuous-flow FAB were applied. ESI and APCl were implemented in the mid 1990s [39]. The group evaluated both Q-TOF and multistage MS" with an ion-trap instrument for the dereplication of flavonoids in erode plant extracts [12], and pioneered the application of on-line LC-NMR in this field [39]. 

Although significant data are available from the dereplication process, the mass accuracy of spectra produced by TOF instruments ( 5 ppm) is often insufficient to allow for the proposal of a single molecular formula for an unknown. This case is especially true for the higher molecular-weight molecules that are often encountered in nature. In these instances, the increased mass accuracy of the MS, MS/MS, and MS data provided by FTMS systems can prove critical to structure elucidation. 

The isolation and purification of a bioactive compound is a rate-limiting step in a natural products chemistry project, and significant improvement in this area is urgently needed. We have approached this problem with a view toward exploring the application of sophisticated modern scientific instruments. Our goal was to develop a process that is not only capable of effective fractionation, but also yields sufficient quantities necessary for structure elucidation and extensive biological evaluation. In addition, the process would allow us to distinguish between known and new compounds (dereplication) at an earlier phase of the project. 

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