Structure dereplication system

The system relies upon preliminary fractionation of the microbial crude extract by dualmode countercurrent chromatography coupled with photodiode array detection (PDA). The ultraviolet-visible (UV-Vis) spectra and liquid chromatography-mass spectrometry (LC-MS) of biologically active peaks are used for identification. Confirmation of compound identity is accomplished by nuclear magnetic resonance (NMR). Use of an integrated system countercurrent chromatography (CCC) separation, PDA detection, and LC-MS rapidly provided profiles and structural information extremely useful for metabolite identification (dereplication, Figure 14.1). 

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. 

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