In this application note, capsaicins are used as a model for compounds difficult to resolve with flash chromatography. Capsaicin compounds possess very similar structures making them difficult to resolve from each other. Although these compounds can be resolved on flash chromatography columns, such as the RediSep® Rf Gold C18, preparative high pressure liquid chromatography (prep HPLC) can provide improved resolution due to their smaller particle size and better packing compared to Flash columns. The Teledyne Isco CombiFlash® EZ Prep is a dual function system that is ideal for performing the initial purification of crude mixtures on inexpensive flash columns, with final purification on prep HPLC in a single system requiring lab space similar to a flash-only system. The flash column captures material that would be permanently retained on the HPLC column, and thus enables higher loading of the desired compound(s) on the HPLC column. Undesired materials are removed using the flash column. Detection and identification of the compounds was done with a PurIon mass spectrometer.
Capsaicin compounds are often used as a model for plant extracts. These compounds are of interest for pain relief1, suppression of tumorigenesis2 to increase bladder capacity, and reduce nausea3. Compounds in the capsaicin family are very similar in structure and polarity making them difficult to resolve. A high quality flash column such as a RediSep Rf Gold C18 column, has been shown to resolve a mixture of capsaicins sufficiently well to purify and identify three compounds4 (Figure 1).
A fragment common to the capsaicin compounds is the peak at m/z=137 created from the phenolic portion of the molecule (Figure 2)5. This fragment allows easy identification of those peaks which are capsaicinoids from those peaks not containing this compound family. For example, peak 4 in Figure 1 and Table 1 does not exhibit this fragment and is therefore presumed not to be a capsaicinoid.