Structure determination of minor red pigment in carthamus red colorant isolated by preparative LC/MS.

Carthamin is a well-known major pigment in carthamus red colourant. When analysed by HPLC on an ODS column, the colorant separated into two distinct reddish pigments, with both components having almost identical photodiode array spectra. LC/MS analysis suggested one of the compounds was carthamin, whilst the other was an unknown minor pigment. The minor pigment was purified and isolated from the colorant by preparative LC/MS collecting the faction based on monitoring the deprotonated molecule [M-H](-) m/z 953 in electrospray negative-ion mode. The structure was elucidated as a hydroxyethyl ether of carthamin, a novel compound, by means of NMR and HR-FAB-MS analyses.