Betalains are water-soluble pigments that may be used as alternatives to artificial colorants in the food industry. In addition, the betalain profile may be of taxonomic significance to some higher plants. Djulis (Chenopodium formosanum) is an emerging crop grown by Taiwan aboriginal communities, and its various cultivars contain different betalain compositions. To develop an authenticity method for evaluating djulis cultivars, we performed comprehensive betalain profiling with HPLC-Q-Orbitrap high-resolution mass spectrometry (HRMS). An HRMS method for betalain annotation was developed and used to identify 68 betalains, including 10 betacyanins, 24 betacyanin derivatives, and 34 betaxanthins. The profile of betacyanins and their derivatives could be utilized to classify different cultivars of djulis, while betaxanthins were less informative. Furthermore, the betalain profiles were indicative of the geographic origin of djulis. This HRMS method and analytical platform for betalains may be helpful to guide further investigations of natural pigments in other plants.
Keywords: authenticity; betacyanins; betaxanthins; djulis (Chenopodium formosanum); geographic origin; high-resolution mass spectrometry.