Comprehensive chromatographic and NMR methods for the separation and identification of glucosinolates from mustard seeds

Glucosinolates are an important group of natural occurring thioglycosides which are the flavor precursors of cruciferous vegetables, condiments, relishes and other vegetables. Much effort has been devoted to developing methods for the efficient isolation and identification of glucosinolates due to their health benefits as well as oral care benefit, e.g., elimination of bad breath. In this study, we have isolated glucosinolates from 3 different commercially available mustard seeds, namely, black mustard seed, organic black mustard seed and yellow mustard seed by solvent extraction and followed by gel chromatographic separation. An ion-pair HPLC method was developed with a C-18 reverse column. We have observed that sinigrin and sinalbin are the main constituents in the organic black mustard seed and in the yellow mustard seed, respectively. In contrast to previous reports, we observed that gluconapin was the main constituent in the (non-organic) black mustard seed. All three glucosinolates were further purified by gel chromatograph. Their structures were analyzed by ¹H NMR.