Biosynthesis of Mustard Oil Glucosides: I. Administration of C14-Labelled Compounds to Horseradish, Nasturtium, and Watercress

Biosynthetic investigations with C14-labelled compounds indicate that the aromatic isothiocyanate moieties of mustard oil glucosides obtained from garden nasturtium (Tropaeolum majus L.) and watercress (Nasturtium officinale R.Br.) are derived from phenylalanine. Similar investigations on sinigrin, the mustard oil glucoside isolated from horseradish (Armoracia lapathifolia Gilib.) demonstrate that glycine is incorporated into allyl isothiocyanate. The methyl carbon of acetate was readily incorporated into sinigrin and gluconasturtium and was found almost exclusively in the 'isothiocyanate carbon'; on the other hand the carboxyl carbon is a poor precursor of sinigrin.