Glucosinolate Profile of Croatian Stenoendemic Plant Fibigia triquetra (DC.) Boiss. ex Prantl

As part of our ongoing investigation of the stenoendemic plants belonging to the Brassicaceae family, we report on the chemistry of Fibigia triquetra (DC.) Boiss. ex Prantl for the first time. Different plant parts (flower, leaf, stem, and seed) of F. triquetra were characterized and quantified for glucosinolates (GLs) according to the ISO 9167-1 EU official method based on the HPLC analysis of desulfo-GLs. A taxonomic screening showed that F. triquetra contained relatively high levels of C-4 GLs, namely but-3-enyl GL (gluconapin, 1a), 4-methylsulfanylbutyl GL (glucoerucin, 3a), and 4-methylsulfinylbutyl GL (glucoraphanin, 5a). GC-MS analysis of the volatile fractions obtained after enzyme hydrolysis and/or HPLC-ESI-MS of intact GLs confirmed the GL profile. Four minor GLs, namely isopropyl GL (glucoputranjivin, 6a), sec-butyl GL (glucocochlearin, 7a), pent-4-enyl GL (glucobrassicanapin, 2a), and 5-methylsulfanylpentyl GL (glucoberteroin, 4a) were also identified and quantified while 4-methylpentyl GL, 5-methylhexyl GL, and n-heptyl GL, were tentatively identified by GC-MS of their degradation products. Based on the major, as well as the minor GLs, this study shows differences in chemotaxonomy between F. triquetra and the related Degenia velebitica (Degen) Hayek as well as other investigated species of the genus Fibigia.