Determination of glucosinolates and breakdown products in Brassicaceae baby leafy greens using UHPLC-QTOF/MS and GC/MS

Abstract

Brassica vegetables (Brassicaceae) produce a unique class of compounds known as glucosinolates. The breakdown products of glucosinolates, including isothiocyanates, are recognized as the primary sources of bioactivity and characteristic taste, flavor and aroma of these vegetables. An emerging market trend is to harvest leafy greens at the immature stage known as “baby greens”, however, much is still unknown about the phytochemistry at this earlier stage of development. Glucosinolates and their breakdown products were examined in three members of the Brassicaceae family: Eruca vesicaria subsp. sativa ‘Arugula’, Brassica juncea ‘Garnet Giant’ (mustard greens) and Brassica oleracea var. acephala ‘Red Kale’. A total of 16 glucosinolates were tentatively identified using UHPLC-QTOF/MS and seven volatile breakdown products were identified using GC/MS. Nine putative glucosinolates and one isothiocyanate are reported for the first time in these plant species and varieties. Glucobarbarin, glucocheirolin, glucoiberin, gluconapin and neoglucobrassicin were newly identified in Eruca vesicaria subsp. sativa. Glucoalyssin, glucobarbarin, glucobrassicanapin and glucotropaeolin were newly identified in B. oleracea var. acephala, and butane isothiocyanate was newly identified in B. oleracea. Future work will focus on correlating chemistry data with sensory analyses to determine the impact of these specific glucosinolates and breakdown products on taste, flavor and aroma.

Keywords

• Glucosinolate
• Isothiocyanate
• Controlled-environment agriculture (CEA)
• Arugula
• Kale
• Mustard greens