Glucobrassicanapin

High-purity (>98%) GSL standards were purchased from PhytoLab GmbH & Co. KG (Vestenbergsgreuth, Middle Franconia, Germany): sinigrin (SIN), gluconapin (NAP), glucobrassicanapin (GBN), progoitrin (PRO), glucoerucin (ERU), glucoraphenin (RAE), glucoraphanin (RAA), glucobrassicin (GBC), glucotropaeolin (TRO) and gluconasturtiin (NAS). 4-Methoxyglucobrassicin (4ME) and neoglucobrassicin (NEO) were purchased from Extrasynthese (Z.I Lyon Nord, Genay Cedex France) and glucoalyssin (ALY) was purchased from Shanghai ZZBIO Co., Ltd. (Shanghai, China). HPLC-grade methanol, LC/MS-grade methanol and LC/MS-grade formic acid were supplied by Fisher Scientific (Pittsburgh, PA, USA). Ultrapure water was obtained using Milli-Q purification systems (Millipore, MA, USA). Individual stock solutions of the 13 GSLs were prepared in 70% methanol.

All the reagents employed for both extraction and analysis in this study were analytical-grade products obtained from Sigma-Aldrich (St. Louis, MO, USA) and ThermoFisher Scientific Korea (Seoul, Republic of Korea). Among the 17 GSL standards, 6 GSLs including Progoitrin (PRO), EpiProgoitrin (EPI), Glucobrassicanapin (GBN), Glucoiberin (GIB), Glucoraphenin (GRE), and Sinalbin (SNB) were purchased from Phytolab (Martin Baue, KG, Germany) and the remaining 11 GSL were purchased from Phytoplan (Neuenheimer, Heidelberg, Germany). All standards had a purity of ≥98%.