Glucoerucin

Broccoli seeds (BHL106) were obtained from the Vegetable Research Center of the Beijing Academy of Agricultural and Forestry Sciences. Methanol, formic acid, ammonium acetate, acetonitrile, Sinigrin (SIN), Gluconapin (NAP), Progoitrin (PRO), Glucotropaeolin (TRO), Glucoerucin (ERU), Gluconasturtiin (NAS), Glucoraphenin (RAE), Glucobrassicin (GBC), Glucoalyssin (ALY), 4-MethoxyGlucobrassicin (4ME), NeoGlucobrassicin (NEO), and glucoraphanin were purchased from PhytoLab GmbH & Co. KG (Vestenbergsgreuth, Middle Franconia, Germany). The purity of all chemical substances was >99%. Individual stock solutions of the 13 GSLs were prepared in 70% methanol. Ultrapure deionized water (18.2 MΩ) was prepared using Milli-Q purification systems (Millipore, MA, USA).

All glucosinolates and phytohormones used in this study is purchased from suppliers. The glucosinolates include sinigrin (allyl glucosinolate, PN#S0156, Tokyo Chemical Industry, Japan), gluconapin (3-butenyl glucosinolate potassium salt, PN#89688, phytolab, U.S.A.), glucoerucin (4-(methylthio)butyl glucosinolate potassium salt, PN#89686, phytolab, U.S.A.), glucoraphanin (4-(methylsulfinyl)butyl glucosinolate potassium salt, PN#89,215, phytolab, U.S.A.), sinalbin (p-hydroxybenzyl glucosinolate potassium salt, PN#89793, phytolab, U.S.A.), glucotropaeolin (benzyl glucosinolate potassium salt, PN#G0397, Tokyo Chemical Industry, Japan), and glucobrassicin (3-indolylmethyl glucosinolate potassium salt, PN#80593, phytolab, U.S.A.). The phytohormones includes IAA (3-indoleacetic acid, PN# I2886, Sigma-Aldrich, U.S.A.), SA (salicylic acid, PN#1901-2150, Showa Chemical Industry, Japan), JA (jasmonic acid, PN#J0004, Tokyo Chemical Industry, Japan), GA (gibberellin A3, PN#G0029, Tokyo Chemical Industry, Japan), ABA ((±)-abscisic acid, PN#A1049, Sigma-Aldrich, U.S.A.).

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.