Desulfation of glucosinolates

As per the ISO 9067-1 method, columns were prepared with 0.5 ml Sephadex slurry (2 g DEAE Sephadex beads in 30 ml 2 M acetic acid.) and activated with 2 ml imizadole formate (6 M). Columns were washed twice with 1 ml water. The column was washed twice with 1 ml 20 mM sodium acetate (pH 4.0) and 75 µl of purified sulfatase was added (5 or 0.3 U/ml). Columns were incubated at room temperature for either 12, 24 or 48 h before elution of desulfoglucosinolates with two 1 ml volumes of water. For the reduction of disulphide linkages, from dimerized desulfoglucosatavin in E. sativa extracts 3 g TCEP (Tris(2-carboxyethyl)phosphine hydrochloride powder Sigma, C4706) was added to 1 ml of desulfated extract. Desulfoglucosinolates were stored at −20 °C before high performance liquid chromatography analysis (Additional file 1).

For the high sulfatase treatment, between 0.5 and 1 ml of sample was added due to insufficient sample volume remaining.