Purification of Crude Methanol Extracts using SPE

Crude grain extracts were purified using 100 mg Strata-X RP cartridges (Phenomenex, Torrance, CA, USA) according to a previously described method [7 (link)]. Briefly, 30 mL of the diluted crude methanol extracts (extract:water, 1:9) or 3.0 mL of the hydrolyzed extracts were applied to the SPE cartridges, washed with 4.0 mL of Milli-Q water, and dried with a flow of air. The compounds bound to the cartridges were eluted with 2.0 mL of 70% (v/v) aqueous methanol. The resulting extracts were filtered through syringe filters with a pore size of 0.20 µm (Chromafil Xtra-20/13; cellulose acetate; Macherey-Nagel, Düren, Germany) and then stored at −80 °C until liquid chromatography–mass spectrometry analysis (LC-MS).