Preparative HPLC method for the purification of sulforaphane and sulforaphane nitrile from Brassica oleracea

An extraction and preparative HPLC method has been devised to simultaneousl y purify sulforaphane and sulforaphane nitrile from the seed of Brassica ol eracea var, italica cv. Brigadier. The seed was defatted with hexane, dried , and hydrolyzed in deionized water (1:9) for 8 h. The hydrolyzed seed meal was salted and extracted with methylene chloride. The dried residue was re dissolved in a 5% acetonitrile solution and washed with excess hexane to re move nonpolar contaminants. The aqueous phase was filtered through a 0.22-m um cellulose filter and separated by HPLC using a Waters Prep Nova-Pak HR C -18 reverse-phase column. Refractive index was used to detect sulforaphane nitrile, and absorbance at 254 nm was used to detect sulforaphane. Peak ide ntification was confirmed using gas chromatography and electron-impact mass spectrometry. Each kilogram of extracted seed yielded approximately 4.8 g of sulforaphane and 3.8 g of sulforaphane nitrile. Standard curves were dev eloped using the purified compounds to allow quantification of sulforaphane and sulforaphane nitrile in broccoli tissue using a rapid GC method. The m ethodology was used to compare sulforaphane and sulforaphane nitrile conten t of autolyzed samples of several broccoli varieties.