Determination of sinigrin and glucoraphanin in Brassica species using a simple extraction method combined with ion-pair HPLC analysis

Distribution of sinigrin (2-propenylglucosinolate) and glucoraphanin (4-methylsulphinylbutylglucosinolate) concentration was determined in seeds and seedlings of Brassica species: B. oleracea, B. nigra, B. juncea, B. rapa and B. napus using a simple and reliable extraction method. Glucosinolates were extracted from seeds and seedlings using boiling water and were analysed by reverse phase ion-pair chromatography with UV detection. High concentrations of sinigrin were found in B. nigra, B. juncea var. rugosa (mustard greens) and B. oleracea (Brussels sprouts, cabbage, cauliflower, and Chinese broccoli). Sinigrin was absent from B. rapa and B. napus and was present in negligible concentrations in B. oleracea var. italica (broccoli). The concentration of sinigrin in the seed was similar to that in the cotyledon and hypocotyl tissues (7-day-old seedling) in most Brassica species tested. Glucoraphanin was found at high concentrations in B. oleracea var. italica and moderate concentrations in B. oleracea var. capitata (cabbage), whilst was absent in B. nigra, B. juncea, B. rapa and B. napus. Glucoraphanin concentration was between 44.2 and 274.1 mumol g(-1) DW among broccoli genotypes. Kalibrini(R), a new hybrid line between broccoli and Chinese broccoli (kailan) contained a moderate concentration of glucoraphanin (145.3 mumol g(-1) DW) compared to its parent lines (274.1 mumol g(-1) DW in broccoli but only 1.2 mumol g(-1) DW in kailan). Glucoraphanin concentration in seedlings was significantly lower than that in the seed of broccoli while there was no significant difference in sinigrin concentration in seedlings of most Brassica species tested. The study has shown the extensive variability in sinigrin and glucoraphanin concentrations among Brassica species and genotypes that is available for selection and breeding. New elite lines can be produced for use as commercial crops in the health food or nutraceutical industries. (C) 2002 Elsevier Science B.V All rights reserved.