Quantitative profiling of glucosinolates by LC–MS analysis reveals several cultivars of cabbage and kale as promising sources of sulforaphane

Sulforaphane is an isothiocyanate well known for its potential health benefits. With the aim of finding sulforaphane supply sources, its precursor, glucoraphanin, was widely searched for among Brassica oleracea varieties. Quantitative profiling of seven glucosinolates by LC–MS analysis was performed on 6 cultivars of broccoli, 32 of cabbage and 24 cultivars of kale. The glucoraphanin levels found in three cultivars of cabbage and six cultivars of kale were comparable with, or even higher than, the highest of broccoli (119.4 mg/100 g FW). The most promising group belonged to the black kale, Cavolo nero. Use of a C30 column and an ammonium formate buffer in LC–MS and a micro plate solid phase extraction technique was highly effective.