Profiling of sulforaphane content in forty-seven Chinese broccoli germplasms

Chinese broccoli [Brassica oleracea var. alboglabra (L. H. Bailey) Musil] is an annual herbaceous healthy vegetable plant mainly cultivated in southern China. Previous studies have been primarily focused on investigating the nutritional ingredients of this plant, little is known about its medicinal potentials. Here we report the profiling of sulforaphane, an active ingredient with potent anticancer activities, in 47 Chinese broccoli germplasms collected from China and some southeast-Asian countries. High-performance liquid chromatography technology was used to systemically quantify the sulforaphane content in leaf, stem, and flower bud clusters of all 47 Chinese broccoli germplasms. The results indicated a diverse distribution pattern of sulforaphane among different tissues. Flower bud contained the highest average of sulforaphane, roughly twice as much as in leaf and stem tissues. Interestingly, different germplasms exhibited great differences in terms of sulforaphane abundance. Germplasm BOK15-20 is extremely rich in sulforaphane in all tissues tested, similar to 2,500 times of BOK15-15 in leaf, 66 times of BOK15-42 in the stem, and 77 times of BOK15-40 in flower bud. The tremendous disparity of sulforaphane content among different germplasms suggests considerable variations in germplasms' medicinal potentials. In addition, we systemically characterized a series of morphological and phenotypic traits of all 47 Chinese broccoli germplasms. Cluster analysis through NTSYSpc v2.2 showed that the 47 germplasms were classified into five different groups, respectively, based on sulforaphane content and qualitative phenotypic traits. Our results not only confirmed the medicinal values of Chinese broccoli but also provided crucial information that will eventually benefit future germplasm development and new variety breeding.