Distribution of primary and secondary metabolites among the leaf layers of headed cabbage (Brassica oleracea var. capitata).

The present study investigated the distribution of several primary metabolites (soluble sugar, protein, and mineral) and secondary metabolites (carotenoids, vitamin C, anthocyanin, flavonoids, and total phenolic compounds) among the leaf layers of headed cabbage. The leaf layers of two cultivars were separated and numbered sequentially from the outer to the inner leaves. The fructose and glucose content of the inner leaf layers was significantly greater than that of the outer layers. Similarly, the level of glucosinolates increased gradually from the outer leaves to the umbilicus of the leaf head. However, the content of antioxidants decreased from the outer leaves to the core of the leaf head, in line with the antioxidant capacity. The levels of soluble protein and mineral shared the similar decreasing trend. These results provide a reference for consumers to choose optimal fractions of whole cabbage heads in order to cater to their particular dietary needs.