Effect of nitrogen and sulfur fertilization on glucosinolates in the leaves and roots of broccoli sprouts (Brassica oleracea var. italica)

Broccoli (Brassica oleracea L. var. italica cv. Marathon) sprouts are a rich source of glucosinolates, particularly 4-methylsulfinylbutyl glucosinolate (glucoraphanin), the precursor of the chemoprotective isothiocyanate, sulforaphane. Sulfur and nitrogen fertilization have been shown to influence the pattern and levels of glucosinolates in mature broccoli, but little information is available on the fertilization of sprouts, a transient stage of broccoli growth, which have been recommended for salads. Therefore, an experiment was set up to evaluate the effect of N and S fertilization on the glucosinolate content of the aerial part and roots of broccoli sprouts. Nitrogen was tested at 0, 45.5, 91.0 mgL(-1) and sulfur at 0, 14.6 and 29.2 mgL(-1). The results showed that total glucosinolates in the aerial part were significantly higher (P < 0.001) than in the roots. The major glucosinolates in the aerial part were 4-methylsulfinylbutyl and 3-methylsulfinylpropyl whereas in the roots they were 2-phenylethyl and 4-methylthiobutyl. Fertilization of broccoli sprouts had a significant (P < 0.001) detrimental effect on the levels of aliphatic glucosinolates whereas the opposite was noted for indole and aromatic glucosinolates, for some of the fertilization combinations tested. Overall, the results indicate that broccoli sprouts do not benefit from fertilization. (c) 2006 Society of Chemical Industry.