Glucoraphanin, sulforaphane and myrosinase activity in germinating broccoli sprouts as affected by growth temperature and plant organs

Abstract

The effect of growth temperature on glucoraphanin, sulforaphane and myrosinase activity in germinating broccoli sprouts was firstly evaluated, and then their distributions in the cotyledon, hypocotyl and root at the optimum temperature were investigated. The profiles of isothiocyanates and nitrile in seeds, sprouts and different organs were also analyzed. Glucoraphanin content and sulforaphane formation declined with sprouts growth. Myrosinase activity in sprouts, stable for the first 3 days of germination, slowly increased threefold by day 7. The highest levels of glucoraphanin and sulforaphane were recorded in non-germinated seeds. Sprouts grown at 25 °C had higher glucoraphanin content and sulforaphane formation than that grown at 20 and 30 °C. In addition, cotyledon had significantly higher glucoraphanin content and sulforaphane formation than hypocotyl and root. Glucoraphanin and sulforaphane were barely detectable in root, despite its high myrosinase activity. The most abundant hydrolysis product in seeds and sprouts, cotyledon and hypocotyl was sulforaphane.