Effects of metal ions on myrosinase activity and the formation of sulforaphane in broccoli seed

Effects of six metal ions on the formation of sulforaphane and the liberation of glucose upon hydrolysis of glucoraphanin by myrosinase at neutral pH were studied. The yields of sulforaphane and glucose were determined by HPLC. Copper ion and magnesium ion decreased the yields of sulforaphane and glucose. Ferrous ion and ferric ion inhibited the formation of sulforaphane, but had no effects on the liberation of glucose. Calcium ion increased the yield of glucose liberation, but inhibited the formation of sulforaphane. Only zinc ion was beneficial to the liberation of glucose and accelerated the formation of sulforaphane at initial reaction intervals.