Sulforaphane
A sulphur compound formed when cruciferous vegetables are cut or chewed, derived from the conversion of glucoraphanin, and studied for its activation of cellular antioxidant defences.
Sulforaphane does not exist as such in the vegetable. It forms when the tissues of cruciferous vegetables are damaged (cut, chewed, bitten), which brings glucoraphanin into contact with an enzyme, myrosinase, previously kept apart in another part of the cell.
Broccoli is the best-known source, and young broccoli sprouts contain far more than the mature vegetable. Cabbage, cauliflower, Brussels sprouts, rocket and radish also provide it.
Cooking destroys the enzyme, not the precursor, and this dictates how to prepare these vegetables. Broccoli boiled for a long time loses its myrosinase: the glucoraphanin is still there but is no longer converted. Two workarounds are documented: chop the vegetables and then wait about forty minutes before cooking, which lets the reaction take place; or pair a raw source of myrosinase, such as rocket, mustard or radish, with the cooked vegetable.
Its mode of action sets it apart from classic antioxidants: rather than directly neutralising free radicals, it activates a cellular pathway (Nrf2) that increases the production of the body’s own antioxidant enzymes. The research is promising but still largely experimental: it is an argument for eating cruciferous vegetables, not for buying a supplement.