Glucosinolate hydrolysis and bioavailability of resulting isothiocyanates: Focus on glucoraphanin

There is a growing interest in the health benefits of broccoli. Sulforaphane, the major bioactive component in broccoli, is an unstable isothiocyanate stored in the plant as glucoraphanin. Myrosinase enzymes release sulforaphane when the plant is crushed. Extraction during supplement formulation or heat processing can destroy myrosinase. When myrosinase activity is lost, colonic microbiota perform this hydrolysis in vivo. Here we review hydrolysis by myrosinase and microbiota. Myrosinase acts fast to generate a bolus of SF that is rapidly absorbed high in the gut and rapidly excreted. Microbial metabolism is slow and delayed. Sulforaphane absorption, distribution and excretion are discussed.