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Isothiocyanate concentrations and interconversion of sulforaphane to erucin in human subjects after consumption of commercial frozen broccoli compared to fresh broccoli
Author(s) -
Saha Shikha,
Hollands Wendy,
Teucher Birgit,
Needs Paul W.,
Narbad Arjan,
Ortori Catharine A.,
Barrett David A.,
Rossiter John T.,
Mithen Richard F.,
Kroon Paul A.
Publication year - 2012
Publication title -
molecular nutrition and food research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.495
H-Index - 131
eISSN - 1613-4133
pISSN - 1613-4125
DOI - 10.1002/mnfr.201200225
Subject(s) - sulforaphane , glucoraphanin , myrosinase , blanching , chemistry , bioavailability , food science , glucosinolate , sinigrin , asparagus , isothiocyanate , mercapturic acid , urine , brassica , brassica oleracea , biochemistry , cysteine , botany , pharmacology , enzyme , medicine , biology
Scope Sulforaphane (a potent anticarcinogenic isothiocyanate derived from glucoraphanin) is widely considered responsible for the protective effects of broccoli consumption. Broccoli is typically purchased fresh or frozen and cooked before consumption. We compared the bioavailability and metabolism of sulforaphane from portions of lightly cooked fresh or frozen broccoli, and investigated the bioconversion of sulforaphane to erucin. Methods and results Eighteen healthy volunteers consumed broccoli soups produced from fresh or frozen broccoli florets that had been lightly cooked and sulforaphane thio‐conjugates quantified in plasma and urine. Sulforaphane bioavailability was about tenfold higher for the soups made from fresh compared to frozen broccoli, and the reduction was shown to be due to destruction of myrosinase activity by the commercial blanching‐freezing process. Sulforaphane appeared in plasma and urine in its free form and as several thio‐conjugates forms. Erucin N ‐acetyl‐cysteine conjugate was a significant urinary metabolite, and it was shown that human gut microflora can produce sulforaphane, erucin, and their nitriles from glucoraphanin. Conclusion The short period of blanching used to produce commercial frozen broccoli destroys myrosinase and substantially reduces sulforaphane bioavailability. Sulforaphane was converted to erucin and excreted in urine, and it was shown that human colonic flora were capable of this conversion.