Isothiocyanate concentrations and interconversion of sulforaphane to erucin in human subjects after consumption of commercial frozen broccoli compared to fresh broccoli

Institute of Food Research, Norwich Research Park, Norwich, UK.
Molecular Nutrition & Food Research (Impact Factor: 4.6). 12/2012; 56(12). DOI: 10.1002/mnfr.201200225
Source: PubMed


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.
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.
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.

35 Reads
  • Source
    • "The anaerobic incubation ex vivo of ceacal microbiota from male F344 rats with glucoraphanin yielded only the hydrolysis product erucin NIT in relatively low concentrations [9]. Similarly, glucoraphanin metabolism in human gut microbiota showed the bioconversion of glucoraphanin to glucoerucin and the production of sulforaphane (trace amounts), erucin and corresponding NITs [10]. However, there was no identification of bacterial strains responsible for this bioconversion. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Certain myrosinase-positive human gut bacteria can metabolize glucosinolates (GSLs) to produce isothiocyanates (ITC) as chemopreventive agents. We investigated glucoerucin, glucoiberin, and glucoraphanin (present in broccoli) metabolism by human gut strains. All tested bacteria metabolized glucoerucin to completion within 16 h to erucin and erucin nitrile (NIT). Lactobacillus agilis R16 metabolized only 10% of glucoiberin and glucoraphanin with no detectable products. Enterococcus casseliflavus CP1, however, metabolized 40-50% of glucoiberin and glucoraphanin producing relatively low concentrations of iberin and sulforaphane. Interestingly, Escherichia coli VL8 metabolized 80-90% of glucoiberin and glucoraphanin and also bioconverted glucoraphanin and glucoiberin to glucoerucin and glucoiberverin, respectively, producing erucin, erucin NIT, iberverin, and iberverin NIT from the two GSLs. The putative reductase enzyme in the cell-free extracts of this bacterium required both Mg(2+) and NAD(P)H as cofactors for bioconversion. The cell-free extract of E. coli VL8 containing the reductase enzyme was able to reduce both the GSL glucoraphanin and its hydrolysis product sulforaphane to glucoerucin and erucin/erucin NIT, respectively. The composition and metabolic activity of the human gut bacteria can indirectly impact on the potential chemopreventive effects of GSL-derived metabolites.
    Molecular Nutrition & Food Research 04/2014; 58(4). DOI:10.1002/mnfr.201300377 · 4.60 Impact Factor
  • Source
    • "Interestingly, more recent SF bioavailability studies in human subjects consuming broccoli showed its bioconversion into isothiocyanate erucin (isothiocyanato-4- (methylthio)-butane) (ER), a sulfide analog [25] [26]. Whether this conversion from SF to ER is important for the health promoting effects of glucosinolate still remains to be determined although some reports provide a glimpse into the possibility of differing activities between these two isothiocyanates [27– 29]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: A wide variety of acute and chronic neurodegenerative diseases, including ischemic/traumatic brain injury, Alzheimer's disease, and Parkinson's disease, share common characteristics such as oxidative stress, misfolded proteins, excitotoxicity, inflammation, and neuronal loss. As no drugs are available to prevent the progression of these neurological disorders, intervention strategies using phytochemicals have been proposed as an alternative form of treatment. Among phytochemicals, isothiocyanate sulforaphane, derived from the hydrolysis of the glucosinolate glucoraphanin mainly present in Brassica vegetables, has demonstrated neuroprotective effects in several in vitro and in vivo studies. In particular, evidence suggests that sulforaphane beneficial effects could be mainly ascribed to its peculiar ability to activate the Nrf2/ARE pathway. Therefore, sulforaphane appears to be a promising compound with neuroprotective properties that may play an important role in preventing neurodegeneration.
    Oxidative medicine and cellular longevity 08/2013; 2013:415078. DOI:10.1155/2013/415078 · 3.36 Impact Factor
  • Source
    • "Norwich 2011 samples were analysed at IFR. All glucosinolates were analysed by methods based on the determination of glucosinolates in Rapeseed ISO 9167-1 with some modifications as previously described (Saha et al., 2012). Other major sulphur-containing metabolites (methionine, cysteine, glutathione, S-methyl cysteine sulphoxide) were analysed in florets of three plants each of 1199, 1639, HG1, Emerald and Ironman grown in Norwich in 2011. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Diets rich in broccoli (Brassica oleracea var italica) have been associated with maintenance of cardiovascular health and reduction in risk of cancer. These health benefits have been attributed to glucoraphanin that specifically accumulates in broccoli. The development of broccoli with enhanced concentrations of glucoraphanin may deliver greater health benefits. Three high-glucoraphanin F1 broccoli hybrids were developed in independent programmes through genome introgression from the wild species Brassica villosa. Glucoraphanin and other metabolites were quantified in experimental field trials. Global SNP analyses quantified the differential extent of B. villosa introgression The high-glucoraphanin broccoli hybrids contained 2.5–3 times the glucoraphanin content of standard hybrids due to enhanced sulphate assimilation and modifications in sulphur partitioning between sulphur-containing metabolites. All of the high-glucoraphanin hybrids possessed an introgressed B. villosa segment which contained a B. villosa Myb28 allele. Myb28 expression was increased in all of the high-glucoraphanin hybrids. Two high-glucoraphanin hybrids have been commercialised as Beneforté® broccoli. The study illustrates the translation of research on glucosinolate genetics from Arabidopsis to broccoli, the use of wild Brassica species to develop cultivars with potential consumer benefits, and the development of cultivars with contrasting concentrations of glucoraphanin for use in blinded human intervention studies.
    New Phytologist 04/2013; 198(4). DOI:10.1111/nph.12232 · 7.67 Impact Factor
Show more