The cancer-chemopreventive effects of broccoli may be attributed, in part, to isothiocyanates (ITCs), hydrolysis products of glucosinolates. Glucosinolates are hydrolyzed to their respective ITCs by the enzyme myrosinase, which is inactivated by heat. In this study, the metabolic fate of glucosinolates after ingestion of steamed and fresh broccoli was compared in 12 male subjects in a crossover design. During each 48-hour baseline period, no foods containing glucosinolates or ITCs were allowed. The subjects then consumed 200 g of fresh or steamed broccoli; all other dietary sources of ITCs were excluded. Blood and urine samples were collected during the 24-hour period after broccoli consumption. Total ITC equivalents in broccoli and total ITC equivalents in plasma and urine were assayed by high-performance liquid chromatography as the cyclocondensation product of 1,2-benzenedithiol. The content of ITCs in fresh and steamed broccoli after myrosinase treatment was found to be virtually identical (1.1 vs. 1.0 micromol/g wet wt). The average 24-hour urinary excretion of ITC equivalents amounted to 32.3 +/- 12.7% and 10.2 +/- 5.9% of the amounts ingested for fresh and steamed broccoli, respectively. Approximately 40% of total ITC equivalents in urine, 25.8 +/- 13.9 and 6.9 +/- 2.5 micromol for fresh and steamed broccoli, respectively, occurred as the N-acetyl-L-cysteine conjugate of sulforaphane (SFN-NAC). Total ITC metabolites in plasma peaked between 0 and 8 hours, whereas urinary excretion of total ITC equivalents and SFN-NAC occurred primarily between 2 and 12 hours. Results of this study indicate that the bioavailability of ITCs from fresh broccoli is approximately three times greater than that from cooked broccoli, in which myrosinase is inactivated. Considering the cancer-chemopreventive potential of ITCs, cooking broccoli may markedly reduce its beneficial effects on health.
Phytochemicals, especially the secondary metabolites synthesized by
plants, play key roles in human
nutrition, health, wellness, and disease prevention. Some
phytochemicals may be harmful to human
health. For example, two closely related 4-methylsulfinylbutyl
glucosinolate [glucoraphanin]
hydrolysis products from broccoli (Brassica oleracea L. var.
Botrytis), 1-isothiocyanato-4-(methylsulfinyl)butane (sulforaphane) and
5-(methylsulfinyl)pentanenitrile (sulforaphane nitrile), may
have
beneficial or deleterious effects on human health, respectively.
Preliminary studies using a gas
chromatography/mass spectrometry (GC/MS) system operated under
split/splitless conditions
revealed that ≈80% of sulforaphane was degraded to 3-butenyl
isothiocyanate. A GC/MS method
was developed wherein thermal degradation of sulforaphane was reduced
to 5% through the use of
an appropriate injector liner and precise control of the carrier gas
flow rates. The method provides
a simple, rapid technique for the analysis of both sulforaphane and
sulforaphane nitrile that is
suitable for routine screening of plant materials.
Keywords: Sulforaphane; sulforaphane nitrile; GC/MS; isothiocyanate;
Brassica oleracea; broccoli
Relationships between dietary nutrients and plasma and fecal estrone, estradiol-17 beta, testosterone, and plasma prolactin concentrations were studied in young Seventh-day Adventist men: 18 nonvegetarians (NVs), 20 lactoovovegetarians (LOVs), and 15 vegans (V). Blood samples and 3-d dietary records were obtained. Contemporaneously collected diet composites and stool samples were analyzed for fiber. Vs and LOVs consumed significantly more fiber than did the omnivores, whereas NVs and LOVs consumed more saturated fatty acids than did Vs. Although plasma steroid-hormone status did not differ, Vs had significantly higher fecal estrogen concentrations than did NVs or LOVs. Plasma prolactin concentrations were significantly higher in NVs and LOVs than in Vs. Significant relationships were observed for the combined groups between dietary and fecal fiber components and fecal, but not plasma, steroid hormones. For the combined groups, prolactin concentrations were positively correlated with saturated fatty acid intake. Further research on the effects of dietary nutrients on endocrine homeostasis in other age groups is warranted.
The accumulation of sulforaphane and vitamin C was studied in developing he& and leaves of broccoli. Sampling was conductedfrom early head initiation through commercial maturity. Whole plant fresh mass, plant height and also head mass, diameter and height were recorded from three composite samples. Gas chromatography and redox titration were used to analyze for sulforaphane potential (SP)' and vitamin C (VC) concentration, respectively. Results were reported on a dry mass basis (dmb). Sulforaphane potential in heads increased through muturity from 3. % to 30.11 pmol.g-'. In leaves, SP peaked 82 days after sowing and decreased until sampling ended with values ranging from 0.13 ' Contact author. T E L : 9 0 9 -8 6 9 -2 1 8 0 ; F A X : 9 0 9 -8 6 9 -5 0 7 8 ; E M A I L :mboteroomary@csupomona.edu * SP is a expressed as a measure of the amount of the glucosinolate or the parent compound glucoraphanin present in broccoli. This parameter was determined by hydrolysis of the latter with a standardized myrosinase enzyme.
Journal of FoodQuality 26 (2003) 523-530. All Rights Reserved. 'Gpyright 2003 by Food & Nutrition Press. Inc.. Trumbull, Connecticut. 523 524 M.B. OMARY ETAL. to 0.73 pnol.g-'. Vitamin C concentration increased in heads and leaves during development ranging from 2.2 to 13.8 mg.g-' and from 5.6 to 13.5 mg.g-', respectively. Head diameter showed a high correlation with SP, offering potential as a nondestructive and easily measured maturity index.
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