Disposition of Glucosinolates and Sulforaphane in Humans After Ingestion of Steamed and Fresh Broccoli

Disposition of Glucosinolates and Sulforaphane in Humans After Ingestion of Steamed and Fresh Broccoli

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 glucosinola...

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Bibliographic Details
Published in:Nutrition and cancer Vol. 38; no. 2; pp. 168 - 178
Main Authors: Conaway, C. Clifford, Getahun, Serkadis M., Liebes, Leonard L., Pusateri, Donald J., Topham, Debra K. W., Botero-Omary, María, Chung, Fung-Lung
Format: Journal Article
Language:English
Published: Philadelphia, PA Lawrence Erlbaum Associates, Inc 01-01-2000
Taylor& Francis
Subjects:
Adult
Anticarcinogenic Agents - analysis
Anticarcinogenic Agents - pharmacokinetics
Biological and medical sciences
Biological Availability
Brassica - chemistry
Brassica - enzymology
Carcinogenesis, carcinogens and anticarcinogens
Chromatography, High Pressure Liquid
Cooking
Cross-Over Studies
Foods and miscellaneous
Glucose - analogs & derivatives
Glucose - analysis
Glucosinolates - analysis
Glucosinolates - pharmacokinetics
Glycoside Hydrolases - metabolism
Humans
Imidoesters - analysis
Intestinal Absorption
Isothiocyanates
Male
Medical sciences
Middle Aged
Thiocyanates - analysis
Thiocyanates - pharmacokinetics
Tumors
Human
Bakery product
Broccoli
Glucosinolate
Food intake
Fresh product
Adult
Male
Bioavailability
Anticarcinogen
Water vapor
Nutritional status
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Summary: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 μmol/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 μmol 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.
ISSN:0163-5581
1532-7914
DOI:10.1207/S15327914NC382_5