Broccoli sprouts: an exceptionally rich source of inducers of enzymes that protect against chemical carcinogens

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 94; no. 19; pp. 10367 - 10372
• Main Authors: Fahey, J.W, Zhang, Y.S, Talalay, P
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences of the United States of America 16.09.1997; National Acad Sciences; National Academy of Sciences; The National Academy of Sciences of the USA
• Subjects: 9,10-Dimethyl-1,2-benzanthracene; ACTIVADOR ENZIMATICO; ACTIVATEUR D'ENZYME; ACTIVIDAD ENZIMATICA; ACTIVITE ENZYMATIQUE; ADMINISTRACION ORAL; ADMINISTRATION ORALE; Animals; Anticarcinogenic Agents - isolation & purification; Anticarcinogenic Agents - pharmacology; Biological Sciences; Brassica - chemistry; Brassica - growth & development; BRASSICA OLERACEA ITALICA; BRASSICACEAE; BROCCOLI; BROCOLI; Cancer; CARCINOGENOS; CARCINOGENS; CRUCIFERAE; CRUCIFEROUS VEGETABLES; DIMETHYLBENZ(A)ANTHRACENE; ENFERMEDADES GLANDULAS MAMARIAS; ENZYME ACTIVATORS; Enzyme Induction; Enzymes; ENZYMIC ACTIVITY; EXTRACTOS VEGETALES; EXTRAIT D'ORIGINE VEGETALE; Female; Germination; GLUCORAPHANIN; GLUCOSINOLATE; GLUCOSINOLATES; Glucosinolates - isolation & purification; Glucosinolates - pharmacology; GLUCOSINOLATOS; HIDROLASAS; HORTALIZAS DE HOJA; HYDROLASE; HYDROLASES; Indoles; ISOTHIOCYANATES; Isothiocyanates - isolation & purification; Isothiocyanates - pharmacology; LEAF VEGETABLES; LEGUME FEUILLE; MALADIE DES GLANDES MAMMAIRES; MAMMARY GLAND DISEASES; Mammary Neoplasms, Experimental - chemically induced; Mammary Neoplasms, Experimental - prevention & control; Medical research; MYROSINASE; NEOPLASMAS; NEOPLASME; NEOPLASMS; ORAL ADMINISTRATION; OXIDOREDUCTASES; OXIDORREDUCTASAS; OXYDOREDUCTASE; PLANT EXTRACTS; Plants; PREVENTION; QUINONE REDUCTASE; RAT; RATA; RATS; Rats, Sprague-Dawley; Solvents; Sprouts; SUBSTANCE CANCERIGENE; SULFORAPHANE; THIOCYANATE; THIOCYANATES; THIOGLUCOSIDASE; TIOCIANATOS; Tumors; Vegetables
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.94.19.10367

Induction of phase 2 detoxication enzymes [e.g., glutathione transferases, epoxide hydrolase, NAD(P)H: quinone reductase, and glucuronosyltransferases] is a powerful strategy for achieving protection against carcinogenesis, mutagenesis, and other forms of toxicity of electrophiles and reactive forms of oxygen. Since consumption of large quantities of fruit and vegetables is associated with a striking reduction in the risk of developing a variety of malignancies, it is of interest that a number of edible plants contain substantial quantities of compounds that regulate mammalian enzymes of xenobiotic metabolism. Thus, edible plants belonging to the family Cruciferae and genus Brassica (e.g., broccoli and cauliflower) contain substantial quantities of isothiocyanates (mostly in the form of their glucosinolate precursors) some of which (e.g., sulforaphane or 4-methylsulfinylbutyl isothiocyanate) are very potent inducers of phase 2 enzymes. Unexpectedly, 3-day-old sprouts of cultivars of certain crucifers including broccoli and cauliflower contain 10-100 times higher levels of glucoraphanin (the glucosinolate of sulforaphane) than do the corresponding mature plants. Glucosinolates and isothiocyanates can be efficiently extracted from plants, without hydrolysis of glucosinolates by myrosinase, by homogenization in a mixture of equal volumes of dimethyl sulfoxide, dimethylformamide, and acetonitrile at -50 degrees C. Extracts of 3-day-old broccoli sprouts (containing either glucoraphanin or sulforaphane as the principal enzyme inducer) were highly effective in reducing the incidence, multiplicity, and rate of development of mammary tumors in dimethylbenz(a)anthracene-treated rats. Notably, sprouts of many broccoli cultivars contain negligible quantities of indole glucosinolates, which predominate in the mature vegetable and may give rise to degradation products (e.g., indole-3-carbinol) that can enhance tumorigenesis. Hence, small quantities of crucifer sprouts may protect