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SECOND INTERNATIONAL SYMPOSIUM
ON THE ROLE OF SOY
IN PREVENTING AND TREATING CHRONIC DISEASE

September 15-18, 1996
Brussells, Belgium

POSTER ABSTRACTS

Soybean Extract Induces Quinone Reductase Activity in Hepa1c1c7 Cells and Murine Lung, but Suppresses Arylhydrocarbon Hydroxylase Activi-ty in Murine Organs.
Jong-Sang Kim and Tai-Wan Kwon
Food Science Institute, Inje University, Obang-dong, Kimhae, Kyongnam 621-749, Republic of Korea.

Soybean intake has been reported to be associated with lowered incidence of some tumors including human breast and prostate carcinomas. Soybean extracts were screened for anticarcinogenic substances by testing their ability to induce quinone reductase (NAD(P)H:(quinone acceptor) oxidoreductase, EC 1.6.99.2), one of phase II detoxication enzymes, in murine hepatoma cells and mouse organs. Although 80% methanol extract of defatted soyflour did not increase quinone reductase activity of hepa 1c1c7 cells, its acid-hydrolysate resulted in the significant induction of the enzyme. Thin layer chromatography of the breakdown products of soybean extract produced 4 major bands. The fastest moving band was responsible for quinone reductase induction and showed the same Rf value as daidzein and genistein which are two marjor isoflavones present in soybean. Genistein strongly induced quinone reductase while daidzein did not have any effect, suggesting genistein is one of quinone reductase inducers in soybean. Further study in which mice were fed diet containing 10% acid-hydrolysate of methanol extract of defatted soyflour showed that quinone reductase was induced in lung while its activity in other organs remained unchanged or slightly suppressed. Arylhydrocarbon hydroxylase involved in the activation of some procarcinogens tended to decrease by soybean hydrolysate. These findings support the notion that soy components including genistein have a potential to function favorably in preventing chemical carcinogenesis.

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