Eleven flavonoid compounds were compared with aminoglutethimide (AG), a pharmaceutical aromatase inhibitor, for their abilities to inhibit aromatase enzyme activity in a human preadipocyte cell culture system. Flavonoids exerting no effect on aromatase activity were catechin, daidzein, equol, genistein, β-naphthoflavone (BNF), quercetin and rutin. The synthetic flavonoid, α-naphthoflavone (ANF), was the most potent aromatase inhibitor, with an I50 value of 0.5 μM. Three naturally-occurring flavonoids, chrysin, flavone, and genistein 4′-methyl ether (Biochanin A) showed I50 values of 4.6, 68, and 113 μM, respectively, while AG showed an I50 value of 7.4 μM. Kinetic analyses showed that both AG and the flavonoids acted as competitive inhibitors of aromatase. The Ki values, indicating the effectiveness of inhibition, were 0.2, 2.4, 2.4, 22, and 49 μM for ANF, AG, chrysin, flavone, and Biochanin A, respectively. Chrysin, the most potent of the naturally-occurring flavonoids, was similar in potency and effectiveness to AG, a pharmaceutical aromatase inhibitor used clinically in cases of estrogen-dependent carcinoma. These data suggest that flavonoid inhibition of peripheral aromatase activity may contribute to the observed cancer-preventive hormonal effects of plant-based diets.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of Steroid Biochemistry and Molecular Biology|
|State||Published - Sep 1993|
Bibliographical noteFunding Information:
Acknowledgements--This work was supported by Minnesota Agricultural Experiment Station project 18-34, a University of Minnesota Graduate School Grant-in-Aid and an International Life Science Institute-Nutrition Foundation Future Leader Award (MSK). The authors would like to thank T. Hase and K. W/ih~il/i for the preparation of equol. The authors are grateful to the staff of Surgicare of Minneapolis, Ltd (Edina, MN) and Dr Bruce Cunningham (Department of Surgery, University of Minnesota) for assistance obtaining adipose tissue.