Flavonoids, aromatase inhibition

Ibrahim, A.R. and Abdul-Hajj, Y.J., Aromatase inhibition by flavonoids, J. Steroid Biochem. Mol. Biol, 37, 257, 1990. 

Out of a series of 42 compounds isolated and characterized in our investigation on B. papyrifera [41], comprising benzofurans, coumarins, and various types of flavonoids (biphenylpropanes, chalcones, flavans, flavanones, and flavones), only certain representatives of the latter class of compounds showed potent aromatase inhibition activity (Table 2). Flavanone 39 (2S)-2, 4 -dihydroxy-2"-(l -hydroxy- 1-methylethyl)-... 

The conversion of androstenedione to estrone is catalyzed by aromatase. Inhibition of aromatase (human estrogen synthetase) by several naturally occurring flavonoids, including quercetin, chrysin, and apigenin, has been described. The synthetic flavone 7,8-benzoflavone was most active. Aromatization of androstenedione was affected by several flavonoids, of which 7-hydroxy-flavone and 7,4-dihydroxyflavone were the most potent. 

Inhibition by 7-hydroxyflavone was competitive with respect to the substrate androstenedione. Flavonoids of the 5,7-dihydroxyflavone series could bind to the active site human cytochrome P-450 aromatase with affinity. The flavonoid kaempferol inhibited aromatase enzyme activity competitively in a human Glyoxalase cell culture system. Such results suggest that diets rich in these compounds could contribute to the control of estrogen-dependent conditions, such as breast cancer. 

C Wang, T Makela, T Hase, H Adlercreutz, MS Kurzer. Lignans and flavonoids inhibit aromatase enzyme in human preadipocytes. J Steroid Biochem Molec Biol 50 205-212, 1994. 

Hargrove JL, Greenspan P, Hartle DK, Dowd C. Inhibition of aromatase and a-amylase by flavonoids and proanthocyanidins from Sorghum bicolor bran extracts. J. Med Food 14(7-8), 799-807, 2011. 

There is a clear correlation between adiposity and breast cancer, which is almost certainly due to synthesis of oestradiol in adipose tissue enterolactone and some of the other flavonoid phyto-oestrogens inhibit aromatase and will therefore reduce synthesis of oestradiol in adipose tissue. 

Bail, J, Laroche,T, Marre-Foumier, F and Habrioux, G (1998) Aromatase and 17P-hydroxysteroid dehydrogenase inhibition by flavonoids. Cancer Lett., 133, 101-106. 

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