The Journal of Clinical Endocrinology & Metabolism Vol. 89, No. 4 1779-1787
Copyright © 2004 by The Endocrine Society

Phytoestrogens Are Potent Inhibitors of Estrogen Sulfation: Implications for
Breast Cancer Risk and Treatment
R. M. Harris, D. M. Wood, L. Bottomley, S. Blagg, K. Owen, P. J. Hughes, R.
H. Waring and C. J. Kirk
School of Biosciences and Medical School, University of Birmingham,
Edgbaston, Birmingham B15 2TT, United Kingdom

Address all correspondence and requests for reprints to: C. J. Kirk, School
of Biosciences and Medical School, University of Birmingham, Edgbaston,
Birmingham B15 2TT, United Kingdom. E-mail: .

We investigated the ability of 37 flavonoids and flavonoid sulfoconjugates,
including some abundant dietary constituents, to act as substrates and/or
inhibitors of the sulfotransferase and sulfatase enzymes that interconvert
active estrogens and inactive estrogen sulfates in human tissues. The
enzymes studied include estrogen sulfotransferase, the thermostable
phenolsulfotransferase that acts on a range of substrates including
estrogens; steroid sulfatase; and two related enzymes, monoamine
phenolsulfotransferase and arylsulfatase A. Several dietary flavonoids,
including the soy isoflavones genistein and daidzein, were sulfated by these
human sulfotransferases. Many flavonoids were potent inhibitors of
thermostable phenolsulfotransferase. Genistein and equol were potent mixed
inhibitors of hepatic estrogen sulfotransferase, with inhibitory constant
values of 500 nM and 400 nM, respectively. Monoamine phenolsulfotransferase
activity was relatively unaffected by flavonoids, but this enzyme was mainly
responsible for the sulfation of flavonoids at concentrations greater than 1
µM. Of the compounds tested, only daidzein 4,7-bisulfate, a trace metabolite
in humans, significantly inhibited steroid sulfatase in the micromolar
concentration range. Hence, dietary flavonoids may be able to influence the
bioavailability of endogenous estrogens, and disrupt endocrine balance, by
increasing the ratio of active estrogens to inactive estrogen sulfates in
human tissues.

Laurie wrote:

....
>
> We investigated the ability of 37 flavonoids and flavonoid
> sulfoconjugates, including some abundant dietary constituents, to act as
> substrates and/or inhibitors of the sulfotransferase and sulfatase enzymes
> that interconvert active estrogens and inactive estrogen sulfates in human
> tissues. The enzymes studied include estrogen sulfotransferase, the
> thermostable phenolsulfotransferase that acts on a range of substrates
> including estrogens; steroid sulfatase; and two related enzymes, monoamine
> phenolsulfotransferase and arylsulfatase A. Several dietary flavonoids,
> including the soy isoflavones genistein and daidzein, were sulfated by
> these human sulfotransferases. Many flavonoids were potent inhibitors of
> thermostable phenolsulfotransferase. Genistein and equol were potent mixed
> inhibitors of hepatic estrogen sulfotransferase, with inhibitory constant
> values of 500 nM and 400 nM, respectively. Monoamine
> phenolsulfotransferase activity was relatively unaffected by flavonoids,
> but this enzyme was mainly responsible for the sulfation of flavonoids at
> concentrations greater than 1 µM. Of the compounds tested, only daidzein
> 4,7-bisulfate, a trace metabolite in humans, significantly inhibited
> steroid sulfatase in the micromolar concentration range. Hence, dietary
> flavonoids may be able to influence the bioavailability of endogenous
> estrogens, and disrupt endocrine balance, by increasing the ratio of
> active estrogens to inactive estrogen sulfates in human tissues.

It sounds like it may be interesting and important, but could someone
translate it into English so that the rest of us can understand it?


--
Andy Rugg
The Cheerful Pickle
to email me please remove "postheap" from my email address. Thanks.

soy messes with your endocrine system, this can be useful in certain forms
of cancer (breast and prostate), but probably carries risks as well