Iron-binding and anti-Fenton properties of baicalein and baicalin.
Perez CA, Wei Y, Guo M.
J Inorg Biochem. 2008 Nov 19.
Department of Chemistry and Biochemistry, University of Massachusetts,
Dartmouth, MA 02747-2300, USA.

Baicalein and baicalin, the major bioactive compounds found in the
Chinese herb Scutellaria baicalensis, have been shown to be effective
against cancer, bacterial infections and oxidative stress diseases.
However, little is known about their mechanisms of action.
To probe whether iron homeostasis modulation may play a role in their
bioactivity, we have investigated their iron binding characteristics
under physiologically relevant conditions.
A 2:1 baicalein-ferrous complex was readily formed in 20mM phosphate
buffer, pH 7.2, with a binding constant approximately 2-9x10(11)M(-2),
whereas a 1:1 baicalein-ferric complex was formed, under the same
conditions, with an apparent binding constant approximately 1-3x10(6)M
Baicalein appears to bind the ferrous ion more strongly than
ferrozine, a well known iron(II) chelator.
Using (1) H NMR and Zn(2+) and Ga(3+) as probes, the iron-binding site
on baicalein was elucidated to be at the O6/O7 oxygen atoms of the A-
No binding was observed for baicalin under the same NMR conditions.
Furthermore, baicalein strongly inhibits the Fe-promoted Fenton
chemistry via a combination of chelation and radical scavenging
mechanism while baicalin can provide only partial protection against
radical damage.
These results indicate that baicalein is a strong iron chelator under
physiological conditions and hence may play a vital role in modulating
the body's iron homeostasis.
Modulation of metal homeostasis and the inhibition of Fenton chemistry
may be one of the possible mechanisms for herbal medicine.

PMID: 19108897

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