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Iron-binding and anti-Fenton properties of baicalein and baicalin.

ABSTRACT: 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 2-9 x 10(11)M(-2), whereas a 1:1 baicalein-ferric complex was formed, under the same conditions, with an apparent binding constant approximately 1-3 x 10(6)M(-1). 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-ring. 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.

SUBMITTER: Perez CA

PROVIDER: S-EPMC2659571 | biostudies-literature | 2009 Mar

REPOSITORIES: biostudies-literature

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Iron-binding and anti-Fenton properties of baicalein and baicalin.

Perez Carlos A CA Wei Yibin Y Guo Maolin M

Journal of inorganic biochemistry 20081119 3

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 ...[more]

PMID: 19108897

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Project description:Introduction: Ulcerative colitis (UC) is an inflammatory bowel disease with a high incidence rate and a difficult treatment regimen. Recently, significant advances in the treatment of intestinal diseases, particularly UC, have been made with the use of the drugs baicalin and baicalein, separately or in combination. However, the therapeutic efficacy and mechanism of action of baicalin, baicalein, and their combination therapy, in the treatment of UC has not been fully elucidated. Materials and Methods: we constructed a UC rat model that encompassed a variety of complex factors, including a high-sugar and high-fat diet, a high temperature and humidity environment (HTHE), excess drinking, and infection of Escherichia coli. Model rats were then treated with baicalin, baicalein, or a combination of the two. Results: The results showed significant differences in the therapeutic effects of baicalin, baicalein, and the combination therapy, in the treatment of UC, as well as differences in the inhibition of inflammation via the nuclear factor-κB and MAPK pathways. The rat model of UC was established as described above. Then, the rats were treated for 7 days with baicalin (100 mg kg-1), baicalein (100 mg kg-1), or both (100 mg kg-1, baicalin: baicalein = 4:1/1:1). Clinical symptoms and signs, body temperature, organ indices, histopathology, blood biochemistry, and metabolites were examined to compare treatment effects and indicators of UC. Baicalin, YSR (Young Scutellaria baicalensis ratio of baicalin and baicalein), baicalein, and WSR (Withered Scutellaria baicalensis ratio of baicalin and baicalein) had significantly different effects in terms of clinical symptoms and signs, body temperature, organ indices, serum inflammatory cytokine levels, blood biochemistry, and histopathology changes in the main organs; YSR exhibited the best treatment effects. LC-MS/MS was used to detect the conversion of baicalin, baicalein, or both, into the six types of metabolites: baicalin, wogonoside, oroxin A, baicalein, wogonin, and oroxylin A. The levels of the six metabolites under the different treatment conditions were significantly different in the large intestine, small intestine, and lungs, but not in the blood. The levels of the six metabolites were significantly different in the large intestine, small intestine, and lung, but not in the serum. Conclusion: All these results indicate that baicalin and baicalein should be used more accurately in specific diseases, especially baicalin or high content of baicalin in Scutellaria baicalensis (Tiaoqin) should be preferred in treatment of UC.

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Iron-binding and anti-Fenton properties of baicalein and baicalin.

Publications

Iron-binding and anti-Fenton properties of baicalein and baicalin.

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