Quercetin – a key substance in heavy metal uptake of plants?


Quercetin – a key substance in heavy metal uptake of plants?

Geipel, G.; Drewitz, S.; Viehweger, K.; Bernhard, G.; Henle, T.

Recently it could be reported, that uranium can occur in its tetravalent oxidation state on the Surface of roots of Arabidopsis halleri /1/. Nevertheless it is very unusual to find uranium in this oxidation state in soil compartments located close to the earth surface, where oxidizing conditions dominate. The oxidation state +6 should be the stable under these conditions.
Flavonoids are widely distributed in plants and have multifunctional properties. They are known for there antioxidant activity Within this class of compounds quercetin is very widespread. Considering that quercetin may be involved in the reduction process we carried out experiments to reduce uranium-(VI) by quercetin. The experiments were carried in under N2-atmosphere to avoid reoxidation of the formed uranium-(IV). Under these in vitro conditions quercetin was able to reduce up to 10% of the uranium. Uranium-(IV) was determined directly by Laser-Induced Photoacoustic Spectroscopy and UV-Vis spectroscopy.
However, this does not explain the existence of uranium-(VI) on the roots. The redox potential of quercetin was measured as function of pH. The shift of the redox potential supports the reduction of uranium with increasing pH /2/. Additionally quercetin can act as complex forming agent. We studied the complex formation of quercetin with uranium-(IV) and uranium-(VI). In both cases a 1:1 complex was found and the stability constants were determined to be log β11 = 20.36 /2/ and log β11 = 13.8 /3/, respectively. This shows a strong stabilization of the uranium-(IV) in its complex with quercetin.
/1/ K. Viehweger, G. Geipel, Environmental and Experimental Botany 69 (2010) 39–46
/2/ S. Drewitz, Diploma thesis, TU Dresden 2010
/3/ K. Viehweger, G. Geipel, In Wissenschaftlich-Technische Berichte FZD-511, Annual Report 2008, (2009) 41.

  • Contribution to proceedings
    Biometals 2010, 25.-30.07.2010, Tucson, USA

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Publ.-Id: 14215