Affiliations: Unit\'e de Toxicologie Nutritionnelle, Institut
National de la Recherche Agronomique, 17 rue Sully, 21034 Dijon Cedex,
France
Note: [] Unit\'e de Toxicologie Nutritionnelle, Institut National de la
Recherche Agronomique, 17 rue Sully, 21034 Dijon Cedex, France. Tel.: +33 3 80
69 32 21; Fax: +33 3 80 69 32 25; E-mail:siess@dijon.inra.fr
Abstract: Flavonoids, widespread in edible plants, have been studied
extensively for their anticarcinogenic properties. However, only few studies
have been done with these constituents being administered by the dietary route.
In our research, the effects of feeding rats with flavone, flavanone,
tangeretin, and quercetin were investigated on two steps of aflatoxin B1
(AFB_1)-induced hepatocarcinogenesis (initiation and
promotion). Nonpolar flavonoids such as flavone, flavanone and tangeretin
administered through the initiation period, decreased the number of
\gamma-glutamyl transpeptidase-preneoplastic foci. In the
same conditions of administration, quercetin, a polyhydroxylated flavonoid,
showed no protective effect. Moreover, feeding rats with flavanone during the
phenobarbital-induced promotion step significantly reduced the areas of
placental glutathione S-transferase preneoplastic foci. Quercetin, flavone, and
tangeretin, administered in the same conditions, caused no significant effect.
Therefore flavanone act as an anti-initiator as well as an anti-promotor.
Several mechanisms were involved in the anti-initiating effects of flavone,
flavanone, and tangeretin: enhancement of enzymes involved in the detoxication
of AFB_1 (glutathione S-transferase, UDP-glucuronyl
transferase), increase of the formation of AFB_1-glutathione
conjugates and inhibition of the binding of AFB_1 to DNA.
Although the relevance of these data to the human situation remains to be
demonstrated, they confirm that several flavonoids administered by the dietary
route possess promising chemoprotective effects.
Journal: BioFactors, vol. 12, no. 1-4, pp. 193-199, 2000
