Abstract
Quercetin and galangin can change the activity of glutathione reductase. Quercetin (a catechol structure in the B-ring) and galangin (any hydroxyl group in the B-ring) have different biological activities but, both possess high antioxidant abilities. Quercetin during the antioxidative action, is converted into an oxidized products (o-semiquinone and o-quinone), and subsequently glutathionyl adducts may be formed or SH-enzyme can be inhibited. We have tried to see whether inhibition of glutathione reductase (GR) can be influenced by preincubation of enzyme with NADPH (a creation of reduced form of enzyme, GRH(2)) and whether diaphorase activity of the enzyme is decreased by these flavonoids. The results confirmed that quercetin inhibits GRH(2) and inhibition is reduced by addition of EDTA or N-acetylcysteine. Both of flavonoids have no effect on diaphorase activity of glutathione reductase and this enzyme could increase the production of free radicals by catalysis of reduction of o-quinone during action of quercetin in vivo.
Highlights
Flavonoids are frequently components of human diet and multiple mechanisms have been identified for their biological and pharmacological effects[1,2,3]
Flavonoids can modify redox state of glutathione, GS-flavonoid conjugate or oxidation of GSH to GSSG can arise from reactions of GSH with o-semiquinone[8]
We have studied the modulation of cis-Pt induced apoptosis by quercetin and galangin
Summary
Flavonoids are frequently components of human diet and multiple mechanisms have been identified for their biological and pharmacological effects[1,2,3]. Our work hypothesis is that one of the reason of the diverse action of quercetin and galangin is related with uneven effect of flavonoids on the glutathione reductase. In this paper we have investigated the influence of these flavonoids at low concentration (from 25 to 100 μM) on the activities of the glutathione reductase from yeast, GSSG-reductase activity and diaphorase activity of GR has been examined.
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