The flavonoid 7-mono-O-(β-hydroxyethyl)-rutoside is able to protect endothelial cells by a direct antioxidant effect

The flavonoid 7-mono-O-(β-hydroxyethyl)-rutoside (monoHER) is an effective protector against doxorubicin induced toxicity which has been related to the antioxidant activity of monoHER. The present study examines the potential relevance of the direct scavenging activity of the flavonoid. The potency of the direct antioxidant effect was confirmed by its instantaneous protection against intracellular oxidative stress in human umbilical vein endothelial cells at therapeutically achievable concentrations (EC50=60 nM) underpinning the involvement of a direct scavenging activity. This direct effect of monoHER is substantiated by (i) its site specific scavenging effect, i.e. on a molecular level monoHER is positioned at the location of radical formation, (ii) its position in the antioxidant network, i.e. on a biochemical level oxidized monoHER quickly reacts with ascorbate or glutathione, (iii) its location in the vascular system, i.e. on a cellular level monoHER is localized in the endothelial and smooth muscle cells in the vascular wall. It is concluded that the flavonoid monoHER can display a physiologically important direct antioxidant effect.