In vitro anti-nitrosative, antioxidant, and cytotoxicity activities of plant flavonoids: a comparative study

Abstract

The ability of eight flavonoids to react with the biologically relevant reactive nitrogen species, nitric oxide, peroxynitrite, and nitrous acid were investigated in vitro, for the first time. All the investigated flavonoids were found to be potent reactive nitrogen and oxygen species scavengers and resulted in a significant inhibition of 3-nitrotyrosine (3-NT) formation in a dose-dependent manner. All the IC50s were found at the μM level. The results reveal that, the presence of C5–OH and C4’–OH, in the flavonoid skeleton, enhanced the anti-nitrosative activity. The absence of the C2=C3 double bond and/or C4-carbonyl group resulted in slight decrease of the anti-nitrosative activity. However, the presence of C6- and/or C3’-methoxy groups together with C4’–OH dramatically decrease the inhibition capacity. Especially the free hydroxyl groups at 3’ and 4’ of the catechol containing ring B flavonoids as well as both hydroxyl groups at C3 and C5 are necessary for better antioxidant activity. The absence of both C3–OH and/or C3’–OH groups resulted in a remarkable decrease in the antioxidant activity. The cytotoxicity results indicate that the investigated flavonoids are safe to be used up to a concentration of 100 μM and may be utilized as promising sources of therapeutics.