A potential mechanism of action of dietary anthocyanins: modulation of endothelial superoxide production by phenolic acid metabolites

[...] cyanidin-3-glucoside and protocatechuic acid did not appear to attenuate superoxide production at physiological concentrations, although both the glucuronide [87.9 (sd 4.1) and -1.4 (sd 18.9)% inhibition] and methyl 0.5 (sd 17.7) and 67.6 (sd 26.3)% inhibition conjugates of protocatechuic acid demonstrated significant inhibitory effects. [...] the ability of phenolic acids to inhibit superoxide release appeared to be inversely associated with the number of aryl hydroxyls ([left right arrow with stroke]OH=[arrow up]bioactivity), which was in express opposition to their antioxidant potential ([arrow up]OH=[arrow up]antioxidant potential), as established via Fe/ion reduction and xanthane oxidase inhibition assays.