Protective effects of an aqueous extract of Welsh onion green leaves on oxidative damage of reactive oxygen and nitrogen species

Antioxidant effects of Welsh onion green leaves on reactive oxygen and nitrogen species were investigated. The results showed that aqueous extract of Welsh onion green leaves (WOE) in the range 0.05–1.0 mg/ml showed a potent concentration-dependent reduction of xanthine oxidase activity, and this inhibitory action of WOE correlated well with total flavonoid content (r = 0.99, p < 0.05). Furthermore, WOE also showed scavenging of superoxide radical (p < 0.05), hydroxyl radical (p < 0.05), nitric oxide (p < 0.05) and chelating metal ions (p < 0.05) in a dose-dependent manner. In addition, the oxidative damage of albumin, induced by hydroxyl radical (OH) and hypochlorous acid (HOCl) in an acellular system, was inhibited by 0.1–2.0 mg/ml of WOE. Protein tyrosine residue nitration in mouse heart homogenates was obviously decreased by 2 mg/ml WOE. Thus, these positive effects might contribute to the protective effect of Welsh onion against oxidative damage of protein.