Antioxidant efficacy of Nasturtium officinale extracts using various in vitro assay systems

Nasturtium officinale R. Br. (watercress), of the family Brassicaceae, has been long used as a home remedy or a medicinal plant by the people of southeastern Iran. The aim of this study was to investigate the antioxidant activity of N. officinale extract using various in vitro assay systems, including the ferric reducing antioxidant power and 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonate) assays, 1,1-diphenyl-2-picrylhydrazyl, hydrogen peroxide, nitric oxide radical scavenging, and ferrous ion chelating activity, as well as the inhibitory effect on ferrous ion/ascorbate induced lipid peroxidation, in rat liver homogenate. The results revealed that N. officinale extract possesses potent reducing power in a ferric reducing antioxidant power assay, concentration-dependent scavenging ability on 2,2'-azinobis 3-ethylbenzothiazoline-6-sulfonate, 1,1-diphenyl-2-picrylhydrazyl, nitric oxide radicals, and hydrogen peroxide, as well as chelating ability on ferrous ions. Furthermore, N. officinale extract prevented thiobarbituric acid reactive substances formation in ferrous ion/ascorbate induced lipid peroxidation in rat liver homogenate in a dose-dependent manner. In addition, this N. officinale extract had the phenolic and flavonoid contents of 96.2 mg gallic acid equivalents/g dried extract and 63.2 mg catechin equivalents/g dried extract, respectively. The cumulative results clearly indicate that N. officinale extract possesses potent antioxidant properties probably mediated through direct trapping of free radicals, reducing power, and also through metal chelating. Based on its antioxidative potential, N. officinale extract might find applications in the prevention of free radical-related diseases.