Aim: As a typical Chinese herbal medicine, Radix Codonopsis has been used in traditional Chinese medicine for about 250 years. The study tried to investigate its antioxidant activity, then to discuss the antioxidant mechanism. Methods: Radix Codonopsis was extracted by ethanol to obtain ethanolic extract of Radix Codonopsis. The extract was then determined by various antioxidant methods, including DNA damage assay, DPPH (1,1-diphenyl-2-picryl-hydrazl radical), ABTS [2,2′-azino-bis(3-ethylbenzo- thiazoline-6-sulfonic acid) radical] assay, Fe3+-reducing assay and Cu2+-reducing assay. Finally, the contents of total phenolics and flavonoids in the extract were determined by spectrophotometric method. Results: The ethanolic extract of Radix Codonopsis showed protective effect against hydroxyl-induced DNA damage (IC50 1180.28±137.73 μg/mL ) and exhibited DPPH· scavenging, ABTS+• scavenging, Fe3+ reducing, and Cu2+ reducing abilities, and the IC50 values were 3857.79±35.51, 271.82±5.66, 759.99±31.65, and 733.02±9.67 μg/mL, respectively. The contents of total phenolics and flavonoids in the extract were calculated as 12.56±0.56 and 11.95±0.52 mg quercetin/g, respectively. Conclusion: Radix Codonopsis can effectively protect against hydroxyl-induced DNA damage. One mechanism of protective effect may be radical-scavenging which is via donating hydrogen atom (H·), donating electron (e). Its antioxidant ability can be mainly attributed to the existences of flavonoids or phenolic acids. [J Intercult Ethnopharmacol 2013; 2(1.000): 1-8

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