A study on the antioxidant activity and tissues selective inhibition of lipid peroxidation by saponins from the roots of platycodon grandiflorum

Platycodi Radix is the root of Platycodon grandiflorum (Jacq.) A. DC and has been used as a traditional medicine in China. According to the theory of traditional Chinese medicine, Platycodi Radix (PR) possesses the character of lung meridian tropism (Guijing) and has selective effects on the lung and respiratory system. The aim of this study was to confirm the antioxidant effects of saponins from Platycodi Radix (PRS), with emphasis on its selective inhibition of lipid peroxidation in different tissues. The hydroxyl radical scavenging activity was determined by a H₂O₂/Fe ²⁺ system; a modified thiobarbituric acid reactive species assay was used to measure the lipid peroxide in rats' tissues. These antioxidant activities were compared to ascorbic acid (Vc). The results showed that PRS had antioxidant activities in various antioxidant systems. And the inhibition capability of lipid peroxidation of PRS and Vc were excellent, but differed greatly in different tissues. These results suggested that PRS had antioxidant effects and selective inhibition of lipid peroxidation. It indicated that the mechanism of Platycodi Radix to treat some diseases might be related to its antioxidant activity, especially its tissue selective effects. However, further study is needed.